Data creation device, data creation method, base station, mobile station, synchronization detection method, sector identification method, information detection method, and mobile communication system

The present invention relates to E-UTRA (Evolved-UTRA) standard mobile communication that employs a multi-carrier communication method, and in particular, creates synchronization channel (SCH) data included in a downlink (downlink transmission) signal. Data creation device, data creation method, base station, mobile station, synchronous detection method, sector identification method, information detection method, and mobile communication system.

In recent years, third-generation mobile communications (3G), including the W-CDMA system, have become widespread worldwide. Currently, 4th generation mobile communication (4G), which realizes a communication speed of 100Mb / s to 1Gb / s in downlink, is being studied. However, the complete transition from 3G to 4G is not easy. For this reason, E-UTRA (Evolved-UTRA), which uses the 3G frequency band and introduces new 4G technology to speed up communication, is drawing attention. Active proposals are also being made at 3GPP (3rd Generation Partnership Project).

In a mobile communication system, a mobile station needs to identify a cell and a sector to be connected by the mobile station for initial synchronization establishment or handover. That is, it is necessary to detect the base station to be communicated and the antenna of the base station. In the third generation mobile communication, a so-called three-step cell search method is adopted in order to perform a high-speed cell search. In addition, "cell search" is a concept including "sector search".

Three-stage cell search in third-generation mobile communications generally uses a synchronization channel (SCH) and a common pilot channel (CPICH). First, the reception timing of the SCH is detected (first step), and then the frame timing and the scrambled code group are identified by the correlation detection of the SCH code (second step). Then, the scrambled code is identified by correlation detection using CPICH (third step).

In E-UTRA, the next-generation mobile communication standard, OFDM (Orthogonal Frequency Division Multiplexing) is used as the modulation method, but for cell search, a technology that follows the concept of the above three-stage cell search. Have been proposed (see, for example, Patent Document 1, Patent Document 2, Non-Patent Document 1 and Non-Patent Document 2).

Patent Document 1 discloses a technique of frequency-multiplexing a second synchronization code (S-SCH signal) for identifying a scrambled code group among a plurality of subcarriers in a three-step cell search in a multi-carrier communication method using OFDM. There is.

Patent Document 2 discloses a technique for multiplexing a cell identification code on a common pilot channel (CPICH) in a three-step cell search in a multi-carrier communication system using OFDM.

Further, Non-Patent Document 1 proposes standardization of a one-cell repetitive communication method adopting OFDM. Further, a standardization plan has been proposed in which one cell is divided into three sectors and base stations arranged in each sector communicate with a plurality of mobile stations in the cell at the same time. In this technique, the common pilot channel (CPICH) is doubly multiplied by the cell-specific spreading code and the sector-specific spreading code. Therefore, the mobile station can identify cells (and sectors) by performing despreading and correlation detection with each spreading code replica.

In addition, Non-Patent Document 2 discloses a technique for identifying cells (and sectors) by a three-step cell search similar to the third-generation technique in a multi-carrier communication method adopting OFDM. In this technique, similar to the technique disclosed in Non-Patent Document 1, one cell is divided into three sectors, and the same synchronization channel code (SCH code) is used between each sector. Further, regarding the transmission of the SCH code, time synchronization is performed between the sectors, and the SCH transmission for each sector is performed at the same time. Then, the identification of cells and sectors, that is, the selection of cells and sectors giving the maximum received power is performed by the correlation detection by the replica of the diffusion code using the pilot channel in the third step.

In this way, even in the next-generation communication standard E-UTRA, proposals have been made to adopt a technology that follows the 3G three-stage cell search using SCH and CPICH. In particular, regarding sector identification, as disclosed in Non-Patent Document 1 and Non-Patent Document 2, the common pilot channel is multiplied by the sector-specific diffusion code, and received by the back diffusion and correlation detection processing in the third step. The sector with the highest power is detected.

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2003-179522</text></patcit><patcit num="2"><text>Japanese Patent Application Laid-Open No. 2005-198232</text></patcit></p>

<p><nplcit num="1"><text>3GPP "TR 25.814," Physical Layer Aspects for Evolved UTRA (Release 7) v.0.3.1 "2005/10/18</text></nplcit><nplcit num="2"><text>3GPP "R1-060042," SCH Structure and Cell Search Method in E-UTRA Downlink "2006/1/19</text></nplcit></p>

<p> As mentioned above, it has been proposed that E-UTRA, which is the next-generation communication standard, also uses SCH and CPICH to adopt a technology that follows the 3G 3-step cell search. In this case, sector identification is performed by backdiffusion and correlation detection processing using CPICH (common pilot channel) in the third step. In other words, with the conventional technology, sectors and cells cannot be identified without going through three steps of processing. Therefore, in the three-step cell search, there is a limit to shortening the process required for the cell and sector identification process.</p><p> Further, in the third step, in addition to the back-diffusion and correlation detection processing for cell identification using CPICH, it is necessary to further perform the same processing for sector identification. That is, in the final stage of the three-stage cell search, it is necessary to detect the cell ID by backdiffusion using the replica code and determine from which sector in the same cell the signal strength is strong. Therefore, as a result, it is necessary to perform correlation detection using replica signals of (the number of cell IDs included in the cell ID group) × (the number of sector IDs). Therefore, the time required for correlation detection in the third step increases in proportion to the number of sectors contained in one cell.</p><p> Further, in order to compare the correlation values corresponding to each replica signal, a memory having a capacity for accumulating the correlation calculation result by each replica signal is required. That is, a memory for accumulating the correlation calculation results for (the number of cell IDs included in the cell ID group × the number of sector IDs) is required, which causes an increase in the memory capacity.</p><p> Further, as disclosed in Non-Patent Document 2 above, the same SCH data is simultaneously transmitted for each sector in the same cell. Therefore, in the mobile station near the sector boundary, there is a possibility that a frequency band in which the received power is lowered may occur due to mutual interference of signals from a plurality of sectors or fading due to the propagation environment. In this case, the cell and sector identification probabilities may decrease.</p><p> The present invention has been made in view of such circumstances, and an object of the present invention is to shorten the time required for cell search processing including sector identification and to store the correlation detection result using the pilot channel. To reduce capacity. Further, it is intended to improve the interference resistance or fading resistance characteristics of the cell search process including the sector identification, and to realize the cell search including the sector identification more easily and accurately without increasing the load on the transmission / reception device.</p>

<p> (1) In order to achieve the above object, the present invention has taken the following measures. That is, the data creation device of the present invention is a data creation device that creates data of a synchronization channel transmitted by a base station that controls a cell containing a plurality of sectors, and is used as a sector identification number for identifying the sector. It is characterized in that the data of the synchronization channel for each sector is created by using the corresponding sector-specific code.</p><p> With this configuration, it is possible to perform sector identification using a synchronous channel without using a pilot channel by multiplying the sector common code by a sector-specific code.</p><p> (2) Further, in the data creation device of the present invention, the sector-specific codes are characterized in that they are orthogonal to each other.</p><p> This configuration enables highly accurate sector identification or synchronous detection.</p><p> (3) Further, in the data creation device of the present invention, the sector-specific code is common among adjacent cells.</p><p> This configuration enables efficient sector identification or synchronous detection.</p><p> (4) Further, the data creation device of the present invention is characterized in that the pilot channel data for each sector is created by using the orthogonal code corresponding to the sector identification number.</p><p> This configuration shortens the time required for the cell search process including sector identification, reduces the capacity of the memory for storing the correlation detection result using the pilot channel, and further reduces the interference resistance of the cell search process including sector identification. It is possible to realize cell search including faster and more accurate sector identification without increasing the load on the transmitter / receiver by improving the properties or fading resistance characteristics.</p><p> (5) Further, the data creation method of the present invention is a data creation method for creating data of a synchronization channel transmitted by a base station having jurisdiction over a cell including a plurality of sectors, and is a sector for identifying the sector. It is characterized in that the data of the synchronization channel for each sector is created by using the sector-specific code corresponding to the identification number.</p><p> With this configuration, it is possible to perform sector identification using a synchronous channel without using a pilot channel by multiplying the sector common code by a sector-specific code.</p><p> (6) Further, the data creation method of the present invention is characterized in that the pilot channel data for each sector is created by using the orthogonal code corresponding to the sector identification number.</p><p> This configuration shortens the time required for the cell search process including sector identification, reduces the capacity of the memory for storing the correlation detection result using the pilot channel, and further reduces the interference resistance of the cell search process including sector identification. It is possible to realize cell search including faster and more accurate sector identification without increasing the load on the transmitter / receiver by improving the properties or fading resistance characteristics.</p><p> (7) Further, the base station of the present invention is a base station that controls a cell including a plurality of sectors, and is synchronized for each sector using a sector-specific code corresponding to the sector identification number for identifying the sector. It is characterized by including a storage unit for storing channel data and a transmission unit for transmitting data of the synchronization channel corresponding to the sector to each sector.</p><p> With this configuration, it is possible to perform sector identification using a synchronous channel without using a pilot channel by multiplying the sector common code by a sector-specific code.</p><p> (8) Further, the base station of the present invention is a base station that controls a cell including a plurality of sectors, and uses a sector-specific code corresponding to a sector identification number for identifying the sector for each sector. It is characterized by including a synchronization channel data creation unit that creates synchronization channel data and a transmission unit that transmits data of the synchronization channel corresponding to the sector to each sector.</p><p> With this configuration, it is possible to perform sector identification using a synchronous channel without using a pilot channel by multiplying the sector common code by a sector-specific code.</p><p> (9) Further, in the base station of the present invention, the synchronous channel data creation unit creates pilot channel data for each sector by using the orthogonal code corresponding to the sector identification number, and the transmission unit is the transmission unit. The feature is that the data of the pilot channel corresponding to the sector is transmitted to each sector.</p><p> This configuration shortens the time required for the cell search process including sector identification, reduces the capacity of the memory for storing the correlation detection result using the pilot channel, and further reduces the interference resistance of the cell search process including sector identification. It is possible to realize cell search including faster and more accurate sector identification without increasing the load on the transmitter / receiver by improving the properties or fading resistance characteristics.</p><p> (10) Further, the mobile station of the present invention is a mobile station that communicates with a base station that controls a cell containing a plurality of sectors, and has a sector-specific code corresponding to a sector identification number for identifying the sector. It is characterized in that a signal including the used synchronization channel is received from the base station.</p><p> With this configuration, it is possible to perform sector identification using a synchronous channel without using a pilot channel by multiplying the sector common code by a sector-specific code.</p><p> (11) Further, the mobile station of the present invention is characterized in that sector identification is performed based on the synchronization channel.</p><p> This configuration enables highly accurate sector identification.</p><p> (12) Further, the mobile station of the present invention is characterized in that synchronous detection is performed based on the synchronous channel.</p><p> With this configuration, it is possible to perform high-precision synchronous detection.</p><p> (13) Further, in the mobile station of the present invention, the sector-specific codes are characterized in that they are orthogonal to each other.</p><p> This configuration enables highly accurate sector identification or synchronous detection.</p><p> (14) Further, in the mobile station of the present invention, the sector-specific code is common among adjacent cells.</p><p> This configuration enables efficient sector identification or synchronous detection.</p><p> (15) Further, the mobile station of the present invention is characterized in that synchronous detection is performed by correlating the signal with the sector-specific code.</p><p> With this configuration, SCH timing detection on the time axis (first step) by the autocorrelation method using the periodicity of the SCH or the cross-correlation method using the time waveform of the replica code of the sector-specific code, and on the frequency axis It is also possible to complete the cell search by informed sector ID and cell ID identification (second step). Therefore, the search process can be shortened as compared with the conventional three-stage cell search.</p><p> (16) Further, the mobile station of the present invention includes a synchronization channel signal processing unit, and the synchronization channel signal processing unit performs the synchronization detection by correlating the signal with a replica corresponding to the sector-specific code. It is characterized by doing.</p><p> With this configuration, correlation detection using a replica of the sector-specific code becomes possible.</p><p> (17) Further, the mobile station of the present invention is characterized in that sector identification is performed by correlating the signal with the sector-specific code.</p><p> This configuration enables highly accurate sector identification.</p><p> (18) Further, in the mobile station of the present invention, the synchronous channel signal processing unit is characterized in that the sector is identified by correlating the signal with a replica corresponding to the sector-specific code.</p><p> With this configuration, correlation detection using a replica of the sector-specific code becomes possible.</p><p> (19) Further, the mobile station of the present invention is characterized in that a plurality of replicas corresponding to the plurality of sectors are stored in advance.</p><p> With this configuration, correlation detection using a replica of the sector-specific code becomes possible.</p><p> (20) Further, in the mobile station of the present invention, the synchronous channel signal processing unit is characterized in that each of the plurality of replicas and the signal are correlated in parallel.</p><p> With this configuration, correlation detection can be performed efficiently.</p><p> (21) Further, in the mobile station of the present invention, the synchronous channel signal processing unit is characterized in that the sector is identified by specifying the sector-specific code having the maximum correlation value.</p><p> This configuration enables highly accurate sector identification.</p><p> (22) Further, in the mobile station of the present invention, the synchronous channel signal processing unit is characterized in that the sector is identified by converting the signal into a frequency domain and correlating with the sector-specific code. ..</p><p> This configuration enables highly accurate sector identification.</p><p> (23) Further, the mobile station of the present invention is further provided with a sector-specific code storage unit that stores a plurality of sector-specific codes corresponding to the plurality of sectors.</p><p> With this configuration, sector identification or synchronous detection can be performed efficiently and quickly, and it becomes easy to increase the number of sector-specific codes as the number of sectors increases.</p><p> (24) Further, in the mobile station of the present invention, the synchronous channel signal processing unit is characterized in that each of the plurality of sector-specific codes and a signal converted into a frequency domain are correlated in parallel. ..</p><p> With this configuration, highly accurate sector identification or correlation detection can be performed efficiently.</p><p> (25) Further, in the mobile station of the present invention, the synchronous channel signal processing unit uses the orthogonal code of the pilot channel corresponding to the sector identified by the synchronous channel to obtain information contained in the pilot channel. It is characterized by detecting.</p><p> This configuration shortens the time required for the cell search process including sector identification, reduces the capacity of the memory for storing the correlation detection result using the pilot channel, and further reduces the interference resistance of the cell search process including sector identification. It is possible to realize cell search including faster and more accurate sector identification without increasing the load on the transmitter / receiver by improving the properties or fading resistance characteristics.</p><p> (26) Further, the synchronous detection method of the present invention is created by using a sector-specific code corresponding to a sector identification number for identifying the sector, which is transmitted from a base station having jurisdiction over a cell containing a plurality of sectors. It is a synchronous detection method used when receiving a signal including a synchronous channel in a mobile station, and is characterized in that synchronous detection is performed by correlating the signal with the sector-specific code. ..</p><p> With this configuration, SCH timing detection on the time axis (first step) by the autocorrelation method using the periodicity of the SCH or the cross-correlation method using the time waveform of the replica code of the sector-specific code, and on the frequency axis It is also possible to complete the cell search by informed sector ID and cell ID identification (second step). Therefore, the search process can be shortened as compared with the conventional three-stage cell search.</p><p> (27) Further, the sector identification method of the present invention is created by using a sector-specific code corresponding to a sector identification number for identifying the sector, which is transmitted from a base station having jurisdiction over a cell containing a plurality of sectors. It is a sector identification method used when receiving a signal including a synchronous channel in a mobile station, and is characterized in that sector identification is performed by correlating the signal with the sector-specific code. ..</p><p> This configuration enables highly accurate sector identification.</p><p> (28) Further, the sector identification method of the present invention is characterized in that synchronous detection is performed by correlating the signal with the sector-specific code.</p><p> With this configuration, SCH timing detection on the time axis (first step) by the autocorrelation method using the periodicity of the SCH or the cross-correlation method using the time waveform of the replica code of the sector-specific code, and on the frequency axis It is also possible to complete the cell search by informed sector ID and cell ID identification (second step). Therefore, the search process can be shortened as compared with the conventional three-stage cell search.</p><p> (29) Further, the information detection method of the present invention is created by using a sector-specific code corresponding to a sector identification number for identifying the sector, which is transmitted from a base station having jurisdiction over a cell containing a plurality of sectors. An information detection method for detecting information contained in the pilot channel in a mobile station that receives a signal including the synchronous channel and the pilot channel created by using the orthogonal code corresponding to the sector identification number. It is characterized in that information contained in the pilot channel is detected by using the orthogonal code of the pilot channel corresponding to the sector identified by the synchronization channel.</p><p> This configuration shortens the time required for the cell search process including sector identification, reduces the capacity of the memory for storing the correlation detection result using the pilot channel, and further reduces the interference resistance of the cell search process including sector identification. It is possible to realize cell search including faster and more accurate sector identification without increasing the load on the transmitter / receiver by improving the properties or fading resistance characteristics.</p><p> (30) Further, the mobile station of the present invention has a receiving unit that receives a signal from a base station that controls a cell containing a plurality of sectors, and a sector identification unit that identifies a sector that is a source of the signal based on the received signal. Based on the sector identification by the sector identification unit, a sector having good reception characteristics is identified and handover is performed, and the reception unit has a sector-specific code corresponding to the sector identification number for identifying the sector. It is characterized by receiving the data of the synchronization channel for each sector using.</p><p> With this configuration, high-speed and high-precision handover can be performed.</p><p> (31) Further, the mobile communication system of the present invention controls a cell including a plurality of sectors, and obtains data of a synchronization channel for each sector using a sector-specific code corresponding to the sector identification number for identifying the sector. It is composed of a base station that transmits to each sector and a mobile station that receives the data from the base station.</p><p> With this configuration, it is possible to perform sector identification using a synchronous channel without using a pilot channel by multiplying the sector common code by a sector-specific code.</p><p> (32) Further, the mobile communication system of the present invention is characterized in that the communication method between the base station and the mobile station is a multi-carrier communication method.</p><p> This configuration enables high-speed, large-capacity transmission in the downlink. In addition, it can contribute to the practical application of a communication method compliant with E-UTRA.</p><p> (33) Further, the mobile communication system of the present invention is characterized in that OFDM is applied to the multi-carrier communication system.</p><p> This configuration enables high-speed, large-capacity transmission in the downlink. In addition, it can contribute to the practical application of a communication method compliant with E-UTRA.</p>

<p> According to the present invention, by multiplying the sector common code by the sector-specific code, it is possible to identify the sector only by backdiffusion and correlation detection using SCH without using a pilot channel. Therefore, regarding sector identification, despreading and correlation detection processing using the pilot channel become unnecessary, and the memory capacity used for the correlation calculation using the pilot channel can be reduced.</p><p> Further, since the SCH itself is multiplied by the sector-specific code, interference between sectors can be eliminated even at the sector boundary, and the effect of improving the fading resistance characteristic due to the randomization effect of code multiplication can also be obtained. The sector-specific code (alsh-Hadamard code) assigned to each sector can be easily increased in accordance with the increase in the number of sectors, and can flexibly correspond to the sector configuration.</p><p> Also, if the number of subcarriers (multiplyed by the cell-specific code) of SCH is sufficient, the cell ID can be directly identified only by SCH. In this case, the cell search process including sector identification can be performed in two steps using only SCH (two-step cell search), and the search time can be shortened as compared with the conventional three-step cell search. it can.</p><p> In addition, by devising the configuration and contents of the cell-specific code and sector-specific code to be multiplied and the arrangement on the frequency axis in SCH, it is possible to prevent the sector-specific information and the cell-specific information from adversely affecting each other. It is also possible to suppress a decrease in information transmission accuracy. Also, each piece of information can be demodulated independently (that is, by parallel processing). As a result, the processing time of the cell search including the sector search can be shortened.</p><p> That is, the code of the 2m chip is formed by combining two codes that are orthogonal to each other in the m chip, the m chip is used for sector identification, the remaining m chip is used for the identification of cell-specific information, and the cell-specific information is used. The information is sector-specific and cell-specific by transmitting as phase-difference information between subcarriers (preferably placed adjacent on the frequency axis) that are multiplied by sector-specific code elements of the same value. Information can be efficiently transmitted, and both can be efficiently separated and taken out on the receiving side.</p><p> Further, in the cell search method of the present invention, the timing of SCH on the time axis is detected by the autocorrelation method using the periodicity of SCH or by the cross-correlation method using the time waveform of the replica code of the sector-specific code (No. 1). It is also possible to complete the cell search by 1 step) and identification of the sector ID and cell ID based on the information on the frequency axis (2nd step). Therefore, the search process can be shortened as compared with the conventional three-stage cell search. In addition, since correlation detection using the pilot channel is only required when demodulating the data channel and is not required for cell search, the hardware burden for correlation calculation by the pilot channel should be reduced (memory capacity). (Reduction, etc.) can be achieved. Further, since the sector-specific code is superimposed on the SCH, it is possible to obtain the effect of being resistant to interference and fading between sectors in terms of sector identification. However, if the number of subcarriers is not sufficient, the cell ID cannot be directly identified by SCH alone, and the cell ID group information may be detected only. In this case, the process of the third step. As a result, the cell ID can be identified by performing backdiffusion and correlation detection using a pilot channel.</p><p> Further, the multi-carrier transmission / reception device of the present invention enables high-speed, large-capacity transmission in the downlink.</p><p> As described above, according to the present invention, the time required for the cell search process including sector identification is shortened, the capacity of the memory for storing the correlation detection result using the pilot channel is reduced, and further, sector identification is included. It is possible to improve the interference resistance or fading resistance characteristics of the cell search process, and realize a cell search including faster and more accurate sector identification without increasing the load on the transmitter / receiver.</p><p> In addition, the present invention includes various variations (specific examples, modifications, application examples), and these variations contribute to the practical application of a communication method compliant with E-UTRA (Evolved-UTRA).</p><p> For example, in the first step of cell search processing (SCH timing detection processing), in addition to the autocorrelation method, a cross-correlation method focusing on a special time waveform can be adopted. In this case, the correlator The effect of simplifying the configuration can be obtained. In addition, by unifying all the codes of the subcarriers that serve as the phase reference on the frequency axis to, for example, "1", it is necessary to make a set of six subcarriers at the time of reverse diffusion using the sector-specific code. It is possible to eliminate the restriction. Further, when the mobile station knows various sector-specific codes transmitted from the base station, the latest sector detection is detected by using the cross-correlation based on the time waveform before FFT, not by backdiffusion. You can also do it. Further, when the number of sectors increases, a "sector group-specific code" can be adopted as the "sector-specific code".</p>

<figref num="1">It is a flowchart which shows an example of the main procedure of the multi-carrier transmission processing which concerns on this invention.</figref><figref num="2">It is a flowchart which shows an example of the main procedure of the multi-carrier reception processing which concerns on this invention.</figref><figref num="3">It is a figure which shows the concept which is the basis of the generation of the orthogonal code.</figref><figref num="4">It is a figure for demonstrating an array of code elements constituting three orthogonal codes (code 1, code 2, code 3), and the principle in the case of demodulating only code 2.</figref><figref num="5">It is a figure for demonstrating the method of superimposing cell-specific information (sector ID, broadcast channel bandwidth, antenna arrangement, GI length, etc.) on SCH.</figref><figref num="6">(a) to (d) are diagrams for explaining a code format for superimposing and transmitting sector-specific information and cell-specific information on the SCH, respectively.</figref><figref num="7">It is a figure which shows the sub-carrier index (sub-carrier number) on the frequency axis.</figref><figref num="8">(a) is a figure which shows the allocation of the sector common code on the frequency axis. (b) is a diagram showing the configuration of three sector-specific codes. (c) is a diagram showing the concept underlying the generation of sector-specific codes.</figref><figref num="9">It is a figure which shows the structure of the code sequence for transmitting the cell-specific information on the frequency axis.</figref><figref num="10">It is a block diagram which shows the configuration example of the physical layer and the MAC (Media Access Control) sublayer in the base station (multi-carrier transmitter) of a mobile communication system.</figref><figref num="11">It is a block diagram which shows the specific structure of the transmission circuit part shown in FIG.</figref><figref num="12">It is a block diagram which shows an example of the structure of the multi-carrier receiver which concerns on this invention.</figref><figref num="13">It is a block diagram which shows the structural example of the circuit which has the function of timing detection and frequency error detection.</figref><figref num="14">It is a figure which shows the specific content of the back diffusion processing for sector identification.</figref><figref num="15">It is a figure for demonstrating the demodulation processing of a cell-specific information.</figref><figref num="16">It is a figure which shows the subcarrier (that is, the composition of SCH on the frequency axis) to which SCH is assigned arranged on the frequency axis.</figref><figref num="17">(a) is a diagram showing the arrangement of the sector common code to be multiplied by SCH on the frequency axis in the third embodiment, and (b) is a diagram showing the arrangement of the three sector-specific codes in the third embodiment. It is a figure which shows.</figref><figref num="18">It is a figure which shows the arrangement of the cell-specific code in 3rd Embodiment.</figref><figref num="19">It is a figure which shows the frame structure in 3rd Embodiment.</figref><figref num="20">It is a figure which shows the specific content example of the correlation calculation processing using a sector-specific code.</figref><figref num="21">It is a figure which shows the demodulation method of a cell-specific code in 3rd Embodiment.</figref><figref num="22">It is a figure which shows the frame structure of the downlink of the multi-carrier communication system used in this invention.</figref><figref num="23">It is a figure which shows an example of the structure of a cell and a sector.</figref><figref num="24">It is a figure which shows an example of the arrangement position of the synchronization channel (SCH) in a frame.</figref><figref num="25">It is a figure which shows the configuration example of SCH.</figref><figref num="26">It is a block diagram which shows the structure of the receiver for detecting the repeating waveform of SCH and performing time synchronization.</figref><figref num="27">It is a figure which shows an example of the synchronization channel (SCH) assigned to the subcarrier on a frequency axis.</figref><figref num="28">It is a figure which shows an example of the structure of the resource block in the OFDM communication system examined by 3GPP.</figref><figref num="29">(a) is a diagram showing the allocation of sector-specific codes on the frequency axis, (b) is a diagram showing the configuration of three sector-specific codes, and (c) is a diagram showing the basics of sector-specific code generation. It is a figure which shows the concept which becomes, and shows the vector on the complex phase plane.</figref><figref num="30">It is a figure which shows the structure on the frequency axis of the code sequence for transmitting cell-specific information.</figref><figref num="31">It is a block diagram which shows the structure of the receiver for detecting the time position of SCH by a replica signal, and performing time synchronization.</figref><figref num="32">It is a figure which showed 76 subcarriers used in 5th Embodiment for each of the functions.</figref><figref num="33">A subcarrier in which the cell-specific information is multiplied (SCH subcarrier for cell-specific information detection) and a subcarrier that serves as a phase reference subcarrier (SCH subcarrier for cross-correlation detection) according to the fifth embodiment. It is a figure which shows the relationship of.</figref><figref num="34">(a) is a diagram showing the allocation of sector common codes on the frequency axis in the fifth embodiment, and (b) is a diagram showing the configuration of three sector-specific codes in the fifth embodiment. Yes, (c) is a diagram showing a concept underlying the generation of sector-specific codes in the fifth embodiment, and shows a vector on a complex phase plane.</figref><figref num="35">In (a) to (d), in the fifth embodiment, the waveform in the time domain formed by combining a plurality of SCH subcarriers in the SCH symbol period is the reference waveform (or its reference) within one symbol period. It is a figure for demonstrating that the waveform (the waveform which inverted the waveform) is repeated.</figref><figref num="36">It is a figure which shows the structure on the frequency axis of the code sequence for transmitting the cell-specific information in 5th Embodiment.</figref>

First, the basic technology and the basic concept of the multi-carrier communication used in the present invention will be described.

(Basics of multi-carrier communication) In the following explanation, OFDM is used as the digital modulation method. In the OFDM communication system, standardization is being promoted in consideration of the fact that a base station that controls one cell as, for example, three communication control areas (sectors) communicates with a plurality of mobile stations in the cell at the same time. .. In the OFDM communication system, the wireless communication frame (hereinafter referred to as "frame") described below is divided into small pieces so that they can be used by a plurality of mobile stations (hereinafter, this division unit is referred to as a "resource block"). The communication speed is improved by allocating the resource block of the above to a mobile station with a good communication environment.

In addition, frames are transmitted at the same timing in each sector controlled by one base station. That is, the frame transmissions are synchronized. Also, use the same frequency band. Therefore, in the vicinity of the cell boundary and the sector boundary, the signal used in the adjacent cell or the adjacent sector and the desired received signal interfere with each other, resulting in a decrease in communication speed (throughput). In the above method of Non-Patent Document 1, the sector-specific code (in the following example, three sector-specific codes) is used for the pilot subcarrier, which is a subcarrier for estimating the propagation path assigned to the same subcarrier between sectors. Multiplies (meaning code series). Then, by back-spreading M (M is an integer of 2 or more) pilot subcarriers determined by the code sequence, interference due to signals of adjacent sectors can be eliminated and more accurate propagation path estimation can be performed. As you can see, the system is designed.

On the other hand, with respect to the interference with the adjacent cell, the interference signal due to the signal used in the adjacent cell is designed to be randomized by multiplying the pilot channel and the data channel by the diffusion code peculiar to the cell. That is, the pilot channel is doubly multiplied by the sector-specific orthogonal code and the cell-specific diffusion code.

(Frame description) FIG. 22 is a diagram showing a downlink frame configuration of the multi-carrier communication system used in the present invention. This frame configuration is the same as the general frame configuration used in the OFDMA communication method. That is, in this frame configuration, a fixed time interval (frame section) is divided into a plurality of parts, and the frequency domain is also divided into a certain bandwidth composed of a plurality of subcarriers. One of these divided areas is referred to herein as a resource block. Generally, a unit obtained by dividing a frame in the time domain is referred to as a subframe, and a unit divided in the frequency domain may be referred to as a subchannel. In FIG. 22, it is composed of 6 subchannels from F1 to F6 in the frequency axis direction and 10 subframes from SF1 to SF10 in the time axis direction. However, the number of block divisions and the block size are not limited to this. In addition, each mobile station shares these blocks. In particular, in order to improve communication characteristics (throughput), each block is scheduled to a mobile station with a good propagation path environment. Further, when there are a plurality of mobile stations communicating with a small amount of data, one resource block can be further divided and shared.

(Cell search) When starting communication, each mobile station selects a base station having good reception characteristics from a plurality of base stations, connects to the base station, and then starts wireless communication. Good reception characteristics mean that the received power of the received signal is high. Such an operation at the start of wireless communication is generally called a cell search. The cell search includes selection of a base station having good communication characteristics, acquisition of cell-specific information including information such as a base station ID, frame synchronization, symbol synchronization, and the like. Note that symbol synchronization means FFT window synchronization or window synchronization.

FIG. 23 is a diagram showing an example of the configuration of cells and sectors. As shown, base stations (BS1 to BS3) are installed in the center of one cell (CL1 to CL3). Further, each cell (CL1 to CL3) is divided into three sectors (SC1 to SC3). There are a plurality of mobile stations (UE1, etc.) in each cell, and each mobile station selects the base station having the best reception quality and performs wireless communication. For example, assuming that the base stations (BS1 to BS3) shown in FIG. 23 are performing downlink wireless communication with the same transmission power, the mobile station UE1 connects to BS1 having the least propagation loss and performs communication. In this way, it is necessary to detect a plurality of base stations, select the base station having the best communication quality from among them, and perform a cell search in order to connect them. Further, in Non-Patent Document 1 described above, since the cell-specific code is multiplied by the data channel, it is necessary to obtain the cell-specific code information at the time of cell search.

(3-step cell search) As described above, a cell search method divided into 3 steps called a 3-step cell search method has been proposed. In the first step, SCH time correlation detection is used to detect symbol synchronization, frequency offset, and 1 / N frame timing. This 1 / N frame timing detection is a detection performed when N SCHs are multiplexed in the time direction. Details will be described later.

FIG. 24 is a diagram showing an example of the arrangement position of the synchronization channel (SCH) in the frame. As shown, the SCH is located at the last symbol of the 5th subframe (SF5) and the 10th subframe (SF10). As described above, in the first step, synchronization is performed at a cycle of 1/2 of the frame interval by detecting the temporal positions of the two SCHs in the frame. By constructing the SCH using a specific subcarrier described later, a characteristic waveform is formed in the time axis region. In the first step, this waveform characteristic is used for time synchronization.

In the second step, the data constituting the SCH is demodulated by correlation detection in the frequency domain, and cell-specific information (for example, cell ID or cell ID group, cell configuration, number of base station antennas, broadcast information notification bandwidth, etc.) is obtained. get.

In the third step, the cell ID is identified by the correlation between the cell ID multiplied by the corresponding base station-specific spread code and the replica signal of the pilot channel generated by the mobile station.

FIG. 25 is a diagram showing a configuration example of SCH. In FIG. 25, the vertical axis represents the frequency axis and the horizontal axis represents the time axis. In the figure, each small square is a subcarrier that constitutes the SCH, and constitutes a channel with a length of one symbol. In this way, the SCH is composed of a plurality of subcarriers, and the even-numbered subcarrier from the low frequency side and the center frequency subcarrier (DC subcarrier) are null subcarriers, and an odd number excluding the center frequency subcarrier. A signal for SCH is assigned to the second subcarrier. The null subcarrier is a subcarrier with zero power to which no signal is assigned.

Hereinafter, the subcarrier of the SCH to which the data is assigned is referred to as a "SCH subcarrier". With this configuration, the symbol to which the SCH is assigned becomes a waveform in which the same signal having a symbol length of 1/2 is repeated twice in the time domain. Time synchronization is performed by arranging one or more symbols of such a channel configuration at a predetermined position of the frame and detecting the repeating waveform with the receiver.

FIG. 26 is a block diagram showing a configuration of a receiver for detecting a repeating waveform of SCH and performing time synchronization. As shown, the receiver has a delay unit 91 that delays the received signal 90, a complex conjugate calculation unit 92, a multiplication unit 93, an average unit 94, and a peak detection unit 95. The synchronization timing signal 96 is output from the peak detection unit 95.

This receiver multiplies the received signal by the complex conjugate of the previously received signal with a 1/2 effective symbol delay. As a result, when it matches the SCH timing of the above-described configuration, the synchronization timing is detected by utilizing the fact that the correlation value becomes high. As shown in FIG. 24, in the case of a system in which the SCH is arranged at the positions where the frames are divided into N at the same time interval (N = 2 in FIG. 24), this multiplied signal is divided into 1 / N frame intervals. By averaging with and detecting the peak position, it is possible to perform accurate synchronization and symbol synchronization in 1 / N frames. However, the number N of SCHs in the frame and their respective positions are known to the mobile station.

FIG. 27 is a diagram showing an example of a SCH assigned to a subcarrier on the frequency axis. FIG. 27 shows a method of acquiring SCH information by calculating the phase difference P of adjacent SCH subcarriers. The information by the phase difference P between these SCH subcarriers shows the cell ID group, the information indicating the number of multiple SCHs in the frame, the cell configuration, and the number of base station antennas (second step). Create a pilot symbol replica signal corresponding to each cell ID included in the cell ID group detected as described above. Then, the cell ID can be detected by correlating with the pilot symbol arranged in the subframe.

FIG. 28 is a diagram showing an example of the configuration of the resource block in the OFDM communication method studied in 3GPP. Figure 28 shows a typical resource block when SCH is included. In the figure, in addition to SCH, pilot channels and data channels (including control information channels, etc.) are arranged. The pilot symbol is multiplied by a cell-specific diffusion code for randomizing interference and an orthogonal code for making the pilot symbols orthogonal between sectors within the same cell. The pilot channel located at the first symbol of the frame is used for channel estimation in each sector. However, near the sector boundary, at a position where transmission signals from different sectors of the same cell can be received, transmission signals from adjacent sectors in the same symbol act as interference signals, so that the channel estimation accuracy deteriorates. .. Therefore, in such an environment, the characteristic of the orthogonal code that is multiplied by the pilot symbol and has an orthogonal relationship between the sectors is used. That is, a propagation path estimation method that eliminates the interference signal from the adjacent sector is applied by multiplying the subcarrier of the pilot channel by the complex conjugate of the orthogonal code used in the desired sector and applying backdiffusion.

In the conventional cell search method, when detecting the cell ID by the replica signal, it is necessary to detect the cell ID and determine from which sector in the same cell the signal strength is strong. Therefore, it is necessary to detect the correlation with the replica signal included in the cell ID group (number of cell IDs x number of sector IDs). That is, in the first step and the second step, it was not possible to determine the received power of the transmission signal from each sector by using the SCHs simultaneously transmitted from the sectors in the same cell. Therefore, the amount of processing required for correlation detection in the three-stage cell search increases in proportion to the number of sectors included in the cell.

Further, in order to compare the correlation values corresponding to each replica signal, when a storage unit for storing the results corresponding to a plurality of replica signals is provided, it is included in the cell ID group (number of cell IDs x number of sector IDs). It is necessary to prepare a storage unit for the number of. Furthermore, since the same SCH data is transmitted from each sector of the same cell at the same time, in a mobile station near the sector boundary, depending on the condition of the signal propagation path from a plurality of sectors, fading is performed continuously in the frequency domain. Subcarriers with very small amplitudes are created, which may reduce the probability of cell ID identification.

Therefore, in the present invention, it is decided that the synchronization channel (SCH) has a sector and cell identification function. As a result, cell search that does not rely on correlation detection by the pilot channel is realized, and the above-mentioned inconvenience is overcome. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) In the first embodiment, the cell search method according to the present invention will be described. FIG. 1 is a flowchart showing an example of a main procedure of the multi-carrier transmission process according to the present invention. As shown, a base station of a multi-carrier mobile communication system adopting an OFDM communication method generates a synchronization channel (SCH) included in a downlink by multiplying three types of codes. That is, "common sector common code in the same cell", "sector-specific code (different orthogonal code for each sector in the same cell)", and "cell-specific code (for each cell for transmitting cell-specific information)" Multiply (different sign) (step S1). The sector common code may be a code common to a plurality of cells.

Next, the SCH and pilot channel are assigned to the subcarriers of the resource block by the allocation (mapping) in the time / frequency plane (step S2). Then, multiplication of the diffusion code and IFFT processing are performed (steps S3 and S4). Next, GI (Guard Interval: guard interval, CP: also called Cyclic Prefix) is inserted and D / A conversion processing is performed (steps S5 and S6). Finally, frequency conversion is performed and multicarriers are transmitted from the directional antennas of each sector (step S7).

FIG. 2 is a flowchart showing an example of a main procedure of the multi-carrier reception process according to the present invention. The mobile station receives the multicarrier signal from the base station and performs frequency conversion and A / D conversion (step S10). The mobile station includes a mobile phone terminal, a PDA terminal, and a portable personal computer.

Next, the SCH position is detected and SCH symbol synchronization is established by the autocorrelation method focusing on the cyclic waveforms of the SCHs arranged periodically (step S2). This step S2 corresponds to the first step (step a) of the cell search. Next, GI removal (step S12), series / parallel transform, and FFT (Fast Fourier Transform) are performed (step S13).

Hereinafter, the sector identification process and the cell identification process are performed at the same time (second step (step b) of the cell search). That is, the sector-specific code that gives the maximum received power is detected by despreading using the sector-specific code, and the optimum sector (the antenna of the base station to be communicated with) is identified (step S14). In parallel with this, demodulation of the cell-specific code (more, if necessary, correlation detection with the cell-specific code) is performed to acquire cell-specific information (cell ID, etc.) (step S15).

If the number of subcarriers is sufficient, the cell and sector identification is completed by this two-step cell search. However, when the number of subcarriers is insufficient, the cell ID cannot be directly identified in step S15, and only the cell ID group is identified. In this case, the cell ID is identified by correlation detection using the pilot channel (step S16). In this case, this is the cell search (step c) of the third step.

Next, the generation of sector-specific codes (codes orthogonal to each sector) will be described. Here, a case where the number of sectors is set to "3" and three codes orthogonal to each other are generated will be described.

FIG. 3 is a diagram showing the concept underlying the generation of the Walsh-Hadamard code. As shown, three vectors are set on the complex topological plane. The complex phase plane is an IQ plane, the I axis corresponds to the real axis, and the Q axis corresponds to the imaginary axis. On this complex phase plane, three vectors P1, P2, and P3 having an amplitude of "1" and forming an angle of 120 degrees with each other are set. When vector addition is performed on these three vectors, the imaginary axis components of the vectors P2 and P3 are canceled. Moreover, since the result (= -1) of adding the real number axis components of the vectors P2 and P3 and the vector P1 (= + 1) are canceled, the result of the vector addition is "0". Three orthogonal codes are generated using three vectors having such a relationship.

FIG. 4 is a diagram for explaining an array of code elements constituting three orthogonal codes (code 1, code 2, code 3) and a principle when demodulating only code 2. In the figure, the horizontal axis is the time axis and the vertical axis is the frequency axis. As shown in FIG. 4, (reference numeral 1) = (P1, P1, P1), (reference numeral 2) = (P1, P2, P3), and (reference numeral 3) = (P1, P3, P2). .. Each code is constructed by using any of the three vectors shown in FIG. 3 as a code element. Code 2 and code 3 use the same code elements, but differ in their arrangement on the frequency axis.

Here, for example, it is assumed that only the reference numeral 2 is demodulated. In this case, each of the sign elements P1, P2, and P3 of sign 2 is multiplied by their respective complex conjugates. As a result, the phase is rotated and the imaginary axis component disappears. Then, when each multiplication result is added, three real number axis components (= 1) are added, so that the correlation detection result is "3". The same complex conjugate is similarly multiplied and added to sign 1 and sign 2. As a result, the phase of each code element is rotated for each code, but in the end, the vectors of P1, P2, and P3 remain indefinitely. Therefore, when they are added, the addition result is "0" (see Fig. 3). In this way, only reference numeral 2 can be extracted. The same applies to the case where only the reference numeral 1 is taken out or the case where only the reference numeral 3 is taken out. In this way, reference numerals 1 to 3 in FIG. 4 are orthogonal to each other as a set of three code elements (3 chips).

In the present invention, the number of sectors is not limited to "3". The number of sectors may be 4 or more. Also in this case, if the above idea is used, the orthogonal code corresponding to the number of sectors can be easily generated. That is, the number of orthogonal vectors in FIG. 3 is increased, and those vectors are arranged on the frequency axis by using the method of FIG. This allows more codes to be generated. That is, the larger the number of sets of code elements arranged on the frequency axis, the more orthogonal codes can be generated. Therefore, even when the number of sectors increases, it can be flexibly dealt with.

Next, how to superimpose the cell-specific information on the SCH will be described. This cell-specific information includes cell ID, broadcast channel bandwidth, antenna arrangement, GI length, and the like.

FIG. 5 is a diagram for explaining a method of superimposing cell-specific information on the SCH. In FIG. 5, the horizontal axis is the time axis and the vertical axis is the frequency axis. In FIG. 5, reference numeral A is assigned to the subcarrier that serves as the phase reference. Then, adjacent to the subcarrier serving as the phase reference, a subcarrier to which a code (C1, C2, C3 ...) Indicates a phase difference from the subcarrier is assigned is arranged. A cell-specific code for transmitting cell-specific information is formed by the phase reference code "A" and the code indicating the phase difference (C1, C2, C3 ...). That is, the cell-specific information is transmitted not as the absolute phase of the subcarriers but as information indicating the relative phase difference of the pair of subcarriers. In FIG. 5, K1, K2, K3 ... Enclosed by a dotted line indicate a pair of subcarriers.

Next, the characteristics of the code format for simultaneously transmitting sector-specific information and cell-specific information using SCH will be described. As shown in FIG. 4, if each of the three sectors is to be distinguished, it is sufficient to have a code having a three-chip period orthogonal to each other. However, if cell-specific information is to be transmitted at the same time, the simple configuration code shown in FIG. 4 cannot handle it. In particular, when the relative phase difference information between the subcarriers as shown in FIG. 5 is used, it is difficult to transmit the cell-specific information with the code having the configuration shown in FIG.

That is, both sector-specific information and cell-specific information are transmitted by subcarrier phase modulation, but one piece of information must not adversely affect the other. At the same time, the receiving side must be able to demodulate both pieces of information at the same time in order to speed up the cell search. Therefore, as shown in FIG. 4, two sets of three orthogonal chips (three code elements) are used. They are arranged in combination on the frequency axis, and the 6 chips (6 code elements) are combined as a set (that is, the 6 chips are used as a constituent unit) to form a code.

6 (a) to 6 (d) are diagrams for explaining a code format for transmitting sector-specific information and cell-specific information superimposed on the SCH, respectively. In FIG. 6A, two sets of three orthogonal chips (three code elements) shown in FIG. 4 are used, and they are arranged in combination on the frequency axis. Then, an example of the arrangement of each chip when forming a code by using the 6 chips (6 code elements) as a set is shown. Here, the 6 chips are used as one constituent unit.

In FIG. 6 (a), the three chips (= P1, P2, P3) and the other three chips (= P1, P2, P3) are arranged so that the sign elements having the same value are adjacent to each other on the frequency axis. It shows how they are arranged in an alternating manner. As a result, 6-chip codes (= P1, P1, P2, P2, P3, P3) as shown in FIG. 6 (b) are generated. Three of these six-chip codes are used as sector-specific codes, and the remaining three chips are used to multiply cell-specific information.

That is, as shown in FIG. 6 (c), the odd-numbered 3 chips (= P1, P2, P3) are used for correlation detection (sector identification) by the method shown in FIG. On the other hand, the even-numbered 3 chips (= P1, P2, P3) are multiplied by symbols (C1 to C3) indicating relative phase difference information as cell-specific information. As shown in FIG. 5, the "relative phase difference information" is "phase difference information between subcarriers to which cell-specific codes of the same value are multiplied". In FIG. 6 (c), the subcarrier in which each of the odd-numbered three chips (= P1, P2, P3) is arranged is the subcarrier serving as the phase reference.

For example, two subcarriers to which sector-specific codes of the same value (P1, P1) are assigned are paired, P1 on the high frequency side is multiplied by C1 indicating the phase difference, and this C1 is cell-specific. It is a code for transmitting information. Similarly, pair two subcarriers to which the sector-specific code of the same value (P2, P2) is assigned, multiply P2 on the high frequency side by C2 indicating the phase difference, and multiply this C2 by the cell. It is a code for conveying unique information. In FIG. 6C, the reference numerals C1, C2, and C3 indicating the phase difference information are circled by dotted lines. Cn = (C0, C1, C2 ...) is the cell-specific code.

In the above description, for convenience, the "sector-specific code" is assigned to the subcarrier, and then the "cell-specific code" is further assigned, and so on. However, in reality, the allocation (multiplication) of the "cell-specific code" may take precedence over the allocation (multiplication) of the "sector-specific code". Whichever multiplication comes first, the result is the same. That is, as a result, the sector common code (s)₀), The cell-specific code, and the sector-specific code are triple-multiplied by SCH. Therefore, it does not matter which is faster, cell-specific code multiplication or sector-specific code multiplication. In addition, the above-mentioned "sector common code (s)₀) Is a code common to a plurality of sectors in the same cell, and may be simply referred to as a sector common code in the present specification.

In the case of the code configuration as shown in FIG. 6 (c), since the subcarriers to which the sector-specific codes of the same value are assigned are arranged adjacent to each other on the frequency axis, both subcarriers have equivalent propagation paths. There is a high probability that it will reach the receiving side via. Therefore, there is an advantage that the phase rotation due to the difference in the transfer function of the propagation path can be ignored. Therefore, the receiving side can accurately detect only the phase difference of the adjacent subcarriers due to the cell-specific code. As a result, the cell-specific information can be demodulated.

However, the configuration of the sector-specific code is not limited to the configuration as shown in FIG. 6 (b). For example, as shown in FIG. 6 (d), the sectors 3 chips (P1, P2, P3) may be arranged so as to simply overlap each other in two stages on the frequency axis. Regarding the transmission of cell-specific information, for example, two subcarriers to which sector-specific codes of the same value (P1, P1) are assigned are paired, and C1 indicating the phase difference is multiplied by P1 on the high frequency side. However, the point that this C1 is used as cell-specific information is the same as in the case of FIG. 6 (c).

Thus, in the present invention, the synchronization channel (SCH) is multiplied by a sector-specific code that is orthogonal to each sector. That is, the SCH that was non-orthogonal with respect to the sector is orthogonalized. Then, sector identification was made possible by receiving power measurement using SCH, and high-quality sector identification was made possible by good frequency characteristics even at sector boundaries. Furthermore, the cell ID can be identified by multiplying the SCH by the cell-specific code and transmitting it at the same time.

Therefore, a new two-step cell search method can be realized instead of the conventional three-step cell search method using SCH and CPICH together. As a result, the cell search processing process including sector identification can be shortened. Further, in order to achieve both sector identification and cell identification, it is necessary to devise a code configuration for multiplying SCH, but in the present invention, orthogonal codes having a plurality of chips as a unit are used as a pair. That is, one of the codes having the same value is further multiplied by a code indicating the relative phase difference, and the cell-specific information is transmitted by the relative phase difference. This makes the code simple and compact, and makes it possible to transmit identification information for both sectors and cells.

As a result, no special burden is generated in the multi-carrier transmitter / receiver. Further, in the multi-carrier receiving device, identification of the sector ID and demodulation of cell-specific information can be performed at the same time, and efficient cell search can be performed.

(Second Embodiment) In the present embodiment, a cell search method including SCH data structure and sector identification will be described by taking the case where the SCH is arranged at the rear end of the subframe as an example.

The cellular system is a mobile communication system composed of a plurality of cells, but in the cellular system used in the present embodiment, each cell uses the same frequency band and the OFDMA communication method is used as the communication method. It is a one-cell repetitive communication system. As shown in FIG. 23, this communication system divides a cell into three communication areas (sectors) and wirelessly communicates with mobile stations located in multiple sectors by one base station installed in the center of the cell. To do. Although the same frequency band is used in each sector, accurate propagation path estimation can be performed even near the sector boundary by multiplying the pilot channel by a sector-specific orthogonal code and using backdiffusion.

The downlink communication method is the same OFDM communication method as described above. The configuration of the communication frame and resource block is of the same format as shown in FIGS. 22 and 28, respectively. In addition, the SCH is arranged at the rear end of the time period when the frame is divided into Ss equal parts (Ss is a divisor of the number of subframes Sf (natural number)). As a result, the SCHs are periodically arranged on the time axis. In the embodiment shown in FIG. 24, Sf is 10 and Ss is 2.

As for the pilot channel, in the present embodiment, a method (CDM: Code Division Multiplex) of multiplexing the same symbol with the same subcarrier between sectors is used. However, the pilot channels between sectors are mutually different, such as the method of multiplexing to different subcarriers with the same symbol (FDM) or the method of multiplexing to the same subcarrier with different symbols (TDM: Time Division Multiplex). It can be applied to a method having an orthogonal relationship.

In the present embodiment, a signal obtained by multiplying the code sequence corresponding to the orthogonal code multiplied by the pilot channel is transmitted by CDM as a SCH transmitted from each sector. As a result, the mobile station can realize good frequency characteristics even at the sector boundary due to the diffusion effect of the code when determining the received power of the signal from the base station. At the same time, it becomes possible to determine the received power for each sector. The code sequence corresponding to the orthogonal code multiplied by the pilot channel does not necessarily have to be the same as the code sequence multiplied by the pilot channel.

First, in the mobile communication system of the present embodiment, the physical channel (hereinafter referred to as "SCH") for the mobile station to synchronize the time and frequency with respect to the transmission signal transmitted from the base station is concerned. A specific configuration will be described.

FIG. 7 is a diagram showing a subcarrier index (subcarrier number) on the frequency axis. As shown, the number of the subcarrier on the low frequency side (lowermost end) is 1, and the number of the subcarrier at the center frequency is "n + 1". In the following description, this subcarrier index will be used as appropriate.

8 (a) to 8 (c) are diagrams for explaining the data structure of the SCH transmitted simultaneously from three sectors in the same cell. FIG. 8A is a diagram showing the allocation of sector common codes on the frequency axis, and FIG. 8B is a diagram showing the configuration of three sector-specific codes. Then, FIG. 8 (c) is a diagram showing a concept underlying the generation of a sector-specific code, and shows a vector on a complex phase plane.

The frame of the signal transmitted from the base station is composed of a plurality of symbols. FIG. 8 is illustrated focusing on the SCH data of the plurality of symbols. In FIG. 8, the vertical axis is shown as the frequency axis and the horizontal axis is shown as the time axis. For each subcarrier, as in the case shown in FIG. 4, the even-numbered subcarriers (subcarrier indexes 2, 4, 6, ..., 2n) from the low frequency side and the center frequency subcarrier are set as null subcarriers. There is. Then, the odd-numbered subcarriers (subcarrier indexes 1, 3, 5, ..., 2n + 1) excluding the center frequency subcarrier are used as the subcarrier for data allocation.

The signal shown in FIG. 8A shows a common sector code. S for each SCH subcarrier₀Is assigned. s₀Is an arbitrary value represented by A * exp (jω). Here, A is the amplitude, j is the imaginary unit, and ω is the phase. However, in the present specification, the amplitude A will be described as 1. Sector common code s₀Is common to all sectors in each cell and can be used to randomize the signals between cells.

Next, the sector-specific code will be described. FIG. 8 (b) shows the case where the sector-specific code is used in three sectors. The reference numerals are unique to each sector in the same cell, and the reference numerals 1 to 3 correspond to the three sectors of the present embodiment. It is assumed that the mobile station and the base station know in advance the correspondence between these codes and the sector IDs in the same cell. As a sector-specific code, the code sequence to be multiplied by the SCH subcarriers is from the low frequency side to the odd SCH subcarriers (subcarrier indexes 1, 5, 9, ...) To the even SCH subcarriers (subcarrier indexes 3, 7). , 11, ...) Are 0 °, 0 °, and 0 ° in each sector. The phase difference from the even-numbered SCH subcarriers to the odd-numbered SCH subcarriers is 0 °, 120 °, and 240 ° in each sector.

Each sign is a sign with an amplitude of 1. Moreover, since these code sequences are repeated on 6 chips (1 cycle on 6 chips), the number n of SCH subcarriers is an integral multiple of 6. Looking at one repeating part (6 chips) of these three code sequences, multiply each code sequence by the complex conjugate of any code sequence and add 3 chips every other code sequence to select any code sequence. When multiplied by a code sequence other than, the sum becomes 0. Moreover, when it is multiplied by an arbitrary code sequence, the sum becomes 3.

For example, sign 1 (exp (j0π), exp (j0π), exp (j0π), exp (j0π), exp (j0π), exp (j0π)) and sign 2 (exp (j0π), exp (j0π)) , Exp (j2π / 3), exp (j2π / 3), exp (j4π / 3), exp (j4π / 3)) and code 3 (exp (j0π), exp (j0π), exp (j4π / 3)) , Exp (j4π / 3), exp (j2π / 3), exp (j2π / 3)). If you choose sign 2 as the sign, the complex conjugate of sign 2 is (exp (j0π), exp (j0π), exp (-j2π / 3), exp (-j2π / 3), exp (-j4π / 3). ), Exp (-j4π / 3)). The signs obtained by multiplying each of signs 1 to 3 by the complex conjugate of sign 2 are (exp (j0π), exp (j0π), exp (-j2π / 3), exp (-j2π / 3), exp (-), respectively. j4π / 3), exp (-j4π / 3)), (exp (j0π), exp (j0π), exp (j0π), exp (j0π), exp (j0π), exp (j0π)), (exp (j0π)) ), Exp (j0π), exp (j2π / 3), exp (j2π / 3), exp (-j2π / 3), exp (-j2π / 3)). Furthermore, when the odd and even numbers of each chip are vector-added, they become (0,0), (3,3), and (0,0), respectively, and the sum of the signs other than the sign 2 selected as an arbitrary sign is added. It is a code sequence with the characteristic of becoming 0. This means that if SCHs of the same data obtained by multiplying each sector by the orthogonal code (Fig. 8 (b)) corresponding to each sector are simultaneously transmitted from each sector in the same cell, the mobile station that received the SCH will use the SCH. It means that the signal from an arbitrary sector and the interference signal from an adjacent sector can be separated by back-spreading every three predetermined chips.

Next, a code sequence for transmitting cell-specific information will be described. FIG. 9 is a diagram showing a configuration of a code sequence for transmitting cell-specific information on the frequency axis. Since the code sequence shown in FIG. 9 is a code sequence for transmitting cell-specific information, a different code sequence is used between each cell. However, the same code sequence is used between sectors in the same cell. The cell-specific information includes information on the cell ID or the unique diffusion code used in the cell, information on the number of antennas of the base station, and information on the system bandwidth. The cell-specific information includes the information required when the mobile station first connects to the base station.

However, since the diffusion code information has a very large number of codes depending on the code lengths constituting the spread code information, the code shown in FIG. 9 may lack the amount of information for notification. In such a case, it is possible to group several cells (diffusion codes) and create a code series with the same information in the cells belonging to the group. In this case, since the cell-specific diffusion code cannot be completely identified from the information from the SCH, the final cell-specific diffusion code is identified by the pilot channel multiplied by the diffusion code.

The code sequence in FIG. 9 is composed of 6 chips as a set from the low frequency side. The 6th chip assigns the same code to the odd-numbered SCH subcarriers (subcarrier indexes 1, 5, 9). Further, the even-numbered SCH subcarriers (subcarrier indexes 3, 7, 11) are assigned a code obtained by multiplying the odd-numbered code by the cell-specific code. The code assigned to the odd-numbered subcarriers is the same within the 6 chips, but does not have to be the same as the code used by the other 6 chips. Each chip forming the code sequence has an amplitude of 1. Further, when the number of SCH subcarriers is n, a code sequence having a code length of n / 2 is required to form the even-numbered SCH subcarriers. Since the code length depends on the number of SCH subcarriers, when the number of SCH subcarriers is sufficiently long, it is generally possible to generate a large number of code sequences having better correlation characteristics. Therefore, it is possible to configure the code sequence including the information directly indicating the cell ID instead of the code sequence indicating the cell ID group as described above.

The three types of code sequences shown above are the code sequences constituting the SCH, and the SCH is transmitted from the transmitter of each sector by multiplying these code sequences. Next, the configuration of the base station will be described.

FIG. 10 is a block diagram showing a configuration example of a physical layer and a MAC (Media Access Control) sublayer in a base station (multicarrier transmitter) of a mobile communication system. As shown, the base station maps the logical channel and the physical channel, performs scheduling processing, and controls the physical layer section, and outputs the data input from the upper layer to the physical layer section, while inputting from the physical layer section. The MAC unit 10 that outputs the output data to the upper layer, the MAC unit 10 converts the transmission data input from this MAC unit 10 into a wireless transmission signal, and the conversion of the wireless reception signal received by the antenna unit into transmission data. It is provided with physical layer units 20a to 20c, which are performed based on the control information from.

The MAC unit 10 receives data from the transmission circuit control unit 16 that controls the transmission circuit unit based on the allocation information of each resource block of the frame notified from the upper layer, and the data of the data channel and the pilot channel of each resource block. It includes a transmission data output unit 14 that inputs to the transmission circuit unit according to a scheduled timing, and a SCH data generation unit 12 that generates or stores cell-specific information for allocating to the SCH.

In the present embodiment, the SCH is a channel for the mobile station to synchronize with the frames and symbols transmitted from the base station in time and acquire cell-specific information. Therefore, if the SCH data is not variable, it is not always necessary to generate data from the MAC unit 10 for each transmission, and it is stored inside the MAC unit 10 or in each physical layer unit (20a to 20c) corresponding to the sector. It can be transmitted periodically by assigning it to the symbol according to the SCH transmission timing. In the present embodiment, the SCH data generation unit 12 in the MAC unit 10 generates SCH data, but it is also possible to provide this function to the physical layer units (20a to 20c) of each sector.

The SCH data is input from the MAC unit 10 to the physical layer unit (20a to 20c) together with the data of other data channels. The SCH data and data of the data channel are input to the physical layer section (20a to 20c) together with the allocation control information of each resource block notified from the transmission circuit control section 16 of the MAC section 10, and are input to each resource according to the allocation information of the resource block. Data is assigned.

The physical layer section (20a to 20c) modulates the data channel, pilot channel, and SCH input from the MAC section 10 and multiplies the sector-specific code, multiplexes them in the resource block, and then performs the analog circuit section (26a to 20c). The transmission circuit section (24a to 24c) to be input to 26c), the reception circuit section (22a to 22c) to demodulate the output from the analog circuit section (26a to 26c) and input it to the MAC section 10, and the transmission circuit section (24a). An analog circuit unit (22a to 22c) that converts the transmission signal input from ~ 24c) into a radio frequency and converts the reception signal received from the antenna unit (28a to 28c) into a frequency band that can be processed by the reception circuit unit (22a to 22c). 26a to 26c) and the antenna unit 28 (directional antenna 28a to 28c corresponding to each sector) that transmits the transmission signal input from the analog circuit unit (26a to 26c) to the wireless space and receives the signal in the wireless space. ) And.

Next, a specific internal configuration of the transmission circuit unit (24a to 24c) will be described. FIG. 11 is a block diagram showing a specific configuration of the transmission circuit unit shown in FIG. The transmission circuit unit 24 (reference numerals 24a to 24c in FIG. 10) encodes and modulates the data channel and pilot channel input from the MAC unit 10, and after modulating the SCH data described above, assigns a sector-specific code. It is multiplied, and the data channel, pilot channel, and allocation unit multiplex and transmit to the resource block based on the control signal from the MAC unit.

The SCH data in FIG. 11 refers to code data obtained by multiplying a sector common code (see FIG. 8 (a)) by a cell-specific code (see FIG. 9). Then, the code data multiplied by the sector-specific code (see FIG. 8B) at the physical layer of each sector is transmitted.

The transmission circuit unit 24 (24a to 24c) shown in FIG. 11 is the same as the signal processing unit 50 (50a to 50c) that performs signal processing of transmission data for each resource block for the data channel input from the MAC unit 10. It includes a SCH data processing unit 60 that modulates the SCH data input from the MAC unit 10 and multiplies the sector-specific code. In addition, the pilot channel data processing unit 70, which also modulates the pilot channel data input from the MAC unit 10 and multiplies the sector-specific orthogonal code, and the output signal and SCH data processing from the signal processing unit 50 (50a to 50c). It includes an allocation unit 81 that allocates the output signal from the unit 60 and the output signal from the pilot channel data processing unit 70 to each subcarrier of the resource block.

In addition, the diffusion code multiplication unit 82 that multiplies the diffusion code using the diffusion code generated by the diffusion code generation unit 83 and IFFT (Inverse Fast) that converts the data signal sequence in the frequency region that has undergone the diffusion process into a time waveform. Fourier Transform) 84, P / S transform 85 that converts the output of IFFT 84 in parallel and series, GI insert 86 that inserts GI into the output of P / S transform 85, and GI insert 86 It is equipped with a D / A converter 87 that converts the output signal of the above from a digital signal to an analog signal. Both the allocation unit 81 and the diffusion code multiplication unit 82 perform processing based on the control information from the MAC unit 10. The allocation unit 81 allocates each physical channel to a desired subcarrier. The spread code multiplication unit 82 multiplies the physical channels excluding SCH by the spread code.

The signal processing unit 50 (50a to 50c) includes an error correction coding unit 51 that performs error correction coding of transmitted data, an S / P conversion unit 52 that performs parallel series conversion of the error correction coding unit output, and an S / P. It is composed of a modulation unit 53 that performs modulation processing such as BPSK, QPSK, and 16QAM on the output of the conversion unit.

Further, the SCH data processing unit 60 includes a SCH modulation unit 61 that performs modulation processing on the SCH data input from the MAC unit 10, a multiplication unit 62 that multiplies the output of the SCH modulation unit by a sector-specific code, and a sector-specific code. It is composed of a sector-specific code generation unit 63 that generates (or stores) the above.

Further, the pilot channel processing unit 70 includes a pilot data modulation unit 71 that performs modulation processing on the pilot data input from the MAC unit 10, a multiplication unit 72 that multiplies the output of the pilot data modulation unit 71 by a sector-specific code, and the like. It is composed of a code generation unit 73 that generates (or stores) a sector-specific code.

The output of the signal processing unit 50 (50a to 50c) is appropriately assigned to the appropriate subcarrier based on the control information notified from the transmission circuit control unit (reference numeral 16 in FIG. 10) of the MAC unit 10. After being assigned to a subcarrier, it is output to IFFT section 84.

However, when the code 1 shown in FIG. 8 (b) is used as the sector-specific code, the multiplication part (62, 72) and the code generation part (63, 73) are omitted because all the codes are 1. It is possible to do. Further, as described above, when the SCH data is set to a fixed value, it is not always necessary to output the SCH data from the MAC unit 10 for each SCH transmission. Therefore, instead of the SCH data processing unit 60, a SCH data storage unit or the like may be provided to store the SCH data. As a result, each time a SCH is transmitted, SCH data can be read from the SCH storage unit and multiplexed with the data channel and the pilot channel by the allocation unit 81.

The output of the D / A conversion unit 87 passes through an analog circuit unit (reference numerals 26a to 26c in FIG. 10) that performs frequency conversion to a radio frequency, and then from an antenna unit 28 (directional antennas 28a to 28c in FIG. 10) to the atmosphere. Is transmitted as a radio signal inside.

As described above, in the transmitter of the base station that controls a plurality of sectors, the sector-specific code is multiplied by the SCH data and the same SCH data is multiplied, and the SCH data is simultaneously transmitted from the antenna corresponding to each sector. This enables SCH reception with high quality frequency characteristics. At the same time, the optimum cell can be selected at the time of SCH reception, and the sector with good reception can be selected.

Next, the configuration of the multi-carrier receiver will be described. FIG. 12 is a block diagram showing a configuration of a multi-carrier receiver according to the present invention. This multi-carrier receiver corresponds to a mobile phone terminal, a PDA terminal, a portable personal computer, and the like. As shown, the multi-carrier receiver includes an antenna unit 100, an analog receiver circuit unit 101, an A / D converter 102, a timing detection unit 103, a GI removal unit 104, and an S / P (series / series /). (Parallel) Conversion unit 105, FFT unit 106, spread code multiplication unit 107, subcarrier compensation unit 108, demodulation unit 109, error correction decoding unit 110, diffusion code generation unit 111, and SCH signal processing unit. It has 200 and. The SCH signal processing unit 200 includes a despreading unit 210 for sector identification, a sector power determination unit 220, and a SCH data demodulation unit 230 for demodulating cell-specific information.

This multi-carrier receiver (hereinafter, may be simply referred to as receiver) basically performs a cell search including sector identification according to the flowchart shown in FIG. First, the receiver detects the SCH timing from the received signal in order to correct the time synchronization and frequency deviation with the signal transmitted from the base station. That is, the radio signal transmitted from the base station is received by the antenna unit 100, and the received radio signal is converted from the radio frequency band to the baseband frequency band by the analog receiving circuit unit 101. Then, the A / D (analog / digital) conversion unit 102 converts the analog signal converted into the baseband frequency band into a digital signal.

Next, the timing detection unit 103 performs SCH detection processing from the received data converted into digital data by the A / D conversion unit 102 in order to perform symbol synchronization. Here, the circuit configuration of the timing detection unit 103 will be described.

FIG. 13 is a block diagram showing a configuration example of the timing detection unit 103. The timing detection unit 103 has a function of timing detection and frequency error detection. As shown in FIG. 13, the timing detection unit 103 includes a delay unit 301, a complex conjugate calculation unit 302, a multiplier 303, an average unit 304, a peak detection unit 305, and an arc tangent as a frequency error detection unit. It includes a calculation circuit 307.

As is clear from this configuration, the timing detection unit 103 repeats the same waveform of 1/2 effective symbols by multiplying the received signal by the complex conjugate of the signal delayed by 1/2 effective symbols and the received data. It is a circuit in which peaks are sometimes detected. That is, the peak is detected when the timing of the SCH data using the odd-numbered subcarriers (subcarrier indexes 1, 3, 5, ..., 2n + 1) from the low frequency side described above is reached. Multiple peaks are detected by signals from multiple cells, but in general, the timing with the highest absolute value of the correlation value or the peak of the real part is determined as the timing of the SCH transmitted from the nearest cell, and the base is used. Start the connection operation with the station.

In the case of the frame configuration shown in FIG. 24, synchronization can be performed at half the time interval of the frame, which is the interval at which the SCHs are arranged. Symbol synchronization is performed by synchronizing with the SCH symbol at the same time. In addition, by fixing the position of the SCH symbol in the subframe, synchronization in the subframe cycle can be performed at the same time.

In FIG. 12, after the timing detection unit 103 finishes the synchronization in the symbol period, the GI removal unit 104 removes the GI unit attached in front of the effective symbol from each symbol in accordance with the symbol period described above. The symbol from which the GI has been removed is converted from a series signal to a parallel signal by the S / P (series / parallel) conversion unit 105, and FFT processing is performed by the FFT unit 106.

The data in the SCH symbol section is input from the FFT section 106 to the SCH signal processing section 200 that processes the SCH data. Further, the data channel including the pilot channel and the control information to the mobile station is input from the FFT unit 106 to the diffusion code multiplication unit 107. When the mobile station makes the first connection to the base station, since the cell-specific information and the sector-specific information have not been acquired, the processing in the SCH signal processing unit 200 is prioritized. In the SCH signal processing unit 200, SCH symbol data is simultaneously input from the FFT unit 106 to each of the three multiplication units 212 corresponding to the number of sectors of the present embodiment and the SCH data demodulation unit 230.

In the multiplication unit 212, the sector-specific code (FIG. 8 (b)) generated or stored in the sector-specific code generation unit 211 is multiplied by the control information from the MAC unit (not shown). In each multiplication unit 212, the complex conjugate of the sector-specific code input from the sector-specific code generation unit 211 is calculated, and the odd-th SCH subcarrier (subcarrier indexes 1, 5, and) of the SCH symbol input from the FFT unit 106 is calculated. 9, ...) Is multiplied by the complex conjugate code so as to correspond to the subcarrier multiplied by the sector-specific code at the time of transmission from the base station. Further, the multiplied data of the complex conjugate is input to the addition unit 214, and the in-phase addition is performed. That is, the data of 3 subcarriers multiplied by the complex conjugate of the 6 subcarriers, which is the repetition period of the sector-specific code, is added. The state of this process is shown in Process 1 and Process 2 of FIG.

FIG. 14 is a diagram showing a specific content of the back diffusion process for sector identification. In FIG. 14, px is a sector-specific code shown in FIG. 8 (b), and x represents a sector index. Further, f indicates a propagation path, and is constant within the band of 9 subcarriers, which is the subcarrier interval for performing backdiffusion.

Further, in FIG. 12, the data subjected to the reverse diffusion processing is multiplied by 1/3, and the squared average data is input to the sector power determination unit 220. The root mean square data from each sector serves as an index for determining the received power in the sector power determination unit 220.

The sector power determination unit 220 compares the data indicating the addition result input from the addition unit 214 corresponding to each of the three sectors. Then, the sector having the highest reception power, that is, the sector having the best reception environment and making a connection is determined. The sector detection result is notified to the MAC unit by a control signal.

On the other hand, in FIG. 12, the SCH symbol data (data obtained by multiplying the sector common code by the cell-specific information) input from the FFT unit 106 to the SCH data demodulation unit 230 is demodulated by the demodulation method shown in FIG.

FIG. 15 is a diagram for explaining the demodulation process of the cell-specific information. In the process of FIG. 15, the complex conjugate of the cell-specific code assigned to the subcarrier on the low frequency side of the pair of subcarriers is multiplied by the subcarrier on the high frequency side, whereby the relative phase difference is obtained. This is the process of demodulating information (that is, cell-specific information).

In the SCH data demodulator 230 in FIG. 12, the complex conjugate of the data of the odd-numbered SCH subcarriers (subcarrier indexes 1, 5, 9, ...) From the low frequency side of the SCH symbol and the even number on the high frequency side thereof. Multiplies the data of the SCH subcarriers (subcarrier indexes 3, 7, 11, ...).

As shown in FIG. 15, the ideal value of the multiplication result is composed of the propagation path f between each sector and the mobile station and the cell-specific code c. Since c is a complex number with an amplitude of 1, it can be easily obtained by deriving the phase. Here, x of fxy indicates a sector ID (corresponding to a sector identification number and also referred to as a sector index), and y is an index in the frequency direction in the propagation path of the two subcarriers to be multiplied. We also assume that the propagation paths between the two subcarriers to be multiplied are the same.

When demodulating cell-specific information, the SCH data demodulation unit 230 creates a replica of the candidate code (Cn) that may be used for notification of cell-specific information at the base station from the code sequence of cell-specific information. .. Then, the cell-specific information can be determined and acquired by actually taking a cross-correlation with the result calculated by the above method. Actually, it is desirable to make a judgment by cross-correlation processing in this way.

In the present embodiment, two SCH symbols are set in the frame, and at the time of symbol synchronization due to delay correlation, the synchronization is performed at a cycle of 1/2 of the frame. In order to perform synchronization in a frame period, the information indicated by the cell-specific code c described above includes information indicating either SCH in the frame. Alternatively, information may be assigned to a symbol whose temporal position from the SCH is constant.

Further, as described above, since the diffusion code information has a very large number of codes depending on the code length constituting the spread code information, the amount of information for notifying the cell-specific information may be insufficient. That is, depending on the number of subcarriers used for SCH, there is not enough information to notify the cell-specific information, so the group is divided into several groups instead of the information indicating the cell-specific diffusion code. It is also possible that the information indicating the above is notified. In that case, the following detections need to be made for all possible spread codes of the grouped cells.

That is, the pilot channel is used to detect the spread code of the cell, and a replica signal is created by multiplying the pilot channel by the code multiplied by the pilot channel (cell-specific code and orthogonal code). The cross-correlation between the created replica signal and the actual received signal is detected for the diffusion code candidates for all the cells in the cell group described above. After all correlation detection is completed, the spreading code candidate showing the highest correlation value is determined as the spreading code used by the nearest base station. This is a common method. However, in the present embodiment, the cross-correlation detection process can be shortened by using only the orthogonal code of the sector determined by the sector determination described above.

It is more desirable that the code sequence of the cell-specific code c is a code having excellent cross-correlation characteristics with a code indicating information of other cells. Specifically, a Walsh-Hadamard code sequence or a Generalized Chirp Like (GCL) code sequence is desirable.

The SCH data demodulated as described above is sent to the MAC section. The MAC unit can receive information according to this information and connect to the base station. Generally, the following configuration is required to receive a data channel transmitted from a base station. It is also possible to use a receiving circuit other than this.

In FIG. 12, the data channel and the pilot channel subjected to the FFT process by the FFT unit 106 are spread by the cell-specific spreading code included in the cell-specific information. Therefore, the spread code multiplication unit 107 multiplies the complex conjugate of the cell-specific spread code. The cell-specific diffusion code is output from the diffusion code generation unit 111. In the diffusion code generation unit 111, the diffusion code of a desired cell is selected from a plurality of diffusion codes by a control signal from the upper layer.

At the same time, the sector-specific orthogonal code is also selected by the diffusion code generation unit 111 and input to the diffusion code multiplication unit 107. The input orthogonal code is multiplied by the pilot channel by the diffusion code multiplication unit 107. The code-multiplied data is input to the demodulation unit 109 after subcarrier compensation is applied by the subcarrier compensation unit 108 using the pilot channel as a reference signal. The demodulation unit 109 demodulates the data channel, and the error correction / decoding unit 110 performs error correction / decoding.

(Third Embodiment) Next, the third embodiment of the present invention will be described. In the second embodiment described above, a SCH is inserted for each frame (Fig. 24), and a null subcarrier is set every other subcarrier accordingly (Fig. 25).

In the present embodiment, as shown in FIG. 16, the subcarriers excluding the subcarrier (DC subcarrier) in the center of the band are defined as SCH subcarriers. Further, as shown in FIG. 19, the arrangement of the SCH symbols in the frame is such that the same SCH symbols are arranged two consecutively at a specific temporal position in the frame. FIG. 19 is a diagram showing a frame configuration according to the third embodiment.

That is, in this embodiment, since the number of SCH subcarriers is doubled as compared with the second embodiment described above, the code length that can be used for cell-specific information becomes longer. Therefore, it is possible to transmit and receive a SCH signal having a larger amount of information.

FIG. 16 is a diagram showing subcarriers to which SCH is assigned. In this embodiment, the SCH is configured as shown in FIG. 16 on the frequency axis. That is, FIG. 16 is illustrated by paying attention to the SCH data of a plurality of symbols constituting the frame of the signal transmitted from the base station, and the vertical axis is shown as the frequency axis and the horizontal axis is shown as the time axis. As shown in FIG. 16, each subcarrier is used as a subcarrier that allocates SCH data to subcarriers other than the central subcarrier (DC subcarrier).

Hereinafter, the following description will be described assuming that the number of subcarriers (SCH subcarriers) constituting the SCH is 2n. 17 (a) and 17 (b) are diagrams showing the data structure of SCH in the third embodiment. FIG. 17 (a) is a diagram showing the arrangement of sector common codes to be multiplied by SCH on the frequency axis, and FIG. 17 (b) is a diagram showing three sector-specific codes.

FIG. 17 (a) shows a common sector code. For each SCH subcarrier (subcarrier indexes 1, 2, 3, ...) s₀Is assigned. s₀Is an arbitrary value represented by A * exp (jω). Here, A is the amplitude, j is the imaginary unit, and ω is the phase. Sector common code s₀Is common to all sectors in each cell (three sectors in this embodiment). Similar to the second embodiment described above, the s known to the mobile station₀Can be used to decode the cell-specific code multiplied by SCH by using.

FIG. 17B shows an example in which the sector-specific code is used in the three sectors according to the third embodiment. The reference numerals are unique to each sector in the same cell, and the reference numerals 1 to 3 correspond to the three sectors according to the second embodiment. It is assumed that the mobile station and the base station know in advance the correspondence between these codes and the sector IDs in the same cell. As a sector-specific code, the code sequence to be multiplied by the SCH subcarrier is the odd-numbered SCH subcarrier (subcarrier indexes 1, 3, 5, ...) From the low frequency side to the even-numbered SCH subcarrier (subcarrier). The phase difference to indexes 2, 4, 6, ...) Is 0 °, 0 °, 0 ° in each sector, and the phase difference from the even-numbered SCH subcarrier to the odd-numbered SCH subcarrier is. It is 0 °, 120 °, and 240 ° in each sector. Each sign is a sign with an amplitude of 1. Moreover, since these code sequences are repeated on 6 chips (1 cycle on 6 chips), the number 2n of SCH subcarriers is an integral multiple of 6.

Looking at one repeating part (6 chips) of these sector-specific codes, multiply each code sequence by the complex conjugate of any code sequence and add 3 chips every other sign, except for the selected code sequence. When multiplied by a code sequence, the sum is 0, and when multiplied by an arbitrary code sequence, the sum is 3.

For example, sign 1 (exp (j0π), exp (j0π), exp (j0π), exp (j0π), exp (j0π), exp (j0π)) and sign 2 (exp (j0π), exp (j0π)) , Exp (j2π / 3), exp (j2π / 3), exp (j4π / 3), exp (j4π / 3)) and sign 3 (exp (j0π), exp (j0π), exp (j4π / 3)) , Exp (j4π / 3), exp (j2π / 3), exp (j2π / 3)), if sign 2 is selected as an arbitrary sign, the complex conjugate of sign 2 is (exp (j0π), It becomes exp (j0π), exp (-j2π / 3), exp (-j2π / 3), exp (-j4π / 3), exp (-j4π / 3)). The signs multiplied by the complex conjugate of are (exp (j0π), exp (j0π), exp (-j2π / 3), exp (-j2π / 3), exp (-j4π / 3), exp (-j4π / 3), respectively. )), (Exp (j0π), exp (j0π), exp (j0π), exp (j0π), exp (j0π), exp (j0π)), (exp (j0π), exp (j0π), exp (j2π /) 3), exp (j2π / 3), exp (-j2π / 3), exp (-j2π / 3)).

Furthermore, when the odd-numbered and even-numbered chips of each chip are vector-added, they become (0,0), (3,3), and (0,0), respectively, and the sum of the codes other than the code 2 selected as an arbitrary code is added. It is a code sequence with the characteristic of becoming 0. This means that if SCHs of the same data obtained by multiplying each sector by the orthogonal code (Fig. 17 (b)) corresponding to each sector are simultaneously transmitted from each sector in the same cell, the mobile station that received the SCH will use the SCH. By back-spreading every three predetermined chips, it means that the signal from an arbitrary sector and the interference signal from an adjacent sector can be separated.

FIG. 18 is a diagram showing the arrangement of cell-specific codes in the third embodiment. Since the code sequence shown in FIG. 18 is a code sequence for transmitting cell-specific information, different code sequences are used in each cell, but the same code sequence is used between sectors in the same cell. Cell-specific information includes information on the unique diffusion code used in the cell, the number of antennas of the base station, and system bandwidth, and the information required when the mobile station first connects to the base station. include.

However, since the diffusion code information can have a very large number of codes depending on its code length, the amount of information may be insufficient with the code shown in FIG. In such a case, it is possible to group some cells and create a code sequence with the same information in the cells belonging to the group. In this case, since the cell-specific diffusion code cannot be completely identified from the information from the SCH, the final cell-specific diffusion code is identified by the pilot channel multiplied by the diffusion code.

The code sequence shown in FIG. 18 is composed of 6 chips as a set from the low frequency side. Of the 6 chips, the odd-numbered SCH subcarriers are assigned the same code, and the even-numbered SCH subcarriers are assigned a code obtained by multiplying the odd-numbered code by the cell-specific code. The code assigned to the odd-numbered subcarriers is the same within the 6 chips, but does not have to be the same as the code used by the other 6 chips. Each chip forming the code sequence has an amplitude of 1. Further, when the number of SCH subcarriers is 2n, the code length is required to form an even-numbered subcarrier with a code sequence having a code length of n.

Since the code length depends on the number of SCH subcarriers, when the number of SCH subcarriers is sufficiently long, it is generally possible to generate a large number of code sequences having better correlation characteristics. Therefore, as described above, it is possible to configure the code sequence including the information directly indicating the cell ID instead of the code sequence indicating the cell ID group.

The code to be multiplied by the subcarriers constituting the above SCH is assigned the same code by two consecutive symbols. The above three types of code sequences are the code sequences constituting the SCH in the third embodiment, and the SCH is transmitted from the transmitter of each sector by multiplying these code sequences.

Since the SCH transmission method and the transmitter configuration in this embodiment are the same as those in the second embodiment described above, the description thereof will be omitted. The difference from the second embodiment is the code generated by the sector-specific code generation unit 63 in the SCH data processing unit 60 (see FIGS. 17 and 18) and the SCH data input from the MAC unit 10. Further, in the present embodiment, the same SCH symbol is transmitted two consecutive symbols (see FIG. 19). FIG. 19 is a diagram showing the arrangement of SCHs in the frame section. The receiver configuration and receiving method in this embodiment are basically the same as those in the above-described embodiment. However, in the timing detection unit 103 (FIG. 13) in the second embodiment, the position of the SCH symbol is detected by delaying the received signal by 1/2 effective symbol section and multiplying the signal, but in the present embodiment, the position of the SCH symbol is detected. The SCH symbol is detected by delaying the received symbol by one symbol and multiplying it by the signal.

The cell search procedure will be described below. The mobile station receives the radio signal transmitted from the base station by the antenna unit 100 as in the second embodiment. The analog receiving circuit unit 101 converts the received radio signal from the radio frequency band to the baseband frequency band. The A / D (analog / digital) conversion unit 102 converts the signal converted into the baseband frequency band from an analog signal to a digital signal.

Next, the timing detection unit 103 performs SCH detection processing for performing symbol synchronization based on the received data converted into digital data by the A / D conversion unit 102. Then, by multiplying the received signal by the complex conjugate of the signal delayed by one symbol and the received data, the peak is detected when the waveform of the same symbol is repeated. That is, the peak is detected when the same SCH symbol of the two symbols described above is received. Multiple peaks are detected by signals from multiple cells, but in general, the timing with the highest correlation value peak is determined as the timing of the SCH transmitted from the nearest cell, and the connection operation with the base station is performed. Start.

In the present embodiment, since the SCH of two symbols is arranged at the end of the frame, frame synchronization can be performed by detecting the correlation peak of the SCH signal by the above-mentioned method. Symbol synchronization is performed by synchronizing with the SCH symbol at the same time. Then, after the synchronization in the symbol cycle is completed, the GI section attached in front of the effective symbol is removed from each symbol by the GI removing section 104 in accordance with the symbol cycle described above. The symbol from which the GI has been removed is converted from a series signal to a parallel signal by the S / P (series / parallel) conversion unit 105, and FFT processing is performed by the FFT unit 106.

The data of the SCH symbol section is input from the FFT section 106 to the SCH signal processing section 200 that processes the SCH data. Further, the FFT unit 106 inputs the data channel including the control information to the pilot channel and the mobile station to the diffusion code multiplication unit 107. When the mobile station makes the first connection to the base station, the cell-specific information and the sector-specific information are not acquired, so that the processing by the SCH signal processing unit 200 is prioritized. In the SCH signal processing unit 200, SCH symbol data is input from the FFT unit 106 to each of the three multiplication units 212 corresponding to the number of sectors of the present embodiment and the SCH data demodulation unit 230. The sector-specific code generated or stored in the sector-specific code generation unit 211 is input to the multiplication unit 212 according to the control information from the MAC unit (not shown).

Each multiplication unit 212 calculates the complex conjugate of the sector-specific code input from the sector-specific code generation unit 211, and each odd-th subcarrier (subcarrier indexes 1, 3, and) of the SCH signal input from the FFT unit 106. 5, ...) Is multiplied by the complex conjugate code so as to correspond to the subcarrier multiplied by the sector-specific code at the time of transmission from the base station. This is shown in Process 1 of FIG. FIG. 20 is a diagram showing a specific content example of the correlation calculation process using the sector-specific code. The multiplied data of the complex conjugate is input to the despreading unit 210 and subjected to the despreading process. The despreading process is performed by adding the data of 3 subcarriers multiplied by the complex conjugate of the 6 subcarriers, which is the repetition period of the sector-specific code (see process 2 in Fig. 20).

Further, the data subjected to the reverse diffusion processing is halved, the root mean square data is calculated, and the data is input to the sector power determination unit 220. The root mean square data from each sector serves as an index for determining the received power in the sector power determination unit 220. In FIG. 20, px is the sector-specific code shown in FIG. 17 (b), and x represents the sector index. In addition, f indicates a propagation path, which is constant within the band of 5 subcarriers, which is the subcarrier interval for backdiffusion.

The sector power determination unit 220 determines the sector with the highest reception power, that is, the sector with the best reception environment and connection, by obtaining the above values from the despreading units 210 corresponding to the three sectors and comparing them. To do. This decision is notified to the MAC unit as a control signal.

On the other hand, the SCH symbol data input from the FFT unit 106 to the SCH data demodulation unit 230 is demodulated by the demodulation method shown in FIG. FIG. 21 is a diagram showing a method of demodulating the cell-specific code in the third embodiment. In the SCH data demodulator 230, the complex conjugate of the data of the odd-numbered SCH subcarriers (subcarrier indexes 1, 3, 5, ...) From the low frequency side of the SCH symbol and the even-numbered SCH on the high frequency side thereof. Multiply the data of subcarriers (subcarrier indexes 2, 4, 6, ...).

As shown in FIG. 21, the ideal value of the multiplication result is composed of the propagation path f between each sector and the mobile station and the cell-specific sign c, and c is a complex number having an amplitude of 1, so that the phase is derived. Is more easily sought. Here, x in fxy indicates the sector ID, and y is an index in the frequency direction of the propagation paths of the two subcarriers to be multiplied. We also assume that the propagation paths between the two subcarriers to be multiplied are the same.

When demodulating cell-specific information, the SCH data demodulation unit creates a candidate replica that may be used for notification of cell-specific information at the base station from the code sequence of cell-specific information shown below, and actually described above. The cell-specific information can also be determined and acquired by taking a cross-correlation with the result calculated by the above method. Further, in the third embodiment, since the same SCH symbol is transmitted continuously for two symbols, more reliable demodulation can be performed by performing the above-mentioned demodulation continuously in the two symbol section. it can.

The SCH data demodulated as described above is sent to the MAC section. The MAC unit can receive information according to this information and connect to the base station. In this third embodiment, the SCH is placed on the last two symbols of one frame period. As a result, the SCHs are arranged periodically on the time axis, and when the same SCH symbol is transmitted two consecutive symbols, the amount of information increases, so that the receiving side is more reliable. High demodulation can be performed. In addition, since SCH can be transmitted using subcarriers of all frequency bands, the code length that can be used for transmission of cell-specific information (relative phase difference information) when transmitting different information for each symbol. Can be lengthened, and more cell-specific information can be transmitted.

(Fourth Embodiment) Next, the fourth embodiment of the present invention will be described. In the present embodiment, an example in which the SCH timing detection in the first step of the cell search is performed by the cross-correlation method using the time waveform of the replica of the sector-specific code will be described.

In the second and third embodiments described above, symbol synchronization, frequency offset, and 1 / N frame timing are detected by using SCH time correlation detection in the first step of the three-step cell search described above. Was there. In the present embodiment, the SCH timing detection in the first step of the above-mentioned three-step cell search is performed by cross-correlation processing between the received signal and the replica signal created by the mobile station. In order to make this possible, it is necessary to devise the data structure of SCH.

The SCH position detection method of the first step shown in the present embodiment can be realized by using the frame configuration and the SCH arrangement shown in the second or third embodiment as they are. The second step or the third step can also be carried out in the same manner as in the above-described embodiment.

Even when the SCH data structure as in the present embodiment is adopted, the point that the SCHs are periodically arranged in one frame period is the same as in the above-described embodiment. Therefore, it is also possible to carry out SCH position detection using the same autocorrelation method as in the second and third embodiments (that is, establishment of symbol synchronization by autocorrelation using a repeating waveform). However, in the detection of the SCH position using the cross-correlation, a sharper correlation peak can be obtained, so that the SCH position can be detected with higher accuracy.

The SCH timing detection method of the first step in the present embodiment is a detection method to which a detection method called a cross-correlation detection (or replica detection) method is applied. As described above, the detection peak can be detected sharply as compared with the autocorrelation detection method using the continuous SCH waveforms shown in the second and third embodiments. That is, this embodiment can use a different method for the first step of the three-step cell search as compared with the second and third embodiments described above. Therefore, more accurate SCH timing detection is possible.

In the present embodiment, the OFDM communication method is used as the downlink communication method similar to the second embodiment. Further, it is assumed that the configuration of the communication frame and the resource block has the same format as that shown in FIGS. 22 and 28. First, the specific configuration of the physical channel for synchronization (SCH), which is a feature of the present embodiment, will be described.

29 (a) to 29 (c) are diagrams for explaining the data structure of the SCH transmitted simultaneously from three sectors in the same cell, respectively, as in the second embodiment. FIG. 29 (a) is a diagram showing the allocation of sector common codes on the frequency axis, FIG. 29 (b) is a diagram showing the configuration of three sector-specific codes, and FIG. 29 (c) is a diagram showing sectors. It is a figure which shows the concept which is the basis of the generation of a eigencode, and shows a vector on a complex phase plane. The basic configuration is the same as that of the second embodiment, but some configuration codes are different so that the cross-correlation detection method can be applied to the first step of the three-stage cell search.

The signal shown in (a) of FIG. 29 indicates the sector common code constituting the SCH. Every 6 chips for each SCH subcarrier₀₁From s_{0n / 6}Is assigned. s₀Is an arbitrary value represented by A * exp (jω). Here, A is the amplitude (however, this is explained as 1 in the present invention), j is the imaginary unit, and ω is the phase.

One of the features of this embodiment is that, unlike the second and third embodiments, this sector common code is a code common to all cells. That is, the sector common code is also the cell common code. Another feature is that the code element that serves as the phase reference among the cell-specific codes is also common to all cells. This enables correlation detection using a replica of the sector-specific code.

That is, the SCH is configured by multiplying three types of codes (sector common code, sector-specific code, and cell-specific code). Here, assuming that the sector common code is also common between cells and that the code element that serves as the phase reference among the cell-specific codes is also common to the cells, the subcarriers multiplied by the code element that serves as the phase reference are The codes to be multiplied are (sector common code common to all cells), (sector unique code), and (cell unique code common to all cells), and substantially (sign common to all cells) to (sector). The unique sign) is multiplied. That is, with respect to the subcarrier to which the sign element serving as the phase reference is multiplied, three kinds of signs are multiplied, but two of them are common to all cells. Therefore, the only difference is the sector-specific code. This means that correlation detection using a replica of the sector-specific code is possible.

Therefore, the receiver side prepares the time waveform of the replica code of the sector-specific code corresponding to each sector, and multiplies the received signal before FFT by the time waveform of the replica code to detect the correlation peak. , The timing of SCH in the received signal can be detected with high accuracy. Therefore, subsequent sector identification and cell identification can be performed more efficiently. However, even if such a special SCH structure is adopted, the SCHs are still arranged periodically during one frame period, so the autocorrelation method (that is, the received signal is determined). It is also possible to perform position detection by a method of detecting the correlation between a signal delayed by a period and the original received signal).

Hereinafter, a specific description will be given with reference to the drawings. First, the sector-specific code will be described. FIG. 29 (b) shows an example of a sector-specific code (here, the number of sectors is "3"). Here, a code similar to the code shown in the second embodiment is used.

Next, a code sequence for transmitting cell-specific information will be described. FIG. 30 is a diagram showing a configuration on the frequency axis of a code sequence for transmitting cell-specific information. In the present embodiment, cell-specific information is transmitted by the code sequence shown in FIG. 30, but unlike the second and third embodiments, different code sequences are used for each cell and common codes are used between the cells. It is composed of series. Specifically, c shown in FIG._ik(K is a natural number from 1 to n / 6, n is the number of SCH subcarriers) is the "common code between cells", c_l(L is a natural number from 1 to n / 2) is a "cell-specific sign".

The code sequence of FIG. 30 is composed of 6 chips as a set in order from the low frequency side. The 6th chip assigns a "common code between cells" to the odd-numbered SCH subcarriers (subcarrier indexes 1, 5, and 9). The even-numbered SCH subcarriers (subcarrier indexes 3, 7, 11) are assigned a code obtained by multiplying the odd-numbered code by the cell-specific code (that is, a code having phase difference information with respect to the phase reference code). .. The code assigned to the odd-numbered subcarriers is the same within the 6 chips, but does not have to be the same as the code used by the other 6 chips.

The three types of code sequences shown above are the code sequences that make up the SCH, and these code sequences are multiplied to form the SCH. Then, a multi-carrier signal including SCH is transmitted from the transmitter of each sector.

Since the SCH transmission method and the transmitter configuration in this embodiment are the same as those in the second embodiment described above, the description thereof will be omitted. The difference is the code generated by the sector-specific code generation unit 63 in the SCH data processing unit 60 (see FIGS. 29 and 30).

The receiver configuration and receiving method in this embodiment are basically the same as those in the above-described embodiment except for the first step. The timing detection unit 103 (FIG. 13) in the second embodiment described above detects the position of the SCH symbol by delaying the received signal by 1/2 effective symbol interval and multiplying it by the signal. In the present embodiment, the SCH symbol is detected by calculating the cross-correlation value between the received signal and the replica signal of the SCH symbol generated or stored by the mobile station. The cell search procedure will be described below.

The mobile station receives the radio signal transmitted from the base station at the antenna unit 100 as in the second embodiment. The analog receiving circuit unit 101 converts the received radio signal from the radio frequency band to the baseband frequency band. The A / D (analog / digital) conversion unit 102 converts the signal converted into the baseband frequency band from an analog signal to a digital signal. Next, the timing detection unit 103 performs SCH detection processing for performing symbol synchronization based on the received data converted into digital data by the A / D conversion unit 102.

FIG. 31 is a block diagram showing a configuration (including a correlator) of the symbol synchronization circuit in the present embodiment. The symbol synchronization circuit of FIG. 31 has an m-stage shift register 400, an adder 402, and a multiplier 404. In the symbol synchronization circuit of FIG. 31, the received signal is input to the m-stage shift register 400. The signal output from the shift register 400 is a replica signal (r) created by the mobile station or stored in the mobile station in advance._m: m is multiplied by the complex conjugate of the natural number).

The replica signal is derived from the value obtained by multiplying the three codes constituting the SCH subcarriers described above, but the data regarding the odd-numbered SCH subcarriers (subcarrier indexes 1, 5, 9 ...) Is used. Be done. Since the received signal is data in the time axis direction, the replica signal is also calculated in the time axis direction from the data using the SCH subcarrier described above.

The odd-numbered data of the SCH subcarrier is used to create such a replica signal. As described above, the odd-numbered subcarriers of the SCH subcarrier have the sector common code s that is common to all cells.₀(See FIG. 29 (a)) is multiplied by a code (a code that serves as a phase reference) that indicates a part of cell-specific information that is common to all cells, as shown in FIG. That is, in the odd-numbered subcarriers of the SCH subcarriers, only the sector-specific code shown in FIG. 29 (b) differs between cells. Therefore, in the present embodiment, the SCH time position can be detected by creating three replica signals similar to the number of sector-specific codes and monitoring the received signal and the cross-correlation value.

As in the second and third embodiments, a plurality of peaks are detected by signals from a plurality of cells, but in general, the timing with the highest correlation value peak is transmitted from the nearest cell. Judging as the timing of SCH, the connection operation with the base station is started.

As described above, in the first step of the cell search in the present embodiment, symbol synchronization is realized by using the cross-correlation value of the received signal and the replica signal. Since the second step and the third step of the cell search method in this embodiment are the same as those in the second embodiment described above, the description thereof will be omitted.

(Fifth Embodiment) Next, the fifth embodiment of the present invention will be described. In this embodiment, each of the following points 1 to 5 will be described.

[1. Materialization of the first step of cell search] Here, a specific variation of the technology for detecting the timing of SCH in the first step of cell search by the cross-correlation method using the time waveform of the replica of the sector-specific code. Is shown. This is a modification of the fourth embodiment. That is, in the above-described embodiment, the total number of subcarriers (excluding DC subcarriers) is basically a multiple of 6, but in this embodiment, the number of subcarriers is 75 (excluding DC subcarriers). Prescribed in. Regarding the subcarriers that are multiplied by the code element that serves as the phase reference, the point that (sector-specific code) is substantially multiplied by (code common to all cells), and this subcarrier is used. The point that the timing of SCH is detected by the cross-correlation method is the same as that of the fourth embodiment. However, in the present embodiment, subcarriers (subcarriers multiplied by a dummy code) that do not contribute to the detection of cell-specific information are included. Similar to the fourth embodiment, the autocorrelation method may be used as well as the cross-correlation method.

[2. Formation of characteristic time waveform by symmetrical arrangement of subcarriers as phase reference] Subcarriers to which the code element serving as phase reference is multiplied are on the low frequency side and high frequency side with reference to the center frequency. Arranged symmetrically. Since the subcarrier to which the sign element serving as the phase reference is multiplied is the SCH subcarrier used for detecting the SCH timing by the cross-correlation method, it is referred to as "SCH subcarrier for cross-correlation detection" in the following description. In some cases. In the fourth embodiment, since the embodiment is assigned with the low frequency side as a reference, it is not necessary to satisfy the condition of the present embodiment in which the arrangement is symmetrical with respect to the center frequency.

SCH subcarriers for cross-correlation detection are placed in the target at predetermined intervals with reference to the center frequency. The time waveform of the signal in which those subcarriers are combined can be obtained by using, for example, the second, sixth, tenth, and so on subcarriers from the center in one symbol period (the period in which the SCH is arranged). (1/4) For each symbol, the amplitude is the same and the polarity is the same, such as "B", "-B", "B", "-B" (B is an arbitrary signal amplitude: reference waveform). The inverted waveform is repeated to form a time waveform with a characteristic periodicity. Also, by using the 4th, 8th, 12th, etc. subcarriers from the center, "D", "D", "D", "D" (D is an arbitrary signal) for each 1/4 symbol. A time waveform such as (amplitude: reference waveform) is formed. Therefore, the replica time waveform prepared for cross-correlation detection on the receiver side is also "B", "-B", "B", "-B" or "D", for each (1/4) symbol. It may be a time waveform that changes like "D", "D", "D". In other words, it is only necessary to be able to detect the characteristic signal waveform in units of (1/4) symbols. Therefore, the configuration of the correlator can be simplified.

[3. Sector identification in the second step of cell search] Here, reverse diffusion using a sector-specific code is performed to improve the degree of freedom in the operation of detecting the sector showing the maximum correlation value. The codes that are multiplied by the subcarriers (subcarriers for cross-correlation detection) multiplied by the code element that serves as the phase reference are (sector common code common to all cells), (sector unique code), and (common to all cells). The point that it is a cell-specific code) is the same as that of the fourth embodiment. However, in the present embodiment, the sector common code (reference code) common to all cells and the cell-specific code common to all cells are both "1" for all the subcarriers serving as the phase reference in the total subcarriers. ". In the fourth embodiment, the cell-specific code (C in FIG. 30)._i1, C_i2C_{in / 6}) Is a new code every 6 subcarriers. So the first 6 subcarriers are C_i1, C for the next 6 subcarriers_i2It has become. In this case, when performing despreading for sector identification, it is necessary to perform despreading sequentially for each of the six subcarriers. In this respect, the degree of freedom in sector identification is limited. However, as mentioned above, C_i1, C_i2C_{in / 6}If all of) are set to "1", all cell-specific codes multiplied by the subcarriers that are the phase reference in the total subcarriers are "1". Therefore, what is multiplied by the subcarrier is "1 (sector common code common to all cells)" x "1 (cell unique code common to all cells)" x "sector unique code (P1, P2, P3) Either: see Figure 29 (b)) ". After all, it is the sector-specific code (either P1, P2, or P3) that is multiplied by each of the subcarriers that serve as the phase reference. This eliminates the need for backdiffusion with 6 subcarriers as a set, and identifies the sector common code (P1, P2, P3) by selecting one of the subcarriers among the total subcarriers. It can be used to carry out backdiffusion. Therefore, when identifying sectors, there is no restriction that backdiffusion is performed every 6 subcarriers. As a result, the degree of freedom in the sector identification process is improved.

[4. Consideration that sector identification is performed by cross-correlation of time waveform before FFT, not by correlation value peak judgment by back diffusion after FFT processing] When adopting the code configuration of (3) above, the cross-correlation method using the replica time waveform described in (1) above does not require backdiffusion using the orthogonal codes (P1, P2, P3) after FFT. It is possible to identify the latest sector before FFT processing by using. That is, before the FFT processing, the cross-correlation peak is detected using the replica time waveform of the sector-specific code (the time waveform formed by any of the code 1, code 2, or code 3 in FIG. 34), and the maximum peak is detected. By specifying the given code (any of code 1, code 2, or code 3 in FIG. 34), it is possible to identify the nearest sector. In particular, when SCH timing synchronization is performed by the replica correlation method in the first step of cell search, sector identification is performed by comparing the correlation values calculated at the time of timing synchronization between different sector-specific codes. Therefore, it is not necessary to perform the sector identification operation again after that. In order to apply the cross-correlation method using this replica time waveform, it is a condition that the mobile station knows various sector-specific codes transmitted from the base station. Whether to use the method of detecting the correlation by backdiffusion by the orthogonal code or the method of detecting the cross-correlation by the replica time waveform as the sector identification method, considering the required detection accuracy and the restrictions on the circuit, etc. It can be determined as appropriate.

[5. Clarification that the sector-specific code includes not only the code for directly identifying the sector but also the sector group-specific code] If the number of sectors becomes too large, more to secure the orthogonal code. A set of the number of subcarriers is required, and it is assumed that the number of subcarriers may be insufficient. In this case, a plurality of sectors may be grouped to introduce the concept of "sector group", and the sector group may be specified by a sector-specific code. That is, the above-mentioned "sector-specific code" does not necessarily have to be a code for directly identifying a sector, and may be a code indicating a sector group in which a plurality of sectors are grouped together. This applies in common to all of the above embodiments. Each of these points will be specifically described below.

In the first to fourth embodiments described above, the total number of subcarriers is 2n + 1 (including the central DC subcarrier), but in the present embodiment, the total number of subcarriers is 76. The case (including the central DC subcarrier) will be described. In this embodiment, 75 subcarriers are used excluding the DC subcarriers, so that the number of subcarriers differs between the low frequency side and the high frequency side in the band centering on the DC subcarriers. However, also in this embodiment, since the cell-specific information is notified by the phase difference of the subcarriers constituting the SCH, the subcarriers essentially used are 2n + 1 including the DC subcarrier (n = in this embodiment). 37).

In the present embodiment, as in the fourth embodiment, the SCH timing detection in the first step of the three-step cell search is performed by cross-correlation processing between the received signal and the replica signal created by the mobile station. Further, by arranging the subcarriers to be subjected to the cross-correlation processing using the replica signal at a specific position, a characteristic time waveform can be obtained. In order to realize the above, it is necessary to devise the data structure and subcarrier arrangement of SCH.

The SCH position detection method of the first step shown in the present embodiment can be realized by using the frame configuration and the SCH arrangement shown in the fourth embodiment as they are. The second step or the third step can also be carried out in the same manner as in the above-described embodiment.

According to the SCH data structure shown in the present embodiment, the SCH showing a periodic waveform (repeated waveform) within one symbol required for the autocorrelation detection method is realized as in the fourth embodiment. At the same time, it is possible to realize a SCH to which a detection method using a cross-correlation detection method using a replica signal can also be applied. The autocorrelation detection method can generally be realized with a simpler circuit configuration than the cross-correlation detection method, but on the other hand, it is known that the peak of the correlation value is detected more slowly than the cross-correlation detection method. There is. The cross-correlation detection method enables more accurate time synchronization because the peak of the correlation value can be detected sharply, but on the other hand, it is known that the circuit configuration and its processing become complicated. For this reason, in some wireless LAN communication methods, coarse time synchronization is performed by the autocorrelation detection method at the time of time synchronization, and accurate time synchronization is performed by the cross-correlation detection method in a somewhat limited time interval. It is done. A similar method can be used in this embodiment as well.

As described above, two detection methods can be applied to the SCH timing detection method of the first step in the present embodiment. Since the autocorrelation detection method is a method using a repeated waveform in the time domain in the SCH symbol determined by the position of the frequency domain of the subcarrier used for SCH, it will be described in detail in the second or third embodiment. It is no different from the method used. Therefore, a cross-correlation detection method using a replica signal, which is a feature of this embodiment, will be described below. This cross-correlation detection method utilizes a characteristic signal waveform formed by the arrangement of subcarriers.

In the present embodiment, the OFDM communication method is used as the downlink communication method similar to the second embodiment. Further, it is assumed that the configuration of the communication frame and the resource block has the same format as that shown in FIGS. 22 and 28. First, the specific configuration of the physical channel for synchronization (SCH), which is a feature of the present embodiment, will be described.

FIG. 32 is a diagram showing 76 subcarriers used in the present embodiment for each function. As shown in the figure, the central DC subcarrier and the odd-numbered subcarrier from the center are null subcarriers, and the other subcarriers are used as SCH subcarriers. Of the SCH subcarriers, the odd-numbered SCH subcarrier from the center is used as the subcarrier used for cross-correlation detection, that is, the subcarrier that serves as a phase reference when detecting cell-specific information (SCH subcarrier for cross-correlation detection). use. Further, the even-numbered SCH subcarrier from the center is used as a subcarrier multiplied by cell-specific information (in the following description, it may be referred to as a cell-specific information detection subcarrier).

Here, the odd-numbered SCH subcarriers from the center are the 2, 6, 10, 14 ... th subcarriers from the center as a whole. However, the center is 0th. The even-numbered SCH subcarriers from the center are the fourth, eighth, twelfth, and so on subcarriers from the center as a whole.

As described above, the SCH subcarriers for cross-correlation detection are symmetrically arranged on the low frequency side and the high frequency side with respect to the center frequency. Further, the subcarriers for cross-correlation detection are arranged at intervals of three subcarriers, such as the second, sixth, tenth, etc., when the center frequency is the 0th. It differs from the fourth embodiment in that it is based on the center frequency. In FIG. 32, the number of cross-correlation detection SCH subcarriers arranged is different between the high frequency side and the low frequency side with respect to the center frequency. That is, on the high frequency side, 10 lines (1) to (10) are arranged, while on the low frequency side, 9 lines (11) to (19) are arranged. However, the point that the SCH subcarrier for cross-correlation detection (subcarrier serving as a phase reference) and the SCH subcarrier for cell-specific information detection are used as a pair is the same as in the fourth embodiment. When a pair of subcarriers is used as a unit, in the case of FIG. 32, one cross-correlation detection subcarrier (phase reference subcarrier: subcarrier (10) in FIG. 32) is left over on the high frequency side. However, a dummy code (1 in this embodiment) is assigned to this subcarrier (10).

FIG. 33 shows the relationship between a subcarrier multiplied by cell-specific information (SCH subcarrier for cell-specific information detection) and a pair of subcarriers serving as a phase reference subcarrier (SCH subcarrier for cross-correlation detection). It is a figure which shows. In the case of 76 subcarriers in this embodiment, 37 subcarriers can be used as SCH subcarriers. Therefore, the information P1 (x) (where x = 1 to 18) having a code length of 18 is set as a relative value between the above-mentioned phase reference subcarrier (cross-correlation detection subcarrier) and cell-specific information detection subcarrier. It is possible to do. However, since information is assigned as a pair, one subcarrier is not used for code assignment in the present embodiment. That is, the reference numeral S19 in FIG. 33 is a dummy reference numeral (1 in the present embodiment).

34 (a) to 34 (c) are diagrams for explaining the data structure of the SCH transmitted simultaneously from three sectors in the same cell, respectively, as in the fourth embodiment. FIG. 34 (a) is a diagram showing the allocation of sector common codes on the frequency axis, and FIG. 34 (b) is a diagram showing the configuration of three sector-specific codes. Then, FIG. 34 (c) is a diagram showing a concept underlying the generation of a sector-specific code, and shows a vector on a complex phase plane.

The basic configuration is the same as that of the fourth embodiment, but the positional relationship on the frequency axis between the subcarrier used for cross-correlation detection and the subcarrier for multiplying the cell-specific information is different as described above. As shown in FIG. 32, the SCH subcarrier uses even-numbered subcarriers on the higher frequency side and the lower frequency side than the central DC subcarrier, respectively.

Figures 35 (a) to 35 (d) show that multiple SCH subcarriers are combined during the SCH symbol period by devising the arrangement of SCH subcarriers for cross-correlation detection on the frequency axis and the number of SCH symbols on the time axis. It is a figure for demonstrating that the waveform in the time domain formed by the above is the repetition of the reference waveform (or the waveform which inverted the reference waveform) within one symbol period.

In this embodiment (including the above-described embodiment), SCH subcarriers are periodically arranged at frequency intervals of every other subcarrier on the frequency axis (see, for example, FIG. 25). When the SCH subcarriers in the 1-symbol period arranged periodically in this way are synthesized, the 1-effective symbol period (the period in which the GI is inserted is excluded from the 1-symbol period) as shown in Fig. 35 (a). In (period), a time waveform (waveform in the time domain before FFT) in which the reference waveform (referred to as A) is repeated in (1/2) symbol units is obtained. Therefore, as described in the above-described embodiment, the correlation peak is obtained by delaying the time waveform by (1/2) effective symbols and correlating with the original time waveform. Therefore, it is possible to detect the SCH position (processing of the first step of cell search by the autocorrelation method).

As shown in FIG. 19, when SCHs are arranged consecutively in the last two symbols of one frame period, they are the same in two adjacent effective symbol periods as shown in FIG. 35 (c). The time waveform (let's call it C) will be repeated. Therefore, if the time waveform is delayed by one symbol and correlated with the original time waveform, a correlation peak is obtained. Therefore, it is possible to detect the SCH position (processing of the first step of cell search by the autocorrelation method).

On the other hand, in the fifth embodiment, the SCH for cross-correlation detection is further arranged symmetrically on the low frequency side and the high frequency side with reference to the center frequency. That is, as described above, the subcarriers are used as the second, sixth, tenth, 14th ... th (every three thereafter starting from the second) from the central DC subcarrier. As a result, the signal is repeated in the 1/2 section of the effective symbol, and the time waveform in which the polarity of the amplitude is inverted is created in the (1/2) section, that is, the entire (1/4) section as a unit. A characteristic time waveform that repeats is formed. Specifically, as shown in FIG. 35 (b), a time waveform in which B, -B, B, and -B are repeated is formed. This phenomenon occurs due to the symmetry in the time direction with respect to the frequency relationship of the subcarriers orthogonal to each other in the OFDM communication method. In this case, the SCH position can be specified by detecting the characteristic periodicity in units of (1/4) valid symbols. Utilizing this feature, it becomes possible to create a correlator used for cross-correlation detection with a simpler circuit. That is, a correlator with a simple configuration enables highly accurate SCH timing detection.

In addition, by using the subcarriers of the SCH for cross-correlation detection as the 4th, 8th, 12th, 16th ... It is also possible to form a characteristic time waveform in which the signal is repeated at. Specifically, as shown in FIG. 35 (d), a time waveform in which D, D, D, and D are repeated is formed.

Next, the most simplified subcarrier configuration in which all cell-specific codes common to all cells are set to "1" will be specifically described. It can be said that this subcarrier configuration is advantageous for practical use.

The signal shown in (a) of FIG. 34 indicates the sector common code constituting the SCH. In the fourth embodiment, as shown in FIG. 29 (a), each SCH subcarrier has s every 6 chips.₀₁From s_{0n / 6}Was assigned. In this embodiment, all SCH subcarriers are s₀Is assigned. Here s₀Is an arbitrary value represented by A * exp (jω). Here, A is the amplitude (however, this is explained as 1 in this embodiment), j is the imaginary unit, and ω is the phase. S for all SCH subcarriers₀Is multiplied, and the sign of the subcarrier that serves as the phase reference is uniformly set to "1" (described later). As a result, it is not always necessary to perform the power calculation for sector identification in units of a set of six subcarriers. That is, taking the code 2 in FIG. 34 (b) as an example, each code of "P1", "P2", and "P3" is selected from any of the SCH subcarriers on the frequency axis, and the power calculation process is performed. It will be possible to do. However, since the subcarriers used for the power calculation process must be considered to have the same propagation path, the accuracy will decrease if subcarriers separated on the frequency axis are selected. Therefore, adjacent subcarriers are used. It is desirable to use.

In the present embodiment, as in the fourth embodiment, the sector common code is a code common to all cells. In addition, the code element that serves as the phase reference among the cell-specific codes is also common to all cells.

The SCH is constructed by multiplying three types of codes (sector common code, sector-specific code, and cell-specific code). Here, the sector common code is also common between cells, and the code element that serves as a phase reference among the cell-specific codes is also common to cells. As a result, with respect to the subcarriers whose phase reference code elements are multiplied, the multiplied codes are (sector common code common to all cells), (sector unique code), and (cell common to all cells). It becomes a unique code), which means that (a code common to all cells) is substantially multiplied by (a sector-specific code). That is, with respect to the subcarrier to which the sign element serving as the phase reference is multiplied, three kinds of signs are multiplied, but two of them are common to all cells. Therefore, the only difference is the sector-specific code. This means that correlation detection using a replica of the sector-specific code can be easily performed.

Therefore, the receiving device prepares the time waveform of the replica code of the sector-specific code corresponding to each sector, and multiplies the received signal (signal before FFT) by the time waveform of the replica code to detect the correlation peak. By doing so, the SCH timing in the received signal can be detected with high accuracy. Therefore, subsequent sector identification and cell identification can be performed more efficiently.

Further, in the present embodiment, by arranging the subcarrier position used for cross-correlation detection at a specific position, the same signal waveform is repeated in the 1/2 effective symbol length interval as shown in FIG. 35 (b). Is done. In addition, a signal waveform whose sign is inverted in the 1/4 effective symbol length interval is formed. Thereby, it is possible to form a simpler correlator using this characteristic.

However, even when such a special SCH structure is adopted, since the repeated signal waveform is still formed in the SCH symbol section, it is possible to perform position detection by the autocorrelation method. This autocorrelation method is a method of detecting the correlation between a signal obtained by delaying a received signal by a predetermined period and the original received signal.

Hereinafter, a specific description will be given with reference to the drawings. First, the sector-specific code will be described. FIG. 34 (b) shows an example of a sector-specific code (here, the number of sectors is "3"). Here, a code similar to the code shown in the fourth embodiment is used.

Next, a code sequence for transmitting cell-specific information will be described. FIG. 36 is a diagram showing a configuration on the frequency axis of a code sequence for transmitting cell-specific information. In this embodiment, cell-specific information is transmitted according to the code sequence shown in FIG. The cl (l is a natural number from 1 to 18) shown in FIG. 36 is a cell-specific code and notifies the mobile station of the cell-specific information. cl is a sign sequence with an amplitude of 1.

The code sequence of the fourth embodiment shown in FIG. 30 is configured as a set of 6 chips in order from the low frequency side, but the code sequence of the present embodiment shown in FIG. 36 is shown in FIG. 30. It is a special form in which all the code series cik of are set to "1". As a result, when calculating the sector power described above, there is no restriction that a set of six adjacent subcarriers on the frequency axis is always selected, and the degree of freedom in the sector identification process is improved.

The three types of code sequences shown above are the code sequences that make up the SCH, and these code sequences are multiplied to form the SCH. Then, a multi-carrier signal including SCH is transmitted from the transmitter of each sector.

Since the SCH transmission method and the transmitter configuration in this embodiment are the same as those in the second embodiment described above, the description thereof will be omitted. The difference is the code generated by the sector-specific code generation unit 63 in the SCH data processing unit 60 (see FIGS. 35 and 36).

Further, since the receiver configuration and the receiving method in this embodiment are the same as those in the fourth embodiment described above, the description thereof will be omitted. Further, when the code configuration as shown in FIG. 36 is adopted, the replica time is the same as the processing of the first step of the cell search, even if the back diffusion using the orthogonal codes (P1, P2, P3) is not performed after the FFT. It is also possible to identify the most recent sector before FFT processing by using the cross-correlation method using waveforms.

That is, before the FFT processing, the cross-correlation peak is detected using the replica time waveform of the sector-specific code (the time waveform formed by any of the code 1, code 2, or code 3 in FIG. 34), and the maximum peak is detected. By specifying the given code (any of code 1, code 2, or code 3 in FIG. 34), it is possible to identify the nearest sector.

In particular, when SCH time synchronization is performed by the cross-correlation method in the first step of the cell search, it is possible to perform sector identification using the result as it is. That is, it is possible to perform SCH time synchronization according to the position of the correlation value in the time direction by cross-correlation detection, and determine from which sector the received power is high based on the amplitude.

As the sector identification method, whether to use the method of detecting the correlation by backdiffusion by the orthogonal code or the method of detecting the cross-correlation by the replica time waveform is appropriate in consideration of the required detection accuracy and the restrictions on the circuit. , Can be decided.

Further, if the number of sectors becomes too large, a set of a larger number of subcarriers is required to secure the orthogonal code, and it is assumed that the number of subcarriers may be insufficient. In this case, a plurality of sectors may be grouped to introduce the concept of "sector group", and the sector group may be specified by a sector-specific code. That is, the above-mentioned "sector-specific code" does not necessarily have to be a code for directly identifying a sector, and may be a code indicating a sector group in which a plurality of sectors are grouped together. This applies in common to all of the above embodiments.

As described above, according to the present invention, by multiplying the sector common code by the sector-specific code, the sector can be identified only by reverse diffusion using SCH and correlation detection without using a pilot channel. Can be done. Therefore, regarding sector identification, despreading and correlation detection processing using the pilot channel become unnecessary, and the memory capacity used for the correlation calculation using the pilot channel can be reduced.

Further, since the SCH itself is multiplied by the sector-specific code, interference between sectors can be eliminated even at the sector boundary. In addition, the effect of improving the fading resistance characteristic due to the randomization effect can also be obtained. The sector-specific code (alsh-Hadamard code) assigned to each sector can be easily increased in accordance with the increase in the number of sectors, and can flexibly correspond to the sector configuration.

Further, if a sufficient number of subcarriers can be secured by multiplying the SCH by the cell-specific code, the cell ID can be directly identified only by the SCH. In this case, the cell search process including sector identification can be performed in two steps using only SCH (two-step cell search), which can shorten the search process compared to the conventional three-step cell search. it can.

Further, by making the configuration and contents of the cell-specific code and the sector-specific code to be multiplied by the SCH and the arrangement on the frequency axis as in the present invention, the sector-specific information and the cell-specific information do not adversely affect each other. It is also possible to suppress a decrease in information transmission accuracy. In addition, each piece of information can be demodulated independently (that is, by parallel processing), which can further reduce the processing time of the cell search including the sector search.

That is, the code of the 2m chip is formed by combining two orthogonal codes of the m chip, the m chip is used for sector identification, and the remaining m chip is used for identification of cell-specific information. The cell-specific information is transmitted as the phase difference information between the subcarriers (preferably arranged adjacent to each other on the frequency axis) to which the sector-specific code elements of the same value are multiplied, so that the cell-specific information can be combined with the sector-specific information. Cell-specific information can be efficiently transmitted, and both can be efficiently separated and retrieved on the receiving side.

Further, in the cell search method of the present invention, the timing of SCH on the time axis is detected by the autocorrelation method using the periodicity of SCH or by the cross-correlation method using the time waveform of the replica code of the sector-specific code (No. 1). It is also possible to complete the cell search by 1 step), identification of the frame timing based on the information on the frequency axis, and identification of the sector ID and the cell ID (2nd step). Therefore, the search process can be shortened as compared with the conventional three-stage cell search.

In addition, reverse diffusion and correlation detection using the pilot channel are only required when demodulating the data channel and are not required for cell search, so the hardware burden for correlation calculation using the pilot channel should be reduced. (Reduction of memory capacity, etc.) can be achieved. Further, since the sector-specific code is superimposed on the SCH, it is possible to obtain the effect of being resistant to interference and fading between sectors in terms of sector identification. However, if the number of subcarriers is not sufficient, the cell ID cannot be directly identified by SCH alone, and the cell ID group information may be detected only. In this case, the process of the third step. As a result, the cell ID can be identified by performing backdiffusion and correlation detection using a pilot channel.

Further, the multi-carrier transmission / reception device of the present invention enables high-speed, large-capacity transmission in the downlink.

As described above, according to the present invention, it is possible to shorten the process required for the cell search process including sector identification and reduce the capacity of the memory for storing the correlation detection result using the pilot channel. Further, the interference resistance or fading resistance of the cell search process including sector identification can be improved, and faster and more accurate cell search including sector identification can be realized without increasing the load on the transmitter / receiver. ..

In addition, the present invention includes various variations (specific examples, modifications, application examples), and these variations contribute to the practical application of a communication method compliant with E-UTRA (Evolved-UTRA). For example, in the processing of the first step of the cell search (SCH timing detection processing), in addition to the autocorrelation method, a cross-correlation method focusing on a special time waveform can be adopted. In this case, the effect that the configuration of the correlator can be simplified can be obtained. In addition, by unifying all the codes of the subcarriers that serve as the phase reference on the frequency axis to, for example, "1", it is necessary to make a set of six subcarriers at the time of reverse diffusion using the sector-specific code. Restrictions can be eliminated. Further, when the mobile station knows various sector-specific codes transmitted from the base station, the latest sector detection is detected by using the cross-correlation based on the time waveform before FFT, not by backdiffusion. You can also do it. Further, when the number of sectors increases, a "sector group-specific code" can be adopted as the "sector-specific code".

The present invention can also be configured as a synchronous channel (SCH) data structure. That is, in the data structure of the present invention, one cell is divided into a plurality of sectors, and a downlink signal is transmitted from a base station having jurisdiction over the cell to a mobile station in the cell by multi-carrier communication, and the downlink signal is transmitted to the mobile station. The synchronization channel in a mobile communication system that employs a multi-carrier communication method, wherein the link signal includes a synchronization channel (SCH), and the synchronization channel (SCH) can be used for cell search including sector identification. In the data structure of (SCH), the sector common code common to multiple sectors in the same cell is multiplied by a different sector-specific code for each sector in the same cell, thereby using the synchronization channel (SCH). It is possible to carry out cell search including sector identification.

As the data structure of the synchronization channel (SCH: hereinafter, sometimes simply referred to as "SCH") included in the downlink of the multi-carrier mobile communication system, a new structure including sector-specific information is adopted. That is, the sector common code is multiplied by the sector-specific code so that the sector can be identified only by backdiffusion and correlation detection using the synchronous channel (SCH) without using the pilot channel. That is, in the present invention, the SCH that has been commonly used between sectors in one cell (that is, that is non-orthogonal with respect to the sector) is changed to an orthogonal channel unique to each sector in the present invention, and the SCH is changed. It can be used to directly identify sectors. Therefore, regarding sector identification, despreading and correlation detection processing using the pilot channel become unnecessary, and the memory capacity used for the correlation calculation using the pilot channel can be reduced. Further, since the SCH itself is multiplied by the sector-specific code, interference between sectors can be eliminated even at the sector boundary, and the effect of improving the fading resistance characteristic due to the randomization effect can also be obtained. In addition, if the information superimposed on the SCH can be increased, it is possible to directly identify the cell ID itself only by the SCH. In this case, the cell search process including the sector identification is performed only by the SCH. This can be achieved by the two-step processing (two-step cell search) used.

Further, in the data structure of the synchronous channel (SCH) of the present invention, the sector-specific code has m (m is a natural number of 2 or more) code elements as a set, and the set of code elements is the frequency axis. Each of the sector-specific codes corresponding to each sector, which is configured by repeatedly assigning to the above subcarriers, is orthogonal to each other.

It is clear that sector-specific codes are repeatedly assigned to subcarriers on the frequency axis in units of m code elements as a set, and that m code elements are orthogonal to each sector. It is the one. The term "sign element" distinguishes between a "sign as a higher-level concept" meaning a "code string" and an individual code ("sign as a lower-level concept") that is a component of the code string. It is used for convenience, for example, and corresponds to, for example, a "chip" which is a unit of back diffusion. Further, by assigning a code element to a subcarrier on the frequency axis, for example, the phase of the subcarrier changes, whereby sector-specific information can be transmitted. Here, for example, when m = 3, the code M1 corresponding to sector 1 has M1 = (m1, m2, m3, m1, m1, m1, m1) on the frequency axis in units of code elements (m1, m2, m3). m2, m3, ...), etc., are repeatedly assigned from the low frequency side to the high frequency side with three code element periods. Similarly, the code M2 in sector 2 has three code element periods, such as M2 = (m4, m5, m6, m4, m5, m6, ...), from the low frequency side to the high frequency side. It has been repeatedly assigned. Then, (m1, m2, m3) and (m4, m5, m6), which are the constituent units of the symbols M1 and M2, are orthogonal to each other.

For example, when the complex conjugates of m1, m2, and m3 are multiplied by the signs M1 and M2 (reverse diffusion) and the results are added, the sign M1 shows a high correlation value, but the sign M2 shows a correlation value. Becomes "0", which means that both signs can be distinguished and extracted. An example of the basic idea for creating a Walsh-Hadamard code is shown below. On a complex phase plane (IQ plane, where the I axis corresponds to the real axis and the Q axis corresponds to the imaginary axis), for example, three amplitudes "1" arranged at an angle of 120 degrees. Vectors (P1, P2, P3) are set. Since these three vectors have a relationship of becoming "0" when vector addition is performed, it is possible to easily create an orthogonal code (in the case of m = 3) by using this. For example, the code M1 = (P1, P1, P1), the code M2 = (P1, P2, P3), and the code M3 = (P1, P3, P2) are orthogonal to each other. For example, when each complex conjugate of the sign elements (P1, P2, P3) of the sign M2 is multiplied by each of the signs M1, M2, and M3 and the sign elements are added to each other, the correlation value of the sign M2 is "3". However, in the case of the symbols M1 and M3, in the end, the relationship between the vectors P1, P2, and P3 is simply maintained as the relative relationship between the code elements. Therefore, if they are added, it becomes "0". In the above example, three vectors that are orthogonal to each other are used, but if the number of vectors is increased (for example, if four vectors that form an angle of 90 degrees are used), the number of sign elements can be further increased. It can be increased, thereby increasing the number of orthogonal codes (in the above example, the number of codes is "3" because the three codes that can be generated are M1, M2, and M3). You can do a lot. Therefore, even if the number of sectors included in one cell increases, it is possible to easily create an orthogonal code corresponding to the number of sectors by using the above concept.

Further, in the data structure of the synchronous channel (SCH) of the present invention, in addition to the sector common code and the sector-specific code, a cell-specific code (a code indicating cell-specific information or cell-specific cell It is multiplied by a code that contains an ID (or information indicating a cell ID group that is common to several cells).

By multiplying the SCH by the cell-specific code, if the desired conditions are satisfied, the cell ID can be directly identified only by the SCH in addition to the sector identification by the SCH. In this case, the cell search process including sector identification can be performed in two steps using only SCH (two-step cell search), which shortens the search process compared to the conventional three-step cell search. be able to.

Further, in the data structure of the synchronization channel (SCH) of the present invention, the cell-specific code is a code indicating cell-specific information acquired by the mobile station at the time of cell search. It is clarified that the cell-specific code indicates cell-specific information (cell ID, etc.).

Further, in the data structure of the synchronous channel (SCH) of the present invention, the sector common code is assigned to a subcarrier on the frequency axis, and the sector-specific signal is assigned to the subcarrier to which the sector common code is assigned. Each of the code elements that are assigned and constitute the cell-specific code indicates relative phase difference information between a pair of subcarriers among the subcarriers to which the sector common code is assigned. Therefore, in the subcarrier to which the sector common code is assigned on the frequency axis, one of the pair of subcarriers is multiplied by the code element serving as a phase reference, and the other subcarrier has a relative position. The sign elements indicating the phase difference are multiplied.

Cell-specific information (cell ID, antenna placement, BCH (notification channel) bandwidth, GI (Guard Interval: guard interval, CP: Cyclic Prefix) length, etc.) is placed on the frequency axis in two subs. It is clarified that the point is transmitted by the information of the relative phase difference between the carriers. That is, the cell-specific code does not indicate the absolute phase of each subcarrier, but adopts a method of indicating the relative phase of the paired subcarriers, whereby the cell-specific code is generated. It is simplified, and the information can be notified to the mobile station by associating it with the cell-specific information by using, for example, a GCL code or a Walsh-Hadamard code. If the number of subcarriers is sufficient, all the information necessary for cell identification can be transmitted by SCH.

Further, in the data structure of the synchronous channel (SCH) of the present invention, each of the sector common code and the phase reference code element constituting the cell-specific code has a code common to all cells.

In this way, in order to enable the signal processing (signal processing for detecting the position of the SCH in the received signal) in the first step of the cell search by the cross-correlation method using the replica of the sector-specific code, the SCH The data structure of is devised. Since the SCHs are arranged periodically in one frame period, the position can be detected by the "autocorrelation method" that utilizes the periodicity, but if the "cross-correlation method" that uses the replica code is used, A sharper detection peak is realized, and more accurate SCH timing detection becomes possible. The SCH is constructed by multiplying three types of codes (sector common code, sector-specific code, and cell-specific code). Here, the sector common code is common to all cells, and the code element serving as a phase reference among the cell-specific codes is also common to all cells. Then, the codes that are multiplied by the subcarriers whose phase reference code elements are multiplied are (sector-specific code common to all cells), (sector-specific code), and (cell-specific code common to all cells). In effect, (a code common to all cells) is multiplied by (sector-specific code). That is, with respect to the subcarrier to which the code element serving as the phase reference is multiplied, although three types of codes are multiplied, two of them are common to all cells. Therefore, the only difference is the sector-specific code. This means that correlation detection using a replica of the sector-specific code is possible. Therefore, the receiving device prepares the time waveform of the replica code of the sector-specific code corresponding to each sector, and multiplies the received signal (signal before FFT) by the time waveform of the replica code to detect the correlation peak. By doing so, the position of the SCH in the received signal can be detected with high accuracy. Therefore, subsequent sector identification and cell identification can be performed more efficiently. However, even if the SCH structure as described above is adopted, the SCHs are still arranged periodically during one frame period, so the autocorrelation method (that is, the received signal is set for a predetermined period).

Further, in the data structure of the synchronous channel (SCH) of the present invention, the sector-specific code is a set of 2 m (m is a natural number of 2 or more) code elements, and the set of code elements is on the frequency axis. The 2m code elements are composed of repeatedly assigned to the subcarriers of the above, and the 2m code elements are a set of m code elements orthogonal to each sector according to claim 2 or 3. M pieces of the 2m code elements, which are configured by preparing sets and assigning each set to subcarriers so as to be adjacent on the frequency axis and which is a constituent unit of the sector-specific code, are half. Each of the code elements of is multiplied by a code element constituting the cell-specific code, which has the same value as the code element and indicates a relative phase difference with respect to each of the other half m code elements. There is.

If SCH is used only for sector identification, as described above, it is sufficient to repeatedly arrange orthogonal codes having m code elements as constituent units on the frequency axis, but further, when cell-specific information is also transmitted. , The conditions become stricter. That is, in order to superimpose and transmit both sector-specific information and cell-specific information to the SCH, it is a condition that the sector-specific information and cell-specific information do not adversely affect each other, and each information is independent. It is also important to be able to restore to (that is, by parallel processing) in order to reduce the processing time. In order to satisfy these conditions, here, two sets of m code elements, which are constituent units of the orthogonal code for sector identification, are prepared, and they are superposed in two stages on the frequency axis to be 2 m. Each code element is used as a new building unit, and this is repeatedly arranged on the frequency axis. The m code elements are used to identify the sector. The remaining m sign elements are used to multiply the cell-specific sign. Since the cell-specific code indicates the relative phase difference of the pair of subcarriers as described above, each of the remaining m code elements has each of the other m code elements having the same value (that is,). A sign indicating the phase difference is multiplied for each of the sign elements of the sector-specific sign. For example, the orthogonal code for sector identification consisting of the code elements of (m1, m2, m3) is superposed on the frequency axis in two stages, and the code is repeatedly arranged from the low frequency side to the high frequency side in this unit. Consider the case of formation. For example, the code M1 = (m1, m2, m3, "m1", "m2", "m3" ...). "" Is added to distinguish between sign elements with the same value. Then, "m1" is multiplied by the sign "c1" indicating the phase difference for m1 having the same value on the low frequency side, and "m2" and "m3" are also for m2 and m3 on the low frequency side, respectively. Multiply the signs "c2" and "c3" that indicate the phase difference.

As a result, the sector and cell identification code M1 becomes M1 = (m1, m2, m3, m1, c1, m2, c2, m3, c3 ...). As described above, since (m1, m2, m3) are orthogonal between sectors, sector-specific codes can be distinguished and extracted by complex conjugate multiplication and correlation detection. Also, for example, for "m1 and c1", if the complex conjugate of m1 (the sign multiplied by the subcarrier that serves as the phase reference) is multiplied, m1 becomes invisible and "c1" with cell-specific information is obtained. It can be retrieved, and c2 and c3 can be retrieved as well. Thus, basically, by detecting the phase difference of the other subcarrier with respect to the phase reference subcarrier, the cell conjugate code (Cn) (However, in order to improve the demodulation accuracy, it is desirable to take the mutual correlation with the candidate cell-specific sign Cn). Sector identification by inverse diffusion and correlation detection using sector-specific codes (m1, m2, m3) and demodulation processing of cell-specific information Cn (c1, c2, c3 ...) by multiplication of complex conjugates are independent of each other. Can be implemented (in parallel). Regarding the transmission of cell-specific information, for example, two subcarriers multiplied by the same value "m1" are paired, one is a phase-based subcarrier, and the other subcarrier is cell-specific. assigning a code Cn, as much since it is possible to provide a relative phase difference between the subcarriers phase reference, without interference by the sector specific code, only the cell specific information, the relative between subcarriers It can be transmitted as target phase difference information. Therefore, cell-specific information can be efficiently transmitted.

Further, in the data structure of the synchronous channel (SCH) of the present invention, the sector-specific code is a set of 2 m (m is a natural number of 2 or more) code elements, and the set of code elements is on the frequency axis. The 2m code elements are configured by being repeatedly assigned to subcarriers, and two sets of m code elements that are orthogonal to each sector of the present invention are prepared, and the same value in each code is used. The 2m pieces, which are constituent units of the sector-specific code, are configured by alternately allocating the code elements of each set to subcarriers so that the code elements are arranged adjacent to each other on the frequency axis. Among the code elements, one of the code elements having the same value assigned to adjacent subcarriers on the frequency axis shows the relative phase difference with respect to the code element serving as the phase reference of the other. The sign elements that make up are multiplied.

In the above example, two sets of m code elements (orthogonal codes for sector identification: for example, (m1, m2, m3)) were prepared and they were simply overlapped on the frequency axis. In the present invention, the same code elements of each set are arranged in an intricate form so as to be adjacent to each other on the frequency axis. For example, the code M1 = (m1, m1, m2, m2, m3, m3). Then, one of the code elements having the same value is multiplied by the cell-specific code indicating the relative phase difference. Therefore, the sector and cell identification code is M1 = (m1, m1, c1, m2, m2, c2, m3, m3, c3). Then, sector identification is performed using the odd-numbered code elements (m1, m2, m3), and for each of the even-numbered (m1, c1, m2, c2, m3, c3), the subcarriers of the adjacent phase reference are used. The cell-specific sign (c1, c2, c3 ...) Can be demodulated by multiplying each complex conjugate of m1, m2, m3 multiplied by. The advantage of the present invention is that the code elements having the same value are arranged next to each other in the sector-specific code element sequence before the cell-specific code Cn is multiplied (that is, "m1, m1", "m2, m2", "m3, m3" It is arranged in pairs on the frequency axis. Since the codes with the same value are arranged on the adjacent frequency axes, the transfer function of the propagation path of the subcarrier to which the code is assigned can also be regarded as equivalent (that is, the subcarriers on the frequency axis. If the transfer function of the propagation path of each subcarrier is different due to the difference in the position of, the phase will rotate due to this effect, and this will transmit the cell-specific information due to the relative phase difference between the two subcarriers. This will result in an error, and the demodulation accuracy of cell-specific information may decrease). In the present invention, since the two subcarriers are arranged adjacent to each other on the frequency axis, there is a high probability that the propagation conditions of each subcarrier can be estimated to be the same. Therefore, cell-specific information (that is, the position of the two subcarriers). Phase difference) can be transmitted with higher accuracy.

Further, in the data structure of the synchronous channel (SCH) of the present invention, Sf (Sf is a natural number) subframes are arranged over one frame period in the time axis direction, and a plurality of subchannels are arranged in the frequency axis direction. It is arranged over the entire band, which constitutes a frame in multicarrier communication, and the synchronization channel (SCH) is each of the time periods in which the one frame period is equally divided into Ss (Ss is a divisor of Sf). It is arranged in the last one symbol of, and its synchronization channel (SCH) is periodically arranged on the frequency at predetermined subcarrier intervals. Therefore, the time waveform formed by combining the subcarriers used for sector identification is a time waveform having a periodicity in which a predetermined waveform is repeated within one symbol period, and the periodicity of this time waveform is used. This makes it possible to detect the SCH position by the autocorrelation method.

SCH is assigned to the last (one) symbol of the time period obtained by dividing one frame period equally by a predetermined number, and it is used for sector identification among the subcarriers to which the SCH is assigned. The subcarriers are periodically arranged at predetermined intervals on the frequency axis. According to this arrangement, the time waveform formed by combining the subcarriers due to the frequency relationship of the orthogonal subcarriers in the OFDM communication method, that is, the symmetry in the time direction, is a predetermined waveform within one symbol period. A time waveform having a periodicity in which is repeated (for example, if a predetermined waveform is A, a time waveform in which A is repeated every 1/2 symbol) can be obtained. By using the periodicity of the time waveform, it is possible to detect the SCH position by the autocorrelation method or the cross-correlation method.

Further, in the data structure of the synchronization channel (SCH) of the present invention, a plurality of subframes are arranged over a period of one frame in the time axis direction, and a plurality of subchannels are arranged over the entire band in the frequency axis direction. Then, a frame in the multi-carrier communication is formed by this, and the same synchronization channel is arranged in the predetermined two symbols of the synchronization channel (SCH) in the one frame period. Therefore, the time waveform formed by combining the subcarriers used for sector identification is a time waveform having a periodicity in which the same waveform is repeated every one symbol period in the two symbol period, and this time waveform. It is possible to detect the SCH position by the autocorrelation method by using the periodicity of.

SCH is assigned to two symbols, and among the subcarriers to which SCH is assigned, the subcarriers used for sector identification are periodically arranged at predetermined intervals on the frequency axis. In the case of the present invention, since SCH is assigned over two symbols, as a result, the same time waveform appears for each symbol (for example, if the waveform of one symbol period is C, then in the two symbol period. , The time waveform is such that C is repeated every 1 symbol period). By utilizing the periodicity of the time waveform for each symbol period, it is possible to detect the SCH position by the autocorrelation method. In addition, since SCH can be transmitted using subcarriers of all frequency bands, the code length that can be used for transmission of cell-specific information (relative phase difference information) when different information is transmitted to each symbol. Can be lengthened, and more cell-specific information can be transmitted.

Further, the cell search method of the present invention receives a multi-carrier signal from the multi-carrier transmitter and utilizes the synchronization channel (SCH) of the present invention including cell and sector identification information included in the received signal. A cell search method for identifying sectors and cells, the first step of detecting the synchronization channel (SCH) position in a received signal by the autocorrelation method or the intercorrelation method, and the synchronization arranged on the frequency axis. The synchronization channel (SCH) is assigned in parallel with detecting the sector-specific code that gives the maximum received power and identifying the sector by despreading processing by the sector-specific code of the channel (SCH). The cell-specific code is demodulated by detecting the phase difference between the phase reference subcarrier and the subcarrier corresponding to the subcarrier in which the sign element of the cell-specific code is multiplied. Then, if necessary, a correlation detection process with the cell-specific code to be detected is performed, and this is executed by the second step of detecting the cell-specific code.

As described above, if a predetermined condition is satisfied by superimposing information for identifying a sector and a cell on the downlink SCH of multi-carrier communication (that is, a sufficient number of subcarriers can be obtained, and a pair of subcarriers can be obtained. If the relative phase difference between them can transmit all the required cell-specific information), the cell search, including sector identification, can be completed using only the SCH, without the use of pilot channels. That is, the detection of SCH timing on the time axis (first step) and the information on the frequency axis by the autocorrelation method using the periodicity of SCH or the cross-correlation method using the replica of the sector-specific code. The cell search is completed by the identification of the frame timing based on the identification, the sector ID and the cell ID (second step). Therefore, the search process can be shortened as compared with the conventional three-stage cell search. Further, in this case, backdiffusion and correlation detection using the pilot channel are only required when demodulating the data channel and are not required in the cell search, so that the hardware burden for the correlation calculation by the pilot channel is increased. Reduction (reduction of memory capacity, etc.) can be achieved. Further, since the sector-specific code is superimposed on the SCH, it is possible to obtain the effect of being resistant to interference and fading between sectors in terms of sector identification. However, if the number of subcarriers is not sufficient, the cell ID cannot be directly identified by SCH alone, and the cell ID group information may be detected only. In this case, the process of the third step is performed. As a result, backdiffusion and correlation detection using a pilot channel are performed to identify the cell ID.

Further, in the multi-carrier transmitter of the present invention, an allocation means for allocating a synchronization channel (SCH) having the structure of the present invention on the frequency axis during a frame period and the synchronization channel (SCH) are assigned on the frequency axis. It has a transmitting means including a directional antenna provided for each of a plurality of sectors for transmitting a multi-carrier signal.

This makes it possible to transmit a multicarrier signal in which sector-specific information and cell-specific information are assigned on the frequency axis from the antenna for each sector.

Further, the multi-carrier receiving device of the present invention receives the multi-carrier signal transmitted from the multi-carrier transmitting device of the present invention, and includes a synchronization channel (SCH) included in the received signal and multiplied by a sector-specific code. It is a multi-carrier receiving device that identifies sectors by using it, and detects the synchronization channel (SCH) position in the received signal by utilizing the fact that the synchronization channels (SCH) are periodically arranged on the time axis. Timing detection means for detecting the sector-specific code that gives the maximum received power by back-spreading processing by the sector-specific code multiplied by the synchronization channel (SCH), which is arranged on the frequency axis. Have.

Thereby, the multi-carrier signal can be received and the sector identification process (sector search) by SCH can be performed.

Further, the multi-carrier receiving device of the present invention receives a multi-carrier signal transmitted from the multi-carrier transmitting device, and uses a synchronization channel (SCH) included in the received signal in which a common code is adopted between cells. A multi-carrier receiver that identifies a sector by using the sector-specific code element that is a phase reference of the code elements constituting the cell-specific code and is multiplied by a subcarrier to which the code element is assigned. Code replica The timing detection means for detecting the synchronization channel (SCH) position in the received signal by the mutual correlation method using the time waveform of the code, and the sector-specific of the synchronization channel (SCH) arranged on the frequency axis. It has a sector identification means for detecting a sector-specific code that gives the maximum received power by back-spreading processing by a code.

In the multi-carrier receiving device of the present invention, in the first step of detecting the position of the SCH included in the received signal, a method of multiplying the received signal by the time waveform of the replica code of the sector-specific code to obtain the correlation (cross-correlation method). ) Is adopted. This makes it possible to detect the SCH timing with high accuracy.

Further, in the multi-carrier receiving device of the present invention, in parallel with the detection processing of the sector-specific code by the sector identification means, in the sub-carrier to which the synchronization channel (SCH) is assigned, the sub-carrier serving as the phase reference is used. , The cell-specific code is demodulated by detecting the phase difference between the subcarrier corresponding to this subcarrier and the subcarrier on which the code element of the cell-specific code is multiplied, and if necessary, the cell-specific code to be detected is unique. It further has a cell identification means for performing a correlation detection process with a code, thereby detecting a cell-specific code, and detecting a cell ID or a cell ID group information.

This makes it possible to receive the multicarrier signal and perform a cell search including sector identification by the SCH. If the number of subcarriers is sufficient, the sector ID and cell ID can be identified only by SCH.

Further, in the multi-carrier receiving device of the present invention, when the information specified by the cell identification means is cell ID group information, the cell ID is detected by performing reverse diffusion and correlation detection processing using a pilot channel. Further have means for completing the cell identification process.

If this is not enough subcarriers and the SCH identifies only the cell ID grapes, then the pilot channel backdiffusion and correlation detection will identify the cell IDs and complete the cell search. be able to.

Further, in the data structure of the synchronous channel (SCH) of the present invention, the subcarrier (that is, the subcarrier used for sector identification) to which the code element serving as the phase reference constituting the cell-specific code is multiplied is , Symmetrically arranged on the low frequency side and the high frequency side with respect to the center frequency and at predetermined subcarrier intervals, whereby the subcarriers used for the sector identification are combined and formed. The waveform is a time waveform with a periodicity in which the reference waveform or the inverted waveform of the reference waveform is repeated in 1 / M (M is a natural number of 2 or more) symbol unit within one symbol period, and this time. By using the periodicity of the waveform, it is possible to detect the synchronization channel (SCH) position by the autocorrelation method.

Furthermore, by devising the arrangement of the subcarriers used for sector identification on the frequency axis, it is possible to obtain a characteristic time waveform in 1 / N (N is a natural number of 4 or more) symbol unit. By utilizing the characteristic periodicity of this time waveform, more efficient and highly accurate correlation determination becomes possible. Since simple correlation detection focusing on the periodicity in 1 / N units is sufficient, the configuration of the correlator (sometimes called a matched filter) can be simplified.

Further, in the data structure of the synchronous channel (SCH) of the present invention, the subcarrier used for the sector identification is symmetrical with respect to the low frequency side and the high frequency side with respect to the center frequency, and the center frequency is set to 0. In the case of the second, the second, sixth, tenth, 14th ..., and so on, are placed at positions separated by three subcarriers, thereby being used for the sector identification. The time waveform formed by combining the subcarriers is a time waveform with a periodicity in which the reference waveform and the inverted waveform of the reference waveform are alternately repeated in 1/4 symbol units within one symbol period. It becomes.

Assuming that the reference waveform is B, the reference waveform and the inverted waveform of the reference waveform are alternately repeated in 1/4 symbol units, such as B, -B, B, and -B within one symbol period. A time waveform with periodicity can be obtained. In this case, it is sufficient to detect the special periodicity of the time waveform that is repeated in 1/4 symbol units, so that the configuration of the correlator can be simplified.

Further, in the data structure of the synchronous channel (SCH) of the present invention, the subcarrier used for the sector identification is symmetrical with respect to the low frequency side and the high frequency side with respect to the center frequency, and the center frequency is set to 0. In the case of the second, the fourth, eighth, twelfth, 16th ..., and so on, are arranged at positions separated by three subcarriers, thereby being used for the sector identification. The time waveform formed by combining the subcarriers is a time waveform having a periodicity in which the same reference waveform is repeated in 1/4 symbol units within one symbol period.

Assuming that the reference waveform is D, a time waveform having a periodicity in which the same reference waveform is repeated, such as D, D, D, and D, can be obtained in 1/4 symbol units within one symbol period. In this case as well, the configuration of the correlator can be simplified.

Further, in the data structure of the synchronous channel (SCH) of the present invention, each of the sector common code and the phase reference code element constituting the cell-specific code is a code common to all cells, and the above-mentioned The code elements of the sector common code are common to the subcarriers to which the synchronization channel (SCH) on the frequency axis is assigned, and the code element that serves as the phase reference that constitutes the cell-specific code is also the phase on the frequency axis. A code element that is common to the reference subcarriers and is the target of despreading when the sector-specific code that gives the maximum received power is detected and the sector is identified by the despreading process using the sector-specific code. It is not necessary that the subcarriers for obtaining the above are limited to a set of adjacent subcarriers.

When the first step of cell search (SCH position detection process) is performed by cross-correlation, the sub-phase reference code of the sector common code common to all cells and the sector-specific code common to all cells. The code element to be multiplied by the carrier is shared among the subcarriers on the frequency axis (that is, they are all the same), and the simplest code structure is adopted. Thereby, the sector-specific code can be specified by selecting one of the total subcarriers. Therefore, the condition that the subcarriers for obtaining the code element to be despread is limited to a set of adjacent subcarriers becomes unnecessary.

Further, in the cell search method of the present invention, the first step of detecting the position of the synchronization channel (SCH) in the received signal and the code element of the sector-specific code are assigned by the autocorrelation method or the cross-correlation method. The highest correlation value is detected by the cross-correlation method by utilizing the fact that the time waveform formed by combining the subcarriers that serve as the phase reference becomes a characteristic waveform corresponding to the assigned code element. The sector showing the correlation value is identified as the nearest sector, and in parallel with this, the subcarrier serving as the phase reference in the subcarrier to which the synchronization channel (SCH) is assigned and the subcarrier corresponding to this subcarrier. , The cell-specific code is demolished by detecting the phase difference between the subcarrier and the subcarrier on which the code element of the cell-specific code is multiplied, and if necessary, the correlation detection process with the cell-specific code to be detected is performed. Includes a second step, in which the cell unique code is detected.

In the cell search method, it has been clarified that sector identification can be performed not by the correlation value peak determination by the back diffusion after the FFT processing but also by the cross-correlation of the time waveform before the FFT. That is, before the FFT processing, the cross-correlation peak is detected using the replica time waveform of the sector-specific code, and the code that gives the maximum peak is specified, so that the nearest sector can be identified. In order to apply the cross-correlation method using this replica time waveform, it is a condition that the mobile station knows various sector-specific codes transmitted from the base station. As the sector identification method, whether to use the method of detecting the correlation by backdiffusion by the orthogonal code or the method of detecting the cross-correlation by the replica time waveform takes into consideration the required detection accuracy and restrictions on the circuit. , Can be determined as appropriate.

10 MAC section 12 SCH data generation section 14 Transmission data output section 16 Transmission circuit control section 20 (20a ~ 20b) Physical layer section 22 (22a ~ 22c) Reception circuit section 24 (24a ~ 24c) Transmission circuit section 26 (26a ~ 26c) ) Analog circuit section 28 (28a ~ 28c) Antenna section 210 Sector specific code identification despread section 220 Sector power determination section 230 SCH data (including cell specific information) Demodition section 400 Shift register 402 Adder 404 Multiplier CL1 ~ CL3 cell SC1 ~ SC3 sector