Method for generating downlink frame, and method for searching cell

ES 2 380 065 T3

DESCRIPTION

Procedure for generating downlink frame, and procedure for cell search

Technical field

The present invention relates to a method of generating a downlink frame and a method of searching for cells. More particularly, the present invention relates to a method of generating a downlink frame and a method of searching for cells using the downlink frame in an orthogonal frequency division multiplexing (OFDM) based cellular system.

Previous technique

In a direct sequence code division multiple access (DS-CDMA) system, a sequence hopping procedure is applied to a pilot channel so that unique cell identification and cell synchronization information is acquired. According to the sequence hopping method, a mobile station easily performs a cell search without a spacing sync channel by introducing sequence hopping technology on the pilot channel. However, in the OFDM system, a series of channels that are capable of being differentiated by a frequency domain in a symbol duration of a time domain are greater than those that are capable of being differentiated by a CDMA spread in symbol duration. of a time domain. Consequently, when only the time domain is used, resources can be wasted in terms of capacity. For this reason, it is ineffective to apply the sequence hopping procedure directly to the time domain of the pilot channel in the OFDM-based system. Therefore, it is preferable to search the cell using effectively the received signals in the time domain and frequency domain .

An example of an existing technology for searching for a cell in the OFDM system includes a procedure that assigns synchronization information and cell information by dividing a frame into four time blocks. For the procedure described above, two frame structures have been proposed. In a first frame structure, synchronization identification information, cell group identification information, and unique cell identification information are assigned for four time blocks, respectively. In a second frame structure, the synchronization identification information and the unique cell identification information are assigned to a first time block and a third time block, and the synchronization identification information and the group identification information of cells are assigned to a second time block and a fourth time block.

According to the first frame structure, since the symbol synchronization is acquired only in the first time block, it is impossible for the mobile station to perform a fast synchronization acquisition in the prescribed 5 ms during activation or handover between heterogeneous networks. In addition, it is difficult to acquire gain diversity by accumulating timing identification information so that fast timing acquisition is performed.

According to the second frame structure, the unique cell identification information or the cell group identification information is correlated with the synchronization acquisition. Therefore, a cell search procedure is complex and a quick cell search is difficult.

By way of example of another cell search technology, a cell search and synchronization acquisition method using a separate preamble has been proposed. However, this procedure cannot be applied to a system where there is no preamble. On the other hand, the preamble is arranged in the front part of the frame. Consequently, in a case where the mobile station wanted to acquire synchronization at a time location that is not at the beginning of the frame, there would be a problem that it would have to wait for the next frame. In particular, the mobile station should acquire the initial symbol synchronization in 5 msec during the handover between a GSM mode, a WCDMA mode and a 3GPP LTE mode, but can acquire the synchronization by one frame unit. For this reason, in some cases, the mobile station cannot acquire the initial symbol timing in 5 msec.

As an example of another cell search technology, there is a cell search procedure by assigning two short sequences to a secondary sync channel and matching the cell ID information to a combination of two short sequences. According to this procedure, since interference occurs between cells when the same short sequence is assigned to sectors adjacent to each other, there is a problem that the performance of the cell search is reduced.

This problem was addressed in ZTE: "Randomization Procedure for S-SCH", Draft 3GPP R1-072910, in which a randomization procedure was proposed that used two short sequences for the secondary sync channel based on Fourier series sequences . Furthermore, two of the randomization procedures for two short sequences were evaluated at Motorola: "Randomization procedure for two S-SCH short codes", 3GPP Draft R1-072661.

ES 2 380 065 T3

DETAILED DESCRIPTION

Technical problem

The present invention has been prepared in an effort to provide a method of generating a downlink frame that is capable of averaging the interference between sectors and an efficient method of searching for cells by receiving the downlink frame.

Technical solution

An illustrative embodiment of the present invention provides a method of generating a downlink frame, including: generating a first short sequence and a second short sequence indicating cell group information; generating a first scrambling sequence and a second scrambling sequence determined by the primary sync signal; generation of a third randomization sequence determined by a group of short sequences - a wireless communication system uses a plurality of short sequences and the plurality of short sequences are grouped into a plurality of groups of short sequence - to which the first is assigned short sequence; scrambling the first short sequence with the first scrambling sequence and scrambling the second short sequence with the second scrambling sequence and the third scrambling sequence; and mapping of the secondary sync signal including the first scrambled short sequence and the second scrambled short sequence to a frequency domain.

Another illustrative embodiment of the present invention provides a method of generating a downlink frame, including: generating a first short sequence and a second short sequence indicating cell group information; generating a first scrambling sequence and a second scrambling sequence determined by the primary sync signal; generation of a third randomization sequence determined by a group of short sequences - a wireless communication system uses a plurality of short sequences and the plurality of short sequences is grouped into a plurality of short sequence groups - to which the first is assigned short sequence and a fourth randomization sequence determined by a group of short sequences to which the second short sequence is assigned; scrambling the first short sequence with the first scrambling sequence and scrambling the second short sequence with the second scrambling sequence and the third scrambling sequence; scrambling the second short sequence with the first scrambling sequence and scrambling the first short sequence with the second scrambling sequence and the fourth scrambling sequence; and correspondence of the secondary sync signal including the first short scrambled sequence with the first scrambled sequence, the second short scrambled sequence with the second scrambled sequence, and the third scrambled sequence, the second short sequence randomized with the first sequence of randomization and the first short sequence randomized with the second sequence of randomization and the fourth sequence of randomization to a frequency domain.

Yet another embodiment of the present invention provides an apparatus for generating a downlink frame including: a sequence generating unit that generates a first short sequence and a second short sequence indicating cell group information, a first scrambling sequence, and a second scrambling sequence determined by the primary sync signal, and a third randomization sequence determined by a group of short sequences - the wireless communication system uses a plurality of short sequences and the plurality of short sequences are grouped into a plurality of groups of short sequences - to which the first sequence is assigned short; and a sync signal generation unit that scrambled the first short sequence with the first scramble sequence and scrambled the second short sequence with the second scramble sequence and the third scramble sequence, and then generated a secondary sync signal including the first randomized short sequence and the second randomized short sequence, respectively.

Yet another embodiment of the present invention provides a method of searching for a cell, including: receiving a downlink frame that includes a primary sync signal and a secondary sync signal; and estimating the cell information using the primary sync signal and the secondary sync signal. In this case, in the downlink frame, a first scrambled short sequence with a first scramble sequence and a second scrambled short sequence with a second scramble sequence and a third scramble sequence are alternately arranged in a plurality of subcarriers, and the first short sequence and the second short sequence indicate cell group information, the first scrambling sequence and the second scrambling sequence are determined by the primary sync signal, and the third scrambling sequence is determined by a group of short sequences - a wireless communication system uses a plurality of short sequences and the plurality of Short sequences are grouped into a plurality of groups of short sequences - to which the first short sequence is assigned.

ES 2 380 065 T3

Yet another embodiment of the present invention provides an apparatus for searching a cell, including: a receiving unit that receives a downlink frame including a primary sync signal and a secondary sync signal; a cell group estimation unit identifying a cell group information using the secondary synchronization signal; and a cell estimation unit that identifies a cell in the group of cells using the primary synchronization signal. In this case, in the downlink frame, a first scrambled short sequence with a first scramble sequence and a second scrambled short sequence with a second scramble sequence and a third scramble sequence are alternately arranged in a plurality of subcarriers, and the first short sequence and the second short sequence indicate cell group information, the first scrambling sequence and the second scrambling sequence are determined by the primary sync signal, and the third scrambling sequence is determined by a group of short sequences - the wireless communication system uses a plurality of short sequences and the plurality of Short sequences are grouped into a plurality of groups of short sequences - to which the first short sequence is assigned.

Yet another embodiment of the present invention provides a recording medium that records a program for executing the downlink frame generation procedure. The recording medium records a program including: generating a first short sequence and a second short sequence indicating cell group information; generating a first scrambling sequence and a second scrambling sequence determined by the primary sync signal; generation of a third randomization sequence determined by a group of short sequences - the wireless communication system uses a plurality of short sequences and the plurality of short sequences are grouped into a plurality of groups of short sequences - to which the first is assigned short sequence; scrambling the first short sequence with the first scrambling sequence and scrambling the second short sequence with the second scrambling sequence and the third scrambling sequence; and mapping of the secondary sync signal including the first scrambled short sequence and the second scrambled short sequence to a frequency domain.

Yet another embodiment of the present invention provides a recording medium that records a program for executing the downlink frame generation procedure. The recording medium records a program including: generating a first short sequence and a second short sequence indicating cell group information; generating a first scrambling sequence and a second scrambling sequence determined by the primary sync signal; generation of a third randomization sequence determined by a group of short sequences - the wireless communication system uses a plurality of short sequences and the plurality of short sequences are grouped into a plurality of groups of short sequences - to which the first is assigned short sequence and a fourth randomization sequence determined by a group of short sequences to which the second short sequence is assigned; scrambling the first short sequence with the first scrambling sequence and scrambling the second short sequence with the second scrambling sequence and the third scrambling sequence; scrambling the second short sequence with the first scrambling sequence and scrambling the first short sequence with the second scrambling sequence and the fourth scrambling sequence; and correspondence of the secondary sync signal including the first short scrambled sequence with the first scrambled sequence, the second short scrambled sequence with the second scrambled sequence, and the third scrambled sequence, the second short sequence randomized with the first sequence of randomization and the first short sequence randomized with the second sequence of randomization and the fourth sequence of randomization to a frequency domain.

Advantageous effects

According to the present invention mentioned above, the interference between sectors can be reduced by scrambling the short sequences due to the scrambling sequences, thereby improving the cell search performance.

Brief description of the drawings

FIG. 1 is a diagram illustrating a downlink frame in an OFDM system in accordance with an illustrative embodiment of the present invention;

fig. 2 is a diagram illustrating a configuration of a secondary sync channel when mapping between two sequences and a frequency domain in a localization manner;

fig. 3 is a diagram illustrating a configuration of a secondary sync channel when two sequences and a frequency domain are mapped in a distribution fashion;

fig. 4 is a block diagram of an apparatus for generating a downlink frame in accordance with the illustrative embodiment of the present invention;

ES 2 380 065 T3 FIG. 5 is a flow chart illustrating a method of generating a downlink frame in accordance with the illustrative embodiment of the present invention;

fig. 6 is a diagram illustrating a first method of generating a secondary sync signal in accordance with the illustrative embodiment of the present invention;

FIG. 7 is a diagram illustrating a second method of generating a secondary sync signal in accordance with the illustrative embodiment of the present invention;

fig. 8 is a diagram illustrating a third method of generating a secondary sync signal in accordance with the illustrative embodiment of the present invention.

fig. 9 is a block diagram of a cell search apparatus in accordance with an illustrative embodiment of the present invention;

fig. 10 is a flow chart illustrating a cell search procedure in accordance with a first illustrative embodiment of the present invention;

fig. 11 is a flow chart illustrating a cell search procedure in accordance with a second illustrative embodiment of the present invention.

Best mode

In the following detailed description, only some illustrative embodiments of the present invention have been shown and described, purely by way of illustration. As those skilled in the art will understand, the described embodiments can be modified in several different ways, always without departing from the scope of the present invention. Furthermore, parts that are irrelevant to the description of the present invention are omitted from the drawings to clarify the present invention. Like reference numerals designate like elements throughout the specification.

Throughout the specification, unless explicitly stated otherwise, the term "comprise" and its variants as "comprises" or "comprising" shall be understood to imply the inclusion of the stated elements but not the exclusion of any other element. Furthermore, the term unit described in the specification means a unit for processing at least one function and operation, and it can be implemented by hardware components or software components and combinations thereof.

First of all, referring to figs. 1 to 3, a downlink frame of an OFDM system and a configuration of a synchronization channel according to an illustrative embodiment of the present invention will be described.

Fig. 1 is a diagram illustrating a downlink frame of an OFDM system in accordance with an illustrative embodiment of the present invention. In fig. 1, the horizontal axis represents a time axis and the vertical axis represents a frequency axis or subcarrier axis.

As shown in fig. 1, a downlink frame 110 according to the illustrative embodiment of the present invention has a time duration of 10 msec and includes ten subframes 120. Each subframe 120 has a time duration of 1 msec and includes two intervals 130. Each interval 130 includes six or seven OFDM symbols. The length of a cyclic prefix in a case where an interval includes six symbols is greater than that of a cyclic prefix in a case where an interval includes seven symbols.

As shown in fig. 1, the downlink frame 110 according to the illustrative embodiment of the present invention includes two synchronization durations 140 in total, including synchronization durations 140 in slot # 0 and slot # 10, respectively. However, it is not necessarily limited to this. The downlink frame 110 can include one synchronization duration in any interval, and can include one synchronization duration or three or more synchronization durations. Since the length in the cyclic prefix can be different in each interval, it is preferable that the synchronization duration is at the end of the interval.

Each interval includes a pilot duration.

The synchronization duration according to the illustrative embodiment of the present invention includes a primary synchronization channel and a secondary synchronization channel, and the primary synchronization channel and the secondary synchronization channel are arranged to be adjacent to each other with respect to at the time. As shown in fig. 1, the primary sync channel is located at the end of the interval, and the secondary sync channel is located just ahead of the primary sync channel.

The primary sync channel includes a primary sync signal that has information for

ES 2 380 065 T3 identify symbol synchronization and frequency synchronization, and some information for cell identification (ID). The secondary sync channel includes a secondary sync signal having residual cell ID information, and information to identify the frame sync. A mobile station identifies the cell ID of the cell by combining the cell ID information of the primary sync channel and the cell ID information of the secondary sync channel.

For example, assuming the total number of cell IDs is 510, if three identification sequences are assigned to the primary sync channel to divide the 510 cell IDs into three groups, and if 170 sequences are assigned to the secondary sync channel (3 x 170 = 510), it is possible to represent the information in the 510 cell IDs.

Another method is that the 510 cell IDs are divided into 170 groups using 170 secondary sync signals that are assigned to the secondary sync channel, and the information about cell IDs in each group of cells can be represented by three primary sync signals that they are assigned to the primary sync channel.

Since the secondary sync channel includes the information for identifying the frame sync as well as the information for the cell ID, two secondary sync channels included in a frame are different from each other.

Fig. 2 is a diagram illustrating a configuration of a secondary sync channel when mapping between two short sequences and a frequency domain in a localization manner, and FIG. 3 is a diagram illustrating a configuration of a secondary sync channel when two short sequences are mapped to a frequency domain in a distribution pattern.

With reference to fig. 2 and fig. 3, a secondary sync signal, which is input to a secondary sync channel, according to an illustrative embodiment of the present invention is formed by combining two short sequences. A correspondence is established between the cell group information and the frame synchronization information and the two short sequences.

As shown in fig. 2, a first short sequence can be assigned locally to subcarriers, and then the second short sequence can be assigned locally to the remaining subcarriers. Furthermore, as shown in FIG. 3, the first short sequence can be assigned to all even-numbered subcarriers (n = 0, 2, 4, ···, 60), and the second short sequence can be assigned to all odd-numbered subcarriers (n = 1, 3, 6, ···, 61).

The length of the short sequence corresponds to half the number of subcarriers assigned to the secondary sync channel. That is, the number of short sequence elements that can be generated is up to half the number of subcarriers assigned to the secondary sync channel. For example, when the number of subcarriers assigned to the secondary sync channel is 62, the length of the short sequence corresponds to 31 and the number of short sequence elements that can be generated is up to 31.

Since two short sequences are assigned to each secondary sync channel, the number of secondary sync sequences generated by a combination of two short sequences is maximum 961 (= 31 x 31). However, since the information to be included in the secondary sync channel is cell group information and frame boundary information, 170 or 340 (= 170 x 2) secondary sync sequences are required. Consequently, the number 961 is a large enough value compared to the number 170 or 340.

An apparatus for generating a downlink frame according to an illustrative embodiment of the present invention will now be described with reference to FIG. 4. fig. 4 is a block diagram of the downlink frame generation apparatus according to the illustrative embodiment of the present invention.

As shown in fig. 4, the downlink frame generation apparatus according to the illustrative embodiment of the present invention includes a sequence generation unit 410, a synchronization signal generation unit 420, a frequency matching unit 430 and a OFDM transmission unit 440.

The sequence generation unit 410 generates a sequence to acquire time and frequency synchronization, a cell identification sequence, a plurality of short sequences, and a scrambling sequence to reduce interference from adjacent cells, respectively, and transmits them to the synchronization signal generating unit 420.

The timing signal generating unit 420 generates a primary timing signal, a secondary timing signal, and a pilot pattern using sequences received from the sequence generating unit 410.

ES 2 380 065 T3

The synchronization signal generation unit 420 generates the primary synchronization signal using the sequence to acquire time and frequency synchronization and the cell identification sequence. In addition, the synchronization signal generation unit 420 generates the synchronization signal. secondary using the plurality of short sequences and scrambling sequences to reduce interference from adjacent cells.

The sync signal generation unit 420 generates the pilot pattern of downlink signals by assigning a unique assigned scrambling sequence to each cell to encode a common pilot symbol and a cellular system data symbol to the pilot channel.

The frequency mapping unit 430 generates the downlink frame by mapping the primary sync signal, the secondary sync signal, and the pilot pattern that are generated from the sync signal generation unit 420 and information of frame control transmission traffic data that is transmitted from external sources to the time and frequency domains.

The OFDM transmission unit 440 receives the downlink frame from the frequency matching unit 430 and transmits the downlink frame through a given transmitting antenna.

With reference to fig. 5 to fig. 8, a method of generating a downlink frame according to an illustrative embodiment of the present invention will be described. Fig. 5 is a flow chart illustrating the downlink frame generation procedure in accordance with the illustrative embodiment of the present invention.

As shown in fig. 5, the sequence generation unit 410 generates a plurality of short sequences and a plurality of scrambling sequences to reduce interference from a plurality of adjacent cells and transmits them to the synchronization signal generation unit 420 (S510).

The timing signal generating unit 420 generates a secondary timing signal using the short sequences and the scrambling sequences to reduce interference from the plurality of adjacent cells received from the sequence generating unit 410 (S520). In the illustrative embodiment of the present invention, a frame is described as including two secondary sync channels. However, it is not limited to this.

With reference to fig. 6 to fig. 8, three different methods of generating a secondary sync signal in accordance with an illustrative embodiment of the present invention will be described. Fig. 6 is a diagram illustrating the first method of generating a secondary sync signal in accordance with the illustrative embodiment of the present invention, fig. 7 is a diagram illustrating the second method of generating a secondary sync signal in accordance with the illustrative embodiment of the present invention, and FIG. 8 is a diagram illustrating the third method of generating a secondary sync signal in accordance with the illustrative embodiment of the present invention.

A short sequence (wn) is a binary sequence (or binary code) that represents cell group information. That is, the short sequence (wn) is the binary sequence assigned to a cell group number and frame synchronization. On the other hand, the length of the short sequence corresponds to half the number of subcarriers assigned to the secondary synchronization channel. In the illustrative embodiment of the present invention, the number of subcarriers assigned to the secondary sync channel is described as 62. However, it is not limited to this. Consequently, the length of the short sequence according to the illustrative embodiment of the present invention is 31.

The first short sequence w0 is assigned to even-numbered subcarriers of the first secondary sync channel and is defined as indicated in Equation 1.

(Equation 1) w0 = [w0 (0), w0 (1), ..., w0 (k), ..., w0 (30)]

In this case, k denotes an index of the even-numbered subcarriers used for a secondary sync channel.

The second short sequence w1 is assigned to odd-numbered subcarriers of the first secondary sync channel and is defined as indicated in Equation 2.

(Equation 2) w1 = [w1 (0), w1 (1), ..., w1 (m), ..., w1 (30)]

In this case, m denotes an index of the odd-numbered subcarriers used for the secondary sync channel.

ES 2 380 065 T3

The third short sequence w2 is assigned to even-numbered subcarriers of the second secondary sync channel and is defined as indicated in Equation 3.

(Equation 3) w2 = [w2 (0), w2 (1), ..., w2 (k), ..., w2 (30)]

The fourth short sequence w3 is assigned to the odd-numbered subcarriers of the second secondary sync channel and is defined as indicated in Equation 4.

(Equation 4) w3 = [w3 (0), w3 (1), ..., w3 (m), ..., w3 (30)]

In this case, the short sequences w0, w1, w2, and w3 can be different sequences. Furthermore, the relationship between the short sequences w0, w1, w2, and w3 can be represented as w0 = w3 and w1 = w2 (or w0 = w2 and w1 = w3). Since w0 = w3 and w1 = w2, then the pattern of short sequences assigned to the second secondary sync channel can be determined only through the pattern of short sequences assigned to the first secondary sync channel. Consequently, by storing only 170 secondary sync sequences generated by a combination of two short sequences assigned to the first secondary sync channel, a mobile station can reduce the complexity required to obtain cell group information and cell boundary information. plot.

According to the first method of generating a secondary synchronization signal as shown in fig. 6, the first short sequence is assigned to all the even-numbered subcarriers of the first secondary synchronization channel and the second short sequence is assigned to all the odd-numbered subcarriers of the first secondary synchronization channel. Furthermore, the third short sequence is assigned to all the even-numbered subcarriers of the second secondary synchronization channel and the fourth short sequence is assigned to all the odd-numbered subcarriers of the second secondary synchronization channel.

According to the first method of generating the secondary synchronization signal, the secondary synchronization signal is formed by a combination of two short sequences having the length of 31. Consequently, the number of secondary synchronization signals is 961 which is a value large enough compared to the number 170 or 340.

According to the second method of generating the secondary synchronization signal shown in FIG. 7, a first sequence determined by Equation 5 is assigned to all the even-numbered subcarriers of the first secondary synchronization channel (interval 0), and a second sequence determined by Equation 6 is assigned to all the odd-numbered subcarriers of the first secondary sync channel (slot 0). Furthermore, a third sequence determined by Equation 7 is assigned to all the even-numbered subcarriers of the second secondary sync channel (slot 10), and a fourth sequence determined by Equation 8 is assigned to all odd-numbered subcarriers of the second secondary sync channel (slot 10).

A randomization sequence P, 0,1 that randomizes the first short sequence w0 is defined by P, 0,1 = [P, o, i (0), P, o, i (1), ·· ·, P¡, or,₁(k), ···, P¡, o, i (30)], where j (j = 0, 1, 2) is the number of the cell identification sequence assigned to the primary synchronization channel. Consequently, the scrambling sequence Pi, 0.1 is determined by the primary sync signal. The scrambling sequence Pi, 0.1 is a known value when a sequence is unmapped to find a group of cell IDs and a frame boundary at the mobile station.

As indicated in Equation 5, each element of a first sequence c0 according to the second procedure for generating the secondary synchronization signal is a product of each element of the first short sequence w0 and each element of the scrambling sequence P, 0.1 corresponding to it.

(Equation 5) c0 = [w0 (0) P¡, 0,1 (0), w0 (1) P¡, 0,1 (1), ..., w0 (k) P¡, 0,1 ( k), ..., w0 (30) P, 0,1 (30)]

In this case, k denotes an index of the even-numbered subcarriers used for the secondary sync channel.

The randomization sequence that randomizes the second short sequence w1 is Pi, 1,1 and Sw0.

The randomization sequence P, 1,1 is Pj. 1,1 = [Pj, 1,1 (0), Pj, 1,1 (1), ···, Pj, 1,1 (m), · ··, Pj, 1,1 (30)], where j (¡= 0, 1, 2) is the number of the cell identification sequence assigned to the primary sync channel. Consequently, the scrambling sequence Pj, 1,1 is determined by the primary sync signal. Furthermore, the randomization sequence Pj, 1,1 may be the same as the randomization sequence Pj, 0.1 or it may be different from the randomization sequence Pj, 0.1. When the randomization sequence Pj, 1,1 is different from the sequence of

ES 2 380 065 T3 scrambling Pi, 0.1, it may be possible to reduce the interference.

The scrambling sequence Pj, 1,1 is a previously known value when unmapping a sequence to find a group of cell IDs and a frame boundary at the mobile station.

Also, the randomization sequence Sw0 is Sw = [Swü (0), Sw0 (1), ···, Swü (m), ···, Sw0 (30)], and the randomization sequence Sw0 is determined by the first short sequence w0.

At this time, a plurality of short sequences are grouped into a plurality of groups of short sequences and S ,,_: can be determined by a group of short sequences to which the first short sequence is assigned by grouping short sequences.

For example, according to the illustrative embodiment of the present invention, since the length of the first short sequence is 31, there are 31 short sequences. Consequently, short sequences No. 0-7 are assigned to group 0, short sequences No. 8-15 to group 1, short sequences No. 16-23 to group 2 and short sequences No. 24-30 to Group 3. Consequently Sw0 is determined by the correspondence of a scrambling code of length 31 to the group to which the number of the first short sequence is assigned.

Furthermore, the 31 short sequences can be classified into eight groups by grouping the numbers from the first short sequences that have the identical remainder by dividing each number of short sequences by 8. That is, they are assigned: the short sequence number having remainder 0 by dividing the short sequence numbers by 8 to group 0, the short sequence having remainder 1 by dividing the short sequence numbers by 8 to group 1, the short sequence having the remainder 2 when dividing short sequence numbers by 8 to group 2, the short sequence having remainder 3 when dividing short sequence numbers by 8 to group 3, the short sequence having remainder 4 by dividing the short sequence numbers by 8 to group 4, the short sequence having remainder 5 by dividing the short sequence numbers by 8 to group 5, the short sequence having remainder 6 by dividing the short sequence numbers by 8 to group 6 and the short sequence having remainder 7 by dividing the short sequence numbers by 8 to group 7. Consequently Sw0 is determined by the correspondence of a scrambling code of length 31 to the group to which the number of the first short sequence is assigned.

As indicated in Equation 6, each element of a second sequence c according to the second procedure for generating the secondary synchronization signal is a product of each element of the second short sequence w1 and each element of the scrambling sequences Pj, 1 , 1 and Sw0 corresponding to it.

(Equation 6) c = [w1 (0) Swc (0) Pj, 1,1 (0), w1 (1) Swc (1) Pj, 1,1 (1), ···, w1 (m) Swc (m) Pj,₁,₁(m), ..., w1 (30) Swc (30) Pj, 1,1 (30)]

In the present specification, m denotes the index of odd-numbered subcarriers used for the secondary sync channel.

A randomization sequence Pj, 0.2 to randomize a third short sequence w2 is Pj, 0.2 = [Pj, 0.2 (0), Pj, 0.2 (0), ···, Pj, 0, 2 (k) ···, Pj, 0,2 (30)], where j (j = 0, 1, 2) is the number of the cell identification sequence assigned to the primary sync channel. Consequently, the scrambling sequence Pj, 0.2 is determined by the primary sync signal. Furthermore, the scrambling sequence Pj, 0.2 is a previously known value when the sequence is unmapped to find the group of cell IDs and the frame boundary at the mobile station.

As indicated in Equation 7, each element of a third sequence c2 according to the second procedure for generating the secondary synchronization signal is a product of each element of the third short sequence w2 and each element of the scrambling sequence Pj, 0 , 2 corresponding to it.

(Equation 7) c2 = [w2 (0) Pj, 0,2 (0), w2 (1) Pj, 0,2 (1), ..., w2 (k) Pj, 0,2 (k), ..., w2 (30) Pj, 0.2 (30)]

In the present specification, k denotes the index of even-numbered subcarriers used for the secondary sync channel.

The scrambling sequences to randomize a short fourth sequence are Pj, 1,2 and Sw2,

The randomization sequence Pj, 1,2 is Pj, 12 = [Pj, 1,2 (0), Pj, 1,2 (1), ···, Pj, 1,2 (m), ···, Pj, 1,2 (30)], yj (j = 0, 1, 2) is the number of the cell identification sequence assigned to the primary synchronization channel. Consequently, the scrambling sequence Pj, 1,2 is determined by the primary sync signal. The scrambling sequence Pj, 1,2 is a previously known value when a sequence is unmapped to find the group of cell IDs and the frame boundary at the mobile station.

Also, the randomization sequence Sw2 is Sw2 = [Sw2 (0), Sw2 (1), Sw2 (m), ···, Sw2 (30)], and the randomization sequence Sw2 is determined by the third short sequence w2 .

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At that time, Sw2 can be determined by a group of short sequences to which the third short sequence is assigned by grouping short sequences.

For example, according to the illustrative embodiment of the present invention, since the length of the third short sequence is also 31, there are 31 short sequences. Consequently, short sequences No. 0-7 are assigned to group 0, short sequences No. 8-15 to group 1, short sequences No. 16-23 to group 2, and short sequences No. 24-30 to group 2. Group 3. Consequently Sw2 is determined by correspondence of a scrambling code of length 31 to the group to which the number of the third short sequence is assigned.

Furthermore, the 31 short sequences can be classified into eight groups by grouping the numbers of the third short sequences that have the identical remainder when dividing each number of short sequences by 8. That is, the short sequence number that has remainder 0 is assigned when dividing the numbers of short sequences by 8 to group 0, the short sequence that has remainder 1 when dividing the numbers of short sequences by 8 to group 1, the short sequence that has remainder 2 when dividing the numbers of short sequences by 8 to group 2, the short sequence that has remainder 3 when dividing numbers of short sequences by 8 to group 3, the short sequence having remainder 4 by dividing the short sequence numbers by 8 to group 4, the short sequence having remainder 5 by dividing the short sequence numbers by 8 to group 5, the short sequence having remainder 6 by dividing the short sequence numbers by 8 to group 6 and the short sequence having remainder 7 by dividing the short sequence numbers by 8 to group 7. Consequently Sw2 is determined by the correspondence of a scrambling code of length 31 to the group to which the third short sequence number is assigned.

As indicated in Equation 8, each element of a fourth sequence c₃ according to the second method of generating the secondary synchronization signal, it is a product of each element of the fourth short sequence w3 and each element of the scrambling sequences Pj, 1,2 and Sw2 corresponding to it.

(Equation 8) c₃ = [w3 (0) Sw₂(0) P¡, 1,2 (0), w3 (1) Sw2 (1) P¡, 1,2 (1), ..., w3 (m) Sw₂(m) P_i,₁, 2 (m), ..., w3 (30) Sw2 (30) P, 1,2 (30)]

In the present specification, m denotes the index of odd-numbered subcarriers used for the secondary sync channel.

Here, the relationship between randomization sequences and short sequences can be stated as Pj, 0.1 = Pj, 0.2, Pj, 1.1 = Pj, 1.2, Pj, 0.1 ϊ Pj, 1, 1, Pj, 0,2 ϊ Pj, 1,2, and w0 ϊ w1 ϊ w2 ϊ w3 (or w0 = w3 and w1 = w2). In this case, the cell group and the frame identification information are mapped to the combination of the first to fourth short sequences, and the number of descrambling hypotheses in the mobile station with respect to the channel scrambling. secondary sync determined by the cell identification sequence number of the primary sync channel is reduced to 3.

Furthermore, the relationship between randomization sequences and short sequences can be stated as P, 0.1 0,1 Pj, 0.2, Pj, 1.1 ϊ Pj, 1.2, Pj, 0.1 ϊ Pj, 1 , 1, Pj, 0.2 ϊ Pj, 1.2, w0 = w2, and w1 = w3. In this case, the cell group information is mapped to the combination of the first short sequence and the second short sequence, and the frame synchronization information is mapped to the scrambling sequences (Pi, 0.1, Pi, 0.2, Pi, 1.1, Pi, 1.2) of the secondary sync channel determined by the cell identification sequence number of the primary sync channel. Next, the number of descrambling hypotheses of the mobile station with respect to the secondary sync channel scrambling determined by the cell identification sequence number of the primary sync channel is increased to 6. However, the number of combination of cell group identification sequences is reduced by half, and the number of hypotheses of descrambling of the mobile station with respect to the randomization determined by the first and third short sequences is also reduced by the half.

As shown in fig. 8, in the third procedure of generating a secondary synchronization signal, a first sequence determined by Equation 9 is assigned to all even-numbered subcarriers of a first secondary synchronization channel, and a second sequence determined by Equation 10 to all odd-numbered subcarriers of the first secondary sync channel. On the other hand, a third sequence determined by Equation 11 is assigned to all the even-numbered subcarriers of a second secondary synchronization channel, and a fourth sequence determined by Equation 12 is assigned to all the odd-numbered subcarriers of the second channel. secondary sync.

That is, according to the second method of generating the secondary synchronization signal, the first short sequence is scrambled with a first scramble sequence having the length of 31, which is determined by the identification sequence of cells assigned to the synchronization channel primary, and the second short sequence is scrambled with a second scramble sequence having the length of 31, which is determined by the cell identification sequence assigned to the primary sync channel. However, according to the third method of generating the secondary synchronization signal, the first short sequence and the second short sequence are scrambled with a scramble sequence having the length of 62, which is determined by the assigned cell identification sequence. to the channel of

ES 2 380 065 T3 primary synchronization.

Pj, 1 is the scrambling sequence that randomizes the first short sequence and the second short sequence, and P, 2 is the scrambling sequence that randomizes the third short sequence and the fourth short sequence. The randomization sequences Pii and Pi2 are represented as Pi1 = [Pji (0), Pii (1), Pii (k) Pii (61)], and Pi2 =

[Pj, 2 (0), P,₂(1 P,₂(k), ..., Pi, 2 (61)]. '... . . .

In this case, ¡(¡= 0, 1, 2) is the number of the cell identification sequence assigned to the primary synchronization channel. Consequently, the scrambling sequences Pi, i and Pi, 2 are determined by the number of the cell identification sequence assigned to the primary synchronization channel.

According to the third method of generating the secondary synchronization signal, the first sequence c₀ is as indicated in Equation 9, the second sequence ci is as indicated in Equation 10, the third sequence c2 is as indicated in Equation 11 and the fourth sequence c3 is as indicated in Equation 12.

(Equation 9) c0 = [w0 (0) Pi, i (0), w0 (1) Pi, i (1), ..., w0 (k) Pi, i (k), ... , w0 (30) P¡, i (30)] (Equation 10) ci = [w1 (0) Sw0 (0) P¡, i (31), ..., w1 (1) Sw0 (1) P¡ , i (32), w1 (m) Sw0 (m) P, i (31 + m), ..., w1 (30) Sw0 (30) P, i (61)] (Equation 11) c2 = w2 (0) P¡, 2 (0), w2 (1) Pi, 2 (1), ..., w2 (k) P¡, 2 (k), ..., w2 (30) P¡, 2 (30)] (Equation 12) c₃ = w3 (0) Sw2 (0) P¡, 2 (31), w3 (1) Sw2 (1) P¡, 2 (32), ..., w3 (m) Sw2 (m) P¡, 2 ( 31 + m), ..., w3 (30) Sw2 (30) P, 2 (61)]

In Equation 9 through Equation 12, k denotes the index of the even-numbered subcarriers that will be used for the secondary sync channel, and m denotes the index of the odd-numbered subcarriers that will be used for the secondary sync channel.

The frequency mapping unit 430 generates the downlink frame by mapping the secondary sync signal that is generated from the sync signal generating unit 420, and transmission traffic data for the time and time domains. S530 frequencies.

OFDM transmission unit 440 receives the downlink frame from frequency matching unit 430 and transmits the downlink frame through a given transmit antenna S540.

A cell search procedure by the mobile station using the downlink frame generated by the illustrative embodiment of the present invention will now be described with reference to FIG. 9 and fig. eleven.

Fig. 9 is a block diagram of a cell search apparatus in accordance with the illustrative embodiment of the present invention, fig. 10 is a flow chart illustrating a cell search procedure according to a first illustrative embodiment of the present invention, and FIG. 11 is a flow chart illustrating a cell search procedure in accordance with a second illustrative embodiment of the present invention.

As shown in fig. 9, the cell search apparatus according to the illustrative embodiment of the present invention includes a receiving unit 710, a frequency separation compensation and symbol timing estimation unit 720, a unit for Fourier transform 730 and a cell ID estimation unit 740.

Next, a cell search procedure according to the first illustrative embodiment of the present invention will be described with reference to FIG. 10.

As shown in fig. 10, the reception unit 710 receives the frames transmitted from the base station, and the symbol synchronization estimation and frequency separation compensation unit 720 filters the received signal by the bandwidth assigned to the synchronization channel and acquires symbol timing by respectively correlating the filtered received signal and a plurality of known primary timing signals, and compensates for the frequency separation by estimating the frequency synchronization (S810). The symbol synchronization estimation and frequency separation compensation unit 720 respectively correlates the filtered received signal and the plurality of known primary synchronization signals and estimates a time of the maximum correlation value as symbol synchronization, and transmits a number of a primary sync signal having the maximum correlation value to the cell ID estimating unit 740. At that time, the frequency separation can be compensated in the frequency domain after performing the Fourier transform.

ES 2 380 065 T3

The Fourier transform unit 730 performs Fourier transform of the received signals based on the symbol timing estimated by the frequency gap compensation and symbol timing estimation unit 720 (S820).

The cell ID estimating unit 740 estimates a group of cell IDs and frame synchronization by respectively correlating the received Fourier transformed signal with a plurality of known secondary synchronization signals 3830. The cell ID estimating unit 740 respectively correlates a plurality of secondary synchronization signals with the received secondary signal to Fourier transform, and estimates the frame synchronization and group of cell IDs using a secondary synchronization signal having the maximum correlation value, In the present specification, the plurality of secondary synchronization signals are given by the application of P,₀,₁, P,₀,₂, P¡, i, i and P¡,₁,₂ which are determined in accordance with a primary sync signal corresponding to the number of a primary sync signal transmitted from the symbol sync estimation and frequency gap compensation unit 720 for Equation 5 to Equation 8. At that time, in the case where there is a symbol synchronization channel in a slot or an OFDM symbol in a frame, the symbol synchronization becomes frame synchronization, and therefore, it is not necessary to further acquire frame synchronization.

Furthermore, the cell ID estimating unit 740 estimates the cell IDs using the number of a primary sync signal transmitted from the symbol sync estimating and frequency gap compensation unit 720 and the group of cell IDs. S840 estimated. At that time, the cell ID estimating unit 740 estimates the cell ID with reference to a known relationship correspondence between cell ID, group of cell IDs, and a number of the primary sync signal.

The estimated cell ID information can be verified using scrambling sequence information included in the pilot symbol duration.

Next, a cell search method according to the second illustrative embodiment of the present invention will be described with reference to FIG. eleven.

As shown in fig. 11, the reception unit 710 receives a frame transmitted from the base station, and the symbol synchronization estimation and frequency separation compensation unit 720 filters the received signal by a bandwidth assigned to the synchronization channel and acquires symbol timing by respectively correlating the filtered received signal and a plurality of known primary timing signals, and compensates for the frequency separation by estimating the frequency timing S910. The symbol synchronization estimating and frequency separation compensation unit 720 respectively correlates the filtered received signal and the plurality of known primary synchronization signals and estimates a time of the maximum correlation value as symbol synchronization, and transmits a plurality of correlation values ​​of the plurality of known primary sync signals and received signal filtered to the cell ID estimating unit 740. At that time, the frequency separation compensation can be performed in the frequency domain after Fourier transform.

The Fourier transform unit 730 performs a Fourier transform of the received signal with reference to the symbol timing that is estimated by the symbol timing estimating and frequency gap compensation unit 720 S920.

The cell ID estimating unit 740 estimates the cell IDs using the plurality of correlation values ​​transmitted from the symbol synchronization and frequency separation compensation estimating unit 720, and correlation values ​​of the submitted received signal. a Fourier transform and a plurality of known S930 secondary sync signals. The cell ID estimating unit searches for a secondary sync signal having the maximum correlation value by correlating each of the plurality of known secondary sync signals with the Fourier transformed received signal for each of the plurality of signals known primaries. In this case, the plurality of secondary synchronization signals is given by applying Pj, 0,1, Pj, 0,2, Pj, 1,1 and Pj, 1,2 which are determined according to the synchronization signal corresponding primary for Equation 5 to Equation 8.

In addition, the cell ID estimating unit 740 combines the correlation value of each known primary sync signal transmitted from the frequency gap compensation and symbol synchronization estimating unit 720 and the correlation value of the frequency gap signal. secondary sync having the maximum correlation value for each of the plurality of known primary sync signals.

The cell ID estimating unit 740 estimates the frame synchronization and a group of cell IDs using a secondary synchronization signal that has the maximum combined value between the combined values ​​of the correlation values ​​of a primary synchronization signal and a secondary sync signal. Besides, the

ES 2 380 065 T3 cell ID estimation unit 740 estimates a cell ID using the primary sync signal having the maximum combined value and the estimated cell ID group. At that time, the cell ID estimating unit 740 estimates the cell ID with reference to a known relationship correspondence between the group of cell IDs, the cell ID, and the number of the primary sync signal.

The illustrative embodiment of the present invention may not only be implemented by the apparatus and / or method described above, but may be implemented, for example, by a program that achieves the function corresponding to the configuration of the illustrative embodiment of the present invention and a recording medium on which the program is recorded. Those skilled in the art will readily implement this from the above-described illustrative embodiment of the present invention.

Although this invention has been described in connection with what are presently considered practical illustrative embodiments, it should be understood that the invention is not limited to the disclosed embodiments, but rather is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.