Method and apparatus for searching a cell

“METHOD FOR SEARCHING A CELL IN A MOBILE STATION”

DESCRIPTIVE REPORT [Technical Field] [001] The present invention relates to a method for generating a downlink frame and a method for searching cells and, in particular, it concerns a method of generating a downlink frame and a method search for a cell using the downlink frame in a cell system based on orthogonal frequency division multiplexing (OFDM).

[Background Art] [002] In a direct sequence code division multiple access system (DS-CDMA), the code skip method is applied to a pilot channel in order to obtain cell synchronization and adequate identification information. cells. The code skip method introduces a code skip technique in the pilot channel so that a terminal can easily search for the cell without an additional synchronization channel. However, since the number of channels that are distinguishable by the frequency domain in the symbol range is much greater than the number of channels that are distinguishable by spreading CDMA over a time domain symbol range in the OFDM system, the use of the time domain can waste resources with respect to capacity and, therefore, it is difficult to apply the code jump method to the time domain of the pilot channel of the OFDM-based system. Therefore, it is desirable, in the case of OFDM, to search for cells using efficiently the signals received in the time domain and in the frequency domain.

[003] The conventional technique for searching cells in the system

OFDM includes dividing a frame into four blocks of time and allocating synchronization information and cell information. The technique proposes

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2/23 two frame structures. The first frame structure allocates synchronization recognition information, cell group recognition information, appropriate cell recognition information and synchronization recognition information for four blocks of time. The second frame structure allocates synchronization recognition information and appropriate cell recognition information for the first time block and the third time block, and synchronization recognition information and cell group recognition information for the second block of time and for the fourth block of time.

[004] In the case of following the first scheme, since symbol synchronization is achieved in the first block of time, it is impossible to obtain rapid synchronization within the 5 msec standard when a terminal is activated or in the case of a handover (transfer ) between heterogeneous networks. In addition, it is difficult to gain diversity by accumulating synchronization recognition information for rapid synchronization.

[005] In the case of following the second scheme, the cell search process is complicated and it is difficult to search for the cells quickly, since it is required to obtain synchronization and simultaneously correlate the appropriate cell recognition information or cell recognition information. cell group in order to achieve frame synchronization.

[006] Another method for searching for cells using an additional preamble to obtain synchronization and searching for cells has been proposed, but it is inapplicable to a system that has no preamble. In addition, once the preamble is placed on the front of the frame, the terminal must be on standby for the next frame when trying to obtain

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3/23 synchronization in a different time position than the first time position in the frame In particular, when the terminal performs a handover between GSM mode, WCDMA mode and 3GPP LTE mode, initial symbol synchronization must be achieved within 5 msec, but initial symbol synchronization cannot be achieved within 5 msec , since synchronization can be achieved for each frame.

[DETAILED DESCRIPTION] [Technical Problem] [007] The present invention was made in an effort to provide a method for generating a downlink frame for medium interference between sectors, as well as an efficient method for searching cells by receiving frame from downlink.

[Technical Solution] [008] An exemplary embodiment of the present invention provides a method for generating a downlink frame including a first synchronization signal and a second synchronization signal, which includes: generating a first short sequence and a second short sequence for indicate cell group information; generate a first scrambling sequence (scrambling) determined by the first synchronization signal; generate a second scrambling sequence determined by the first short sequence; scrambling the first short sequence with the first scrambling sequence and scrambling the second short sequence with at least the second scrambling sequence; and mapping a second synchronization signal that includes the first scrambled short sequence and the second scrambled short sequence in the frequency domain.

[009] Another embodiment of the present invention provides a device for generating a downlink frame including a

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4/23 first sync signal and a second sync signal, which includes: a sequence generator to generate a first short sequence and a second short sequence that indicate cell group information, a first scrambling sequence determined by the first signal synchronization and a second scrambling sequence determined by the first short sequence; and a sync signal generator for the scrambling of the first short sequence with the first scrambling sequence, the scrambling of the second short sequence with at least the second scrambling sequence and generating a second synchronization signal which includes the first scrambled short sequence and the second scrambled short sequence.

[0010] Yet another embodiment of the present invention provides a recording medium for recording a program for carrying out a method for generating a downlink frame including a first synchronization signal and a second synchronization signal, wherein the method includes: generating a first short sequence and a second short sequence that indicate the cell group information; generate a first scrambling sequence determined by the first synchronization signal; generate a second scrambling sequence determined by the first short sequence; scrambling the first short sequence with the first scrambling sequence and scrambling the second short sequence with at least the second scrambling sequence; and mapping a second synchronization signal including the first scrambled short sequence and the second scrambled short sequence in the frequency domain.

[Advantageous Effects] [0011] In accordance with the present invention, cell search performance is improved by scrambling a short sequence with a scrambling sequence and by reducing interference between sectors.

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5/23 [Brief Description of the Drawings] [0012] FIG. 1 presents a system downlink chart

OFDM according to an exemplary embodiment of the present invention.

[0013] FIG. 2 shows a synchronization channel configuration diagram that indicates a secondary synchronization channel when two sequences are mapped in the frequency domain in a centralized way.

[0014] FIG. 3 shows a synchronization channel configuration diagram that indicates a secondary synchronization channel when two sequences are mapped in the frequency domain in a distributive way.

[0015] FIG. 4 shows a block diagram of a downlink frame that generates a device according to an exemplary embodiment of the present invention.

[0016] FIG. 5 presents a flow chart of a downlink frame that generates the method according to an exemplary embodiment of the present invention.

[0017] FIG. 6 presents a first method for generating a secondary synchronization signal according to an exemplary embodiment of the present invention.

[0018] FIG. 7 shows a second method for generating a secondary synchronization signal according to an exemplary embodiment of the present invention.

[0019] FIG. 8 shows a block diagram of a cell search device according to an exemplary embodiment of the present invention.

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6/23 [0020] FIG. 9 presents a flowchart of a method for cell search according to a first exemplary embodiment of the present invention.

[0021] FIG. 10 presents a flowchart of a method for searching for a cell according to a second exemplary embodiment of the present invention.

[Best Mode] [0022] In the following detailed description, only a few exemplary embodiments of the present invention have been presented and described, simply by way of illustration. As those skilled in the art would realize, the modalities described can be modified in a number of different ways, all without departing from the spirit or scope of the present invention. In order to clarify the drawings in the present invention, the parts that are not related to the description will be omitted and the same part will have the same reference numeral throughout the specification.

[0023] Throughout the specification, unless expressly described to the contrary, the word "understand" and variations such as "understands" or "that understands" will be understood to imply the inclusion of declared elements, but not the exclusion of any others elements. In addition, the expressions a unit, a device and a module in the present specification represent a unit for processing a predetermined function or operation, which can be performed by hardware, software or a combination of hardware and software.

[0024] A downlink frame and a synchronization channel of an OFDM system, according to an exemplary embodiment of the present invention, will now be described with reference to Figures 1 to 3.

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7/23 [0025] Figure 1 shows a downlink frame of an OFDM system according to an exemplary embodiment of the present invention. In Figure 1, the horizontal axis represents the time axis and the vertical axis represents the frequency axis or the axis of a subcarrier.

[0026] As shown in Figure 1, a downlink frame 110, according to an exemplary embodiment of the present invention, has a time interval of 10 msec and includes ten subframes 120. A subframe 120 has a time interval of 1 msec and includes two slots 130 and a slot 130 includes six or seven OFDM symbols. When a slot includes six symbols, it has a cyclic prefix duration that is longer than the case where a slot includes seven symbols.

[0027] As shown in Figure 1, a downlink frame 110, according to an exemplary embodiment of the present invention, includes a synchronization interval 140 in slot 0 and slot 10, respectively, to thus include two synchronization intervals 140. However, the embodiment of the present invention is not limited to this. That is, a downlink frame 110 can include a synchronization interval in a random slot and can include one or at least three synchronization intervals. In addition, since the duration of the cyclic prefix may be different for each slot, it is desirable to provide the synchronization interval for the last position of the slot.

[0028] Each slot includes a pilot range.

[0029] A synchronization interval according to an exemplary 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 positioned adjacent with respect to time. As shown in Figure 1, a primary sync channel is provided for the last slot position and a secondary sync channel is provided.

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8/23 provided before the primary synchronization channel.

[0030] The primary synchronization channel includes information for the identification of symbol synchronization and frequency synchronization and some cell ID (identification) information and the secondary synchronization channel includes information for the identification of other cell ID information and frame synchronization. The mobile station identifies the cell ID by combining cell ID information from the primary and secondary synchronization channels.

[0031] For example, when there are 510 cell IDs, three primary sync signals are allocated to the primary sync channel to divide all 510 cell IDs into three groups and, when 170 secondary sync signals are allocated to the channel secondary synchronization, all information from the 510 cell IDs (3x170 = 510) can be expressed.

[0032] In addition, it is also possible to divide the 510 cell IDs into 170 groups using the 170 secondary sync signals allocated to the secondary sync channel and express the cell ID information in the cell groups by using the three primary synchronization channels allocated to the primary synchronization channel.

[0033] Since the secondary synchronization channel includes information to identify frame synchronization, as well as cell ID information, two secondary synchronization channels included in a frame are different.

[0034] Figure 2 shows a synchronization channel configuration diagram that indicates a secondary synchronization channel when two sequences are mapped in the frequency domain in a centralized way and Figure 3 shows a diagram of

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9/23 synchronization channel configuration that indicates a secondary synchronization channel when two sequences are mapped in the frequency domain in a distributive way.

[0035] Referring to Figure 2 and Figure 3, a secondary synchronization signal inserted in a secondary synchronization channel, according to an exemplary embodiment of the present invention, is configured by a combination of two sequences. The cell group information and the frame synchronization information are mapped over the two sequences.

[0036] As shown in Figure 2, it is possible to allocate the first sequence to the subcarrier and sequentially allocate the second sequence to the other subcarrier and, as shown in Figure 3, it is possible to allocate the first sequence to each even carrier (n = 0 , 2, 4 and ... 60) and the second sequence for each odd carrier (n = 1, 3, 5 and ... 61).

[0037] The length of the sequence is half the number of subcarriers allocated to the secondary synchronization channel. That is, the number of elements in the sequence that can be generated is as much as half the number of subcarriers allocated to the secondary synchronization channel. For example, when the number of subcarriers allocated to the secondary synchronization channel is 62, the sequence length is 31 and up to 31 elements of the sequence can be generated.

[0038] Then, once two streams are allocated to a secondary synchronization channel, 961 (= 31x31) secondary synchronization signals are generated. However, since the information to be included by the secondary synchronization channel includes cell group information and frame limit information, 170 or 340 (= 170x2) secondary synchronization signals are required. That is, 961 is sufficiently greater than 170 or 340.

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10/23 [0039] A downlink frame generation device according to an exemplary embodiment of the present invention will now be described with reference to Figure 4. Figure 4 shows a block diagram of a downlink frame generation device from according to an exemplary embodiment of the present invention.

[0040] As shown in Figure 4, the downlink frame generating device includes a sequence generator 410, a sync signal generator 420, a frequency mapper 430 and an OFDM 440 transmitter.

[0041] Sequence generator 410 generates a sequence for obtaining time and frequency synchronization, a cell identification sequence, a plurality of short sequences and an adjacent cell interference reduction scrambling sequence, and transmits them to the sync signal generator 420.

[0042] The sync signal generator 420 generates a primary sync signal, a secondary sync signal and a pilot model using the sequences transmitted by the sequence generator 410.

[0043] The sync signal generator 420 generates a primary sync signal using a sequence of obtaining time and frequency synchronization and a cell identification sequence. The sync signal generator 420 generates a secondary sync signal using a plurality of short streams and an adjacent cell interference reduction scrambling sequence.

[0044] The synchronization signal generator 420 generates a pilot model of a downlink signal by allocating an appropriate scrambling sequence that is allocated for each cell to the pilot channel, in order to encode a common pilot symbol and a

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11/23 cellular system data.

[0045] Frequency mapper 430 maps the primary sync signal, the secondary sync signal and the pilot model generated by the sync signal generator 420, and frame control information and broadcast traffic data provided from outside the time and frequency domains to generate a downlink frame.

[0046] The OFDM 440 transmitter receives the downlink frame from the frequency mapper 430 and transmits it through a transmitting antenna.

[0047] A method for generating a downlink frame, according to an exemplary embodiment of the present invention, will now be described with reference to Figures 5 and 7. Figure 5 presents a flowchart of a method for generating a downlink frame, according to according to an exemplary embodiment of the present invention.

[0048] As shown in Figure 5, sequence generator 410 generates a plurality of short sequences and a plurality of adjacent cell interference reduction scrambling sequences and transmits them to the sync signal generator 420 (S510).

[0049] The synchronization signal generator 420 generates a secondary synchronization signal using the short sequences and the adjacent cell interference reduction scrambling sequences transmitted by the sequence generator 410 (S520). The exemplary embodiment of the present invention will exemplify the framework that includes two secondary synchronization channels, but is not limited to it.

[0050] Two secondary methods for generating the synchronization signal, according to an exemplary modality of

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12/23 present invention, will now be described with reference to Figure 6 and Figure 7. Figure 6 shows a first method for generating a secondary synchronization signal, according to an exemplary embodiment of the present invention, and Figure 7 shows a second method for generating a secondary synchronization signal according to an exemplary embodiment of the present invention.

[0051] A short string (wn) is a binary string (binary code) that indicates the cell group information. That is, the short sequence (wn) is a binary sequence allocated to the cell group number and the frame synchronization and its length is half the number of subcarriers allocated to the secondary synchronization channel. The exemplary embodiment of the present invention describes the case where the number of subcarriers allocated for the secondary synchronization channel symbol is 62, but is not limited to it. Thus, the length of the short sequence according to the exemplary embodiment of the present invention is 31.

[0052] The first short sequence (w0) is a sequence allocated to the even subcarrier of the first (slot 0) secondary synchronization channel and is expressed in Equation 1.

[Equation 1] w0 = [w0 (0), w0 (1), ..., w0 (k), ..., w0 (30)] [0053] Here, k represents an index of the even subcarrier used for the synchronization channel.

[0054] The second short sequence (w1) is a sequence allocated to the odd subcarrier of the first (slot 0) secondary synchronization channel and is expressed in Equation 2.

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

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13/23 [0055] Here, m represents an index of the odd subcarrier used for the synchronization channel.

[0056] The third short sequence (w2) is a sequence allocated to the even subcarrier of the second (slot 10) secondary synchronization channel and is expressed in Equation 3.

[Equation 3] w2 = [w2 (0), w2 (1), ..., w2 (k), ..., w2 (30)] [0057] The fourth short sequence (w3) is a sequence allocated to the odd subcarrier of the second (slot 10) secondary synchronization channel and is expressed in Equation 4.

[Equation 4] w3 = [w3 (0), w3 (1), ^... , w3 (m), ^... w3 (30)] [0058] w0, w1, w2 and w3 can be different sequences from each other and it may be that w0 = w3 and w1 = w2, or it may be that w0 = w2 and w1 = w3. When it is given that w0 = w3 and w1 = w2, the short sequences of the second secondary synchronization channel can be allocated using the short sequences allocated to the first synchronization channel and a terminal only needs to memorize the 170 short sequences allocated to the first secondary synchronization channel and therefore reduces complexity.

[0059] The first method to generate the secondary synchronization signal is to allocate the first short sequence for each even subcarrier of the first secondary synchronization channel and the second short sequence for each odd subcarrier of the first secondary synchronization channel, as shown in Figure 6 . The first method is then to allocate the third short sequence for each even subcarrier of the second secondary synchronization channel and the fourth short sequence for each odd subcarrier of the second

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14/23 secondary synchronization channel.

[0060] According to the first method for generating the secondary sync signal, since the secondary sync signal is generated by combining two short strings with length 31, the number of secondary sync signals becomes 961, which is sufficiently larger than the required number of 170 or 340.

[0061] The second method to generate the secondary synchronization signal is to allocate the first sequence determined by Equation 5 for each even subcarrier of the first (slot 0) secondary synchronization channel and the second sequence determined by Equation 6 for each odd subcarrier of the first (slot 0) secondary synchronization channel, as shown in Figure 7. The second method also includes the allocation of the third sequence determined by Equation 7 for each even subcarrier of the second (slot 10) secondary synchronization channel and the fourth sequence determined by Equation 8 for each odd subcarrier of the second (slot 10) secondary synchronization channel .

[0062] A scrambling sequence Pj, 1 to scramble the first short sequence w0 is given as Pj, 1 = [Pj, 1 (0), Pj, 1 (1), ... Pj, 1 (k) ... Pj, 1 (30)] and j (j = 0, 1, 2) is a number of a cell identification sequence allocated to the primary synchronization channel. Therefore, Pj, 1 is determined by the primary synchronization signal. Pj, 1 is a known value when the mobile station unmap the sequence in order to know the cell ID group and the frame limit.

[0063] As expressed in Equation 5, the respective elements of the first sequence c0, according to the second method to generate the secondary synchronization signal, are products of the respective elements of the first short sequence w0 and the corresponding elements of Pj, 1.

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15/23 [Equation 5] co = [w0 (0) Pj, i (0), w0 (1) Pj, i (1), ···, w0 (k) Pj, i (k), -, wQ (3Q) Pj, i (30)] [0064] Here, k is an index of the even subcarrier used for the synchronization channel.

[0065] A scrambling sequence Sw0 to scramble the second short sequence wl is given as Sw0 = [Sw0 (0), Sw0 (1), ···, Sw0 (m), ···, Sw0 (30) ] and Sw0 is determined by the first short sequence (w0) · [0066] In this case, it is possible to determine Sw0 according to the short sequence group to which the first short sequence belongs, by combining the short sequences in a group · [0067] For example, since the length of the short sequence is 31 in the exemplary embodiment of the present invention, there are 31 short sequences · Therefore, the short sequences 0 to 7 are defined as belonging to group 0, the short sequences 8 to 15 are defined as belonging to group 1, short sequences 16 to 23 are defined to belong to group 2 and short sequences 24 to 30 are defined to belong to group 3, a scrambling code is mapped in each group and the scrambling code mapped in the group to which the first short sequence belongs is determined to be Sw0 · [0068] You can divide the number of the short sequence by 8, combine the short sequences that have the same residuals and thus classify the 31 short strings into 8 groups · That is, the short sequence number is divided by 8, the short sequence that has the residual 0 is defined to belong to group 0, the short sequence that has residual 1 is defined to belong to group 1, the short sequence that has residual 2 is defined to belong to group 2, the short sequence that has residual 3 is defined to belong to group 3, the sequence

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16/23 short that has residual 4 is defined to belong to group 4, the short sequence that has residual 5 is defined to belong to group 5, the short sequence that has residual 6 is defined to belong to group 6, short sequence that has the residual 7 is defined to belong to group 7, a scrambling code is mapped in each group and the scrambling code mapped in the group to which the first short sequence belongs is determined to be Sw0.

[0069] As expressed in Equation 6, the respective elements of the second sequence c1, according to the second method to generate the secondary synchronization signal, are products of the respective elements of the second short sequence w1 and the corresponding corresponding elements of Sw0.

[Equation 6] c1 = [w1 (0) Sw0, w1 (1) Swo (1), ..., w1 (m) Swü (m), ···, w1 (30) Swo (30)] [0070 ] Here, m is an index of the odd subcarrier used for the synchronization channel.

[0071] The scrambling sequence Pj, 2 to scramble the third short sequence w2 is given as Pj, 2 = [Pj, 2 (0), Pj, 2 (1), ... Pj, 2 (k) ... Pj, 2 (30)] and j (j = 0, 1, 2) is a number of a cell identification sequence allocated to the primary synchronization channel. Therefore, Pj, 2 is determined by the primary synchronization signal. Pj, 2 is a known value when the terminal unmap the code in order to know the cell ID group and the frame limit.

[0072] As expressed in Equation 7, the respective elements of the third sequence c2, according to the second method to generate the secondary synchronization signal, are products of the respective elements of the third short sequence w2 and the corresponding corresponding elements of Pj, 2.

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17/23 [Equation 7]

C2 = [w2 (0) Pj,₂(0), w2 (1) Pj, 2 (1), ···, w2 (k) Pj, 2 (k), ···, w2 (30) Pj,₂(30)] [0073] Here, k is an index of the even subcarrier used for the synchronization channel.

[0074] The scrambling sequence Sw2 to scramble the fourth short sequence is given as Sw2 = [Sw2 (0), Sw2 (1), Sw2 (m), ···

Sw2 (30)] and Sw2 is determined by the third short sequence w2 · [0075] In this case, it is possible to combine the short sequences in a group and determine Sw2 according to the short sequence group to which the third short sequence belongs · [0076 ] For example, since the length of the short sequence, according to the exemplary embodiment of the present invention, is 31, there are 31 short sequences · Therefore, the short sequences from 0 to 7 are defined so that they belong to group 0, short sequences 8 to 15 are defined to belong to group 1, short sequences 16 to 23 are defined to belong to group 2, short sequences 24 to 30 are defined to belong to group 3, a code scrambling code is mapped in each group and the scrambling code mapped in the group to which the third short sequence belongs is determined to be Sw2 · [0077] It is also possible to divide the number of the short sequence by

8, combine the short sequences with the same residuals and classify the 31 short sequences into 8 groups · That is, the short sequence number is divided by 8, the short sequence with the residual 0 is defined to belong to group 0, the sequence short with residual 1 is defined to belong to group 1, the short sequence with residual 2 is defined to belong to group 2, the short sequence with residual 3 is defined to belong to group 3, the short sequence with residual 4 is defined to belong to group 4, the short sequence with residual

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18/23 residual 5 is defined to belong to group 5, the short sequence with residual 6 is defined to belong to group 6, the short sequence with residual 7 is defined to belong to group 7, a scrambling code is mapped in each group and the scrambling code mapped to the group to which the third short string belongs is determined to be Sw2.

[0078] As expressed in Equation 8, the respective elements of the fourth sequence c3, according to the second method to generate the secondary synchronization signal, are the products of the respective elements of the fourth short sequence and the corresponding elements of Sw2.

[Equation 8] c3 = [w3 (0) Sw2 (0), w3 (1) Sw2 (1), ···, w3 (m) Sw2 (m), ··· w3 (30) Sw2 (30)] [0079] Here, m is an index of the odd subcarrier used for the synchronization channel · [0080] Here, it is given that Pj, i = Pj, 2 and wü # w1 # w2 ^ w3 or w0 = w3, w1 = w2 · In this case, the cell group and frame identification information are mapped in the combination of the first to the fourth short strings and the number of terminal descrambling chances for the secondary sync channel scrambling defined by the cell identification sequence number of the channel primary synchronization is reduced · [0081] It is defined that Pj, 1 # Pj, 2 and w0 = w2, w1 = w3 · In this case, the cell group information is mapped in the combination of the first short sequence and the second short sequence and the frame synchronization information is mapped in the scrambling sequences Pj, 1 and Pj, 2 of the secondary synchronization channel defined by the sequence number of primary sync channel cell identification · The number of terminal descrambling chances for scrambling

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19/23 of the secondary sync channel defined by the cell ID sequence number of the primary sync channel is increased, but the complexity is reduced since the combination of cell group ID strings is halved.

[0082] The frequency mapper 430 maps the secondary synchronization signal and the transmission traffic data generated by the synchronization signal generator 420 in the time and frequency domains to generate a frame of the downlink signal (S530).

[0083] The OFDM 440 transmitter receives the frame of the downlink signal and transmits it through the transmitting antenna (S540).

[0084] A method for a terminal to search the cell using a downlink signal according to an exemplary embodiment of the present invention will now be described with reference to Figures 8 to 10.

[0085] Figure 8 shows a block diagram of a cell search device according to an exemplary embodiment of the present invention, Figure 9 shows a flowchart of a method for cell search according to a first exemplary embodiment of the present invention and Figure 10 shows a flow chart of a cell search method according to a second exemplary embodiment of the present invention.

[0086] As shown in Figure 8, the cell finder includes a receiver 810, a symbol sync and frequency offset estimate compensator 820, a Fourier transformer 830 and a cell ID estimator 840.

[0087] A method of searching for a cell according to a first exemplary embodiment of the present invention will now be described with reference to Figure 9.

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20/23 [0088] As shown in Figure 9, receiver 810 receives the base station frame and the symbol sync estimate offset and frequency offset 820 filters the received signal by the bandwidth allocated to the synchronization channel , correlates the filtered received signal and a plurality of predetermined primary synchronization signals to obtain symbol synchronization and estimates the frequency synchronization to compensate for a frequency offset (S910). The symbol sync estimate and frequency offset compensator 820 correlates the filtered received signal and a plurality of predetermined primary sync signals, estimates the time that has the highest correlation value to be symbol sync, and transmits the signal number primary synchronization that has the highest correlation value for the cell ID estimator 840. In this case, the frequency offset is compensated in the frequency domain after the Fourier transformation.

[0089] The Fourier transformer 830 performs a Fourier transformation process on the received signal with reference to the symbol synchronization estimated by the symbol synchronization estimate compensator and frequency offset 820 (S920).

[0090] The cell ID estimator 840 correlates the received signal transformed by Fourier and a plurality of predetermined secondary synchronization signals to estimate a group of cell ID and the frame synchronization (S930). The cell ID estimator 840 correlates the received signal transformed by Fourier and a plurality of secondary synchronization signals that are generated by the application of Pj, 1 and Pj, 2 which are determined by the primary synchronization signal corresponding to the number of the synchronization signal primary transmitted by the symbol synchronization estimate and frequency offset compensator 820 for Equations 5 to 8, and estimates the frame synchronization and the ID group of

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21/23 cell using the secondary sync signal that has the highest correlation value. In this case, when the synchronization channel symbol in a frame is provided within a slot or an OFDM symbol, there is no need to additionally obtain frame synchronization, since symbol synchronization becomes frame synchronization.

[0091] The cell ID estimator 840 estimates the cell ID using the number of the primary sync signal transmitted by the symbol sync estimation and frequency offset compensator 820 and the estimated cell ID group (S940). In this case, the cell ID estimator 840 estimates the cell ID by referring to the mapping ratio of the predetermined primary sync signal number, to the cell ID group and to the cell ID.

[0092] The estimated cell ID information can be verified using the scrambling sequence information included in the pilot symbol range.

[0093] A method of searching for a cell according to a second exemplary embodiment of the present invention will now be described with reference to Figure 10.

[0094] Receiver 810 receives the frame from the base station and the symbol synchronization estimate offset and frequency offset 820 filters the received signal by the bandwidth allocated to the synchronization channel, correlates the filtered received signal and a plurality of predetermined primary synchronization signals to obtain symbol synchronization and estimates frequency synchronization to compensate for frequency offset (S710). The symbol synchronization estimate and frequency offset compensator 820 correlates the filtered received signal and a plurality of predetermined primary synchronization signals to estimate the time that has the highest correlation value to be the synchronization of

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22/23 symbol and transmits a plurality of correlation values ​​that are generated by correlating the primary synchronization signals and the filtered received signal to the cell ID estimator 840. In this case, the frequency offset can be compensated in the frequency domain after the Fourier transformation.

[0095] The Fourier transformer 830 performs a Fourier transformation process on the received signal with reference to the symbol synchronization estimated by the symbol synchronization estimate compensator and frequency offset 820 (S720).

[0096] Cell ID estimator 840 estimates cell ID using a plurality of correlation values ​​transmitted by the symbol synchronization estimate offset and frequency offset 820, the received signal transformed by Fourier and the correlation values ​​of a plurality of predetermined secondary sync signals (S730). The cell ID estimator 840 correlates the received signal transformed by Fourier and a plurality of secondary synchronization signals that are generated by the application of Pj, 1 and Pj, 2 that are determined according to the primary synchronization signals corresponding to Equations 5 to 8 and finds the secondary sync signal that has the highest correlation value, with respect to a plurality of respective primary sync signals.

[0097] The cell ID estimator 840 combines the correlation value of the corresponding primary sync signal transmitted by the symbol sync estimation and frequency offset compensator 820 and the correlation value of the secondary sync signal, which has the highest value of correlation with the received signal transformed by Fourier, among a plurality of secondary synchronization signals, which are generated by the application of Pj, 1 and Pj, 2, which are determined by the primary sync signal

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23/23 corresponding to Equations 5 to 8, with respect to a plurality of respective primary synchronization signals.

[0098] Cell ID Estimator 840 estimates frame sync and cell ID group using the secondary sync signal that has the highest value generated by combining the correlation value of the primary sync signal and the correlation value of the secondary sync signal. The cell ID estimator 840 estimates the cell ID using the estimated cell ID group and the primary sync signal that has the highest value generated by combining the correlation value of the primary sync signal and the correlation value of the signal secondary synchronization. In this case, the cell ID estimator 840 estimates the cell ID by referring to the mapping ratio of the predetermined primary sync signal number, to the cell ID group and to the cell ID.

[0099] The modalities described above can be performed through a program to perform the functions corresponding to the configuration of the modalities or a recording medium for recording the program in addition to the device and / or method described above, which is easily accomplished by a person skilled in the art.

[00100] Although this invention has been described in relation to what are currently considered to be practical exemplary modalities, it should be understood that the invention is not limited to the disclosed modalities, but, on the contrary, it is intended to cover various modifications and equivalent arrangements included in the spirit and scope of the attached Claims.