KR100817496B1 - Apparatus and method for generating downlink signal, and apparatus and method for searching cell - Google Patents

Abstract

A downlink signal generation device and a cell search device are disclosed.

The downlink signal generating apparatus generates a downlink frame, arranges a cell group identification sequence in a synchronization period of the downlink frame, and then converts the downlink frame into a signal in a time domain. The downlink signal generating apparatus replaces a part of the plurality of repetitive patterns with a frame synchronization identification sequence in the signal in the time domain.

The cell search apparatus determines a time synchronization by correlating the received signal with a frame synchronization identification sequence, and extracts a downlink frame in the time domain based on the time synchronization. Next, the cell search apparatus restores the repetition pattern and converts the frame to a frame in the frequency domain. Then, the cell search apparatus extracts a cell group identification sequence in a synchronization period of a frame in the frequency domain to determine a cell group number.

Frame, Sync, Cell Navigation, Cell Group

Description

Apparatus and method for generating a downlink signal, and apparatus and method for performing cell search {APPARATUS AND METHOD FOR GENERATING DOWNLINK SIGNAL, AND APPARATUS AND METHOD FOR SEARCHING CELL}

1 is a frame structure diagram illustrating an OFDM-based downlink frame according to an embodiment of the present invention.

2 is a frame structure diagram illustrating an OFDM-based sync block according to an embodiment of the present invention.

3 is a frame structure diagram illustrating an OFDM-based downlink subframe according to an embodiment of the present invention.

4 is a diagram illustrating bandwidth scalability of a downlink frame according to an embodiment of the present invention.

5 is a diagram illustrating bandwidth scalability of a downlink frame according to another embodiment of the present invention.

6 is a block diagram illustrating an apparatus for generating a downlink signal according to an embodiment of the present invention.

7 is a flowchart illustrating a downlink signal generation method according to an embodiment of the present invention.

8 illustrates a method of applying a cell group identification sequence and a frame synchronization identification sequence according to an embodiment of the present invention.

9 is a diagram illustrating a method of applying a cell group identification sequence and a frame synchronization identification sequence according to another embodiment of the present invention.

10 is a flowchart illustrating a signal conversion process of a synchronization section according to an embodiment of the present invention.

11 is a block diagram illustrating a mobile station for performing cell search according to an embodiment of the present invention.

12 is a flowchart illustrating a cell searching method according to an embodiment of the present invention.

13 is a block diagram illustrating a time synchronization detector according to an embodiment of the present invention.

14 is a block diagram illustrating a frequency synchronization detector according to an embodiment of the present invention.

15 is a diagram illustrating a signal output by the signal extractor according to an exemplary embodiment of the present invention.

The present invention relates to a method for generating a downlink signal and a method for performing cell search, and more particularly, to a method for searching for a cell in an orthogonal frequency division multiplexing (OFDM) based cellular system.

The cellular system must be able to synchronize the time synchronization with the frequency synchronization by the terminal to the signal of the base station for the initial synchronization, and also be able to perform cell search. After the terminal synchronizes initially, it should be able to track time and frequency, and it should be able to perform time and frequency synchronization and cell search of neighbor cells for handover.

As a conventional technique for cell searching, two frame structures were proposed in a paper published in IEEE VTC Fall, OFDM Section IV-6 in September 2005. According to the first scheme, one frame is divided into four time blocks, and four time blocks are allocated synchronization recognition information, cell group recognition information, cell unique recognition information, and synchronization recognition information, respectively. On the other hand, according to the second scheme, one frame is divided into four time blocks, the first time block and the third time block are allocated synchronization recognition information and cell unique recognition information, and the second time block and the fourth time block. The block is allocated sync recognition information and cell group recognition information.

According to the first scheme above, since the symbol synchronization is acquired only in the first time block, it is impossible to obtain a fast synchronization within 4.5 ms specified when the terminal is powered on or when handover between heterogeneous networks. In addition, it is difficult to obtain diversity gain through accumulation of synchronization recognition information for fast synchronization acquisition.

On the other hand, according to the second method above, in order to obtain frame synchronization, cell unique recognition information or cell group recognition information must be correlated simultaneously with acquisition of a cell, so that a cell search process is complicated and fast cell search is difficult.

Meanwhile, as another technique for cell searching, a method of acquiring synchronization using a separate preamble and searching for a cell has been proposed, but this method is not applicable to a system in which a preamble does not exist. In addition, since the preamble is disposed at the beginning of the frame, when the terminal wants to acquire synchronization at a time position other than the beginning of the frame, there is a problem of waiting for the next frame. In particular, when the terminal performs handoff between GSM mode, WCDMA mode, and 3GPP LTE mode, the initial symbol synchronization should be acquired within 4.5 msec, but the initial symbol synchronization can be obtained within 4.5 msec because synchronization can be obtained in units of frames. Occurs when there is no.

An object of the present invention is to provide a cell search method through fast synchronization acquisition and a downlink signal generation method that enables fast synchronization acquisition.

According to an embodiment of the present invention, an apparatus for generating a downlink signal for a predetermined cell includes a frame generator, a signal converter, and a replacer. The frame generation unit generates a downlink frame and arranges a cell group identification sequence corresponding to the predetermined cell in a synchronization period of the downlink frame so that a plurality of repetition patterns are formed in the time domain. The signal converter converts the downlink frame into a time domain signal. The substitution unit generates a downlink signal by replacing a part of the plurality of repetitive patterns with the frame synchronization identification sequence in the time domain signal.

In this case, the frame generation unit generates a downlink frame including a plurality of sync blocks, and a cell group identification sequence corresponding to the predetermined cell in a sync period of each sync block so that a plurality of repeating patterns are formed in a time domain. Can be placed.

In this case, the replacement unit may generate the downlink signal with a plurality of frame synchronization identification sequences respectively corresponding to the plurality of sync blocks.

According to another embodiment of the present invention, a method for generating a downlink signal for a predetermined cell includes generating a downlink frame and the predetermined period in a synchronization period of the downlink frame such that a plurality of repetition patterns are formed in a time domain. Disposing a cell group identification sequence corresponding to a cell in the cell; converting the downlink frame into a time domain signal; and replacing a part of the plurality of repetitive patterns in the time domain signal with a frame synchronization identification sequence Generating a link signal.

In this case, the downlink frame includes a plurality of sync blocks, and the disposing of the cell group identification sequence corresponds to the predetermined cell in a sync interval of each sync block so that a plurality of repetition patterns are formed in a time domain. And disposing a cell group identification sequence.

According to an embodiment of the present invention, an apparatus for searching for a cell includes a time synchronization detector for determining a symbol synchronization and a frame synchronization by finding a point in time at which a correlation value exceeds a predetermined level by correlating a received signal with a frame synchronization identification sequence; A downlink frame extracting unit for extracting a downlink frame of a time domain based on symbol synchronization and the frame synchronization, and a remaining region in a time domain corresponding to the frame sync identification sequence in a downlink frame of the downlink frame of the time domain; A repeating pattern copying unit for copying signals to form a repeating pattern in the synchronization period, a signal converting unit converting the downlink frame in the time domain in which the repeating pattern is formed into a frame in the frequency domain, and a frame of the frequency domain A cell for determining a cell group number by extracting a cell group identification sequence from a sync interval It includes a group determination unit.

In this case, the time synchronization detector may determine the symbol synchronization and the frame synchronization by correlating the received signal with a plurality of frame synchronization identification sequences respectively corresponding to the plurality of sync blocks included in the downlink frame.

According to another embodiment of the present invention, a method of searching for a cell may include correlating a received signal with a frame synchronization identification sequence to determine a time point at which a correlation value is maximized to determine symbol synchronization and frame synchronization; Extracting a downlink frame in the time domain based on the synchronization, and copying signals of the remaining areas in the time domain corresponding to the frame synchronization identification sequence in the downlink frame of the downlink frame in the time domain and repeating the same in the sync interval Forming a pattern, converting a downlink frame of the time domain in which the repeating pattern is formed into a frame of a frequency domain, extracting a cell group identification sequence in a synchronization period of the frame of the frequency domain, and extracting a cell group number Determining.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

In addition, when a part is said to "include" a certain component, which means that it may further include other components, except to exclude other components unless otherwise stated.

Hereinafter, a collection of a plurality of cells is called a cell group, and a collection of a plurality of cell groups is called a cell group set. A cellular system according to an embodiment of the present invention includes a plurality of cell groups, and one cell group includes a plurality of cells. Meanwhile, a cellular system according to another embodiment of the present invention includes a plurality of cell group sets, one cell group set includes a plurality of cell groups, and one cell group includes a plurality of cells.

Next, a structure of an OFDM-based downlink frame according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5.

1 is a frame structure diagram illustrating an OFDM-based downlink frame according to an embodiment of the present invention. In Figure 1 the horizontal axis is the time axis, the vertical axis is the frequency axis or subcarrier (subcarrier) axis.

As shown in FIG. 1, one downlink frame 10 according to an embodiment of the present invention includes four sync blocks 11 with a time interval of 10 msec. One sync block 11 includes five subframes 12 with a time interval of 2.5 msec. One subframe 12 has a time interval of 0.5 msec, and one downlink frame 10 includes a total of 20 subframes 12.

2 is a frame structure diagram illustrating an OFDM-based sync block according to an embodiment of the present invention.

As shown in FIG. 2, one sync block 11 includes five subframes 12, and one subframe 12 includes seven OFDM symbols. As shown in FIG. 2, one sync block 11 according to an embodiment of the present invention includes, but is not limited to, one sync section 13 corresponding to one OFDM symbol section at a start section of the sync block. It doesn't have to be. That is, one sync block 11 may include a sync section 13 in any section within the sync block 11, and may include two or more sync sections 13. According to the embodiment of FIG. 2, the repetition period of the synchronization section 13 is equal to the time occupied by the five subframes 12.

Meanwhile, as shown in FIG. 2, one subframe 12 according to an embodiment of the present invention includes one pilot section 14 including pilot symbols, and one pilot section 14 is 1. Corresponds to the OFDM symbol period, but is not necessarily limited thereto. That is, one subframe 12 may include two or more pilot sections 14. In addition, as shown in FIG. 2, the pilot symbols may be arranged in one OFDM symbol interval according to a time division multiplexing (TDM) structure, but may be arranged in a frequency domain-scattered division multiplexing (SDM) structure. Accordingly, it may be arranged in two or more OFDM symbol intervals.

3 is a frame structure diagram illustrating an OFDM based downlink subframe 12 according to an embodiment of the present invention.

As shown in FIG. 3, the subframe 12 according to the embodiment of the present invention includes a synchronization section 13, a pilot section 14, and a data section 15.

Cell group identification sequences are arranged at regular intervals in the frequency domain corresponding to the common synchronization channel of the synchronization section 13. According to FIG. 3, the cell group identification sequence is arranged with subcarrier spacing 1. Meanwhile, the cell group identification sequence may be expressed as in Equation 1 below.

In Equation 1, k denotes a cell group number, and N _G denotes a length of a cell group identification sequence. According to an embodiment of the present invention, N _G may mean half of the total number of available subcarriers allocated to the common synchronization channel.

Meanwhile, a Hadamard sequence, a gold sequence, a Golay sequence, a KAZAC sequence, a generalized chirp like (GCL) sequence, a pseudo-noise (PN) sequence, and the like may be used to obtain a cell group identification sequence. The element c _n ^(k) of the cell group identification sequence according to the GCL sequence may be expressed as in Equation 2.

Meanwhile, the cell group identification sequence may be arranged in the frequency domain of the common sync channel as shown in FIG. 3. In the mobile communication system supporting the scaleable bandwidth as shown in Figs. 4 and 5, the mobile station using various bandwidths, such as the mobile station using the bandwidth of 1.25 MHz, the mobile station using the bandwidth of 2.5 MHz, may perform the cell group identification sequence. To receive it. According to an embodiment of the present invention, the common synchronization channel may use a central 1.25 MHz or 5 MHz except for a DC subcarrier. When the frequency domain of the common synchronization channel is 1.25 MHz, the number of subcarriers in the frequency domain is 76, so N _G = 38, thus the number of distinguishable cell groups is 38.

The pilot section 14 includes a pilot symbol and may include a data symbol and a cell identification sequence in addition to the pilot symbol.

The data interval 15 includes data symbols and may include a cell identification sequence.

The cell identification sequence may be arranged in the pilot section 14 or may be distributed in the pilot section 14 and the data section 15 in the time domain and the frequency domain.

Next, a downlink signal generating apparatus 100 according to an embodiment of the present invention will be described with reference to FIGS. 6 to 10.

6 is a block diagram illustrating a downlink signal generating apparatus 100 according to an embodiment of the present invention.

As illustrated in FIG. 6, the downlink signal generating apparatus 100 includes a downlink frame generator 110, an inverse fast fourier transform (IFFT) calculator 120, a repeat pattern replacer 130, and a transmitter 140. It includes.

7 is a flowchart illustrating a downlink signal generation method according to an embodiment of the present invention.

First, the downlink frame generator 110 generates a downlink frame as shown in FIGS. 1 to 3 (S110). That is, the downlink frame generator 110 generates a frame including a plurality of sync blocks, and each sync block includes a sync period 13, and the downlink frame generator 110 is located in the time domain. The cell group identification sequence is arranged in the synchronization section 13 to form a plurality of repeating patterns.

Next, the IFFT calculator 120 performs a fast Fourier inverse transform with the downlink frame generated by the downlink frame generator 110 to generate a signal in the time domain (S120).

The repeating pattern replacement unit 130 punctures a part of the plurality of repetitive patterns existing in the synchronization section 13 of the signal in the time domain generated by the IFFT operation unit 120 with a frame synchronization identification sequence to convert the downlink signal. It generates (S130). The frame synchronization identification sequence may be represented by Equation 3 below.

In Equation 3, u is the number of the frame sync identification sequence. N _F is the length of the frame synchronization identification sequence and is determined by the number of samples corresponding to half of one OFDM symbol interval excluding the guard interval. In order to obtain a frame synchronization identification sequence, one of a Hadamard sequence, a Gold sequence, a Golay sequence, a GCL sequence, a KAZAC sequence, and a PN sequence may be used.

Meanwhile, the repeating pattern replacement unit 130 may apply the same frame synchronization identification sequence to every sync block 11, but may apply a different frame synchronization identification sequence to every sync block 11. Specifically, when the cell group identification sequence and the frame synchronization identification sequence applied to one sync block 11 are represented by (k, u), the arrangement information of the cell group identification sequence and the frame sync identification sequences applied to one frame is expressed by the following equation. It can be expressed as 4. Here, k is the number of the cell group identification sequence or the number of the cell group, and u is the number of the frame sync identification sequence.

In Equation 4, k0, k1, k2, and k3 are numbers of cell group identification sequences applied to sync blocks 0 to 3, respectively, and u0, u1, u2 and u3 are frame syncs applied to sync blocks 0 to 3, respectively. Number of the identification sequence. For example, when the downlink signal generating apparatus 100 of the cell group k uses a different frame synchronization identification sequence for each sync block 11, the cell group identification sequence and the frame synchronization identification sequence are [(k, 1), (k, 2), (k, 3), (k, 4)] generates a downlink signal arranged as.

Meanwhile, the repeating pattern replacement unit 130 may use a frame synchronization identification sequence group common to all cell groups, or may use a different frame synchronization identification sequence group for each set of cell groups. These two embodiments are described in FIGS. 8 and 9.

8 illustrates a method of applying a cell group identification sequence and a frame synchronization identification sequence according to an embodiment of the present invention.

The cellular system assigns every cell a cell number identification sequence, a cell-specific orthogonal code for scrambled common pilot symbols or data symbols. In order to increase the number of distinguishable cells, the cellular system bundles a plurality of cells into one cell group and assigns a cell group identification sequence to each cell group. In such a cellular system, a mobile station recognizes a cell group through a cell group identification sequence after acquiring frame synchronization, and recognizes a specific cell through a cell number identification sequence.

According to FIG. 8, the apparatus 100 for generating downlink signals of all cell groups includes a frame synchronization identification sequence group consisting of four frame synchronization identification sequences ({ g ⁽¹⁾ , g ⁽²⁾ , g ⁽³⁾ , g ^{(4 )} . ⁾ }). That is, the downlink signal generating apparatus of cell group k generates a downlink signal having configuration information such as [(k, 1), (k, 2), (k, 3), (k, 4)]. .

The mobile station of the cellular system as shown in FIG. 8 can obtain a time domain diversity gain when obtaining frame synchronization. In the frame structure shown in FIGS. 1 to 3, assuming that the start point of the mobile station to acquire frame synchronization is in the middle of sync block 2, the mobile station acquires frame sync in sync block 3, Detect the cell number. In this case, when the cellular system is a synchronous system, all cells of the cellular system simultaneously transmit a frame sync identification sequence g ⁽⁴⁾ corresponding to sync block 3, and thus a gain such as a macro diversity gain is generated and received. The mobile station can have very good correlation characteristics.

On the other hand, when the frequency domain corresponding to the common synchronization channel is 1.25 MHz, the number of available subcarriers for the cell group identification sequence is 38. In this case, the number of distinguishable cell groups is 38.

9 is a diagram illustrating a method of applying a cell group identification sequence and a frame synchronization identification sequence according to another embodiment of the present invention.

The cellular system according to FIG. 9 uses three frame synchronization identification sequence groups as shown in Equation 5 below.

The cellular system according to FIG. 9 has three cell group sets. When the number of cell groups distinguishable by the cell group identification sequence is M, the first set is composed of cell group M in cell group 1, and the second set is 2M cell in cell group (M + 1). The third set consists of a cell group of 3M to a cell group of (2M + 1). The first set uses the frame sync identification sequence { g ⁽¹⁾ , g ⁽²⁾ , g ⁽³⁾ , g ⁽⁴⁾ }, and the second set uses the frame sync identification sequence { g ^{(1 ')} , g ^{(2 ')} , g ^(3') , g ^{(4 ')} }, and the third set is a frame synchronization identification sequence { g ^{(1 ")} , g ^(2") , g ^{(3 ")} , g ^{(4 ")} }.

If the cellular system uses the cell group identification sequence and the frame synchronization identification sequence as shown in FIG. 9, the diversity gain may be reduced in the cell corresponding to the boundary of the set of cell groups than the cellular system of FIG. 8. However, there is an advantage that the number of distinguishable cell groups can be increased in proportion to the number of frame sync identification sequence groups used.

For example, if the cellular system uses 1.25 MHz as the frequency domain corresponding to the common synchronization channel and uses five frame synchronization identification sequence groups, the number of distinguishable cell groups is 190, 38 times five times.

Subsequently, FIG. 7 is described.

The transmitter 140 converts the downlink signal generated by the repeating pattern replacement unit 130 into an analog signal, modulates and demodulates it, and transmits it to the cell section through the antenna (S140).

10 is a flowchart illustrating a signal conversion process of a synchronization section according to an embodiment of the present invention.

As shown in FIG. 10, the downlink frame generation unit 110 arranges the cell group identification sequence in the synchronization period 13 with a subcarrier interval of 1. In this case, the downlink frame generation unit 110 places 0 symbols in the interval between cell group identification sequences.

As described above, when the synchronization period 13 in which the cell group identification sequence is arranged is inversely fast Fourier transformed, a time domain signal having two repetition patterns is generated as shown in FIG. 10.

The repeating pattern replacement unit 130 generates a downlink signal by replacing one of the generated repeating patterns of the time domain signal with a frame synchronization identification sequence. Since the downlink signal generated according to the embodiment of the present invention has a frame synchronization identification sequence in the time domain, the mobile station can obtain frame synchronization in the time domain.

Next, a mobile station 200 and a cell search method for performing cell search according to an embodiment of the present invention will be described with reference to FIGS. 11 to 14.

11 is a block diagram illustrating a mobile station 200 performing a cell search in accordance with an embodiment of the present invention.

As shown in FIG. 11, the mobile station 200 includes a time synchronization detector 210, a frequency synchronization detector 220, a downlink frame extractor 230, a repeat pattern copyer 240, and a fast fourier transform (FFT) calculator. 250, a cell group determiner 260, and a cell number determiner 270.

12 is a flowchart illustrating a cell searching method according to an embodiment of the present invention.

First, the time synchronization detector 210 correlates a received signal with a frame synchronization identification sequence, finds a sample time point whose correlation value is a predetermined level or more, and determines symbol synchronization and frame synchronization (S210).

Next, the time synchronization detector 210 according to the exemplary embodiment of the present invention will be described in detail with reference to FIG. 13.

13 is a block diagram illustrating a time synchronization detector according to an embodiment of the present invention.

As shown in FIG. 13, the time synchronization detector 210 includes a correlator 211 and a comparator 215.

The correlator 211 correlates the received signal with the frame synchronization identification sequence and outputs a correlation result. In particular, when different frame synchronization identification sequences are applied to each sync block, the correlator 211 outputs a plurality of correlation results by correlating the received signal with the plurality of frame synchronization identification sequences in parallel. Through this, the mobile station 200 may acquire frame synchronization in units of sync blocks. In addition, even when the cellular system uses different frame synchronization identification sequence groups for each cell group set as shown in FIG. 9, the correlator 211 may correlate a received signal with a plurality of frame synchronization identification sequences in parallel to generate a plurality of correlations. Output the result. Through this, the mobile station 200 may not only acquire frame synchronization on a sync block basis, but also grasp the set number of the cell group.

Then, the comparison unit 215 calculates the magnitude (magnitude, I ² + Q ² ) of the correlation result output from the correlation unit 211 to find a sample time point of which the magnitude of the correlation result is equal to or higher than a predetermined level to determine symbol synchronization. do. In addition, the comparison unit 215 determines the frame synchronization by finding the number of the frame synchronization identification sequence so that the magnitude of the correlation result is equal to or greater than a predetermined level. According to the embodiment of FIG. 8, when the frame synchronization identification sequence number 3 is such that the magnitude of the correlation result is greater than or equal to a certain level, the comparison unit 215 indicates that the sample time point before the two synchronization blocks is frame synchronization. You can check it. According to the embodiment of FIG. 9, the comparison unit 215 may determine the frame synchronization and identify the cell group set number by finding the number of the frame synchronization identification sequence that causes the correlation result to have a predetermined level or more.

12 will be described.

The frequency synchronization detector 220 detects a time domain signal replaced with a frame synchronization identification sequence at symbol synchronization determined by the time synchronization detector 210, and differentially correlates the detected signal in the time domain with a delay signal of the detected signal. . The frequency synchronization detector 220 obtains frequency synchronization by estimating the phase of the differentially correlated values (S220).

Next, the frequency synchronization detector 220 according to the exemplary embodiment of the present invention will be described in detail with reference to FIG. 14.

14 is a block diagram illustrating a frequency synchronization detector 220 according to an embodiment of the present invention.

As shown in FIG. 14, the frequency synchronization detector 220 includes a signal extractor 221, a differential correlator 222, and a phase estimator 227, and the differential correlator 222 includes a delay unit 223. ) And a correlator 225.

The signal extractor 221 extracts a signal for detecting frequency synchronization. When zero symbols are used in the guard interval, the signal extractor 221 extracts a signal in a time domain replaced with a frame synchronization identification sequence at a symbol synchronization determined by the time synchronization detector 210, and outputs the signal as a signal for detecting frequency synchronization. do. On the other hand, when a cyclic prefix (CP) is used in the guard interval, the signal extractor 221 detects frequency synchronization by extracting a signal excluding the guard interval from a signal in the time domain corresponding to the frame synchronization identification sequence. Output as a signal to The signal output from the signal extraction unit 221 will be described with reference to FIG. 15.

15 is a diagram illustrating a signal output from the signal extractor 221 according to an exemplary embodiment of the present invention.

As shown in FIG. 15, the signal extractor 221 outputs a signal of a punctured interval when the guard interval is composed of 0 symbols. Outputs the signal of the excluded substitution section.

Subsequently, FIG. 14 will be described.

The signal extractor 221 may accumulate and output signals of a plurality of substituted sections corresponding to a plurality of sync sections in the same frame to increase frequency sync detection as a signal for detecting frequency sync.

The delay unit 223 outputs the delayed signal by delaying the output of the signal extraction unit 221 by one sample or more samples.

The correlator 225 correlates the output of the signal extractor 221 with the output of the delay unit 223 and outputs a correlation result.

The phase estimator 227 estimates the phase of the correlation result output by the differential correlator 225 to obtain frequency synchronization.

12 will be described.

The downlink frame extractor 230 is a downlink frame 10 in the time domain from the received signal based on the symbol synchronization and frame synchronization detected by the time synchronization detector 210 and the frequency synchronization detected by the frequency synchronization detector 220. It is extracted (S230).

The repeating pattern copying unit 240 searches for the sync section 13 in the downlink frame 10 of the time domain extracted by the downlink frame extractor 230, and transmits signals of the remaining regions in the time domain corresponding to the frame sync identification sequence. Copying forms a repeating pattern in the synchronization section 13 (S240).

The fast fourier transform (FFT) calculator 250 performs a fast Fourier operation on the downlink frame 10 having the repetition pattern formed in the synchronization section 13 and outputs the downlink frame 10 in the frequency domain (S250).

The cell group determination unit 250 extracts a cell group identification sequence from the synchronization period 13 of the downlink frame 10 in the frequency domain output by the FFT calculator 260 to thereby use a plurality of cell group identification sequences used by the cellular system. The cell group number is obtained through correlation with (S260).

The cell number determination unit 270 extracts a cell identification sequence distributed in the pilot section 14 or the data section 15 to obtain a cell number (S270). According to the embodiment of FIG. 8, the cell number determination unit 270 may identify the cell through the cell group number and the cell number obtained by the cell group determination unit 250. Meanwhile, according to the embodiment of FIG. 9, the cell number determination unit 270 may further identify a cell by further using the set number of the cell group obtained in step S210. The cell number determination unit 270 may demodulate the broadcast channel (BCH) to verify whether the cell identification sequence included in the broadcast channel is identical to the extracted cell identification sequence and verify the extracted cell identification sequence.

The embodiments of the present invention described above are not implemented only through the apparatus and the method, but may be implemented through a program for realizing a function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded. Implementation may be easily implemented by those skilled in the art from the description of the above-described embodiments.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

According to the present invention, since the downlink signal generating apparatus divides one frame into a plurality of sync blocks and arranges different frame sync identification sequences for each sync block, the mobile station can perform fast sync acquisition and cell search.

In addition, according to the present invention, since the apparatus for generating a downlink signal arranges a frame synchronization identification sequence in the time domain, the mobile station can acquire frame synchronization before performing the FFT, thereby enabling fast synchronization acquisition.

In addition, according to the present invention, since the cellular system regroups the cell groups and allocates the frame synchronization identification sequence group, the number of distinguishable cell groups is increased by linking the cell group identification sequence in the frequency domain with the frame synchronization identification sequence in the time domain. In addition, the mobile station can obtain a macro diversity gain.

Claims (8)

In the method for generating a downlink signal for a predetermined cell, Generating a downlink frame; Disposing a cell group identification sequence corresponding to the predetermined cell in a synchronization period of the downlink frame such that a plurality of repetition patterns are formed in a time domain; Converting the downlink frame into a time domain signal; And Generating a downlink signal by replacing a part of the plurality of repeating patterns with a frame synchronization identification sequence in the time domain signal. The method of claim 1, The downlink frame includes a plurality of sync blocks, Disposing the cell group identification sequence comprises disposing a cell group identification sequence corresponding to the predetermined cell in a synchronization period of each sync block such that a plurality of repetition patterns are formed in a time domain. The method of claim 2, The generating of the downlink signal includes generating the downlink signal with a plurality of frame synchronization identification sequences respectively corresponding to the plurality of sync blocks. The method of claim 3, The generating of the downlink signal includes generating the downlink signal with a frame synchronization identification sequence group corresponding to the predetermined cell among a plurality of frame synchronization identification sequence groups for grouping cell groups. In a method for searching a cell, Correlating the received signal with a frame synchronization identification sequence to find a time point at which the correlation value is maximum to determine symbol synchronization and frame synchronization; Extracting a downlink frame in a time domain based on the symbol synchronization and the frame synchronization; Forming a repetition pattern in the synchronization period by copying signals of the remaining area to the time domain corresponding to the frame synchronization identification sequence in the synchronization period of the downlink frame of the time domain; Converting a downlink frame of the time domain in which the repeating pattern is formed into a frame of a frequency domain; And And extracting a cell group identification sequence in a synchronization period of the frame in the frequency domain to determine a cell group number. The method of claim 5, Determining the symbol synchronization and the frame synchronization And determining the symbol synchronization and the frame synchronization by correlating the received signal with a plurality of frame synchronization identification sequences respectively corresponding to a plurality of sync blocks included in the downlink frame. The method of claim 6, Determining the symbol synchronization and the frame synchronization And correlating the received signal with a plurality of frame synchronization identification sequence groups respectively corresponding to a plurality of cell group sets to determine the symbol synchronization and the frame synchronization and determine a cell group set number. The method of claim 7, wherein Extracting a cell number identification sequence from the sync block to detect a cell number; Identifying said cell via said cell group set number and said cell group number and said cell number.

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