KR101023259B1 - Method for generating downlink signal, 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 may generate a downlink signal using one cell unique identification code group and a plurality of frame synchronization identification sequences, or generate a downlink signal using a plurality of cell unique identification code groups and a plurality of frame synchronization identification sequences. In addition, a downlink signal may be generated using a plurality of cell unique recognition code groups and one frame synchronization identification sequence.

The cell search apparatus acquires frame synchronization through a frame synchronization identification sequence and a cell unique recognition code group, and identifies a cell.

Frame, Sync, Cell Search, Downlink Signal

Description

How to generate a downlink signal, and how to perform cell search {METHOD FOR GENERATING DOWNLINK SIGNAL, 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 a first embodiment of the present invention.

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

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

10 is a conceptual diagram illustrating an operation of a frame synchronization application unit according to an embodiment of the present invention.

11 is a conceptual diagram illustrating an operation of a frame synchronization applying unit according to another embodiment of the present invention.

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

13 is a flowchart illustrating a cell searching method according to the first embodiment of the present invention.

FIG. 14 is a block diagram illustrating a synchronization detector for detecting synchronization in a downlink signal generated according to the embodiment of FIG. 10.

FIG. 15 is a block diagram illustrating a synchronization detector for detecting synchronization in a downlink signal generated according to the embodiment of FIG. 11.

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

17 is a flowchart illustrating a cell searching method according to a second embodiment of the present invention.

18 is a flowchart illustrating a cell searching method according to a third 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 4.5ms 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. It also 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.

The downlink signal generation method according to the characteristics of the present invention
Generating a cell unique identification code group consisting of a combination of a first cell identification code and a second cell identification code; And disposing the cell unique identification code group in a synchronization period of a downlink frame. Here, the combination of the first cell identification code and the second cell identification code represents cell identification information.
A cell search method according to a feature of the present invention
Receiving a cell unique identification code group consisting of a combination of a first cell identification code and a second cell identification code; And extracting cell identification information from the combination of the first cell identification code and the second identification code.
The cell search apparatus according to the characteristics of the present invention
A receiving unit for receiving a cell unique identification code group consisting of a combination of a first cell identification code and a second cell identification code; And a cell identification unit for extracting cell identification information from the combination of the first cell identification code and the second identification code.
Computer-readable media in accordance with aspects of the present invention
On computer
Generating a cell unique identification code group comprising a combination of a first cell identification code and a second cell identification code and representing cell identification information; And a program for executing the step of disposing the cell unique identification code group in a synchronization period of a downlink frame.
An apparatus for generating downlink according to a feature of the present invention is
A cell unique identification code group consisting of a combination of a first cell identification code and a second cell identification code is generated to represent cell identification information, and the cell unique identification code group is arranged in a synchronization period of a downlink frame.
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.

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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.

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.

A plurality of cell unique identification codes (hereinafter also referred to as cell unique identification code groups) are arranged in a frequency domain corresponding to the common synchronization channel of the synchronization section 13. In this case, elements of the plurality of cell unique recognition codes are arranged at regular intervals. According to Fig. 3, two cell unique identification codes are placed in a common sync channel, and elements of the two cell unique identification codes are arranged with subcarrier spacing one. Meanwhile, the cell unique recognition code may be expressed as in Equation 1 below.

In Equation 1, k denotes a cell unique recognition code number, and N _G denotes a length of a cell unique recognition code. 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, or the like may be used to obtain a cell unique recognition code. The element c _n ^(k) of the cell unique recognition code according to the GCL sequence may be expressed as Equation 2.

Meanwhile, the plurality of cell unique identification codes according to the embodiment of the present invention may be arranged in the frequency domain of the common sync channel as shown in FIG. 3. In the mobile communication system supporting the scalable bandwidth as shown in Figs. 4 and 5, a mobile station using various bandwidths such as a mobile station using a bandwidth of 1.25 MHz, a mobile station using a bandwidth of 2.5 MHz, and the like, may use a cell-specific identification code. 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.

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

The data section 15 includes data symbols.

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 shown in FIG. 6, the downlink signal generating apparatus 100 includes a downlink frame generator 110, an inverse fast fourier transform (IFFT) calculator 120, a frame synchronization applier 130, and a transmitter 140. It includes.

7 is a flowchart illustrating a downlink signal generation method according to a first 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 generation unit 110 generates a frame including a plurality of synchronization periods, and arranges the same cell unique recognition code group in the plurality of synchronization periods in the downlink frame. In this case, the downlink frame generation unit 110 may arrange the cell unique recognition code group in the downlink frame such that a plurality of repetition patterns are formed in the time domain. For example, if the downlink frame generator 110 arranges the elements of the cell unique recognition code group in the downlink frame with a subcarrier spacing of 1, two repeating patterns are formed.

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 on a time axis (S120).

The frame synchronization application unit 130 generates a downlink signal by applying a plurality of frame synchronization identification sequences to the synchronization section 13 of the signal on the time axis generated by the IFFT operation unit 120 (S130). In this case, the frame synchronization applying unit 130 applies different frame synchronization identification sequences to the plurality of synchronization periods 13 included in the downlink frame. That is, the plurality of frame synchronization identification sequences applied by the frame synchronization application unit 130 according to the first embodiment of the present invention correspond to the plurality of synchronization sections 13 included in the downlink frame, respectively.

The transmitter 140 converts the downlink signal generated by the frame synchronization application unit 130 into an analog signal, modulates and demodulates the signal, and transmits the demodulated signal to the cell section through the antenna (S140).

According to the downlink signal generation method according to the first embodiment of the present invention, a downlink frame in which a cell unique identification code group and a frame synchronization identification sequence are arranged as in Equation 3 below is generated.

In Equation 3, (m, k) is a cell unique recognition code group disposed in four sync intervals according to the first embodiment of the present invention, and 0 to 3 are frame sync identification sequences respectively applied to four sync intervals. Is the number of.

According to the first embodiment of the present invention, the mobile station can obtain frame synchronization by the frame synchronization identification sequence, and identify the cell by the cell unique recognition code group.

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

First, the downlink frame generator 110 generates a downlink frame as shown in FIGS. 1 to 3 (S210). That is, the downlink frame generation unit 110 generates a frame including a plurality of sync intervals, and arranges a plurality of cell unique recognition code groups in the downlink frame in the plurality of sync intervals. In this case, the plurality of sync sections form one sync section group, and the downlink frame includes a plurality of sync section groups. The plurality of cell unique identification code groups respectively correspond to a plurality of sync interval groups. The downlink frame generation unit 110 arranges the plurality of cell unique identification code groups in the synchronization section of the corresponding synchronization section group.

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 time domain signal (S220).

The frame synchronization application unit 130 generates a downlink signal by applying a plurality of frame synchronization identification sequences to the synchronization period 13 of the time domain signal generated by the IFFT operation unit 120 (S230). In this case, the plurality of frame sync identification sequences respectively correspond to a plurality of sync sections included in the sync section group. Accordingly, the frame sync application unit 130 applies the frame sync identification sequence to the corresponding sync section.

The transmitter 140 converts the downlink signal generated by the frame sync application unit 130 into an analog signal, modulates and demodulates the signal, and transmits the demodulated signal to the cell section through the antenna (S240).

According to the method for generating a downlink signal according to the second embodiment of the present invention, a downlink frame in which a cell unique identification code group and a frame synchronization identification sequence are arranged as in Equation 4 below is generated.

Equation 4 shows a structure of a downlink frame including two sync interval groups. At this time, each sync interval group includes two sync intervals. In Equation 4, (m, k) is a cell-specific identification code group disposed in the preceding two sync intervals among four sync intervals according to the second embodiment of the present invention, and (m, l) is According to the second embodiment, it is a cell-specific identification code group disposed in two later sync intervals. And 0 and 1 are the numbers of the frame sync identification sequence applied to four sync intervals.

According to the second embodiment of the present invention, the mobile station can obtain only a part of the frame synchronization by the frame synchronization identification sequence, and the full frame synchronization can be obtained only by identifying the cell unique recognition code group. In addition, the mobile station can identify the cell through the cell unique identification code group. That is, two cell unique recognition code groups (m, k) and (m, l) indicate one cell.

According to the second embodiment of the present invention, the number of identifiable cells is halved than in the case of the first embodiment of the present invention, but the mobile station can obtain frame synchronization with two frame synchronization identification sequences. Complexity is reduced.

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

First, the downlink frame generator 110 generates a downlink frame as shown in FIGS. 1 to 3 (S310). That is, the downlink frame generation unit 110 generates a frame including a plurality of sync intervals, and arranges different cell unique recognition code groups in the downlink frame in the plurality of sync intervals. That is, the plurality of cell unique identification code groups arranged by the downlink frame generation unit 110 correspond to the plurality of synchronization periods, respectively.

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 on a time axis (S320).

The frame synchronization application unit 130 generates a downlink signal by applying one frame synchronization identification sequence to the synchronization period 13 of the signal on the time axis generated by the IFFT operation unit 120 (S330).

The transmitter 140 converts the downlink signal generated by the frame synchronization application unit 130 into an analog signal, modulates and demodulates it, and transmits the demodulated signal to the cell section through the antenna (S340).

According to the downlink signal generation method according to the third embodiment of the present invention, a downlink frame in which a cell unique identification code group and a frame synchronization identification sequence are arranged as shown in Equation 5 below is generated.

In Equation 5, (m, k), (m, l), (l, m), and (k, m) are cell-specific recognition codes disposed in four sync intervals according to a third embodiment of the present invention. A group, and 0 is a number of a frame sync identification sequence applied to four sync intervals.

According to the third embodiment of the present invention, the mobile station cannot obtain the frame synchronization by the frame synchronization identification sequence, and can obtain the frame synchronization only by identifying the cell unique recognition code group. In addition, the mobile station can identify the cell through the cell unique identification code group. That is, four cell unique recognition code groups (m, k), (m, l), (l, m), and (k, m) indicate one cell.

According to the third embodiment of the present invention, the number of identifiable cells becomes 1/4 compared to the case according to the first embodiment of the present invention, but the mobile station can obtain frame synchronization with one frame synchronization identification sequence. This reduces complexity.

Next, the frame synchronization applying unit 130 according to the embodiment of the present invention will be described with reference to FIGS. 10 and 11.

10 is a conceptual diagram illustrating an operation of a frame synchronization application unit according to an embodiment of the present invention.

According to the embodiment of FIG. 10, one frame sync identification sequence includes two orthogonal identification codes. Accordingly, the frame synchronization application unit 130 according to the embodiment of FIG. 10 multiplies two orthogonal recognition codes by two repetition patterns formed in the synchronization section of the time domain signal generated by the IFFT calculator 120.

The x-th frame synchronization identification sequence may be represented by Equation 6 below.

As in Equation 3, the x-th frame synchronization identification sequence includes a u-th orthogonal recognition code and a v-th orthogonal recognition code. In other words, the number x of the frame synchronization identification sequence is determined by the combination of the numbers u and v of the two orthogonal identification codes.

On the other hand, the u-th orthogonal identification code and the v-th orthogonal identification code can be expressed as in Equation 7 below.

In Equation 7, u and v are numbers of orthogonal recognition codes. N _F is a length of an orthogonal identification code, which is determined by the number of samples corresponding to half of one OFDM symbol interval excluding a guard interval. In order to obtain an orthogonal recognition code, one of a Hadamard sequence, a Gold sequence, a Golay sequence, a GCL sequence, a KAZAC sequence, and a PN sequence may be used.

11 is a conceptual diagram illustrating an operation of a frame synchronization applying unit according to another embodiment of the present invention.

According to the embodiment of Fig. 11, one frame sync identification sequence consists of one orthogonal identification code. Accordingly, the frame synchronization applying unit 130 according to the embodiment of FIG. 11 replaces one of two repetition patterns formed in the synchronization section of the time domain signal generated by the IFFT operation unit 120 with the frame synchronization identification sequence.

12 to 18, a mobile station 200 and a cell search method for performing cell search according to an embodiment of the present invention will be described.

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

As shown in FIG. 12, the mobile station 200 includes a downlink signal receiver 210, a sync detector 220, a sync section symbol extractor 230, a sync section convertor 240, and a fast fourier transform (FFT) calculator. 250, a cell identification unit 260.

13 is a flowchart illustrating a cell searching method according to the first embodiment of the present invention.

First, the downlink signal receiver 210 receives a downlink signal from a channel (S410). The downlink signal receiver 210 according to the embodiment of FIG. 13 receives a downlink signal generated according to the embodiment of FIG. 7.

Next, the synchronization detector 220 applies a plurality of frame synchronization identification sequences respectively applied to a plurality of synchronization periods included in the downlink frame to the downlink signal received by the downlink signal receiver 210 to perform symbol synchronization and frequency synchronization. And frame synchronization (S420). If the downlink frame has a structure according to Equation 3, the synchronization detector 220 uses four frame synchronization identification sequences. The synchronization detector 220 has a different structure depending on how the downlink signal is generated.

FIG. 14 is a block diagram illustrating a synchronization detector 220 that detects synchronization in a downlink signal generated according to the embodiment of FIG. 10.

As shown in FIG. 14, the synchronization detector 220 that detects synchronization in the downlink signal generated according to the embodiment of FIG. 10 includes a multiplier 1110, a differential correlation unit 1120, a comparison unit 1130, and a phase. The estimator 1140 is included. In addition, the differential correlation unit 1120 includes a delay unit 1121 and a correlation unit 1122.

The multiplier 1110 multiplies the downlink signal received by the downlink signal receiver 210 by a frame synchronization recognition code consisting of two orthogonal recognition codes and outputs the multiplication.

The delay unit 1121 delays the output signal of the multiplier 1110 by a time corresponding to half of the length of the OFDM symbol interval, and outputs the delayed signal.

The correlator 1122 correlates the output signal of the multiplier 1110 and the output signal of the delay unit 1121 and outputs a correlation result. According to the embodiment of FIG. 13, the correlation unit 1122 performs correlation in parallel using a total of four frame synchronization identification sequences. Through this, the mobile station 200 may acquire frame synchronization in units of sync blocks.

The comparison unit 213 calculates the magnitude (magnitude, I ² + Q ² ) of the correlation result output by the correlation unit 1122, finds a sample time point of which the magnitude of the correlation result is a predetermined level or more, and symbol synchronization and synchronization period ( 13) to obtain the position. In addition, the comparison unit 213 according to the embodiment of FIG. 13 determines one of the positions of the acquired synchronization section 13 as the frame synchronization by finding the number of the frame synchronization identification sequence so that the magnitude of the correlation result is a predetermined level or more. do.

The phase estimator 1140 obtains frequency synchronization by estimating the phase of the correlation result output from the correlator 1122.

FIG. 15 is a block diagram illustrating a synchronization detector 210 that detects synchronization in a downlink signal generated according to the embodiment of FIG. 11.

As shown in FIG. 15, the synchronization detector 210 for detecting synchronization in the downlink signal generated according to the embodiment of FIG. 11 includes a correlator 1210, a comparator 1220, a signal extractor 1230, A differential correlator 1240 and a phase estimator 1250. The differential correlation unit 1240 includes a delay unit 1241 and a correlation unit 1242.

The correlator 1210 correlates the downlink signal received by the downlink signal receiver 210 with a frame synchronization identification sequence and outputs a correlation result. According to the embodiment of FIG. 13, the correlation unit 1210 performs correlation in parallel using a total of four frame synchronization identification sequences. Through this, the mobile station 200 may acquire frame synchronization in units of sync blocks.

Then, the comparison unit 1220 calculates the magnitude (magnitude, I ² + Q ² ) of the correlation result output from the correlation unit 1210 to find a sample time point where the magnitude of the correlation result is greater than or equal to a predetermined level. The position of the synchronization section 13 is determined. In addition, the comparison unit 213 according to the embodiment of FIG. 13 determines one of the positions of the acquired synchronization section 13 as the frame synchronization by finding the number of the frame synchronization identification sequence so that the magnitude of the correlation result is a predetermined level or more. do.

The signal extractor 1230 extracts a signal for detecting frequency synchronization. When 0 symbol is used in the guard period, the signal extractor 1230 extracts a signal in a time domain corresponding to the frame sync identification sequence by the symbol sync obtained by the comparator 1220 and outputs the signal as a signal for detecting frequency sync. do. On the other hand, when a cyclic prefix (CP) is used for the guard interval, the signal extractor 1230 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 A signal output from the signal extractor 1230 will be described with reference to FIG. 16.

16 is a diagram illustrating a signal output from the signal extractor 1230 according to an embodiment of the present invention.

As shown in FIG. 16, the signal extractor 1230 outputs a signal of a punctured interval when the guard interval is composed of 0 symbols. Outputs the signal of the excluded substitution section.

15 will be described.

The signal extractor 1230 may accumulate the signals of the plurality of substituted sections corresponding to the plurality of synchronization sections in the same frame and output the signal for detecting the frequency synchronization in order to increase the performance of the frequency synchronization detection.

The delay unit 1241 outputs the delayed signal by delaying the output of the signal extraction unit 1230 by one sample or more samples.

The correlator 1242 outputs a differential correlation result by correlating the output of the signal extractor 1230 with the output of the delay unit 1241.

The phase estimator 1250 obtains a frequency offset by estimating the phase of the correlation result output from the correlator 1242.

13 will be described.

The synchronization section symbol extractor 230 extracts a synchronization section symbol in the time domain from the downlink signal based on the symbol synchronization, frequency synchronization, and frame synchronization acquired by the synchronization detector 220 (S430).

The sync section converter 240 converts the sync section symbols of the time domain extracted by the sync section symbol extractor 230 into sync section symbols before the frame sync identification sequence is applied (S440). If the downlink frame 10 of the time domain is generated according to the embodiment of FIG. 10, the sync section converter 240 may apply a frame sync identification sequence to the sync section symbol of the time domain extracted by the sync section symbol extractor 230. Multiply and print. If the downlink frame 10 of the time domain is generated according to the embodiment of FIG. 11, the sync section converter 240 may add a frame sync identification sequence from the sync section symbol of the time domain extracted by the sync section symbol extractor 230. The repetition pattern is formed in the synchronization period symbol 13 by copying signals of the remaining area to the corresponding time domain.

The fast fourier transform (FFT) calculator 250 performs a fast Fourier operation on the synchronization section symbol 13 in the time domain output by the synchronization section transformation unit 240 and outputs the synchronization section symbol 13 in the frequency domain (S450). .

The cell identification unit 260 extracts a cell unique recognition code group from the synchronization interval symbol 13 in the frequency domain output by the FFT calculator 260 and correlates with a plurality of cell unique recognition codes used by the cellular system. Identify (S460). According to the embodiment of FIG. 13, since the same cell unique identification code group is applied to each sync period 13, the cell identification unit 260 obtains one cell unique identification code group, and one cell unique identification code. The group obtains a plurality of cell unique recognition codes. The cell identification unit 260 performs cell identification with another cell when the combination is different through a combination of numbers of the plurality of cell unique recognition codes. According to the embodiment of FIG. 13, the cell identification unit 260 shows a method of performing cell identification in a table as shown in Table 1 below.

In C _{(a, b)} of Table 1, C represents a cell unique number, and a and b each represent a number of the first and second cell unique recognition codes of the cell unique recognition code group.

If the sync channel available band is 1.25 MHz, the total number of available subcarriers is approximately 38. In the embodiment of FIG. 13, if 20 subcarriers are assigned to the first cell unique identification code and 18 subcarriers are assigned to the second cell unique identification code, the total number of distinguishable cells is 360 (= 20 * 18).

The cell identification unit 260 may demodulate the broadcast channel (BCH) to verify whether the cell unique identification code included in the broadcast channel is identical to the extracted cell unique identification code and verify the extracted cell unique identification code.

As described above, according to the embodiment of FIG. 13, the synchronization detector 210 may simultaneously acquire symbol synchronization, frame synchronization, and frequency synchronization in the time domain by performing correlation with frame synchronization identification sequences according to the number of synchronization intervals. .

17 is a flowchart illustrating a cell searching method according to a second embodiment of the present invention.

First, the downlink signal receiver 210 receives a downlink signal from a channel (S510). The downlink signal receiver 210 according to the embodiment of FIG. 17 receives a downlink signal generated according to the embodiment of FIG. 8.

Next, the synchronization detector 220 applies a plurality of frame synchronization identification sequences respectively applied to the plurality of synchronization sections included in the synchronization section group to the downlink signal received by the downlink signal receiver 210 to perform symbol synchronization and frequency synchronization. And primary frame synchronization (S520). If the downlink frame has the structure shown in Equation 4, the synchronization detector 220 uses two frame synchronization identification sequences. Meanwhile, the sync detector 220 may determine the positions of sync sections included in the downlink frame using a plurality of frame sync identification sequences. However, since the embodiment according to FIG. 17 uses a smaller number of frame sync identification sequences than the number of sync sections, the sync detector 220 may recognize only part of the frame sync (ie, primary frame sync). Although the structure of the synchronization detector 220 according to the embodiment of FIG. 17 also varies according to the method of generating the downlink signal as in the embodiment of FIG. 13, a detailed description thereof will be omitted.

The sync section symbol extractor 230 extracts a number of sync section symbols 13 corresponding to at least the first frame sync based on the symbol sync, the frequency sync, and the first frame sync acquired by the sync detector 220 ( S530).

The sync section converter 240 converts the plurality of sync section symbols 13 extracted by the sync section symbol extractor 230 into the sync section symbols 13 before the frame sync identification sequence is applied (S540). If the downlink frame 10 of the time domain is generated according to the embodiment of FIG. 10, the sync section converter 240 synchronizes the frame to the sync section symbol 13 of the time domain extracted by the sync section symbol extractor 230. Output by multiplying the identification sequence. If the downlink frame 10 of the time domain is generated according to the embodiment of FIG. 11, the sync interval converter 240 may output signals of the remaining regions in the time domain corresponding to the frame sync identification sequence in the sync interval symbol 13. By copying, a repeating pattern is formed in the sync section symbol 13.

The fast fourier transform (FFT) calculator 250 performs a fast Fourier operation on the synchronization section symbol 13 in the time domain output by the synchronization section transformation unit 240 and outputs the synchronization section symbol 13 in the frequency domain (S550). .

The cell identification unit 260 extracts a plurality of cell unique recognition code groups from the sync interval symbols 13 of the plurality of frequency domains output by the FFT calculator 260 and then compares them with the plurality of cell unique recognition codes used by the cellular system. The cell is identified through correlation (S560). According to the embodiment of FIG. 17, since the same cell unique identification code group is applied to each sync period group, the cell identification unit 260 obtains a cell unique identification code group corresponding to the number of sync period groups. The cell identification unit 260 may obtain frame synchronization through the extracted plurality of cell unique recognition code groups and the primary frame synchronization obtained by the synchronization detector 220.

According to the embodiment of FIG. 17, a method of performing cell identification by the cell identification unit 260 is shown in Table 2 below.

In Table 2, cell unique recognition code groups (0,0) and (0,1) indicate one cell. However, the cell identification unit 260 may obtain frame synchronization through a cell unique recognition code group that is used in duplicate to indicate one cell.

If the sync channel available band is 1.25 MHz, the total number of available subcarriers is approximately 38. In the embodiment of FIG. 17, if 20 subcarriers are assigned to the first cell unique identification code and 18 subcarriers are assigned to the second cell unique identification code, the total number of distinguishable cells is 180 (= 20 * 18/2). do. That is, the number of distinguishable cells in the embodiment of FIG. 17 is half of the number of distinguishable cells in the embodiment of FIG. However, since the number of frame synchronization identification sequences used when acquiring symbol synchronization and primary frame synchronization can be reduced by half than in the embodiment of Fig. 13, the complexity is reduced.

As described above, according to the embodiment of FIG. 17, the synchronization detector 210 performs correlation with fewer frame synchronization identification sequences than the number of synchronization intervals to obtain symbol synchronization, frequency synchronization, and primary frame synchronization in the time domain. In the frequency domain, frame synchronization may be obtained through cell unique recognition codes.

18 is a flowchart illustrating a cell searching method according to a third embodiment of the present invention.

First, the downlink signal receiver 210 receives a downlink signal from a channel (S610). The downlink signal receiver 210 according to the embodiment of FIG. 18 receives a downlink signal generated according to the embodiment of FIG. 9.

Next, the synchronization detector 220 applies one frame synchronization identification sequence to the downlink signal received by the downlink signal receiver 210 to obtain symbol synchronization and frequency synchronization, and to identify positions of the synchronization sections (S620). ). However, the embodiment according to FIG. 18 uses a smaller number of frame sync identification sequences than the number of sync sections, and therefore the sync detector 220 may not acquire frame sync. The synchronization detector 220 according to the embodiment of FIG. 18 may also have a different structure according to the method of generating the downlink signal as in the embodiment of FIG. 13, but a detailed description thereof will be omitted.

The sync section symbol extractor 230 may have more than or equal to the number of sync section symbols 13 corresponding to one downlink frame based on the symbol sync, frequency sync, and position of the sync sections obtained by the sync detector 220. ) Is extracted (S630).

The sync section converter 240 converts the plurality of sync section symbols extracted by the sync section symbol extractor 230 into a symbol before the frame sync identification sequence is applied (S640). If the downlink frame 10 of the time domain is generated according to the embodiment of FIG. 10, the sync interval converter 240 multiplies the sync interval symbol extracted by the sync interval symbol extractor 230 by the frame sync identification sequence. If the downlink frame 10 of the time domain is generated according to the embodiment of FIG. 11, the sync interval converter 240 may perform a time corresponding to a frame sync identification sequence in the sync interval symbol extracted by the sync interval symbol extractor 230. Signals of the remaining regions are copied to the region to form a repeating pattern in the sync interval symbol.

The fast fourier transform (FFT) calculator 250 performs a fast Fourier operation on the synchronization section symbols in the time domain output by the synchronization section transformation unit 240 and outputs the synchronization section symbols in the frequency domain (S650).

The cell identification unit 260 extracts a plurality of cell unique recognition code groups from the sync interval symbols of the plurality of frequency domains output by the FFT calculator 260 and correlates with a plurality of cell unique recognition codes used by the cellular system. The cell is identified (S660). According to the embodiment of FIG. 18, since a different cell unique recognition code group is applied to each sync period, the cell identification unit 260 obtains a cell unique recognition code group corresponding to the number of sync intervals, The cell unique identification code group indicates one cell. The cell identification unit 260 may obtain frame synchronization based on the extracted plurality of cell unique recognition code groups and the location of the synchronization section obtained by the synchronization detector 220.

According to the embodiment of FIG. 18, a method of performing cell identification by the cell identification unit 260 is shown in Table 3 below.

In Table 2, cell unique recognition code groups (0,0), (0,1), (0,2), and (0,3) indicate one cell. However, the cell identification unit 260 may obtain frame synchronization through a cell unique recognition code group that is used in duplicate to indicate one cell.

If the sync channel available band is 1.25 MHz, the total number of available subcarriers is approximately 38. In the embodiment of FIG. 18, if 20 subcarriers are assigned to the first cell unique identification code and 18 subcarriers are assigned to the second cell unique identification code, the total number of distinguishable cells is 90 (= 20 * 18/4). do. That is, the number of distinguishable cells in the embodiment of FIG. 18 becomes 1/4 of the number of distinguishable cells in the embodiment of FIG. 13. However, since the position of the symbol synchronization and the synchronization interval can be obtained with one frame synchronization identification sequence, the complexity is reduced compared to the embodiment of FIG.

As described above, according to the embodiment of FIG. 18, the synchronization detector 210 obtains the position of symbol synchronization, frequency synchronization, and synchronization interval in the time domain by performing correlation with one frame synchronization identification sequences, and identifies the cell in the frequency domain. Frame synchronization may be obtained through the recognition codes.

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

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

In addition, according to an embodiment of the present invention, since the downlink signal generation apparatus applies the frame synchronization identification sequence to the time domain, the mobile station can acquire the frame synchronization before performing the FFT, thereby enabling fast synchronization acquisition.

In addition, according to an embodiment of the present invention, since the downlink signal generation apparatus uses the cell unique identification code group repeatedly to indicate one cell, and uses the duplicate cell unique identification code group for frame synchronization acquisition, The mobile station can reduce the complexity in obtaining symbol synchronization and frame synchronization.

Claims (20)

Generating a cell unique identification code group consisting of a combination of a first cell identification code and a second cell identification code; And Disposing the cell unique identification code group in a synchronization period of a downlink frame, And the first cell identification code and the second cell identification code combination represent cell identification information. The method of claim 1, And a combination of the first cell identification code and the second cell identification code indicates cell identification information and frame synchronization information. The method of claim 1, One downlink frame includes a plurality of downlink signal generation method. The method of claim 3, The cell unique identification code group included in each sync period existing in one downlink frame is different from each other. Receiving a cell unique identification code group, comprising a combination of a first cell identification code and a second cell identification code, included in a synchronization interval; And And extracting cell identification information from the combination of the first cell identification code and the second cell identification code. The method of claim 5, And extracting frame synchronization information from the combination of the first cell identification code and the second cell identification code. The method of claim 5, One downlink frame includes a plurality of the synchronization periods. The method of claim 7, wherein The cell unique identification code group included in each sync period existing in one downlink frame is different from each other. A receiving unit configured to combine a first cell identification code and a second cell identification code and to be included in a synchronization interval, the cell-specific identification code group receiving; And And a cell identification unit for extracting cell identification information from the combination of the first cell identification code and the second cell identification code. 10. The method of claim 9, And the cell identification unit further extracts frame synchronization information from a combination of the first cell identification code and the second cell identification code. 10. The method of claim 9, One downlink frame includes a plurality of the synchronization period. The method of claim 11, And a cell unique identification code group included in each sync period existing in one downlink frame. On computer Generating a cell unique identification code group comprising a combination of a first cell identification code and a second cell identification code and representing cell identification information; And And a program for recording the cell unique identification code group in a synchronization section of a downlink frame. The method of claim 13, And the combination of the first cell identification code and the second cell identification code is indicative of cell identification information and frame synchronization information. The method of claim 13, The cell unique identification code group is included in a sync interval, and one downlink frame includes a plurality of sync intervals. The method of claim 15, The cell-specific identification code group included in each sync interval present in one downlink frame is different from each other. A downlink generating device, comprising a combination of a first cell identification code and a second cell identification code, generates a cell unique identification code group representing cell identification information and arranges the cell unique identification code group in a synchronization period of a downlink frame. . The method of claim 17, And a combination of the first cell identification code and the second cell identification code indicates cell identification information and frame synchronization information. The method of claim 17, One downlink frame includes a plurality of downlink signal generating apparatus. The method of claim 19, The cell unique identification code group included in each sync period existing in one downlink frame is different from each other.

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