KR101306710B1 - Method for adding additional information to a sequence for synchronization channel - Google Patents

Abstract

The present invention relates to a method of adding a specific number of additional information to a specific channel, and more particularly, to a method of adding additional information to a synchronization channel.

The present invention comprises the steps of generating a sequence for a synchronization channel to achieve the above object; Performing fine constellation modulation to rotate the phase of the sequence according to a phase value corresponding to the additional information to be added; And transmitting a signal including a sequence in which the fine constellation modulation is performed to a receiving end.

Fine constellation modulation, constellation, rotation, phase SCH, side information, additional

Description

Method for adding additional information to a sequence for synchronization channel

1 is a procedure flow diagram illustrating a cell search procedure.

2 is a block diagram illustrating the structure of an SCH following a classified structure.

3 is a block diagram illustrating a SCH that follows a non-hierarchical structure.

4 is a diagram comparing the performance of a classed SCH and a non-classified SCH in a synchronization system.

FIG. 5 is a diagram comparing the performance of classified and non-classified SCHs in an asynchronous system.

6 illustrates residual frequency offset errors in a synchronization system.

7 illustrates residual frequency offset error in an asynchronous system.

8 illustrates a hybrid SCH technique.

9 is a block diagram showing an example of a P-SCH inserted by the first method of the present embodiment.

10A to 10C are block diagrams showing an example of a sequence of masking according to the first method of the present embodiment.

11 illustrates a method of allocating a specific sequence in a frequency domain.

12 is a block diagram illustrating a P-SCH and an S-SCH to include additional information.

13A and 13B are block diagrams showing an example in which one bit of additional information is added.

14A to 14D show an example in which two bits of additional information are added.

15 shows an example of performing the third method and the fine constellation modulation together in this embodiment.

16 is a flowchart illustrating a method of generating a sequence for a synchronization channel according to the present embodiment.

17 is a block diagram showing a transmission apparatus according to the present embodiment.

18 is a block diagram of a communication device for transmitting a P-SCH according to the present embodiment.

The present invention relates to a method of adding a specific number of additional information to a specific channel, and more particularly, to a method of adding additional bits to a synchronization channel.

Hereinafter, a synchronization channel (SCH) will be described as an example of a specific channel.

In a mobile communication system, the first thing a terminal performs to communicate with a base station is to perform synchronization with a base station on a synchronization channel (hereinafter, referred to as 'SCH') and perform cell search. A series of processes for performing synchronization with a base station and acquiring a cell ID to which the mobile station belongs is called a cell search.

In general, the cell search includes an initial cell search performed when the initial UE is powered on, and a neighbor cell where the UE in a connection or idle mode searches for an adjacent base station. It is classified as a neighbor cell search.

1 is a procedure flow diagram illustrating a cell search procedure.

Taking a 3GPP LTE system as an example among various communication systems, the SCH structure for cell searching is divided into a hierarchical structure and a non-hierarchical structure according to a time symbol synchronization and cell search method.

In addition, a cell ID acquisition method includes a first method of searching for a cell group in the SCH and a final cell ID in a reference signal and a second method of obtaining a cell ID only from the SCH. It is becoming.

In the first method, a cell group ID is obtained in the SCH, and in the second method, a final cell ID is obtained in the SCH.

The SCH following the classified structure is described below.

A SCH having a hierarchical structure is classified into a primary SCH (hereinafter referred to as P-SCH) and a secondary SCH (hereinafter referred to as S-SCH) like the SCH of WCDMA.

The P-SCH is a channel in which all cells (or sectors) use the same signal and perform initial symbol synchronization and frequency synchronization. The signal value of the P-SCH is a value previously known to all terminals, and may perform initial time symbol synchronization by performing cross-correlation with a received signal and detecting a maximum peak. This series of procedures is called cross-correlation based detection.

After acquiring time, symbol, and frequency synchronization, cell ID or cell group ID detection is performed at a position of a pre-scheduled S-SCH through time synchronization information acquired by the P-SCH.

Meanwhile, the P-SCH and the S-SCH may be classified into TDM, FDM, and CDM according to a multiplexing method. 2 is a block diagram illustrating the structure of an SCH following a classified structure.

2 is an example of multiplexing using the TDM scheme, and the positions of the P-SCH and the S-SCH and the number of OFDM symbols including the P-SCH and the S-SCH may be different from those of FIG. 2. As shown, the SCH is formed through two OFDM symbols. In addition, only one of one radio frame composed of 20 subframes may transmit the SCH.

2 is an example in which the first and second OFDM symbols provide a SCH. However, the OFDM symbol providing the SCH can be any other OFDM symbol, for example the last OFDM symbol.

Hereinafter, SCHs following a non-hierarchical structure will be described.

The SCH of the non-classified structure exhibits repetitive waveform characteristics in one OFDM symbol in the time domain. This enables the blind detection of the initial time symbol synchronization through the auto-correlation of the received signal by the terminal using the repetitive characteristics of the signal. This detection is called auto-correlation based detection.

After time and frequency synchronization is performed, cell ID or cell group ID detection is performed at the position of the detected SCH.

3 is a block diagram illustrating a SCH that follows a non-hierarchical structure. The OFDM symbol or subframe in which the SCH of FIG. 3 is formed may be freely changed.

In the above-mentioned hierarchical structure, cross-correlation based detection may be performed based on Equation 1 below.

은 상기 R(d)를 최대화하는 값이고, Nf는 무선 프레임(radio frame)의 길이를 의미한다. 또한, P은 각각 averaging을 위해 사용된 P-SCH 심볼 수의 개수를 나타낸다. 또한, Q는 단말의 수신안테나 수를 나타낸다. 또한, L은 M-partial correlation을 하는 part 수를 나타낸다. 또한, N은 FFT 크기를 나타낸다. 그리고,

은 p번째 P-SCH 심볼에서 q 번째 수신 안테나에서 수신되는 신호를 나타낸다. 또한, s(n)은 P-SCH에 삽입된 알려진 시퀀스(known sequence)를 의미한다. 여기서, 주파수 옵셋이 존재하는 환경에서,단순히 상호 상관 기반의 검출(cross-correlation based detection)을 통한 심볼 동기를 수행하면 성능이 열화된다. 따라서, M-partial correlation 방법이 적용될 수 있다. [Y.-P.E. Wang and T. Ottosson, “Cell search in W-CDMA”, Selected Areas in Communications, IEEE Journal on, vol. 18, pp. 1470-1482, Aug. 2000.]In Equation 1, R (d) is a cost function for finding a starting point for synchronization acquisition,

Is a value maximizing R (d), and Nf means a length of a radio frame. In addition, P represents the number of P-SCH symbols used for averaging, respectively. In addition, Q represents the number of reception antennas of the terminal. In addition, L represents the number of parts for M-partial correlation. In addition, N represents the FFT size. And,

Denotes a signal received by the q-th reception antenna in the p-th P-SCH symbol. In addition, s (n) means a known sequence inserted into the P-SCH. Herein, in the environment where the frequency offset exists, performance is degraded by simply performing symbol synchronization through cross-correlation based detection. Therefore, the M-partial correlation method can be applied. Y.-PE Wang and T. Ottosson, “Cell search in W-CDMA”, Selected Areas in Communications, IEEE Journal on, vol. 18, pp. 1470-1482, Aug. 2000.]

A method of estimating frequency offset in the hierarchical structure of FIG. 2 may be represented by Equation 2 below.

In the above formula, fs denotes a sampling frequency and arg {} denotes a phase component with respect to a complex number. The frequency offset is generated by the frequency difference generated by the oscillator provided in each of the base station and the terminal.

The auto-correlation based detection method used in the non-classified structure of FIG. 3 mentioned above is represented by Equation 3 below.

In addition, Equation 4 used to estimate the frequency offset in the non-classified structure is as follows.

The cell search method uses the same method in both classified and non-classified structures.

The SCHs of the classified structure and the non-classified structure will be described below.

Communication systems are divided into synchronous networks and asynchronous networks. A synchronous network is a network in which all sectors have the same transmission start time. In the asynchronous network, sectors in one NodeB have the same transmission start time, but between NodeBs, the transmission start time is random. If it is.

If both synchronous and asynchronous networks are to be supported, it is more preferable to use an SCH of a classed structure.

4 is a diagram comparing the performance of a classed SCH and a non-classified SCH in a synchronization system. FIG. 5 is a diagram comparing the performance of classified and non-classified SCHs in an asynchronous system.

As shown, using a graded SCH improves the performance of cell search. However, in the hierarchical structure, cross-correlation detection method should be used for time synchronization, and the frequency offset estimation performance is relatively degraded compared to the non-hierarchical structure. 6 illustrates residual frequency offset errors in a synchronization system. 7 is a diagram illustrating a residual frequency offset error in an asynchronous system.

In summary, the graded and unclassified SCHs each have disadvantages.

In order to solve each of these disadvantages, a hybrid SCH technique is proposed. The hybrid SCH scheme combines the SCHs of the above-described classified and non-classified structures.

8 illustrates a hybrid SCH technique. As shown in FIG. 8, the hybrid SCH includes a P-SCH and an S-SCH as well as a classed SCH. However, the P-SCH is allocated to the frequency index at specific intervals in a specific OFDM symbol. In other words, the sequence included in the P-SCH has a form in which a specific waveform is repeated a predetermined number of times in the time domain.

 On the other hand, the S-SCH is the same as the graded SCH.

In the case of a hybrid SCH, the P-SCH has a cell common sequence. However, each sequence (P ₀ , P ₁ , P ₂ ,..., P _{N -2} , P _N-1 ) included in the P-SCH is allocated to the frequency domain at specific intervals, thereby retrieving cell search characteristics and frequencies. Improve the offset characteristics.

Equation 5a describes a method of estimating synchronization in a SCH of a hybrid structure, and Equation 5b describes a method of estimating a frequency offset.

The present invention has been proposed to improve the above-described prior art, and an object of the present invention is to propose a method for generating a synchronization channel for transmitting additional information.

Another object of the present invention is to propose a method of generating additional information that does not increase the complexity in synchronous estimation.

It is still another object of the present invention to propose a method of generating a synchronization channel including additional information that can use the conventional synchronization estimation method.

Summary of the Invention

The present invention comprises the steps of generating a sequence for a synchronization channel to achieve the above object; Performing fine constellation modulation to rotate the phase of the sequence according to a phase value corresponding to the additional information to be added; And transmitting a signal including a sequence in which the fine constellation modulation is performed to a receiving end.

Embodiment of the Invention

The operation, features and effects of the present invention will be further embodied by one preferred embodiment of the present invention described below. Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

This embodiment proposes to a synchronization channel, more specifically, it includes additional information to the P-SCH or the S- SCH.

In the case of the above-described graded SCH or hybrid SCH, P-SCH and S-SCH are used. The P-SCH is a cell common sequence in a cell. That is, the P-SCH is typically provided through the same sequence at all base stations (or sectors). In other words, the P-SCH is a sequence that the terminal already knows and is used to obtain time synchronization and frequency synchronization.

In the case of the above-described graded SCH or hybrid SCH, the cell ID and other cell specific information may be obtained through the S-SCH or various control channels (eg, BCH).

This embodiment describes a method of adding additional information to a channel for synchronization, for example, a P-SCH, an S-SCH, or a hybrid SCH.

The method described below can be broadly classified into a method of adding additional information using masking by a code, a method of adding additional information using fine constellation modulation, and a method of using masking and fine constellation modulation together.

The first to third methods described below are examples of a method of using masking by code, and an example of adding additional information to a P-SCH in a synchronization channel will be described. Since a method using masking by a code can be applied to various synchronization channels, an example of applying the P-SCH described below is just one embodiment of the present invention. Therefore, the present invention is not limited to the application example of the P-SCH.

In the P-SCH according to the present embodiment, although additional information is inserted, the complexity according to synchronization estimation does not increase. Moreover, the conventional synchronous estimation method can be used as it is. In addition, the additional information inserted according to the present embodiment can easily detect the additional information inserted by various methods.

1. The first way

The first method according to the present embodiment is a method of generating a P-SCH in the time domain and inserting additional information.

According to the first method, the step of generating a P-SCH and inserting additional information is preferably processed in the time domain.

9 is a block diagram showing an example of a P-SCH inserted by the first method of the present embodiment. As shown, the P-SCH may be allocated to 128 (= N) subcarriers. However, the P-SCH according to the present embodiment is more preferably generated by repeating a specific sequence A in the time domain. In FIG. 9, the A sequence consists of 64 samples of A ₀ to A ₆₃ , and 64 samples are allocated to each subcarrier in the frequency domain. In the sequence of FIG. 9A, two A sequences are repeated in the time domain.

Generating the P-SCH and inserting additional information in the time domain may be divided as follows.

First, in step S101, the P-SCH sequence is inserted in the time domain. In the case of FIG. 9, the P-SCH is generated by repeating a specific sequence A twice in the time domain.

The specific sequence A is preferably a P-SCH according to the hybrid SCH described above, but may be any sequence. That is, it may be a P-SCH according to the above-described graded SCH.

Hereinafter, masking is performed by a specific code in the second step S102. That is, masking is performed on the sequence generated by the step S101. The result of masking a specific sequence is variously generated, and the result of masking means specific additional information. The masking means an operation of performing data processing according to a specific code. There is no limitation on the kind of the specific code and the kind of the data processing. However, it is more preferable that the code used for the masting is an orthogonal or pseudo orthogonal code, and the masking operation more preferably means the operation of multiplying the code by each sample of the sequence generated by the S101 operation. .

10A to 10C are block diagrams showing an example of a sequence of masking according to the first method of the present embodiment.

FIG. 10A illustrates a result of masking the sequence of FIG. 9 using a Walsh code. That is, when the sequence of FIG. 9 is masked using the [1 1] code, the additional information is set to "0", and when the mask of the sequence of FIG. 9 is masked using the [1 -1] code, the additional information is set. Can be set to "1".

FIG. 10B illustrates a result of masking the sequence of FIG. 9 using an arbitrary code. The arbitrary code is a code consisting of samples of size 1 and phase values of 0 or 180 degrees. As shown in FIG. 10B, when the mask of the sequence of FIG. 9 is masked by using the [1 1] code, the additional information is set to "0", and when the mask of the sequence of FIG. 9 is masked by using the code [-1 1]. It can be determined that the additional information is set to "1".

을 통해 마스킹을 수행하는 경우, 도 10c의 내용처럼, r=0인 경우는 부가 정보가 "0"으로 설정된 것이고, r=1인 경우는 부가 정보가 "1"로 설정된 것으로 정할 수 있다. FIG. 10C illustrates a result of masking the sequence of FIG. 9 using a DFT sequence. DFT sequence

When masking is performed through FIG. 10C, when r = 0, the additional information may be set to “0”, and when r = 1, the additional information may be set to “1”.

10A to 10C show an example of masking using two types of codes. 10A to 10C are merely for convenience of description, and according to the exemplary embodiment, masking may be performed using any number of codes. That is, additional information consisting of arbitrary bits can be added. For example, two bits of additional information may be added by increasing the number of Walsh codes to four, and three bits of additional information may be added by increasing the number of Walsh codes to eight. In addition, in the case of the DFT sequence, the size of r and N may be adjusted freely to generate additional information of any size. In addition, in the case of any code, the size of the additional information may be adjusted by adjusting the type of each code.

The sequence generated by the second step S102 is provided to the terminal for synchronous estimation. The sequence according to this embodiment can be used in various communication systems. However, it is more preferably used in a system for transmitting a signal through a plurality of orthogonal subcarriers.

If the system to which the present embodiment is applied is not an OFDM / OFDMA system, the sequence is transmitted through a low pass filter (LPF) corresponding to a transmission bandwidth. In addition, when the DC subcarrier is not considered in the OFDM / OFDMA standard, it is also possible to pass only the LPF without subcarrier insertion.

On the other hand, when the system to which the present embodiment is applied is used for a system using a plurality of orthogonal subcarriers (for example, OFDM, OFDMA, SC-FDMA), it is preferable to further perform the following steps S103 to S106. . That is, since a system using a plurality of orthogonal subcarriers requires a DC subcarrier for removing a DC component and a guard carrier (Null subcarrier or guard subcarrier) for removing a component of a specific band, the following steps are additionally performed. It is desirable to.

Hereinafter, a method (S103) of converting a time-domain sequence into a frequency-domain sequence through an FFT operation will be described according to an embodiment of the present invention.

A method of converting a time domain sequence into a frequency domain sequence in a multi-subcarrier system, wherein a sequence of length N generated in the time domain is transformed into a frequency domain sequence by performing an N-point FFT as shown in Equation 6 below.

When each sample of the sequence generated through the above-described S101 and S102 is a _n , the frequency domain sequence A _k is generated by the above equation.

Hereinafter, a step (S104) of inserting a DC subcarrier and a guard subcarrier according to an embodiment of the present invention will be described.

In general, certain OFDM communication methods may require the insertion of DC subcarriers and the insertion of certain guard subcarriers. If a DC subcarrier protection subcarrier has to be inserted in order to meet a predetermined standard of a specific OFDM communication method, step S104 is performed. Insertion of the DC subcarrier means inserting data 0 into a subcarrier having a frequency of 0 in the frequency domain in order to solve the problem caused by the DC offset in the RF terminal of the transmission and reception.

Hereinafter, step S105 of applying the PAPR attenuation technique to the sequence in which the previous steps are performed according to an embodiment of the present invention will be described.

As described above, the time domain signal may be transformed due to DC subcarrier and guard subcarrier insertion or other data processing to increase the PAPR. In this embodiment, the PAPR attenuation technique may be performed again to reduce the increased PAPR.

Hereinafter, the step S106 of converting the sequence into a time domain sequence through an IFFT operation will be described according to an embodiment of the present invention.

The above step is a method of generating a final signal, which is performed as in Equation 7 below, and the generated sequence may be used for performing synchronization and detecting and distinguishing signals.

2. Second way

The second method, which will be described below, is characterized by generating a sequence having samples of a specific size in the frequency domain. For example, when a P-SCH is generated using a sequence A consisting of N samples (A ₀ , A ₁ , A ₂ , ..., A _N-1 ), a sequence is generated as follows.

First, each sample included in the sequence is assigned to a specific frequency index. The frequency index is an index for identifying a specific subcarrier. When each sample is assigned to a contiguous frequency index, the samples are allocated to a contiguous frequency domain, and when each sample is assigned to a frequency index at a specific interval, The samples are assigned to the corresponding frequency domain.

The second method first inserts a DC subcarrier and a guard carrier (S201). In other words, a component of a specific region in the frequency domain is changed to zero.

Thereafter, a specific A sequence is allocated to the frequency domain at specific intervals using the above-described frequency index (S202).

The size of the specific interval can be freely set. For example, the A sequence may be allocated at two frequency index intervals. In this case, each sample of the A sequence may be allocated to an even frequency index, or each sample of the A sequence may be allocated to an odd frequency index.

11 illustrates a method of allocating a specific sequence in a frequency domain. FIG. 11A illustrates a result of observing the sequence (for example, a sequence consisting of P ₀ to P ₁₂₇ ) in the time domain when a specific sequence is assigned to a continuous frequency index. That is, the signal of FIG. 11A is a result of assigning specific samples P ₀ to P ₁₂₇ to consecutive 128 frequency indexes in the frequency domain.

Meanwhile, P ₀ to P ₁₂₇ When samples are assigned to even-numbered frequency indices, the signal of FIG. 11 (b) can be obtained by the characteristics of oversampling. FIG. 11B is a form in which the waveform B is repeated, and the waveform repeated in FIG. 11B is a form in which the waveform of FIG. 11A is compressed. Since the same waveform is repeated in the time domain, the signal of FIG. 11 (b) may be expressed as a signal of the form [B | B].

Meanwhile, P ₀ to P ₁₂₇ When the samples are assigned to the odd frequency index, the signal of FIG. 11C can be obtained by the characteristics of the DFT operation. The signal of FIG. 11 (c) has a form different from that of FIG. 11 (b). That is, a shift in frequency results in different waveforms on the time axis. Further, due to the nature of the DFT operation, the odd frequency index assigned signal has the form [C | -C] on the time axis.

In summary, the A sequence may be allocated to the frequency index at specific intervals. Further, the number of times the waveform repeats in the time domain and the waveform in the time domain are determined according to the magnitude of the interval and the frequency index to be assigned.

When the base station generates the P-SCH according to the second method, the base station determines the size of the interval and the frequency index to be allocated in advance. As described above, since the waveform of the signal transmitted by the base station is determined differently according to the size of the interval and the assigned frequency index, the method of generating a sequence in the frequency domain should be determined in advance. In addition, since the P-SCH should be a cell common sequence, it is preferable that the terminal also knows in advance how the sequence is generated.

For example, the base station determines to allocate a sample of the A sequence to an even frequency index. In this case, a signal of the form [B | B] is generated as shown in FIG. Since the mobile terminal knows in advance that a signal of the form [B | B] is to be generated, cross-correlation based detection may be performed. In addition, since the signal itself is repeated, autocorrelation based detection is also possible.

The step S202 may be performed before the step S201. There is no limitation in the order of generating the DC / protection subcarrier and generating the P-SCH sequence in the frequency domain. However, generating the P-SCH sequence should be performed before step S203 described below.

In order to add additional information about the P-SCH, a signal must be converted into a time domain signal. Therefore, an IFFT operation is performed on the generated P-SCH (S203).

Masking is performed on the result of S203. Masking for the result of S203 is performed by S102 described above.

In addition, after masking the result of S203, it is preferable to perform the above-described step S103 to S106. That is, it is preferable to insert a DC subcarrier and a guard subcarrier and apply a PAPR reduction technique. The DC subcarrier and the guard subcarrier are already inserted in step S201, but when the step S202 is performed, a non-zero component may be inserted into the DC component and the guard subcarrier component. Therefore, it is more preferable to insert "0" into the DC subcarrier and the guard subcarrier by performing the steps S103 to S106.

In the case of the guard subcarrier, the same effect as that of inserting the guard subcarrier using a specific filter (for example, LPF) can be obtained.

When additional information is added by the first method and the second method described above, synchronization can be obtained using the existing method in the same manner. More specifically, the receiving end (for example, the terminal) obtains time synchronization through the existing graded SCH or hybrid SCH. In addition, since the frequency synchronization is an arc tangent function whose period is pi, the same method as the hybrid method may be performed in the example of the second iteration. That is, despite the addition of the additional information, the method of obtaining time synchronization and frequency synchronization does not change.

In addition, the inserted additional information can detect sign information by using a differential correlation method as shown in Equation 8 after time and frequency synchronization using characteristics having the same absolute value.

As in the above equation, the additional information may be restored using the characteristics of the signal received at the receiving end.

The method of restoring the additional information is very diverse and is not limited to the example of Equation 8 described above.

For example, the additional information may be restored through hypothesis detection using cross-correlation. For example, a transmitting end (for example, a base station) performs additional masking using a Walsh code to insert additional information, the code [1, 1] corresponds to additional information "0", and [1, -1]. The code may correspond to additional information "1". In this case, the signal transmitted by the transmitting end has a form of [A | A] or [A | -A] in the time domain. In addition, since the A waveform is based on a cell common sequence, the terminal also knows. Accordingly, the terminal may measure a cross correlation value for the received signal through the [A | A] and [A | -A] signals known to the terminal. That is, the terminal may check the peak value through hypothesis detection using cross-correlation and restore the additional information.

3. The third way

The third method generates a P-SCH sequence in the frequency domain and adds additional information in the frequency domain.

That is, the DC subcarrier and the guard subcarrier are generated through the same steps as the step S201. In addition, the P-SCH sequence is generated at a specific frequency index interval in consideration of the generated DC subcarrier and the guard subcarrier (S301). For example, when a P-SCH is generated using a sequence A consisting of N samples (A ₀ , A ₁ , A ₂ , ..., A _N-1 ), a sequence is generated as follows.

When the additional information is set to "0", the N samples are allocated to an even frequency index. In this case, as described with reference to FIG. 11, the waveform has a waveform of [B | B] in the time domain. On the other hand, when the additional information is set to "1", the N samples are allocated to the odd frequency index. In this case, as described in FIG. 11, the waveform has a waveform of [C | -C] in the time domain.

There is no limitation on the size of the additional information. If two bits of additional information are added, four different waveforms are needed, and thus the N samples may be allocated at intervals of four frequency indexes. As a result, four types of waveforms are obtained that are repeated four times in the time domain. This allows you to add additional information.

The P-SCH generated in the frequency domain as described above is converted into a signal in the time domain through the IFFT operation in the step S106.

In summary, the third method generates a plurality of cell common sequences. In addition, each of the plurality of sequences means specific additional information. The third method, unlike the first or second method, uses a plurality of cell common sequences. In this case, synchronization acquisition in the terminal may be performed as follows.

First, the terminal knows all of the plurality of cell common sequences. That is, the signal [B | B] for the case where the N samples are allocated to the even frequency index and the [C | -C] signal for the case where the N samples are allocated to the odd frequency index are known. . The terminal may obtain synchronization by obtaining cross-correlation between known [B | B] or [C | -C] and a received signal. That is, synchronization may be performed using cross correlation, but hypothesis detection may be performed to acquire synchronization and additional information may be obtained.

Motivation may be obtained using autocorrelation rather than cross correlation. Since the plurality of cell common sequences are all assigned to frequency indices at regular intervals, the plurality of cell common sequences are repeated. That is, the terminal may acquire synchronization by using the characteristic that the signal is repeated in the time domain.

The first to third methods described above propose a technique for performing masking by a specific code in a sequence generated in a frequency domain or a time domain. The fourth method described below proposes a method of adding additional information using fine constellation modulation.

4. Fourth way

The fourth method is further characterized by performing fine constellation modulation.

At least one information bit to be transmitted to the receiving end is constellation mapped to one symbol. Conventionally known constellation mappings include QPSK, BPSK, 16QAM, and the like. Such symbols, such as QPSK, may be gathered into a single OFDM symbol and transmitted to a receiving end.

In this case, a constellation mapping technique such as QPSK may be referred to as macro constellation modulation, and a modulation technique applied for adding additional information may be referred to as micro constellation modulation.

The symbol on which the large constellation modulation has been performed (eg, a QPSK symbol) is mapped to predetermined positions on the constellation map. If the transmitting end sends additionally rotated by a predetermined angle at predetermined positions, it can be seen that additional information is added through the additional rotated angle.

The basic idea of the fourth method of the present invention is to use two stages of constellation mapping. More specifically, giant constellation modulation is performed on a sequence corresponding to a channel for synchronous estimation. For the sequence in which such giant constellation modulation is performed, fine constellation modulation is additionally applied. In this case, the method of fine constellation modulation is determined in accordance with the additional information to be added.

The following method relates to the general form of M bit addition method.

The fourth method is applicable to both a hierarchical SCH (classified structure), a non-hierarchical SCH (SCH) of a non-classified structure, and a hybrid SCH (hybrid SCH). Hereinafter, for convenience of description, a method of adding additional information to a hierarchical SCH having an hierarchical structure will be described. In addition, a case where multiplexing is performed between the P-SCH and the S-SCH by the TDM scheme will be described. However, since the fourth method can be applied to various synchronization channel structures, the present invention is not limited to the following embodiments.

12 is a block diagram illustrating a P-SCH and an S-SCH to include additional information.

The P-SCH and the S-SCH may be generated according to the above-described method. That is, it can be generated in the frequency or time domain. In addition, if necessary, it may be generated by repetition in the time domain or by arranging sequences at specific frequency index intervals in the frequency domain.

According to the fourth method, a method of adding additional information of M bits is to multiply the P-SCH portion of the figure by the phase function corresponding to the corresponding bits.

If the time-domain sequence of the P-SCH or S-SCH is p (n) (n = 0,1,2, ..., N _fft -1), the sequence p _{bit (n)} after adding bits is expressed by the following equation. Same as 9a.

Here, m represents the mth additional information. For example, in the case of 1 bit with M = 1, m = 0,1 is possible, and in the case of 2 bits with M = 2, m = 0,1,2,3 is possible.

In Equation 9a, N represents the length of a sequence. In addition, p _{bit (n)} is a time domain sequence to which additional information is added, and p (n) is a time domain sequence before additional information is added. In addition, n is a time domain sample index.

Equation 9a may be equivalently expressed by the following equation 9b. Equation 9b is an example represented by a frequency-domain sequence.

Here, P _{bit (k)} is a frequency domain sequence in which additional information is added in the frequency domain, and P (k) is a frequency domain sequence before additional information is added. K denotes a frequency domain index.

13A and 13B are block diagrams showing an example in which one bit of additional information is added. As shown in the figure, one or more bits of additional information may be added by not changing the phase of the sequences included in the P-SCH or rotating the phase by 180 degrees.

13A illustrates an example in which additional information corresponding to 'bit 0' is included, and example of FIG. 13B illustrates an example in which additional information corresponding to 'bit 1' is included.

Of course, this additional information may be added to the P-SCH and the S-SCH, respectively. In addition, it may be added to any one of the P-SCH and S-SCH, and may be added at the same time. In the case of M = 1, the additional information to be added is '+1' and '-1'.

14A to 14D show an example in which two bits of additional information are added. 14A to 14D show an example in which additional information is added to the S-SCH.

Each example of FIGS. 14A to 14D relates to additional information '00', '01', '10', and '11' when M = 2. Of course, this may be applied to the P-SCH and the S-SCH separately or all at the same time.

The search method of the additional information bits according to the present invention may have various methods, but for convenience, the additional information bits are inserted into the P-SCH, and a method of detecting the bits by channel estimation in the S-SCH will be described.

If the P-SCH and the S-SCH are adjacent to each other as shown in FIGS. 14A to 14D, it may be assumed that the channels experienced by the two SCHs are the same. In this case, the radio channel estimated as the S-SCH can be used to detect additional information added to the P-SCH.

For convenience, it is assumed that all subcarriers are used in the frequency portion of the P-SCH. In addition, it is assumed that detecting bit information is performed in a time / frequency synchronization with a P-SCH and cell ID detection in an S-SCH. In this case, the time-domain signal received from the P-SCH is expressed by Equation 9c.

In the above equation, h (n) is the impulse response of the channel, n (n) is the AWGN, and '*' is the convolution operation. The result of Equation 9c may be expressed as Equation 9d below.

The signal of equation 9d represents a signal in the frequency domain. Here, H (k) means the frequency response of the channel, N (k) means AWGN. The time / frequency domain signals received in the S-SCH are shown in Equations 9e and 9f, respectively.

S (k) and s (n) mean S-SCH signals transmitted at frequency / time, respectively.

Channel estimation is performed on the S-SCH according to the above assumptions. For example, if the LS (Least Square) channel estimation, it can be obtained by the following equation (9g).

S (k) is a value already known at the receiving end because the detection of the cell ID is completed as mentioned above.

The P-SCH is recovered using the estimated radio channel as shown in Equation 9h.

By using the compensated R _eq (k), the added bit information may be detected as shown in Equation 9i.

Here, arg {} means a phase component, and {} in the above equation means a complex result of correlation.

The additional method of the additional information described above may be applied to the SCH of the hybrid structure or the SCH of the non-classified structure. That is, the additional information may be added by rotating the phase corresponding to the additional information.

Hereinafter, a new method combining a method of adding additional information by masking proposed in the first to third methods described above and the fourth method described above is proposed.

A fifth method, which will be described below, relates to a method of adding additional information by using masking by code and fine constellation modulation.

5. The fifth way

The fifth method is preferably applied to sequences having a repeating structure in the time domain. For example, applying the fifth method to the hybrid SCH is as follows.

Three methods of adding additional information by masking have been proposed, and the third method is described as follows.

According to the third method described above, the additional information '1' (or '0') is indicated when the sequence is assigned to the odd frequency index, and the additional information '0' is assigned when the sequence is assigned to the even frequency index. (Or '1').

In addition, according to the above description, when a sequence is assigned to an odd frequency index, as shown in FIG. 11 (c) in the time domain, a waveform having the form of [C | -C] is assigned. In the time domain, as shown in FIG. 11B, the waveform has a waveform of the form [B | B].

In addition, fine constellation modulation may be performed. That is, additional information may be added by rotating the phase by 0 degrees or by rotating the phase by 180 degrees.

15 shows an example of performing the third method and the fine constellation modulation together in this embodiment.

When the additional information added in FIG. 15 is '00', the sequence has a form of [B | B]. Therefore, the MSB of the additional information is set to '0'. On the other hand, since the phase changed by 0 degrees due to the fine constellation modulation, the additional information LSB is set to '0'.

When the additional information added in FIG. 15 is '01', the form of the sequence is [B | B]. Therefore, the MSB of the additional information is set to '0'. On the other hand, since the phase has changed by 180 degrees due to the fine constellation modulation, the additional information LSB is set to '1'.

When the additional information added in FIG. 15 is '10', the sequence is in the form of [C | -C]. Therefore, the MSB of the additional information is set to '1'. On the other hand, since the phase changed by 0 degrees due to the fine constellation modulation, the additional information LSB is set to '0'.

When the additional information added in FIG. 15 is '11', the form of the sequence is [C | -C]. Therefore, the MSB of the additional information is set to '1'. On the other hand, since the phase has changed by 180 degrees due to the fine constellation modulation, the additional information LSB is set to '1'.

In order to detect the additional information by the fifth method, a process of determining whether the sequence is in the form of [B | B] or [C | -C] and calculating a rotated phase value by fine constellation modulation is performed. .

The fourth and fifth methods of this embodiment are characterized by using fine constellation modulation.

In the above-described example, the number of additional information added is a power of 2, but the present invention is not limited thereto.

That is, Equation 9a may be modified as in Equation 10a.

Equation 9b may be modified as in Equation 10b.

In this case, Equations 9c to 9h are applied as they are, and Equation 9i is converted to Equation 10c and applied as follows.

The above-described example of FIG. 15 is applicable to classed or non-classified SCHs.

When additional information is added through the non-classified SCH, the additional information may be restored by the following operation.

First, the operation of adding additional information at the transmitting end is the same for both non-classified SCHs and other SCHs.

The receiving end may detect initial synchronization based on an autocorrelation technique. In addition, frequency synchronization can be obtained.

The receiving end then detects the sequence index used in the SCH. The receiving end makes an integer multiple frequency offset estimation using the detected sequence index and corrects the estimated offset.

The receiving end estimates the channel using the detected sequence and compensates the channel accordingly.

After the channel estimation is completed, additional information by fine constellation modulation is obtained.

In the fourth and fifth methods of the present embodiment, the fine constellation modulation may use a positive phase value or a minus phase value. That is, Equations 10a and 10b may be replaced with Equations 11a and 11b below.

Equation 10c is modified as in Equation 11c below.

In the constellation diagram, each symbol (eg, a QPSK symbol, etc.) may be rotated in a clockwise or counterclockwise direction due to the fine constellation modulation.

This method of inserting additional information has the following advantages. First, additional bit information can be inserted without affecting the existing structure. In addition, no additional complexity occurs.

Additional information added in the present method is as follows.

The type of the additional information is not limited, and various information for communication may be included. For example, the additional information may be used as information indicating the length of the cyclic prefix (CP length). For example, the cyclic prefix CP may be divided into a short CP and a long CP according to its length. In this case, the type of the cyclic prefix may be displayed through the additional information.

In addition, the information may include information about an antenna mode. That is, it may be displayed whether the antenna is a single antenna or a multi antenna.

In addition, various information is possible. For example, it may include various information such as subframe synchronization information (indicating whether it is a first subframe or a second subframe) and a BCH bandwidth (1.25MHz or 5MHz). In addition, cell group ID information may be further inserted.

16 is a flowchart illustrating a method of generating a sequence for a synchronization channel according to the present embodiment. 16 shows an example of a P-SCH in a sequence for a synchronization channel.

First, a sequence (eg, a P-SCH sequence, an S-SCH sequence, a hybrid sequence, or a SCH sequence in a non-classified structure) for a synchronization channel is generated according to the five methods described above, and additional information is inserted. (S1001). Inserting the additional information may use any one of the five methods described above. That is, masking for a code, a technique of inserting additional information using fine constellation modulation, or a combination of masking and fine constellation modulation can be used.

The P-SCH generated by the above-described method is converted into a time domain sequence by steps S1003 to S1009 corresponding to steps S103 to S106 and transmitted to the terminal.

In the communication apparatus according to the present embodiment, each step may be provided as an independent module.

17 is a block diagram showing a transmission apparatus according to the present embodiment. The apparatus of FIG. 17 includes a sequence generation and additional information insertion module 21, an FFT module 22, a DC and a guard subcarrier insertion module 23, and a PAPR technique application module according to any one of the five methods described above. 24, and an IFFT module 25.

In addition, the communication apparatus according to the present embodiment may be implemented according to FIG. 18.

18 is a block diagram of a communication device for transmitting a P-SCH according to the present embodiment.

18 includes a serial / parallel converter 11 for converting a serial signal into a parallel signal, a module 12 for performing symbol to subcarrier mapping and PAPR improvement, a module 13 for performing IFFT conversion, A module 14 for converting parallel signals into a serial signal and a module 15 for inserting a cyclic transpose.

The output signals from the steps S1001 to S1009 may be input to the apparatus of FIG. 18 and transmitted to the receiving end. However, since step S1007 is performed by the device of FIG. 12, when transmitting through the device of FIG. 18, step S1007 may be omitted. In addition, since the operation of inserting the guard subcarrier in the step S1005 may be implemented by a filter (not shown) separately provided in the apparatus of FIG. 18, the operation of inserting the guard subcarrier may be omitted.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

The effects of the present invention are as follows.

The present invention proposes a method for generating a synchronization channel for transmitting additional information. Through such a synchronization channel can be provided as information to the terminal without increasing the complexity. Furthermore, according to the present invention, there is an advantageous effect that a conventional synchronous estimation method can be used.

Claims (9)

In the method for transmitting the cell common sequence (cell common sequence) for synchronization, Obtaining the cell common sequence; And Transmitting the obtained cell common sequence to a receiving end, The cell common sequence is generated by allocating samples included in a subsequence in a frequency domain to a frequency index at regular intervals, and the cell common sequence is masked according to a code corresponding to specific information. Transmission method. The method of claim 1, The cell common sequence includes at least one of a first sequence and a second sequence, The first sequence is generated by allocating samples included in the subsequence to an even numbered frequency index, and the second sequence is generated by assigning samples included in the subsequence to an odd numbered frequency index. Method of transmitting cell common sequence. The method of claim 1, And the specific information includes subframe synchronization information through which the cell common sequence is transmitted. The method of claim 1, And the cell common sequence is generated including at least one guard subcarrier. The method of claim 1, And the cell common sequence is not transmitted on a DC subcarrier. The method of claim 1, And performing the masking by multiplying each sample of the code by each sample of the cell common sequence. The method of claim 1, The constant interval is limited to a predetermined range, cell common sequence transmission method. The method of claim 1, And the cell common sequence obtained is transmitted through a secondary synchronization channel (S-SCH) signal. The method of claim 1, And transmitting the obtained cell common sequence to a receiving end is performed using a plurality of orthogonal subcarriers.

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