阅读说明：本技术 一种基于dqpsk同步序列的帧同步方法及系统 (Frame synchronization method and system based on DQPSK synchronization sequence ) 是由 刘武 杨超 罗鸣 于 2021-10-26 设计创作，主要内容包括：一种基于DQPSK同步序列的帧同步方法,涉及通信领域,方法包括：接收数据序列R,所述数据序列R的导码包括两段重复的同步序列S,对数据序列R和同步序列S分别进行差分运算,得到第一序列R～(′)和第二序列S～(′)；在第一序列R～(′)中滑动窗口,截取连续两段与同步序列S等长的信号数据进行自相关运算,由运算后获得的峰值位置确定同步头预估区域；在同步头预估区域内,截取与第二序列S～(′)相同长度的信号数据,再与第二序列S～(′)进行相关运算,确定同步头具体位置；根据同步头具体位置实现帧同步。该方法可以求出数据帧起始位置,在大频偏低SNR条件下仍能稳定准确的实现帧同步。(A frame synchronization method based on DQPSK synchronization sequence relates to the communication field, the method comprises: receiving a data sequence R, wherein a guide code of the data sequence R comprises two repeated synchronous sequences S, and performing differential operation on the data sequence R and the synchronous sequences S respectively to obtain a first sequence R ′ And a second sequence S ′ (ii) a In the first sequence R ′ A middle sliding window intercepts two continuous sections of signal data with the same length as the synchronization sequence S to perform autocorrelation operation, and determines a synchronization head estimation area according to the peak position obtained after the operation; in the synchronous head pre-estimation area, the second sequence S is intercepted ′ Signal data of the same length, and then the second sequence S ′ Performing correlation operation to determine the specific position of the synchronous head; and realizing frame synchronization according to the specific position of the synchronization head. The method can calculate the initial position of the data frame, and can still stably and accurately realize frame synchronization under the condition of large frequency and low SNR.)

1. A frame synchronization method based on DQPSK synchronization sequence is characterized by comprising the following steps:

receiving a data sequence R, wherein a leader code of the data sequence R comprises two repeated synchronous sequences S, and performing differential operation on the data sequence R and the synchronous sequences S respectively to obtain a first sequence R 'and a second sequence S';

sliding a window in the first sequence R', intercepting two continuous sections of signal data with the same length as the synchronization sequence S to perform autocorrelation operation, and determining a synchronization head estimation area according to a peak position obtained after the operation;

intercepting signal data with the same length as the second sequence S 'in the synchronous head pre-estimation area, and then performing correlation operation with the second sequence S' to determine the specific position of the synchronous head;

and realizing frame synchronization according to the specific position of the synchronization head.

2. The method for frame synchronization based on DQPSK synchronization sequence according to claim 1, characterized in that said data sequence R comprises ambles and payload data, said synchronization sequence being coded with DQPSK modulation.

3. The method for frame synchronization based on DQPSK synchronization sequence according to claim 1, characterized in that signal data R in said first sequence R_i' is:

R_i′＝R_i*conv(R_i+1)(i＝1,2,..L-1)

wherein i is a serial number, and L is the length of the data sequence R;

signal data S in said second sequence S_i' is:

S_i′＝S_i*conv(S_i+1)(i＝1,2,..N-1)

where i is the sequence number, N is the length of the synchronization sequence S, and N > 256.

4. The method for frame synchronization based on DQPSK synchronization sequence of claim 3, wherein the two consecutive segments of signal data with the same length as the synchronization sequence S are [ R ]_i′ R′_i+1 … R′_i+N-1]And [ R'_i+N R′_i+N+1 … R′_i+2N-1]The autocorrelation value is:

where k represents the index in two segments of equal length signal data, find W_iThe two sides of the peak value position respectively take a distance equal to the length of the synchronization sequence S, and the distances are used as the estimated area of the synchronization head together.

5. The method of claim 4 for frame synchronization based on DQPSK synchronization sequences, wherein the signal data with the same length as the second sequence S 'is intercepted in the sync header pre-estimation area, and then correlated with the second sequence S' to obtain the value W_i' is:

where Z represents the sync head pre-estimated area, find W_i' the peak position, i value corresponding to the peak position is the specific position of the synchronization head.

6. A frame synchronization system based on DQPSK synchronization sequence, comprising:

the first differential operation module is used for carrying out differential operation on a received data sequence R to obtain a first sequence R', and a guide code of the data sequence R comprises two sections of repeated synchronous sequences S;

the second difference operation module is used for carrying out difference operation on the synchronous sequence S to obtain a second sequence S';

the first correlation operation module is used for sliding a window in the first sequence R', intercepting two continuous sections of signal data with the same length as the synchronization sequence S to perform autocorrelation operation, and determining a synchronization head estimation area according to a peak position obtained after the operation;

the second correlation operation module is used for intercepting signal data with the same length as the second sequence S 'in the synchronous head pre-estimation area, and then performing correlation operation with the second sequence S' to determine the specific position of the synchronous head;

and the frame synchronization module is used for realizing frame synchronization according to the specific position of the synchronization head.

7. The DQPSK synchronization sequence-based frame synchronization system of claim 6, wherein in said first differential operation module, signal data R in first sequence R' is_i' is:

R′_i＝R_i*conv(R_i+1)(i＝1,2,..L-1)

wherein i is a serial number, and L is the length of the data sequence R.

Signal data S in a second sequence S_i' is:

S′_i＝S_i*conv(S_i+1)(i＝1,2,..N-1)

where i is the sequence number, N is the length of the synchronization sequence S, and N > 256.

8. The system for frame synchronization based on DQPSK synchronization sequence according to claim 7, wherein said first correlation operation module intercepts two consecutive pieces of signal data equal in length to synchronization sequence S as [ R ]_i′ R′_i+1 … R′_i+N-1]And [ R'_i+NR′_i+N+1 … R′_i+2N-1]The autocorrelation value is:

where k represents the index in two segments of equal length signal data, find W_iThe two sides of the peak value position respectively take a distance equal to the length of the synchronization sequence S, and the distances are used as the estimated area of the synchronization head together.

9. The system of claim 8, wherein the second correlation operation module intercepts signal data having the same length as the second sequence S 'in the sync header pre-estimation region, and performs correlation operation on the signal data with the second sequence S' to obtain a correlation value W_i' is:

where Z represents the sync head pre-estimated area, find W_i' the peak position, i value corresponding to the peak position is the specific position of the synchronization head.

10. The system for frame synchronization based on DQPSK synchronization sequence according to claim 6, characterized in that said data sequence R comprises ambles and payload data, said synchronization sequence being coded with DQPSK modulation.

Technical Field

The present invention relates to the field of communications, and in particular, to a frame synchronization method and system based on a DQPSK (differential quadrature phase shift keying) synchronization sequence.

Background

The time synchronization of the data frame is one of the key technologies in digital communication, that is, the data receiving end determines the time domain starting point of the data frame sent by the sending end, so as to determine the position of each symbol in the data frame according to the agreed frame structure. The time domain synchronization is mainly based on a method of a synchronization sequence, the method has high synchronization precision and stable performance, and the frame synchronization method based on the synchronization sequence is mainly divided into two types of cross correlation and self correlation: the cross-correlation is to cross-correlate the received baseband data with a locally stored synchronization sequence; the self-correlation is to insert two identical synchronous sequences continuously into the frame header of the sending end, and to intercept two sections of the following data with the same length as the synchronous sequences from the baseband data to perform correlation operation during receiving. After the correlation operation, the peak position of the correlator output value is found, namely the frame start position corresponding to the synchronization sequence.

The frame synchronization algorithm is the basis of the subsequent algorithm, and the extracted synchronization head and the effective data are the basis of the subsequent algorithm and directly influence the signal processing performance of the system, so the precision and the robustness of the synchronization algorithm must be ensured. Meanwhile, the algorithm based on the synchronization sequence occupies a time slot with a certain length, and the correlation operation needs more calculation amount, so how to reduce the complexity of the algorithm and the consumption of hardware resources is also a key problem which must be considered in the algorithm design.

Research finds that when a received signal has large frequency offset and the signal SNR (signal to noise ratio) is low, a correlation peak value found after correlation operation is low, and the accurate position of the correlation peak is extremely difficult to determine, so that how to improve the robustness of the synchronization algorithm under the condition of large frequency offset and low SNR becomes a problem needing continuous improvement.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a method and a system for frame synchronization based on a DQPSK synchronization sequence, which are used for solving the initial position of a data frame and stably and accurately realizing frame synchronization when a received signal has large frequency offset and a signal SNR is low.

In order to achieve the above object, in one aspect, a frame synchronization method based on DQPSK synchronization sequences is adopted, including:

receiving a data sequence R, wherein a leader code of the data sequence R comprises two repeated synchronous sequences S, and performing differential operation on the data sequence R and the synchronous sequences S respectively to obtain a first sequence R 'and a second sequence S';

sliding a window in the first sequence R', intercepting two continuous sections of signal data with the same length as the synchronization sequence S to perform autocorrelation operation, and determining a synchronization head estimation area according to a peak position obtained after the operation;

intercepting signal data with the same length as the second sequence S 'in the synchronous head pre-estimation area, and then performing correlation operation with the second sequence S' to determine the specific position of the synchronous head;

and realizing frame synchronization according to the specific position of the synchronization head.

Preferably, the data sequence R includes a preamble and payload data, and the synchronization sequence is coded by DQPSK modulation.

Preferably, the signal data R 'in the first sequence R'_iComprises the following steps:

R′_i＝R_i*conv(R_i+1)(i＝1，2，..L-1)

wherein i is a serial number, and L is the length of the data sequence R;

signal data S 'in the second sequence S'_iComprises the following steps:

S′_i＝S_i*conv(S_i+1)(i＝1，2，..N-1)

wherein i is a serial number, N is the length of the synchronization sequence S, and N > 256.

Preferably, the two consecutive pieces of signal data equal to the length of the synchronization sequence S are [ R_i′ R′_i+1...R′_i+N-1]And [ R'_i+NR′_i+N+1...R′_i+2N-1]The autocorrelation value is:

where k represents the index in two segments of equal length signal data, find W_iThe two sides of the peak value position respectively take a distance equal to the length of the synchronization sequence S, and the distances are used as the estimated area of the synchronization head together.

Preferably, in the sync header estimation region, the signal data with the same length as the second sequence S' is intercepted, and then the correlation operation is performed with the second sequence SValue W'_iComprises the following steps:

wherein Z represents a synchronous head prediction area, and W 'is found'_iThe value i corresponding to the peak position is the specific position of the synchronization head.

In another aspect, a frame synchronization system based on DQPSK synchronization sequence is provided, including:

the first differential operation module is used for carrying out differential operation on a received data sequence R to obtain a first sequence R', and a guide code of the data sequence R comprises two sections of repeated synchronous sequences S;

the second difference operation module is used for carrying out difference operation on the synchronous sequence S to obtain a second sequence S';

the first correlation operation module is used for sliding a window in the first sequence R', intercepting two continuous sections of signal data with the same length as the synchronization sequence S to perform autocorrelation operation, and determining a synchronization head estimation area according to a peak position obtained after the operation;

the second correlation operation module is used for intercepting signal data with the same length as the second sequence S 'in the synchronous head pre-estimation area, and then performing correlation operation with the second sequence S' to determine the specific position of the synchronous head;

and the frame synchronization module is used for realizing frame synchronization according to the specific position of the synchronization head.

Preferably, in the first differential operation block, the signal data R ' in the first sequence R ' is '_iComprises the following steps:

R′_i＝R_i*conv(R_i+1)(i＝1，2，..L-1)

wherein i is a serial number, and L is the length of the data sequence R.

Signal data S 'in a second sequence S'_iComprises the following steps:

S′_i＝S_i*conv(S_i+1)(i＝1，2，..N-1)

wherein i is a serial number, N is the length of the synchronization sequence S, and N > 256.

Preferably, the first correlation operation module intercepts two consecutive segments of signal data equal to the length of the synchronization sequence S as R'_i R′_i+1...R′_i+N-1]And [ R'_i+NR′_i+N+1...R′_i+2N-1]The autocorrelation value is:

where k represents the index in two segments of equal length signal data, find W_iThe two sides of the peak value position respectively take a distance equal to the length of the synchronization sequence S, and the distances are used as the estimated area of the synchronization head together.

Preferably, the second correlation operation module intercepts signal data with the same length as the second sequence S 'in the synchronization header estimation region, and performs correlation operation on the signal data and the second sequence S'_iComprises the following steps:

wherein Z represents a synchronous head prediction area, and W 'is found'_iThe value i corresponding to the peak position is the specific position of the synchronization head.

Preferably, the data sequence R includes a preamble and payload data, and the synchronization sequence is coded by DQPSK modulation.

One of the above technical solutions has the following beneficial effects:

the invention inserts DQPSK synchronization sequence in the transmitted data, after the receiving end removes the frequency offset through differential operation, the receiving end can calculate the initial position of the data frame through self-correlation operation and cross-correlation operation with the known DQPSK sequence, therefore, the invention can still stably and accurately realize the frame synchronization under the condition of large frequency and low SNR.

Drawings

Fig. 1 is a flowchart of a frame synchronization method based on DQPSK synchronization sequence according to an embodiment of the present invention;

fig. 2 is a frame structure diagram of a DQPSK synchronization sequence;

fig. 3 is a schematic diagram of a frame synchronization system based on a DQPSK synchronization sequence according to an embodiment of the present invention.

Reference numerals:

1. a first difference operation module; 2. a second difference operation module; 3. a first correlation operation module; 4. a second correlation operation module; 5. and a frame synchronization module.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

As shown in fig. 1, the present invention provides an embodiment of a frame synchronization method based on DQPSK synchronization sequence, including the following steps:

and S1, respectively carrying out differential operation on the received data sequence R and the synchronization sequence S to obtain a first sequence R 'and a second sequence S'.

As shown in fig. 2, the received data sequence R includes a preamble and payload data, where the preamble is formed by splicing two repeated synchronization sequences S, and the synchronization sequences S are coded by DQPSK modulation.

S2, sliding a window in the first sequence R', intercepting two continuous segments of signal data with the same length as the synchronization sequence S to perform autocorrelation operation, and determining the estimated region of the synchronization head according to the peak position obtained after the operation.

And S3, intercepting the signal data with the same length as the second sequence S 'in the synchronous head pre-estimation area, and then carrying out correlation operation with the second sequence S' to determine the specific position of the synchronous head.

And S4, realizing frame synchronization according to the specific position of the synchronization head.

In the above step S1, a difference operation is performed according to the data sequence R to obtain a first sequence R', and a signal in the first sequence RData R'_iComprises the following steps:

R′_i＝R_i*conv(R_i+1)(i＝1，2，..L-1)，

wherein i is a serial number, and L is the length of the data sequence R.

Similarly, the signal data S 'in the second sequence S'_iComprises the following steps:

S′_i＝S_i*conv(S_i+1)(i＝1，2，..N-1)

wherein i is a serial number, N is the length of the synchronization sequence S, and N > 256.

In step S2, two consecutive pieces of signal data equal in length to the synchronization sequence S are extracted as [ R'_iR′_{i+ 1}...R′_i+N-1]And [ R'_i+NR′_i+N+1...R′_i+2N-1]Value W of autocorrelation calculation_iComprises the following steps:

where k represents the index in two equal lengths of signal data, from 0, 1 … N-1. Find W_iThe two distances are used as the estimated area of the synchronization head, and the estimated area of the synchronization head can comprise a plurality of corresponding i values.

In step S3, the signal data having the same length as the second sequence S 'is extracted from the synchronization header estimation region, and the extracted signal data is correlated with the second sequence S'_iComprises the following steps:

wherein Z represents a synchronous head prediction area, and W 'is found'_iThe value i corresponding to the peak position is the specific position of the synchronization head.

In the above steps, the received data sequence R is a time domain symbol sequence that is continuously received and processed by the receiving end, and in the received signal processing process, the data sequence R has undergone preprocessing steps such as sampling, clock synchronization, and the like.

In this embodiment, the content and length of the synchronization sequence S may be well defined at the transmitting end and the receiving end.

As shown in fig. 3, an embodiment of a frame synchronization system based on DQPSK synchronization sequences is provided. The system comprises a first difference operation module 1, a second difference operation module 2, a first correlation operation module 3, a second correlation operation module 4 and a frame synchronization module 5.

The first difference operation module 1 is configured to perform difference operation on the received data sequence R, and output a result of conjugate multiplication between previous signal data and next signal data to obtain a first sequence R'. Signal data R 'in a first sequence R'_iComprises the following steps:

R′_i＝R_i*conv(R_i+1)(i＝1，2，..L-1)

wherein i is a serial number, and L is the length of the data sequence R.

And the second difference operation module 2 is used for performing difference operation on the synchronous sequence S to obtain a second sequence S'. Signal data S 'in a second sequence S'_iComprises the following steps:

S′_i＝S_i*conv(S_i+1)(i＝1，2，..N-1)

wherein i is a serial number, N is the length of the synchronization sequence S, and N > 256.

The first correlation operation module 3 is used for sliding a window in the first sequence R', intercepting two continuous sections of signal data with the same length as the synchronous sequence S to perform autocorrelation operation, and taking an absolute value after summing the correlation operation results; and the method is also used for determining the estimated area of the synchronous head according to the peak position obtained after operation. Specifically, two consecutive pieces of intercepted signal data equal in length to the synchronization sequence S are [ R'_iR′_i+1...R′_i+N-1]And [ R'_i+NR′_i+N+1...R′_i+2N-1]The autocorrelation value is:

wherein k represents an index in two sections of equal-length signal data, different values of i are compared, and W is found_iThe two distances are taken as the estimated area of the synchronous head.

And the second correlation operation module 4 is used for intercepting the signal data with the same length as the second sequence S 'in the synchronous head pre-estimation area, and then performing correlation operation on the signal data and the second sequence S' to determine the specific position of the synchronous head. A value W ' obtained by extracting signal data having the same length as the second sequence S ' and correlating the signal data with the second sequence S '_iComprises the following steps:

wherein Z represents a synchronous head prediction area, and W 'is found'_iPeak position of (1), W'_iThe i value corresponding to the peak position is the specific position of the synchronous head.

And the frame synchronization module 5 is used for realizing frame synchronization according to the specific position of the synchronization head.

The present invention is not limited to the above embodiments, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are included in the scope of the claims of the present invention which are filed as the application.