Dual synchronization method and system for multi - level differential phase - shift keying signal

Abstract

The present invention discloses a dual synchronization method and system for multi - level differential phase - shift keying signals, which relates to the field of communication technologies. By utilizing the characteristics of multi - level differential phase - shift keying signals and centering around the frame start marker, the frequency offset estimation value is used for frame synchronization. When frame synchronization is successful, the calculated frequency offset estimation is the final frequency difference estimation value, thus solving the problems of frame synchronization and carrier synchronization simultaneously. On the one hand, without additional pilot consumption, the present invention also performs external synchronization for carrier synchronization, reducing performance loss. On the other hand, while performing frame synchronization, the present invention realizes carrier synchronization, which can significantly reduce the complexity of the receiver compared with the traditional separate synchronization methods.

Description

Technical Field

[0001] The present invention relates to the field of communication technologies, and particularly relates to a dual synchronization method and system for multi - level differential phase - shift keying signals. Background Art

[0002] Synchronization technology is directly related to the performance of the entire communication system. Accurate synchronization technology is a prerequisite for reliable communication. The communication receiving end can use coherent demodulation or non - coherent demodulation to recover information from the modulated signal. Although non - coherent demodulation is relatively easy to implement, its performance is somewhat lost. The main difficulty in implementing coherent demodulation lies in extracting carrier information. Generally speaking, carrier synchronization also includes accurately estimating the phase of the carrier to generate a signal with the same frequency and phase as the carrier for signal demodulation. In the differential phase - shift keying modulation method considered in the present invention, the relative carrier phase value between adjacent symbols is used to carry information, and the receiving end can still demodulate the transmitted information without knowing the absolute carrier phase. Based on the above considerations, the carrier synchronization mentioned in the present invention only includes carrier frequency estimation and does not include carrier phase estimation.

[0003] In a digital system where the transceiver communicates in frames, the receiving end needs to estimate the start time and end time of the data frame. Frame synchronization is the process of extracting the frame start marker and frame end marker. On the one hand, in some frame structures, there is only a frame start marker and no frame end marker, and the end of the frame can be judged according to the frame length information in the frame structure. On the other hand, the frame end marker can be demodulated as an ordinary codeword. Considering the above two aspects, the frame synchronization considered in the present invention only includes synchronizing the frame start marker.

[0004] Synchronization methods are mainly divided into external synchronization methods and self - synchronization methods according to the implementation method. The external synchronization method means that the transmitting end sends a known pilot sequence agreed upon by both the transmitter and the receiver to assist in synchronization; since the known pilot sequence does not contain communication information, when using the external synchronization method, additional pilot consumption will be introduced, affecting the system performance. The self - synchronization method is opposite to the external synchronization method. It does not introduce a dedicated pilot signal, and the receiving end extracts synchronization information from the waveform of unknown information; although no pilot consumption is introduced, when using the self - synchronization method, the design of the receiving end is relatively complex. The inventor found that traditional synchronization technologies need to perform carrier synchronization and frame synchronization separately. Whether using the external synchronization method or the self - synchronization method, the system overheads brought by the separate synchronization processes will accumulate with each other, thus bringing a non - negligible consumption to the system. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that, due to the high modulation order of the multi - level differential phase - shift keying (M - DPSK) signal, it is difficult to reduce the overhead brought by multiple synchronizations while ensuring the synchronization effect. The purpose of the present invention is to provide a dual - synchronization method and system for M - DPSK signals. By utilizing the characteristics of M - DPSK signals and centering around the frame start marker, the frequency - difference estimation value is used for frame synchronization, and the frequency - difference calculated when frame synchronization is successful is the final frequency - difference estimation value, thus solving the problems of frame synchronization and carrier synchronization simultaneously.

[0006] The present invention is realized through the following technical solutions:

[0007] This solution provides a dual - synchronization method for M - DPSK signals, including:

[0008] Step 1, obtain the received signal of the receiver;

[0009] Step 2, pre - process the received signal to obtain the in - phase output signal and the quadrature output signal;

[0010] Step 3, perform symbol - phase sampling on the in - phase output signal and the quadrature output signal to obtain multiple groups of sampling data;

[0011] Step 4, based on the nth group of sampling data and the symbol - phase group corresponding to the frame start marker sequence, calculate the frequency - offset estimation value and the intermediate variable ε;

[0012] Step 5, determine whether the value of the intermediate variable ε is within the threshold range; if so, frame synchronization is successful, and the frequency - offset estimation value corresponding to the best sampling data of the frame header is output as the carrier frequency offset; otherwise, update n to n + 1, and repeat steps 4 - 5 until frame synchronization is successful.

[0013] The working principle of this solution: Generally speaking, the higher the modulation order, the greater the difficulty of synchronization; due to the high modulation order of M - DPSK signals, it poses quite high requirements for synchronization technology, and it is difficult to reduce the overhead brought by multiple synchronizations while ensuring the synchronization effect. The purpose of the present invention is to provide a dual - synchronization method and system for M - DPSK signals. By utilizing the characteristics of M - DPSK signals and centering around the frame start marker, the frequency - offset estimation value is used for frame synchronization, and the frequency - difference estimated when frame synchronization is successful is the final frequency - difference estimation value, thus solving the problems of frame synchronization and carrier synchronization simultaneously.

[0014] To receive the transmitted information frame, the receiver needs to continuously process and sample the received signal, and find the frame start marker in the massive sampled signals. In the scenario considered in this solution, the transmitter and receiver have agreed on the carrier frequency f0. In actual transmission, due to factors such as the Doppler effect and imperfect physical devices, the true frequency of the carrier received by the receiver will deviate from f0 to a certain extent. Therefore, it is necessary to estimate the carrier frequency offset. This solution uses the frequency offset estimate for frame synchronization. When the frame synchronization is successful, the calculated frequency offset estimate is the final carrier frequency offset estimate, and at the same time, the problems of frame synchronization and carrier synchronization are solved; on the one hand, without additional pilot consumption, this invention also performs external synchronization for carrier synchronization, reducing performance loss; on the other hand, this invention realizes carrier synchronization while performing frame synchronization, which can significantly reduce the complexity of the receiver compared with the traditional separate synchronization methods.

[0015] A further optimized solution is that the preprocessing includes the process:

[0016] Divide the received signal into two paths: one path is multiplied by the in-phase carrier component of the receiver local oscillator for mixing, and the other path is multiplied by the quadrature carrier component of the receiver local oscillator for mixing;

[0017] Perform low-pass filtering on the two mixed signals respectively to obtain the in-phase output signal and the quadrature output signal.

[0018] Express the in-phase carrier component of the receiver local oscillator as Express the quadrature carrier component of the receiver local oscillator as where represents the offset between the phase of the receiver local oscillator carrier and the phase of the received signal carrier. Express the p-th M-ary differential phase shift keying symbol received as cos(2π(f0 + Δf)t + φ p ), φ p is the modulation phase of the p-th symbol. Express the outputs of the in-phase and quadrature branches (also known as the I branch and the Q branch) of the receiver multiplier as:

[0019]

[0020]

[0021] Pass the outputs of the in-phase branch and the quadrature branch through low-pass filters respectively to obtain the I-channel signal and the Q-channel signal Based on the I-channel and Q-channel signals, the estimate of can be obtained.

[0022] A further optimized solution is that the preprocessing further includes:

[0023] Calculate the phase difference between adjacent M-ary differential phase shift keying symbols based on the in-phase output signal and quadrature output signal corresponding to the (p + 1)-th M-ary differential phase shift keying symbol, and the in-phase output signal and quadrature output signal corresponding to the p-th M-ary differential phase shift keying symbol;

[0024] The phase difference φ between adjacent symbols can be obtained from the I-channel and Q-channel signals of the (p + 1)-th symbol and the p-th symbol p+1 -φ p , thereby obtaining the modulation information. It should be noted that since the baseband I-channel and Q-channel signals are pulse-shaped at the transmitter, the receiver can obtain accurate in-phase output signals and quadrature output signals only at the optimal sampling moments of the I-channel and Q-channel after the low-pass filter.

[0025] A further optimized solution is that step 3 includes the following sub-steps:

[0026] Sample the in-phase output signal and quadrature output signal at intervals of the number of samples N corresponding to each M-ary differential phase shift keying symbol s to obtain the in-phase sampling signal a i and the quadrature sampling signal a q ;

[0027] When a i is not 0, the symbol phase is:

[0028]

[0029] where arctan(x) is the arctangent function, and the value range is

[0030] When a i is 0, the symbol phase

[0031] Starting from the first symbol phase obtained by sampling, take a value every N s symbol phases, and take a total of N w values to form a set of sampling data, where N w is the total number of symbols of the frame start marker. Denote the first set of sampling data as

[0032]

[0033] Denote the n-th set of sampling data as

[0034]

[0035] Since the operations performed on each set of sampled data are the same, for the sake of convenient description, in the present invention, the frame start marker refers to the synchronization field in the communication frame used to mark the start position of the frame. The symbol phase group corresponding to the frame start marker is denoted as where α k is the phase corresponding to the k-th, k = 1, 2,..., N w , symbol.

[0036] A further optimized solution is that step 4 includes the following sub-steps:

[0037] S41, calculate the phase difference γ between the n-th set of sampled data and the corresponding frame start marker symbol k :

[0038] γ k = β k - α k , k = 1, 2,..., N w ;

[0039] S42, calculate the first phase difference

[0040] S43, based on the first phase difference calculate the intermediate variable δ k , and according to the intermediate variable δ k correct the phase difference γ k ;

[0041] S44, perform linear regression on the corrected phase difference to obtain the linear function parameter b;

[0042] S45, calculate the frequency offset estimate value and the intermediate variable ε based on the linear function parameter b.

[0043] A further optimized solution is that the calculation method of the intermediate variable δ k includes:

[0044] Let δ1 = 0;

[0045] When ; δ k = δ k-1 - 2π;

[0046] When ; δ k = δ k-1 + 2π;

[0047] When ; δ k = δ k-1 .

[0048] A further optimization solution is that the calculation method of the linear function parameter b includes:

[0049] According to the formula Perform correction on γ k ; where Is the corrected phase difference;

[0050] Perform Perform linear regression to obtain the linear function parameter b:

[0051]

[0052] Where Is a real number with equal intervals, take x1 = 1, x2 = 2,...

[0053] A further optimization solution is that the frequency offset estimation value Is calculated according to the formula ; where T is the symbol period; the intermediate variable ε is calculated according to the formula ; where

[0054] A further optimization solution is that step 5 includes the following process:

[0055] When ε n-1 < τ, and ε n > ε n-1 Is established, frame synchronization is successful, it can be judged that the n-1th group of sampling data is the best sampling data corresponding to the frame start marker, and the frequency offset estimation value Corresponding to the best sampling data of the frame header is output as the carrier frequency offset;

[0056] τ is a preset variable threshold, ε n Is the intermediate variable ε of the nth group of sampling data, ε n-1 Is the intermediate variable ε of the n-1th group of sampling data.

[0057] This solution also provides a dual synchronization system for multi - level differential phase - shift keying signals, used to implement the dual synchronization method of multi - level differential phase - shift keying signals described above, including:

[0058] An acquisition module, used to obtain the received signal of the receiver;

[0059] A pre - processing module, used to pre - process the received signal to obtain an in - phase output signal and a quadrature output signal;

[0060] A sampling module, used to perform symbol - phase sampling on the in - phase output signal and the quadrature output signal to obtain multiple groups of sampling data;

[0061] A calculation module, configured to calculate a frequency offset estimation value based on the nth group of sampled data and the symbol phase group corresponding to the frame start marker sequence and an intermediate variable ε;

[0062] A judgment output module, configured to judge whether the value of the intermediate variable ε is within a threshold range; if so, frame synchronization is successful, and the frequency offset estimation value corresponding to the best sampled data of the frame header is output as the carrier frequency offset; otherwise, update n in the calculation module to n + 1, and repeat the calculation until frame synchronization is successful.

[0063] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0064] The present invention provides a dual synchronization method and system for a multi - level differential phase shift keying signal; by utilizing the characteristics of the multi - level differential phase shift keying signal, centering around the frame start marker, the frequency offset estimation value is used for frame synchronization, and the frequency offset estimated when frame synchronization is successful is the final frequency difference estimation value, simultaneously solving the problems of frame synchronization and carrier synchronization. On the one hand, without additional pilot consumption, the present invention also performs external synchronization for carrier synchronization, reducing performance loss; on the other hand, while performing frame synchronization, the present invention realizes carrier synchronization, and compared with traditional separate synchronization methods, can significantly reduce the complexity of the receiver. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following will briefly introduce the drawings required in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other relevant drawings can also be obtained based on these drawings. In the drawings:

[0066] Figure 1 is a schematic diagram of the outline of the dual synchronization method for a multi - level differential phase shift keying signal;

[0067] Figure 2 is a schematic diagram of the flow of the dual synchronization method for a multi - level differential phase shift keying signal. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0068] To make the purpose, technical solutions and advantages of the present invention clearer, the following will further describe the present invention in detail with reference to the embodiments and drawings. The illustrative embodiments and their descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0069] Embodiment 1

[0070] This embodiment provides a dual synchronization method for a multi - level differential phase shift keying signal, asFigure 1 As shown in the figure, it includes:

[0071] Step 1: Obtain the received signal of the receiver;

[0072] Step 2: Preprocess the received signal to obtain the in-phase output signal and the quadrature output signal;

[0073] Step 3: Perform symbol phase sampling on the in-phase output signal and the quadrature output signal to obtain multiple groups of sampling data;

[0074] Step 4: Based on the nth group of sampling data and the symbol phase group corresponding to the frame start marker sequence, calculate the frequency offset estimation value and the intermediate variable ε;

[0075] Step 5: Determine whether the value of the intermediate variable ε is within the threshold range; if so, the frame synchronization is successful, and the frequency offset estimation value corresponding to the best sampling data of the frame header is output as the carrier frequency offset; otherwise, update n to n + 1, and repeat steps 4 - 5 until the frame synchronization is successful.

[0076] Embodiment 2

[0077] This embodiment provides a dual synchronization method for multi - level differential phase - shift keying signals, specifically as Figure 2 shown:

[0078] Step 1: Represent the in - phase carrier component of the receiver locally as Represent the quadrature carrier component of the receiver locally as where represents the offset between the local carrier phase of the receiver and the carrier phase of the received signal; represent the pth multi - level differential phase - shift keying symbol received as cos(2π(f0 + Δf)t+φ p ), φ p is the modulation phase of the pth symbol; represent the outputs of the multipliers of the in - phase branch and the quadrature branch (also known as the I - branch and the Q - branch) of the receiver as:

[0079]

[0080]

[0081] Step 2: Pass the outputs of the in - phase branch and the quadrature branch through low - pass filters respectively to obtain the I - branch signal and the Q - branch signal According to the I - branch and Q - branch signals, the estimation value of can be obtained;

[0082] According to the I - branch and Q - branch signals of the (p + 1)th symbol and the pth symbol, the phase difference φ between adjacent symbols can be obtainedp+1 -φ p , thus obtaining modulation information.

[0083] It should be noted that since the transmitter performs pulse shaping on the baseband I-channel and Q-channel signals, the receiver can obtain accurate I-channel and Q-channel signals only at the optimal sampling moments of the I-channel and Q-channel after the low-pass filter. Assume that the number of samples per symbol is N s ; denote the I-channel sample as a i , and denote the Q-channel sample as a q . When a i is not 0, the corresponding symbol phase is

[0084]

[0085] where arctan(x) is the arctangent function, and the value range is When a i is 0, take

[0086] Record the symbol phases obtained by sampling at the receiver in sequence as Starting from the first symbol phase obtained by sampling, take a value every N s symbol phases, and take a total of N w symbols to form a set of sampling data; denote the first set of sampling data as:

[0087]

[0088] Denote the nth set of sampling data as:

[0089]

[0090] Since the operations performed on each set of sampling data are the same, denote any set of sampling data as Based on the symbol phase group corresponding to the frame start marker sequence and any set of sampling data perform the following operations.

[0091] Step three, calculate γ k = β k - α k , k = 1, 2..., N w , obtaining the phase difference between the sampling data and the corresponding frame start marker symbol.

[0092] Step four, calculate to obtain the first phase difference between γ k and γ k-1 .

[0093] Step five, calculate the intermediate variable δ k, k = 2, 3..., N w :

[0094] Let δ1 = 0;

[0095] 6 k = δ k-1 -2π, k = 2, 3..., N w , when

[0096] δ k = δ k-1 +2π, k = 2, 3..., N w , when

[0097] δ k = δ k-1 , k = 2, 3..., N w , when

[0098] Step six, perform a correction calculation on γ k where is the corrected phase difference.

[0099] Step seven, perform a linear regression on to obtain the linear function parameter b:

[0100]

[0101] where is an arbitrary real number with equal intervals, and x1 = 1, x2 = 2,...,

[0102] Step eight, calculate the frequency offset estimate value where T is the symbol period.

[0103] Step nine, calculate

[0104] Step ten, calculate the intermediate variable

[0105] Step eleven, denote the ε corresponding to the nth group of sampling data as ε n , when ε n-1 < τ, and ε n > ε n-1 at this time, it can be determined that the (n - 1)th group of sampling data is the best sampling data corresponding to the frame start marker. In the formula, τ is a positive constant close to 0. When ε n < τ, it can be considered that ε n is close to 0. The value of τ can be obtained through experience; when frame synchronization is successful, the The value is the final carrier frequency offset estimation value.

[0106] Embodiment 3

[0107] This embodiment provides a dual synchronization system for a multi - level differential phase - shift keying signal, which is used to implement the dual synchronization method for the multi - level differential phase - shift keying signal described in the above - mentioned embodiment, and includes:

[0108] An acquisition module, which is used to obtain the received signal of the receiver;

[0109] A pre - processing module, which is used to pre - process the received signal to obtain an in - phase output signal and a quadrature output signal;

[0110] A sampling module, which is used to perform symbol - phase sampling on the in - phase output signal and the quadrature output signal to obtain multiple groups of sampling data;

[0111] A calculation module, which is used to calculate a frequency offset estimation value and an intermediate variable ε based on the nth group of sampling data and the symbol - phase group corresponding to the frame start marker sequence;

[0112] A judgment and output module, which is used to judge whether the value of the intermediate variable ε is within the threshold range; if so, the frame synchronization is successful, and the frequency offset estimation value corresponding to the best sampling data of the frame header is output as the carrier frequency offset; otherwise, n in the calculation module is updated to n + 1, and the calculation is repeated until the frame synchronization is successful.

[0113] The above - mentioned specific implementation manners further elaborate on the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above - mentioned are only the specific implementation manners of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A dual synchronization method for multi - level differential phase - shift keying signals, characterized in that, Including: Step 1: Obtain the received signal of the receiver; Step 2: Preprocess the received signal to obtain the in-phase output signal and the quadrature output signal; Step 3: Perform symbol phase sampling on the in-phase output signal and the quadrature output signal to obtain multiple sets of sampling data; Including the following sub-steps: With the number of samples N corresponding to each multi - level differential phase - shift keying symbol s as the interval, sample the in - phase output signal and the quadrature output signal to obtain the in - phase sampled signal a i and the quadrature sampled signal a q ; When a i is not 0, the symbol phase is: where arctan(x) is the arctangent function with a range of When a i is 0, the symbol phase is obtained Starting from the phase of the first symbol obtained by sampling, every N s symbol phases are taken once, and a total of N w values are taken to form a set of sampling data. The nth set of sampling data is denoted as Based on the symbol phase group corresponding to the frame start marker symbol Step 4, calculate the frequency offset estimation value based on the nth group of sampled data and the symbol phase group corresponding to the frame start marker sequence and the intermediate variable ε; specifically including the following sub-steps: S41, calculate the phase difference γ between any set of sampled data and the corresponding frame start marker symbol k : γ k = β k - α k , k = 1, 2…, N w ; S42, calculate the first phase difference k = 2, 3…, N w ; S43, based on the first phase difference Calculate the first intermediate variable δ k , and based on the first intermediate variable δ k Correct the phase difference γ k ; S44, for the corrected phase difference perform linear regression to obtain the linear function parameter b; S45, calculating a frequency offset estimation value based on the parameter b of the linear function and an intermediate variable ε; The first intermediate variable δ k The calculation method includes: Let δ1 = 0; When ; δ k = δ k-1 - 2π; When ; δ k = δ k-1 + 2π; When δ k = δ k-1 ; The calculation method of the linear function parameter b includes: According to the formula correct γ k ; where is the corrected phase difference; For perform linear regression to obtain the linear function parameter b: wherein are arbitrarily equally-spaced real numbers, taking The frequency offset estimation value is calculated according to the formula where T is the symbol period; the intermediate variable ε is calculated according to the formula where Step 5, determine whether the value of the intermediate variable ε is within the threshold range; if so, frame synchronization is successful, and the frequency offset estimation value corresponding to the best sampling data of the frame header is output as the carrier frequency offset; otherwise, update n to n + 1, and repeat steps 4 to 5 until frame synchronization is successful.

2. The dual synchronization method for a multi - level differential phase - shift keying signal according to claim 1, characterized in that, The preprocessing includes the process: Divide the received signal into two paths: one path is multiplied by the in-phase carrier component of the receiver local oscillator for mixing, and the other path is multiplied by the quadrature carrier component of the receiver local oscillator for mixing; Perform low-pass filtering on the two mixed signals respectively to obtain the in-phase output signal and the quadrature output signal.

3. The dual synchronization method for a multi - level differential phase - shift keying signal according to claim 1, characterized in that, The preprocessing further includes: Calculate the phase difference between adjacent M-ary differential phase shift keying symbols according to the in-phase output signal and the quadrature output signal corresponding to the (p + 1)-th M-ary differential phase shift keying symbol, and the in-phase output signal and the quadrature output signal corresponding to the p-th M-ary differential phase shift keying symbol; Obtain the modulation information based on the phase difference between adjacent M-ary differential phase shift keying symbols.

4. A dual synchronization method for a multi - level differential phase - shift keying signal according to claim 1, characterized in that, Step 5 includes the following process: When ε n-1 < τ, and ε n > ε n-1 is established, frame synchronization is successful, and the frequency offset estimation value corresponding to the best sampled data of the frame header is output as the carrier frequency offset; τ is a preset variable threshold, ε n is the intermediate variable ε of the nth group of sampling data, ε n-1 is the intermediate variable ε of the (n - 1)th group of sampling data.

5. A dual synchronization system for a multi - level differential phase - shift keying signal, characterized in that, A method for double synchronization of an M-ary differential phase shift keying signal for implementing any one of claims 1-4, including: An acquisition module for obtaining the received signal of the receiver; A preprocessing module for preprocessing the received signal to obtain the in-phase output signal and the quadrature output signal; A sampling module for performing symbol phase sampling on the in-phase output signal and the quadrature output signal to obtain multiple sets of sampling data; A calculation module, configured to calculate a frequency offset estimation value based on the nth group of sampled data and a symbol phase group corresponding to a frame start marker sequence and an intermediate variable ε; A judgment output module is used to judge whether the value of the intermediate variable ε is within the threshold range; if so, frame synchronization is successful, and the frequency offset estimation value corresponding to the best sampling data of the frame header is output as the carrier frequency offset; otherwise, n in the calculation module is updated to n + 1, and the calculation is repeated until frame synchronization is successful.

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