An improved mth power carrier phase recovery algorithm

Abstract

The application discloses an improved M power carrier phase recovery method, which comprises the following steps: firstly, system parameters are acquired and configuration is carried out according to the system parameters to complete system initialization; coarse frame synchronization is carried out on input data Sn, and a frame header matching correlation vector is output; the input data Sn is delayed for a certain time, then the delayed digital signal Sn is multiplied by the output value of a digital oscillator, and the output result Yn is the output of a phase recovery module; M power operation is carried out on Yn, then segmented addition is carried out to obtain a phase offset vector; subsequently, a phase compensation value is calculated through the frame header matching correlation vector and the phase offset vector, and the phase compensation value is output through the digital oscillator; the above steps are repeatedly cycled, and the phase compensation value is continuously updated until phase recovery is completed. Through the introduction of the frame header matching correlation vector, the application is more accurate in the phase compensation process, thereby improving the overall performance of the system, and providing an efficient and reliable solution for the research and application in the related field.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of communication systems, and in particular to an improved Mth power carrier phase recovery algorithm. BACKGROUND

[0002] When a digital communication receiver adopts coherent demodulation, the receiving end needs to provide a coherent carrier consistent with the modulation carrier frequency and phase of the transmitting end. However, due to factors such as system local oscillator frequency error and Doppler effect, the digital down-conversion output carrier may have a frequency offset and phase offset during transmission, thereby causing rotation and jitter of the received signal. Therefore, carrier recovery technology must be used to correct the frequency offset and phase offset between the receiving end and the transmitting end carriers.

[0003] Carrier recovery includes carrier frequency recovery and carrier phase recovery. Even after completing carrier frequency recovery, residual frequency offset and phase offset may still exist in the signal, so further carrier phase recovery is needed. Current carrier phase recovery schemes can be divided into two categories: data-aided (DA) and not data-aided (NDA), according to whether a training sequence or pilot signal is used for assistance.

[0004] In the DA carrier phase recovery algorithm, the pilot insertion method is a commonly used method. This method has the characteristics of being completely independent of the modulation format, has high noise immunity, and can effectively avoid signal cycle slip. For example, Xin Xiangjun proposed a phase recovery scheme based on pilot assistance in the method and system for phase recovery based on pilot assistance. However, this method cannot adapt to scenarios with large residual frequency offset, and is highly dependent on the design and length of the training sequence. If the training sequence is not long enough or is not designed properly, the phase recovery effect will be greatly reduced.

[0005] In the NDA carrier phase recovery algorithm, the Mth power method has been widely used due to its low complexity, small delay, and low resource consumption. Many studies have proposed improved algorithms based on the Mth power method, with the main goal being to reduce the computational complexity of the algorithm. For example, Han Jilong proposed an optimization research on digital signal processing algorithms in coherent optical communication by replacing the modulo operation with the power operation, effectively reducing the computational complexity. Zhang Jie proposed a research on carrier recovery digital signal processing algorithms for coherent optical communication using absolute value operations instead of power operations, also achieving optimization. However, these improvements do not solve the problem of slow convergence speed of the Mth power phase recovery algorithm, so they are not suitable for burst transmission scenarios. In addition, the Mth power method also has a phase ambiguity problem, and the algorithm performance significantly decreases in a low signal-to-noise ratio environment. SUMMARY

[0006] In view of the shortcomings of the existing technology, the technical problem that the present invention actually aims to solve is that in the existing NDA carrier phase recovery algorithm, the traditional pilot-inserted carrier phase recovery algorithm has a large overhead and is difficult to handle large residual frequency offsets, and the carrier phase recovery algorithm based on the Mth power has slow convergence speed, rapid performance degradation under low signal-to-noise ratio conditions, and is unable to accurately estimate and track phase noise. The present invention proposes an improved Mth power carrier phase recovery algorithm. On the basis of the traditional Mth power carrier phase recovery, an improved mechanism of initial phase injection is innovatively introduced to correct the phase estimation value of the Mth power algorithm using the absolute phase error of the frame header matching correlation vector. Through this initial phase injection strategy, the convergence speed of the system and the phase recovery accuracy and stability under low signal-to-noise ratio conditions are effectively improved. At the same time, by adjusting the segment length and step value of the Mth power phase recovery algorithm, its adaptability to systems with different phase noise characteristics is further enhanced.

[0007] Furthermore, the present invention utilizes the absolute phase error of the frame header data for phase offset correction, overcoming the phase ambiguity problem in traditional M-th-power algorithms and simplifying subsequent data processing. This approach not only improves carrier phase recovery performance but also significantly reduces system complexity and resource consumption, providing a more efficient and robust solution for modern communication systems.

[0008] To achieve the above object, the present invention proposes a phase recovery method based on an improved M-th power carrier, comprising the following steps:

[0009] S1, obtain parameters and initialize the module, the parameters include signal modulation mode, frame header template, frame length L0, segment length L1, compensation step maximum value X; initialize the module according to the parameters, including: determining the value of the constellation set M according to the signal modulation mode; determining the value of the delay time T of the Sn delay module according to the frame header template;

[0010] S2, perform coarse frame synchronization on Sn according to the parameters of step S1, and output the frame header matching correlation vector

[0011] S3, delay Sn by T clock cycles according to the delay time T in step S1, and then compare the delayed Sn with the output value of the digital oscillator NCO Multiply and output as Yn; where Φ N is the phase compensation value of the Nth segment of data; where Yn is the output of the carrier phase recovery method;

[0012] S4, the Yn calculated in step S3 is first raised to the Mth power, and then the data is segmented and added according to the frame length L0 and segment length L1 to obtain the Nth segment phase deviation vector The maximum value of N is the total number of segments;

[0013] S5, the frame header matching correlation vector calculated in steps S2, S4 and phase offset vector The input phase offset compensation calculation module is corrected according to the compensation step maximum value X to obtain the phase offset compensation value Φ N , and then output by the digital oscillator NCO

[0014] Further, the value M in step S1 is 2 bit , bit is the number of bits carried by a single symbol in the signal modulation mode.

[0015] Further, the segment length L1 in step S1 is set to be not greater than the frame length L0.

[0016] Further, the calculation formula of Yn in step S3 is

[0017] Further, the calculation formula of in step S4 is

[0018] Further, the phase offset value calculated by the frame header matching correlation vector in step S5 is φ0, and the phase offset value calculated by the phase offset vector is φ N ; wherein the value of N is 1, 2, …, ceil(L0 / (M*L1)); wherein ceil[] represents rounding up.

[0019] Further, the calculation formula of φ0 in step S5 is

[0020] Further, the calculation formula of φ N in step S5 is:

[0021]

[0022] Further, the calculation formula of Φ N in step S5 is

[0023] Further, step S5 is implemented by a finite state machine.

[0024] Further, step S5 is started after the frame header matching correlation vector is input, and then outputs the phase offset compensation value Φ N .

[0025] Technical effects

[0026] The application proposes an improved Mth power carrier phase recovery method, taking a phase offset compensation calculation module as the core.

[0027] Specifically, the application innovatively introduces an initial phase injection improvement mechanism on the basis of the traditional Mth power carrier phase recovery, and corrects the phase estimation value of the Mth power algorithm by using the absolute phase error of the frame header matching correlation vector. Through this initial phase injection strategy, the convergence speed of the system is effectively improved, and the phase recovery accuracy and stability under low signal-to-noise ratio conditions are also improved. At the same time, by adjusting the segment length and step value of the Mth power phase recovery algorithm, the adaptability of the algorithm to systems with different phase noise characteristics is further enhanced.

[0028] In addition, the application corrects the phase offset by using the absolute phase error of the frame header data, which overcomes the phase ambiguity problem in the traditional Mth power algorithm, thereby simplifying the subsequent data processing process. This method not only improves the performance of carrier phase recovery, but also significantly reduces the system complexity and resource consumption, providing a more efficient and robust solution for modern communication systems.

[0029] The concept, specific structure and technical effects of the application will be further described below with reference to the accompanying drawings, so as to fully understand the purpose, features and effects of the application. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a principle block diagram of a traditional Mth power carrier phase recovery algorithm;

[0031] Figure 2 is a system structure schematic diagram of an improved Mth power carrier phase recovery method according to a preferred embodiment of the application;

[0032] Figure 3 is a flowchart of an improved Mth power carrier phase recovery method according to a preferred embodiment of the application;

[0033] Figure 4 is a data phase offset compensation schematic diagram of an improved Mth power carrier phase recovery method according to a preferred embodiment of the application;

[0034] Figure 5is a simulation performance comparison chart of a modified Mth power carrier phase recovery method and a traditional method, which is a preferred embodiment of the present application. DETAILED DESCRIPTION

[0035] In order to make the technical problems to be solved by the present application, technical solutions and beneficial effects clearer, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0036] In the following description, specific details are set forth in order to provide a thorough understanding of the embodiments of the present application for purposes of explanation and not limitation. It will be obvious to those skilled in the art that other embodiments can be realized without these specific details. In other instances, well-known systems, apparatuses, circuits, and methods have not been described in detail in order to avoid unnecessarily obscuring the present application.

[0037] The present application proposes an improved Mth power carrier phase recovery method, which includes the following steps:

[0038] S1, obtain parameters and initialize modules, the parameters including signal modulation mode; frame header template, which is calculated from frame header data, modulation mode and coding mode, used for subsequent identification of the starting point of the transmitted data; frame length L0, representing the total length of a single frame of data; segment length L1, used to divide the data into smaller blocks for processing, which should not be greater than the frame length L0; and compensation step maximum value X, used to adjust the amplitude limit of the phase compensation process, i.e. N Single adjustment amplitude limit. After obtaining these parameters, the system will perform initialization operations, including:

[0039] According to the signal modulation mode, calculate and determine the specific value of the constellation set M, i.e. M = 2 bit , bit is the number of bits carried by a single symbol of the signal modulation mode.

[0040] Using the frame header template, calculate the delay time T of the Sn delay module to ensure that the delayed Sn and the frame header match the related vector Can be aligned.

[0041] Other modules are configured and initialized according to these parameters to ensure that the entire system can work as expected.

[0042] S2, using the initialization parameters, the system performs a coarse frame synchronization operation, identifies and locks the frame boundary, and outputs the frame header matching correlation vector. The system uses the frame header template in the initialization parameters to perform frame header matching on the received signal, and calculates the correlation between the received signal Sn and the frame header template. The correlation vector calculation formula of the frame header and the received signal Sn is:

[0043]

[0044] where Sn[k] is the sampling point of the received signal, Header[k] is the frame header template, and Lheader is the frame header length.

[0045] The complex square sum of the frame header correlation vector is obtained:

[0046] E[n] = |Corr[n]| 2

[0047] When E[n] exceeds the preset threshold, it is considered that the frame header is found, that is, the frame header position npeak is determined. Then the frame header coarse synchronization is completed, and the frame header matching correlation vector is output.

[0048]

[0049] S3, according to the delay time T calculated, the received signal Sn is processed with time delay to realize alignment with the frame header matching correlation vector . Then, the delayed signal T[Sn] is multiplied by the output of the digital oscillator NCO , that is, the input data Sn is phase adjusted, and the adjusted signal Yn is output.

[0050] S4, data segmentation and phase vector calculation. This step first performs M power operation on Yn to remove the modulation phase, where M is the order of the constellation set. According to the frame length L0 and the segmentation length L1, the signal YnM is segmented. For each segment of signal, accumulate according to the segmentation length L1 to calculate the phase deviation vector . This vector reflects the phase deviation value of the signal in different subframes, and its calculation formula is:

[0051]

[0052] S5, the frame header matching correlation vector calculated in step S2 and the phase deviation vector calculated in step S4 are input into the phase deviation compensation calculation module, and the phase deviation compensation vector

[0053]

[0054] wherein N is 1~ceil(L0 / (M*L1)), and ceil is rounding up.

[0055] Then, the phase offset compensation value Φ is corrected according to the compensation step maximum value X N , and the calculation formula is

[0056]

[0057] Then, the phase offset compensation value Φ is input to the digital oscillator module, and the compensation phase vector is output by the digital oscillator NCO N The system output is obtained by the S2 step, Yn is obtained, and the carrier phase recovery process is completed.

[0058] The step S5 is realized by a finite state machine. The finite state machine starts only after the frame header matching correlation vector is input, and then outputs the phase offset compensation value Φ N , otherwise the phase offset compensation value is 0.

[0059] The following will illustrate the specific process of the improved Mth power carrier phase recovery method proposed in the application.

[0060] As shown in Figure 1 , it is a traditional Mth power carrier phase recovery algorithm principle block diagram, which specifically introduces the process of how to calculate the phase compensation value, and the application is improved in structure to realize better performance.

[0061] As shown in Figure 2 , it is a system structure diagram of the application, and the design mainly consists of a coarse frame header synchronization circuit, an Mth power calculation circuit, a phase offset calculation and compensation circuit. The sampling symbol data Sn after timing recovery is input to the carrier phase recovery system, Sn enters the coarse frame synchronization module, and the frame header template is matched in it. When the frame synchronization is successful, the frame header matching correlation vector is output to the phase offset compensation calculation module. Sn passes through a delay module to align the data with the frame header matching correlation vector . The digital oscillator module updates and corrects the compensation value according to the phase correction step value, the digital signal Sn is multiplied by the continuously updated compensation value to complete the phase correction, and Yn is output. The digital oscillator module outputs the default compensation value when the module starts, and the default compensation value corresponds to a correction angle of 0 degrees, which ensures normal work at startup. Then, Yn is operated by Mth power, and the data is segmented and added according to the frame length and the segmentation length to obtain the phase deviation vector Then, it is input to the phase offset compensation calculation module.

[0062] As shown in Figure 3 ​As shown in the figure, this figure is a flow chart of a method based on an improved M-th power carrier phase recovery method according to a preferred embodiment of the present invention. After the system is powered on and reset, it enters the STATE0 state, and the carrier phase recovery system is initialized according to the set parameters. Then, the output Φ value is 0. Then, with the input of Sn, the coarse frame synchronization completes the frame header template correlation matching and outputs the frame header matching correlation vector The state machine receives a valid frame header matching correlation vector That is, jump to STATE1 and match the relevant vector according to the frame header Calculate φ0, and then reset the Φ value, that is, Φ=φ0, Φ is the phase compensation value. Then jump to STATE2 state, and start the M-time method to enable it according to the phase deviation vector calculated in the above step S4. Continuously update φ N , by the continuously updated φ N The Φ value is also continuously updated, that is, If the next valid frame header matches the relevant vector The input phase offset compensation calculation module then jumps back to STATE1 and repeats the above steps to complete the carrier phase recovery step.

[0063] like Figure 4 As shown, Figure 4 This is a diagram of data phase offset compensation based on an improved M-th power carrier phase recovery method in a preferred embodiment of the present invention. The total number of segments N is determined according to the frame length L0 and the segment length L1, and the x-th frame header matches the relevant vector Input the phase bias compensation calculation module to obtain φ0, then assign φ1 to φ0, and use φ1 to perform phase compensation on the first segment of data; then calculate φ1 through the compensated first segment of data, and then assign φ2 to (φ0+φ1), and use it to perform phase compensation on the second segment; repeat the above operation, that is, use the data of the N-1 segment to calculate φ N-1 , then φ0 to φ N-1 Accumulate and get Φ N , and then use the Φ N To perform phase compensation on the Nth segment. When the (x+1)th frame header matches the correlation vector Input phase bias compensation calculation module, recalculate φ0 and reset Φ N value, and repeat the above steps to complete the carrier phase recovery step.

[0064] like Figure 5 As shown, Figure 5is a simulation performance comparison chart of a modified Mth power carrier phase recovery method and a traditional method, which is a preferred embodiment of the present application. The algorithm in this paper and the traditional algorithm both use the same simulation environment; the simulation parameters are set as an information rate of 8192 Kbps, a modulation mode of QPSK, a frame length L0 of 1024 (bit), a frame header data of 32'h1ACFFC1D, a segmentation length L1 of 32, and a compensation step maximum value X of 16°. The simulation generates 20 sets of data with different Eb / N0, then sets the residual frequency offset to 5 kHz, then counts the bit error rate of each group, and then averages the simulation experimental data to obtain the specific results, as shown in the figure; it is clearly found that the method in this paper has a better sensitivity improvement of 0.3 dB compared with the traditional method at the BER of 1x10 (-3) (FEC-Limit).

[0065] The following will take examples to illustrate the specific implementation process of a low-delay bandwidth-adjustable phase correction method of the present application.

[0066] It is assumed that the current signal modulation mode is QPSK, the frame header data is 32'h1ACFFC1D, the frame length L0 is 8192 (bit), the segmentation length L1 is 32, and the compensation step maximum value is 1°. The value of M is determined as 4 according to the signal modulation mode QPSK; the delay period T is determined as (16*Sn symbol interval+3) according to the frame header data and the signal modulation mode, wherein 2 is the delay time of the digital oscillator NCO output determined according to the signal modulation mode, the frame length L0 and the segmentation length L1; when the frame header matching correlation vector is calculated and output, the value of φ0 is calculated through and then assigned to Φ1, and the digital oscillator NCO outputs Then the first segment data of Sn delayed by T periods is multiplied with through the multiplier to obtain the first segment data of Yn; then the first segment Yn is subjected to a 4th power operation, and then the sum of 32 results is obtained to obtain the phase deviation vector of the corresponding segment number and the phase compensation value of the corresponding segment number is obtained from the phase deviation vector of the corresponding segment number Then the compensation step maximum value is modified to obtain φ N , and then the value of Φ N is updated, and finally the digital oscillator NCO outputs Then the corresponding segment number of Yn is multiplied with the corresponding segment number of Sn to obtain the data of the corresponding segment number of Yn. When the next frame header matching correlation vector ​The calculation output resets the value of φ0 and the value of Φ, and then the above steps are repeatedly executed to adjust the phase compensation value, so as to complete the carrier phase recovery process.

[0067] The preferred embodiments of the present application are described in detail above. It should be understood that those of ordinary skill in the art can make modifications and variations without departing from the concept of the present application. Therefore, the technical solutions obtained by logical analysis, reasoning or limited experiments based on the prior art according to the concept of the present application should be within the protection scope defined by the claims.

Claims

1. An improved Mth power carrier phase recovery method, comprising: The method comprises the following steps: S1, acquiring parameters and initializing a module, the parameters comprising a signal modulation mode, a frame header template, a frame length L0, a segment length L1, and a compensation step maximum value X, and initializing the module according to the parameters, which comprises: determining the value of M according to the signal modulation mode; determining the value of the delay time T of the Sn delay module according to the frame header template; S2, performing coarse frame synchronization on Sn according to the parameters of step S1, and outputting a frame header matching correlation vector S3, delaying Sn by T clock cycles according to the delay time T in step S1, and then multiplying the delayed Sn with the output value of the digital oscillator NCO and outputting as Yn; wherein Φ N is a phase compensation value; wherein Yn is the output of the carrier phase recovery method; the calculation formula of Yn in step S3 is S4, the Yn calculated in step S3 is added by first taking the Mth power, then segmenting the data according to the frame length L0 and the segment length L1 to obtain the phase offset vector where N is the total number of segments; the calculation formula of the phase offset vector in step S4 is The calculation formula of the phase offset vector in step S4 is S5, the frame header matching correlation vector calculated in steps S2, S4 and phase offset vector Input phase offset compensation calculation module, according to the compensation step maximum value X correction get phase offset compensation value Φ N , then through the digital oscillator NCO output for The phase offset value calculated in step S5 through the frame header matching correlation vector The phase offset value calculated through the phase offset vector The phase offset value calculated through the phase offset vector N ; wherein the value of N is 1, 2…, ceil (L0 / (M*L1)); wherein ceil() represents rounding up; the formula for calculating φ0 in step S5 is The formula for calculating φ N in step S5 is: The formula for calculating Φ N in step S5 is 2. The method of claim 1, wherein the modified Mth power carrier phase recovery method is characterized by, The value M in the step S1 is 2 bit bit is the number of bits carried by a single symbol in the signal modulation mode.

3. The method of claim 1, wherein the modified Mth power carrier phase recovery method is characterized by, the segment length L1 in the step S1 is set to be not greater than the frame length L0.

4. The method of claim 1, wherein the modified Mth power carrier phase recovery method is characterized by, the step S5 is implemented by a finite state machine.

5. The method of claim 1, wherein the modified Mth power carrier phase recovery method is characterized by, The step S5 matches the frame header by a finite state machine The input is started after the output of the phase offset compensation value Φ N .

Images