Improved M-power carrier phase recovery algorithm

Abstract

The invention discloses an improved M-power carrier phase recovery method. The method comprises the following steps: firstly, acquiring system parameters and configuring the system parameters according to the system parameters to complete system initialization; and performing coarse frame synchronization on the input data Sn, and outputting a frame header matching correlation vector. The input data Sn is delayed for a certain time, then the delayed digital signal Sn is multiplied by the output value of the digital oscillator, and the output result is Yn which is the output of the phase recovery module. And performing M-power operation on the Yn, and then performing segmented addition to obtain a phase deviation value. And then, calculating a phase compensation value through the frame header matching correlation vector and the phase deviation, and outputting the phase compensation value through a digital oscillator. And the steps are repeated, and the phase compensation value is continuously updated until phase recovery is completed. According to the invention, by introducing the frame header matching correlation vector, the phase compensation process is more accurate, so that the overall performance of the system is improved, and an efficient and reliable solution is provided for research and application in related fields.

Description

Technical Field

[0001] The present invention relates to the field of communication systems, and in particular to an improved M-th power carrier phase recovery algorithm. Background Art

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

[0003] Carrier recovery includes two parts: carrier frequency recovery and carrier phase recovery. Even after completing carrier frequency recovery, there may still be residual frequency and phase deviations in the signal, so further carrier phase recovery is required. Current carrier phase recovery schemes can be divided into two categories: data-aided (DA) and non-data-aided (NDA), depending on whether training sequences or pilot signals are used.

[0004] In the DA carrier phase recovery algorithm, the pilot insertion method is a commonly used method. This method is completely independent of the modulation format, has high noise resistance, and can effectively avoid the signal cycle slip phenomenon. For example, Xin Xiangjun proposed a pilot-assisted phase recovery scheme in "A pilot-assisted phase recovery method and system", but this method cannot adapt to scenarios with large residual frequency deviations, and is highly dependent on the design and length of the training sequence. If the training sequence is not long enough or the design is unreasonable, the effect of phase recovery will be greatly reduced.

[0005] In the NDA carrier phase recovery algorithm, the M-th method has been widely used due to its advantages such as low complexity, low latency, and low resource consumption. Many studies have proposed improved algorithms around the M-th method, with the main goal of reducing the computational complexity of the algorithm. For example, Han Jilong effectively reduced the computational complexity by replacing the power operation with the remainder operation in "Research on Optimization of Digital Signal Processing Algorithms in Coherent Optical Communications"; Zhang Jie also achieved optimization by using absolute value operations instead of power operations in "Research on Digital Signal Processing Algorithms for Carrier Recovery in Coherent Optical Communications". However, these improvements did not solve the problem of slow convergence speed of the M-th method phase recovery algorithm, so it is not suitable for burst transmission scenarios. In addition, the M-th method also has phase ambiguity problems, and the algorithm performance is significantly reduced in low signal-to-noise ratio environments. Summary of the invention

[0006] In view of the shortcomings of the prior art, 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 deviations, and the M-th power-based carrier phase recovery algorithm has slow convergence speed, rapid performance degradation under low signal-to-noise ratio conditions, and inability to accurately estimate and track phase noise. The present invention proposes an improved M-th power carrier phase recovery algorithm. On the basis of the traditional M-th power carrier phase recovery, an improved mechanism of initial phase injection is innovatively introduced to correct the phase estimation value of the M-th 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 M-th power phase recovery algorithm, its adaptability to systems with different phase noise characteristics is further enhanced.

[0007] In addition, the present invention uses the absolute phase error of the frame header data to perform phase deviation correction, which overcomes the phase ambiguity problem in the traditional M-th power algorithm, thereby simplifying the subsequent data processing process. This method not only improves the carrier phase recovery performance, but also significantly reduces the 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 the segment length L1 to obtain the Nth segment phase deviation vector The maximum value of N is the total number of segments;

[0013] S5, match the frame header calculated in steps S2 and S4 to the relevant vector and phase deviation vector Input phase deviation compensation calculation module, and correct the phase deviation compensation value Φ according to the maximum compensation step value X N , and then the digital oscillator NCO output is

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

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

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

[0017] Furthermore, in step S4 The calculation formula is

[0018] Furthermore, in step S5, the relevant vector is matched by the frame header The calculated phase deviation value is φ0, which is obtained by using the phase deviation vector The calculated phase deviation is φ N ; The value of N is 1, 2…, ceil(L0 / (M*L1)); ceil[] means rounding up.

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

[0020] Furthermore, in step S5, φ N The calculation formula is:

[0021]

[0022] Furthermore, Φ in step S5 N The calculation formula is

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

[0024] Furthermore, step S5 matches the relevant vector in the frame header through the finite state machine. After the input, it starts to start, and then outputs the phase deviation compensation value Φ N .

[0025] Technical Effects

[0026] The present invention proposes a method for phase recovery based on an improved M-th power carrier, with a phase deviation compensation calculation module as the core. The method corrects the phase deviation compensation value of the M-th power method by utilizing the absolute phase error of the digital signal frame header data, thereby achieving high convergence rate and high-precision carrier phase recovery, and performs well in a channel environment with a low signal-to-noise ratio. By adjusting the segment length L1 and the maximum compensation step value X, the method can effectively adapt to systems with different phase noise characteristics. In addition, the present invention calculates the phase deviation value based on the frame header data, successfully solving the phase ambiguity problem in the traditional M-th power method.

[0027] Specifically, based on the traditional M-th power carrier phase recovery, the present invention innovatively introduces an improved mechanism of initial phase injection, and uses the absolute phase error of the frame header matching correlation vector to correct the phase estimation value of the M-th power algorithm. 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 M-th power phase recovery algorithm, its adaptability to systems with different phase noise characteristics is further enhanced.

[0028] In addition, the present invention uses the absolute phase error of the frame header data to perform phase deviation correction, which overcomes the phase ambiguity problem in the traditional M-th power algorithm, thereby simplifying the subsequent data processing process. This method not only improves the carrier phase recovery performance, 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 present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a principle block diagram of a traditional M-th power carrier phase recovery algorithm;

[0031] Figure 2 It is a schematic diagram of a system structure based on an improved M-th power carrier phase recovery method according to a preferred embodiment of the present invention;

[0032] Figure 3 It is a flow chart of a method for phase recovery based on an improved M-th power carrier according to a preferred embodiment of the present invention;

[0033] Figure 4 It is a schematic diagram of data phase deviation compensation based on an improved M-th power carrier phase recovery method according to a preferred embodiment of the present invention;

[0034] Figure 5It is a simulation performance comparison diagram between an improved M-th power carrier phase recovery method and a traditional method according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0036] In the following description, specific details such as specific internal procedures and techniques are provided for the purpose of illustration rather than limitation so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention can be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary details.

[0037] The present invention proposes a phase recovery method based on an improved M-th power carrier, comprising the following steps:

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

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

[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 relevant vector Able to align.

[0041] Other modules are configured and initialized accordingly based on 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 a frame header matching correlation vector. The system uses the frame header template in the initialization parameters to match the received signal with the frame header, and calculates the correlation between the received signal Sn and the frame header template. The correlation vector calculation formula between 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 frame header matching energy is obtained by summing the complex squares of the frame header related vectors:

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

[0047] When E[n] exceeds the preset threshold, the frame header is considered to be found, that is, the frame header position npeak is determined. The frame header coarse synchronization is completed, and the frame header matching correlation vector is output. The calculation formula is:

[0048]

[0049] S3, according to the calculated delay time T, the received signal Sn is delayed to achieve matching with the frame header correlation vector Then, the delayed signal T[Sn] is aligned with the output of the digital oscillator NCO. Multiply, that is, adjust the phase of the input data Sn and output the adjusted signal Yn is the output of carrier phase recovery.

[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 segment length L1, the signal YnM is segmented. Each segment of the signal is accumulated according to the segment 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, matching the frame headers calculated in step S2 and step S4 with the relevant vectors and phase deviation vector Input phase offset compensation calculation module, and calculate the above two vectors

[0053]

[0054] Where N is 1 to ceil(L0 / (M*L1)), and ceil is rounded up.

[0055] Then, the phase deviation compensation value Φ is obtained according to the maximum compensation step value X. N , and its calculation formula is

[0056]

[0057] Then the phase offset compensation value Φ N Input to the digital oscillator module, and output the compensated phase vector through the digital oscillator NCO After the system output is performed through step S2, Yn is obtained, completing the carrier phase recovery process.

[0058] Step S5 is implemented by a finite state machine. The finite state machine matches the relevant vector in the frame header. After the input, it starts to start, and then outputs the phase deviation compensation value Φ N , otherwise the phase deviation compensation value is 0.

[0059] The specific process of the improved M-th power carrier phase recovery method proposed by the present invention is described below by way of example.

[0060] like Figure 1 The figure shows a principle block diagram of a traditional M-th power carrier phase recovery algorithm, which specifically introduces the process of calculating the phase compensation value. The present invention has made structural improvements to achieve better performance.

[0061] like Figure 2 The system structure diagram of the present invention is shown in FIG. The design is mainly composed of a coarse frame header synchronization circuit, an M-time calculation circuit, and a phase deviation calculation and compensation circuit. The sampled symbol data Sn after timing recovery is input into the carrier phase recovery system, and Sn enters the coarse frame synchronization module, where the initialized frame header template is used for matching correlation. When the frame synchronization is successful, the frame header matching correlation vector in the frame synchronization process is Output to the phase offset compensation calculation module. Sn passes through a delay module to make the data match the frame header related vector Alignment. The digital oscillator module updates the correction compensation value by looking up the table 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 output Yn. The digital oscillator module outputs the default compensation value when the module is started. The default compensation value corresponds to a correction angle of 0 degrees to ensure normal operation at startup. Then Yn is subjected to M-th power operation, and the data is segmented and added according to the frame length and segment length to obtain the phase deviation vector Then it is input into the phase offset compensation calculation module.

[0062] like Figure 3As shown in FIG. 1 , the flowchart of a method for recovering the phase of a carrier based on an improved M-th power is shown in FIG. 1 . 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, and 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 associated 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 The schematic diagram of data phase deviation compensation based on the improved M-th power carrier phase recovery method is 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-advancing 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, 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-1th segment to calculate φ N-1 , then φ0 to φ N-1 Accumulate and get Φ N , and then use this Φ N To perform phase compensation on the Nth segment. When the (x+1)th frame header matches the correlation vector Enter the 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 5This is a simulation performance comparison chart of a preferred embodiment of the present invention, based on an improved M-th power carrier phase recovery method and a traditional method. The algorithm in this paper and the traditional algorithm use the same simulation environment; the simulation parameters are set to an information rate of 8192Kbps, QPSK modulation, frame length L0 of 1024 (bit), frame header data of 32'h1ACFFC1D, segment length L1 of 32, and compensation step maximum value X of 16°. The simulation generates 20 sets of data with different Eb / N0, then sets the residual frequency deviation to 5kHz, then counts the bit error rate of each group, and then averages the simulation experimental data. The specific results are shown in the figure; it is clearly found that the method in this paper is 1×10 (-3) Compared with the traditional method, the sensitivity is improved by 0.3dB at a BER of (FEC-Limit).

[0065] The following is an example to illustrate the specific implementation process of a low-delay, bandwidth-adjustable phase correction method of the present invention.

[0066] Assume that the current signal modulation mode is QPSK, the frame header data is 32'h1ACFFC1D, the frame length L0 is 8192 (bit), the segment length L1 is 32, and the maximum compensation step is 1°. The value of M is determined to be 4 by the signal modulation mode QPSK; the delay period T is determined to be (16*Sn symbol interval + 3) by the frame header data and the signal modulation mode, where 2 is the digital oscillator NCO output calculated by the frame header matching correlation vector The total number of data segments N is determined by the signal modulation mode, frame length L0 and segment length L1 to be (8192 / 2 / 32), i.e., 128; when the frame header matches the relevant vector Calculate the output through Calculate the value of φ0 and assign it to Φ1, which is then output by the digital oscillator NCO. Then the first data of Sn delayed by T cycles is combined with The first segment of Yn data is obtained by multiplying the output through the multiplier; then the first segment of Yn is subjected to a 4th power operation, and then the 32 results are summed to obtain the phase deviation vector of the corresponding segment number. And the phase deviation vector of the corresponding segment number The phase compensation value of the corresponding segment is obtained: Then, the maximum value of the compensation step is corrected to obtain φ N , then update Φ N The value is finally output through the digital oscillator NCO Then multiply it with the corresponding segment delay Sn to get the corresponding segment data of Yn. Calculate the output, reset the φ0 value and Φ value, and then repeat the above steps continuously, continuously adjusting the phase compensation value to complete the carrier phase recovery process.

[0067] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes to the concept of the present invention without creative work. Therefore, any technical solution obtained by a person skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A phase recovery method based on an improved M-th power carrier, characterized in that: The following steps are involved: S1, obtaining parameters and initializing the module, the parameters include signal modulation mode, frame header template, frame length L0, segment length L1, compensation step maximum value X, and initializing the module according to the parameters, which includes: determining the value of M according to the signal modulation mode; Determine the value of the delay time T of the Sn delay module according to the frame header template; S2, perform coarse frame synchronization on Sn according to the parameters of step S1, and output the frame header matching correlation vector 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; where Yn is the output of the carrier phase recovery method; 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 the segment length L1 to obtain the phase deviation vector Where N is the total number of segments; S5, match the frame header calculated in steps S2 and S4 to the relevant vector and the phase deviation vector Input phase deviation compensation calculation module, and correct the phase deviation compensation value Φ according to the maximum compensation step value X N , and then the digital oscillator NCO output is 2. A method for phase recovery based on an improved M-th power carrier according to claim 1, characterized in that: The value M in step S1 is 2 bit ,bit is the number of bits carried by a single symbol in the signal modulation method.

3. A method for phase recovery based on an improved M-th power carrier according to claim 1, characterized in that: The segment length L1 in step S1 is set to be no greater than the frame length L0.

4. The improved M-th power carrier phase recovery method according to claim 1, characterized in that: The calculation formula of Yn in step S3 is: In step S4 The calculation formula is 5. The improved M-th power carrier phase recovery method according to claim 1, characterized in that: In step S5, the frame header is matched with the relevant vector The calculated phase deviation value is φ0, which is obtained by using the phase deviation vector The calculated phase deviation is φ N ; The value of N is 1, 2…, ceil(L0 / (M*L1)); ceil() means rounding up.

6. A method for phase recovery based on an improved M-th power carrier according to claim 5, characterized in that: The calculation formula of φ0 in step S5 is: φ in step S5 N The calculation formula is: The Φ in step S5 N The calculation formula is 7. A method for phase recovery based on an improved M-th power carrier according to claim 6, characterized in that: The step S5 is implemented by a finite state machine.

8. The improved M-th power carrier phase recovery method according to claim 7, characterized in that: In step S5, a finite state machine is used to match the relevant vector in the frame header. After the input, it starts to start, and then outputs the phase deviation compensation value Φ N .

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