Iterative decoding method and system for improving phase estimation performance

Abstract

The invention relates to an iterative decoding method for improving phase estimation performance. The iterative decoding method comprises the following steps: step 1, estimating an initial phase of each hop according to a pilot frequency; step 2, removing phases, obtaining soft information values of all transmission signals after demodulation, and sending the soft information values to a decoder after de-interleaving; step 3, iterating soft information values of all signals through a decoder, comparing the soft information values with the input soft information values one by one, and identifying reliable signals; and 4, carrying out modulation and hopping on decoding output bits again, taking the reliable signal marked in each hop as a new local pilot frequency, carrying out phase estimation again, and carrying out demodulation, de-interleaving and decoding in the step 2 so as to complete a large iteration until a target iteration number is completed. According to the method, on the premise that no waveform constraint is added, reliable data signals can be recognized based on input and output feedback of the decoder in the iterative decoding process, phase estimation is assisted, the accuracy of phase estimation is greatly improved, and then the overall performance of the system is improved.

Description

Technical Field

[0001] The present invention belongs to the field of communication technology, and in particular relates to an iterative decoding method and system for improving phase estimation performance. Background Art

[0002] Modern digital communication systems all have corresponding frequency bands. The system needs to up-convert the information to the specified frequency band before sending it to the transmission medium, while the receiving end needs to down-convert the received signal to the baseband for subsequent processing. Therefore, both the transmitting and receiving ends need to generate corresponding carriers to complete the corresponding up-conversion and down-conversion operations. However, the carrier is not ideal. Since the crystal oscillator and the phase-locked loop that generate the carrier have certain stability, there is a short-term random difference between the carrier frequency and the target frequency, which in turn causes the generated sinusoidal signal to have a random phase jump, which manifests as phase noise. The system performance is often lost to varying degrees. Accurately estimating the phase change is particularly important for improving system performance. Usually, a pilot signal is used for phase estimation, and the local known pilot signal and the received pilot signal are correlated to perform phase estimation. When the number of pilot symbols in each data hop is small, the phase estimation using the pilot is not accurate enough, or under low signal-to-noise ratio, the phase estimation of the pilot symbol of limited length is also not accurate enough, thus affecting the overall performance of the system. However, increasing the number of pilot symbols will reduce the number of effectively transmitted data symbols, which will inevitably reduce the user rate or reduce the coding gain, also affecting the system performance. Summary of the invention

[0003] The purpose of the present invention is to provide an iterative decoding method and system for improving phase estimation performance. Based on the principle of iterative decoding algorithm, reliable information is identified through comparison of soft information input and output of decoder, phase estimation is assisted, and the accuracy of phase estimation is improved. The method is simple to implement, does not impose any waveform constraints, and can effectively improve system performance.

[0004] The present invention provides an iterative decoding method for improving phase estimation performance, comprising the following steps:

[0005] Step 1, estimate the initial phase of each hop based on the pilot signal;

[0006] Step 2, remove the phase, demodulate and obtain the soft information value of all transmitted signals, deinterleave and send to the decoder;

[0007] Step 3, iterate the soft information values ​​of all signals through the decoder, compare them one by one with the input soft information values, and identify reliable signals;

[0008] In step 4, the decoded output bits are re-modulated and hopped, and the reliable signal marked in each hop is used as a new local pilot, and the phase is re-estimated. Then, the demodulation, deinterleaving, and decoding in step 2 are performed to complete a large iteration until the target number of iterations is reached.

[0009] Furthermore, the step 1 comprises:

[0010] The receiving end performs correlation operation based on the known local pilot signal and the received pilot signal to obtain the initial phase estimate.

[0011] Furthermore, the step 3 comprises:

[0012] The soft information values ​​of all signal information bits and check bits, i.e., the posterior log-likelihood ratios, are iteratively obtained through a decoder and compared one by one with the input soft information values. If the sign bits are the same, the signal at that position is considered reliable and the flag is set to 1; otherwise, it is unreliable and the flag is set to 0. The decoder is a Turbo decoder.

[0013] Furthermore, the step 4 comprises:

[0014] The posterior log-likelihood ratio of the decoder output is used for hard decision to obtain the decoded bits of the information bits and check bits. All bits are then interleaved, modulated, and group-hopped, and the flag bits are subjected to the same operation. In each hop, according to the guidance of the flag bit, the signal at the reliable position is treated as a known local pilot and the received signal at that position, and the phase is re-estimated. Then, after demodulation, deinterleaving, and channel decoding in step 2, a large iteration is completed.

[0015] The present invention also provides an iterative decoding system for improving phase estimation performance, comprising an iterative decoding module, wherein the iterative decoding module executes the iterative decoding method for improving phase estimation performance.

[0016] The present invention also provides a non-transitory computer-readable storage medium, which stores computer instructions. When the computer instructions are executed by a processor, the iterative decoding method for improving phase estimation performance is implemented.

[0017] The present invention also provides an electronic device, comprising:

[0018] A memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the iterative decoding method for improving phase estimation performance by executing the computer instructions.

[0019] By means of the above scheme, through the iterative decoding method and system for improving the phase estimation performance, reliable data signals can be identified based on the decoder input and output feedback during the iterative decoding process without adding any waveform constraints, and phase estimation can be assisted, thereby greatly improving the accuracy of phase estimation and thus improving the overall performance of the system.

[0020] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A flow chart of an iterative decoding method for improving phase estimation performance according to the present invention;

[0022] Figure 2 It is a simulation model of the system of the present invention;

[0023] Figure 3 A specific process of an iterative decoding method for improving phase estimation performance in one embodiment of the present invention;

[0024] Figure 4 It is a performance comparison between the present invention and the prior art after M2 iterations;

[0025] Figure 5 The figure is a schematic structural diagram of an electronic device of the present invention. DETAILED DESCRIPTION

[0026] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0027] Ginseng Figure 1 As shown, this embodiment provides an iterative decoding method for improving phase estimation performance, characterized in that it includes the following steps:

[0028] Step 1, estimate the initial phase of each hop based on the pilot signal;

[0029] Step 2, remove the phase, demodulate and obtain the soft information value of all transmitted signals, deinterleave and send to the decoder;

[0030] Step 3, iterate the soft information values ​​of all signals through the decoder, compare them one by one with the input soft information values, and identify reliable signals;

[0031] In step 4, the decoded output bits are re-modulated and hopped, and the reliable signal marked in each hop is used as a new local pilot, and the phase is re-estimated. Then, the demodulation, deinterleaving, and decoding in step 2 are performed to complete a large iteration until the target number of iterations is reached.

[0032] Ginseng Figure 2 As shown in the figure, the transmitter in the system simulation model consists of channel coding, interleaving, pilot group hopping, modulation, up-conversion and other parts. The receiver corresponds to the transmitter and consists of down-conversion, acquisition, phase estimation, demodulation, deinterleaving and channel decoding. A random phase and signal-to-noise ratio (SNR) are added to each hop access signal of the receiver.

[0033] Ginseng Figure 3 As shown, the specific process of the iterative decoding method for improving phase estimation performance is as follows:

[0034] The receiving end performs correlation operations based on the known local pilot signal and the received pilot signal to obtain the initial phase estimate. After removing the phase, the soft information values ​​of all transmitted signals are obtained after demodulation and deinterleaving, and sent to the decoder. Taking Turbo code as an example, the Turbo decoder needs to iterate the soft information values ​​of all signals (information bits and check bits), that is, the a posteriori log-likelihood ratio, and compare them with the input soft information values ​​one by one. If the sign bits are the same, the signal at this position is considered reliable, and the flag position is 1, otherwise it is unreliable and the flag position is 0. The a posteriori log-likelihood ratio output by the decoder is used for hard decision to obtain the decoded bits of the information bit and the check bit, and then all bits are interleaved, modulated, and group-hopped, and the flag bit is also subjected to the same operation. In each hop, according to the guidance of the flag bit, the signal at the reliable position is regarded as the known local pilot and the received signal at this position, and the phase is re-estimated, and then demodulated, deinterleaved, and channel decoded to complete a large iteration. The number of large iterations can be set according to actual conditions.

[0035] The simulation conditions are as follows: 128 hops per data packet, 32 valid symbols per hop, 2 pilot symbols, 2560 bits of information length before encoding, 2 / 3 code rate, MSK modulation, 20 decoder iterations M1, and 1, 2, 4, and 8 maximum iterations M2 respectively. Figure 4 This is a performance comparison between the invention and the prior art after M2 iterations. The simulation results show that compared with the prior art, the invention improves the SNR corresponding to 1% packet error rate by 1dB after 1 iteration; by 1.2dB after 2 iterations; by 1.4dB after 4 iterations; and by 1.5dB after 8 iterations. The number of iterations M1 and M2 can be adjusted according to the actual waveform scheme.

[0036] When the phase estimation is inaccurate due to reasons such as a small number of pilots or a low signal-to-noise ratio (SNR), the overall performance of the system will be affected. The present invention identifies reliable data signals based on decoder input and output feedback during iterative decoding without adding any waveform constraints, and assists in phase estimation, thereby greatly improving the accuracy of phase estimation and thus improving the overall performance of the system. The performance of phase estimation can be improved without adding additional pilot overhead or any waveform constraints; due to the improvement in overall performance, the pilot overhead can be appropriately reduced to improve transmission efficiency or coding gain; it does not increase additional hardware costs and can be achieved by adding software modules.

[0037] The present invention can be applied to civil communication systems or military communication systems that adopt channel coding schemes such as Turbo, but is not limited to Turbo channel coding and decoding, and can also be applied to other types of codecs as long as a one-to-one correspondence between input soft information and output soft information can be achieved.

[0038] This embodiment further provides an iterative decoding system for improving phase estimation performance, including an iterative decoding module, wherein the iterative decoding module executes the iterative decoding method for improving phase estimation performance.

[0039] This embodiment also provides a non-transitory computer-readable storage medium, which stores computer instructions. When the computer instructions are executed by a processor, the iterative decoding method for improving phase estimation performance is implemented.

[0040] Ginseng Figure 5 As shown, this embodiment also provides an electronic device, including:

[0041] A memory 201 and a processor 202, wherein the memory 201 and the processor 202 are communicatively connected to each other, the memory 201 stores computer instructions, and the processor 202 executes the iterative decoding method for improving phase estimation performance by executing the computer instructions.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the technical principles of the present invention, and these improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. An iterative decoding method for improving phase estimation performance, characterized in that: The steps include: Step 1, estimate the initial phase of each hop based on the pilot signal; Step 2, remove the phase, demodulate and obtain the soft information value of all transmitted signals, deinterleave and send to the decoder; Step 3, iterate the soft information values ​​of all signals through the decoder, compare them one by one with the input soft information values, and identify reliable signals; In step 4, the decoded output bits are re-modulated and hopped, and the reliable signal marked in each hop is used as a new local pilot, and the phase is re-estimated. Then, the demodulation, deinterleaving, and decoding in step 2 are performed to complete a large iteration until the target number of iterations is reached.

2. The iterative decoding method for improving phase estimation performance according to claim 1, characterized in that: The step 1 comprises: The receiving end performs correlation operation based on the known local pilot signal and the received pilot signal to obtain the initial phase estimate.

3. The iterative decoding method for improving phase estimation performance according to claim 2, characterized in that: The step 3 comprises: The soft information values ​​of all signal information bits and check bits, i.e., the posterior log-likelihood ratios, are iteratively obtained through a decoder and compared one by one with the input soft information values. If the sign bits are the same, the signal at that position is considered reliable and the flag is set to 1; otherwise, it is unreliable and the flag is set to 0. The decoder is a Turbo decoder.

4. The iterative decoding method for improving phase estimation performance according to claim 3, characterized in that: The step 4 comprises: The posterior log-likelihood ratio of the decoder output is used for hard decision to obtain the decoded bits of the information bits and check bits. All bits are then interleaved, modulated, and group-hopped, and the flag bits are subjected to the same operation. In each hop, according to the guidance of the flag bit, the signal at the reliable position is treated as a known local pilot and the received signal at that position, and the phase is re-estimated. Then, after demodulation, deinterleaving, and channel decoding in step 2, a large iteration is completed.

5. An iterative decoding system for improving phase estimation performance, characterized in that: It includes an iterative decoding module, which executes an iterative decoding method for improving phase estimation performance as described in any one of claims 1-4.

6. A non-transitory computer-readable storage medium, characterized in that: The non-transitory computer-readable storage medium stores computer instructions, and when the computer instructions are executed by a processor, an iterative decoding method for improving phase estimation performance as described in any one of claims 1-4 is implemented.

7. An electronic device, characterized in that: include: A memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the iterative decoding method for improving phase estimation performance as described in any one of claims 1 to 4 by executing the computer instructions.

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