Reserch On Polar Code Enhanced Technology For 5G-Advanced

Diversified mobile services have a profound impact on the way of life and work of modern people.With the increasing business demand,mobile network is required to be more effective and reliable.According to different application scenarios,the fifth generation mobile communication(5G)system plans and requires peak rate,user experience rate,number of device connections and connection density,reliability,delay and other indicators.5G-advanced(5G+)network is the way for 5G to evolve into the sixth generation mobile communication(6G).5G+will further improve the application scenarios and technologies,and expand the application space on the basis of improving the transmission rate.As one of the core technologies of wireless communication physical layer,the improvement of channel coding performance will directly affect the transmission rate and network coverage.Theoretically,the capacity of polar code is reachable,and it is outstanding in short packet transmission.It has been included in the 5G standard.For 5G+,we need to inherit the research results of 5G-Polar code,and further explore the way to improve the performance.Systematic code is easier to combine with other technologies to improve system performance.Even,techniques such as probability shaping and information coupling can only be combined with systematic codes.The 5G-Polar code is a kind of non-systematic code with three structures.Each structure is suitable for different application conditions,such as channel type and code length.Codes with different structures have their own advantages in reliability and complexity.The traditional systematic polar coding method can't convert all the structures of 5G-Polar code into systematic code,which limits the application of the research results of 5G-Polar code in this aspect.The Non-orthogonal multiple access(NOMA)technology can effectively improve the access capability of the system,and can meet the requirements of 5G+system in high frequency spectrum efficiency and connection.The application of polar code in NOMA system can improve the reliability of the system and help to achieve the expected system performance goals.The combination optimization of polar code and NOMA technology is an important research direction.How to design a low complexity receiver algorithm is one of the key problems.Information coupling technology can enhance the performance of codewords by optimizing the coding structure,and it can meet the requirements of higher reliability when applied to polar code.The research of partially information-coupled polar(PIC-Polar)code is still in the exploratory stage,and the existing PIC-Polar code need to be further improved in terms of reliability and complexity.For the above problems,this paper studies the enhancement technology of polar code for 5G+system.The main research work and innovation of this paper are as follows:Firstly,in order to solve the problem that the traditional systematic polar coding methods aren't suitable for 5G-Polar code,this paper has proposed the design principle and implementation method of systematic polar code.Based on the structural characteristics of 5G-Polar code,the design principle of the conversion for polar code from non-systematic form to systematic form has been proposed and proved.According to the difference of the type,position and function of the auxiliary bits in different polar codes,the specific method of systematic polar coding and the scheme of position selection of the auxiliary bits are designed.Simulation results show that compared with the non-systematic structure of 5G standard,the proposed systematic 5G-Polar code has no performance loss in block error rate and achieves lower bit error rate,which meets the basic performance characteristics of the systematic polar code.The design is effective.The proposed systematic polar coding scheme makes full use of the achievements of 5G standard in the optimization of polar code.It applies the advantages of non-systematic polar codes with different structures in terms of reliability and complexity to systematic polar codes.It is beneficial to the combination of polar code and other advanced technologies to achieve the expected performance of the system.Secondly,for the problem of high complexity of receiving algorithm in polar coded NOMA system,a low complexity CRC aided joint iterative detection and SCL decoding(CAJIDS)receiver is proposed based on the sparse code multiple access(SCMA)system.The extrinsic messages reconstruction methods of hard output SCL decoding algorithm is studied,and the application problem of SCL algorithm in iterative receiver is solved.Based on the joint factor graph of SCMA and polar code,a basic joint iterative detection and SCL decoding(BJIDS)receiver is designed by combining the message passing algorithm detector and SCL decoder.Compared with the traditional iterative detection and decoding receiver,the BJIDS receiver achieves a performance gain of 0.82db(at BLER=10-3)with the same complexity.In order to reduce the complexity of BJIDS receiver,a CAJIDS receiver is designed based on distributed CRC and variable decoding list.The CAJIDS receiver correlates the decoding reliability and complexity,and dynamically adjusts the list width of SCL decoder in the next iteration according to the CRC results,so that the complexity decreases with the increase of signal-to-noise-ratio(SNR).The approximate formulas of decoding complexity and latency are derived.Under the additive white Gaussian noise(AWGN)and Rayleigh channel,the key parameters of low complexity receiver are optimized through simulation analysis.Compared with BJIDS receiver,the CAJIDS receiver reduces the complexity by about 60%(at BLER=10-3 under Rayleigh channel),but has no performance loss.Compared with the joint iterative detection and decoding(JIDD)receiver in the literature,the CAJIDS receiver achieves a performance gain of more than 0.8db(at BLER=10-3)under Rayleigh channel.Besides,the problem that the performance of SCMA system based on JIDD receiver is worse than that of LDPC coded SCMA system at low bit rate is solved.Thirdly,to optimize the reliability and complexity of PIC-Polar code,a new PIC-Polar code is designed by combining parity check and distributed CRC.Based on the design principles of systematic polar code and the characteristics of 5G-Polar codes,a joint parity check and distributed CRC aided polar(PCDCA-Polar)code is proposed to optimize the basic structure of PIC-Polar code.This method can enhance the reliability by parity check,and reduce the decoding complexity of error codewords by distributed CRC check.The rule of information coupling is designed,and the coupling position selection scheme is designed based on the difference of auxiliary bits.Then,based on the feed-forward and feed-back mechanism and the basic code characteristics,the decoding method of PIC-PCDCA-Polar code is designed.The theoretical analysis of error probability is carried out.Compared with the original PIC-Polar code,the proposed scheme achieves a gain of about 0.3dB with short code length.The complexity of the proposed scheme is also reduced at different code rates.When the code length is 200 and the code rate is 1/2,the maximum total saved computational complexity ratio is 16%.Based on the idea of variable decoding list and early terminate for iteration,a receiver is designed for PIC-PCDCA-Polar coded SCMA system.Based on the transmission characteristics of extrinsic messages,the reliability sequence and coupling parameters of PIC-PCDCA-Polar code are optimized.Compared with uncoupled polar code,the PIC-PCDCA-Polar code improves the reliability of SCMA system,and achieves more than 0.4dB gain under Rayleigh channel.