Design And Performance Analysis Of Distributed Coded Cooperative System Based On STBC Spatial Modulation

Information transmission by wireless communication systems has involved all aspects of modern society,but the nature of wireless channels is unreliable and unpredictable.Phenomenon such as scattering,diffraction and reflection will cause the signal to decay during its transmission.Initially,the signal fading was combated by increasing the transmission power,but most communication equipment was power limited.Therefore,it is important to use channel coding for error correction.In order to achieve effective and reliable information transmission on fading channels,with distinguishing from the traditional point-to-point communication category,this thesis applies space-time coding space modulation(STBC-SM)and channel coding including polar code to cooperative communication to obtain a high spectral efficiencies,excellent anti-fading ability and low complexity distributed coded cooperative system,and analyze the relevant factors affecting its performance.The specific research contents and innovations are as follows:1)Channel coding is the cornerstone of the STBC-SM distributed coding cooperative system.In the field of binary codes,the iterative coding and decoding technologies of LDPC and Turbo codes approaching Shannon's limit are described.The computational complexity and decoding performance are compared with the polar codes which proved that Shannon's limit can be obtained through mathematical calculations.The article further researched the encoding and decoding technology of polar code,including different channel selection schemes,various decoding algorithms,and analyzing its performance from different angles on AWGN and Rayleigh fading channels through simulation.In the field of non-binary code,the coding and decoding technology of the maximum distance separable code(MDS)is introduced.RS code is an important member of MDS code.Compared with the above binary code,it can achieve a good compromise between error performance and decoding complexity under the condition of short code length,and it has excellent performance in correcting random burst errors.2)The new STBC-SM technology is used in the transmission scheme of the coded cooperative system to obtain high spectral efficiency,because the information bits in the STBC-SM are transmitted together through the symbol pair and antenna pair selection.Because it is not necessary to activate the characteristics of all transmitting antennas,STBC-SM can reduce related interference caused by multiple antennas.STBC-SM minimizes bit error rate by getting diversity coded gain.In addition,in hard decision scenarios,in order to reduce the complexity of high-order modulation,an optimized maximum likelihood demapping algorithm is used.While in soft decision scenarios,a low-complexity STBC-SM soft detection algorithm is used.3)The article first proposed a distributed RS coding collaboration system based on STBC-SM.Two RS codes are placed on the source node and the relay node,and the RS code generation polynomial used by the relay node has a higher degree.Combining the low complexity hard detection algorithm of STBC-SM,two joint decoding schemes are proposed,namely NAIVE algorithm and SMART algorithm.The NAIVE algorithm decodes the signals from the source and the relay separately,and the common decoding output is determined by threshold judgment of the signal-to-noise ratio.The SMART algorithm decodes the signal from the relay,and replaces the part of the signal from the source to the destination with the corresponding decoded output,and finally decodes the combined signal.Simulation results show that the SMART algorithm performs better than the NAIVE algorithm on the quasi-static Rayleigh fading channel,and the performance of the STBC-SM distributed RS coded cooperative system is significantly better than that of the traditional point-to-point system.4)Aiming at the poor performance of ordinary polar codes on fading channels,this thesis designs a distributed polarized coded cooperative system based on multi-level construction and STBC-SM.Because most of the polarized coded cooperation schemes are established for BPSK modulation,one of its main limitations is low spectral efficiency,STBC-SM with high-order modulation can be used in the coding cooperation.By combining multi-level polar codes with STBC-SM,a new polar coded collaborative system is constructed in this thesis,and STBC-SM soft detection with low complexity is used instead of maximum likelihood soft detection to effectively overcome the high detection complexity at the destination degree.In addition,a joint soft SC/SCL decoding algorithm is performed at the destination node,which can decode the source and relay signals at the same time,instead of multi-step decoding at the destination.The simulation results show that the performance of the system on the quasi-static fading channel is obviously better than that of the ordinary polar coded cooperative system,which can greatly improve the decline of error correction ability caused by fading.