| Channel coding and cooperative transmission technologies are important in next-generation wireless communications.In view of the problems of complex wireless channel communication and poor communication quality in modern wireless communication,this paper mainly studies the polar coded cooperation technology.Firstly,the research status of modern wireless communication background,polarization code and cooperative communication are introduced.Then,the principle of polar encoding and decoding is summarized,and a Monte Carlo construction method based on likelihood ratio of information bits is proposed for Gaussian channel.In addition,the cooperation protocol and relay selection strategy are studied: jointing polar code in cooperative communication can optimize the error performance of the relay system,reduce the complexity,and obtain the diversity and coding gain.The full content and contributions are as follows:1.The construction method of polar code under Gaussian channel is studied.Aiming at the problem that the existing Monte Carlo construction method requires a large amount of analog information transmission,which leads to excessive complexity and weak real-time system,a Monte Carlo construction scheme based on bit error rate(BER)is proposed.First,in the analog channel transmission,only the all-zero bit sequence is transmitted,and the encoding operation is omitted in the analog transmission at the originating end.Secondly,the BER of each subchannel is used instead of the Barthel parameter to estimate the subchannel reliability.So,the recursive calculation of original method is removed,which greatly reduces the system complexity.The simulation shows that when the BER is 10-4,the proposed scheme has 0.7 and 0.6d B performance gains compared with the Barthel parameter method and Gaussian approximation method.Compared with the existing Monte Carlo construction method,when the BER is 10-4,the proposed method has a performance gain of about 0.25 d B,and the complexity is also reduced.2.In order to meet the requirements of single relay cooperative low delay and high performance,a improved belief propagation(BP)decoding scheme based on information bit node likelihood ratio is proposed.A selective decoding and forwarding with cyclic redundancy check is used at the relay node.At each iteration,the destination node monitors the information bit node likelihood ratio state,and stops updating for those nodes with greater credibility.At the same time,the early stop iteration mechanism is set.When the reliability of all information bit nodes are large,the iteration is stopped and the decision is decoded.The simulation shows that when the BER is310-,the proposed cooperative scheme can obtain about 0.8 d B channel gain and the complexity is relatively lowcompared with the low density parity check(LDPC)coding cooperation.3.For the complex and variable multi-relay cooperative channel,a variable rate polar coding scheme based on the quality of coding channel is proposed.The information bits is reselected based on coding channel status information.At the same time,the code is constructed using the same design signal-to-noise ratio(design-SNR)within a certain range of transmitted signal-to-noise ratio.In addition,in order to achieve spectral efficiency and diversity gain phase equalization,an optimal relay selection decoding and forwarding protocol is also proposed.Through a central decision unit,the relay node that can successfully decode is selected,then the best relay of the best channel state is selected,and the channel gain is determined according to the channel gain ratio of the source-to-destination link.transmission.The simulation shows that the proposed code rate variable polar coding scheme has a performance gain of 0.4 d B compared to the original Gaussian estimation scheme when the BER is-310.The proposed optimal relay selection decoding and forwarding scheme has a performance gain of about 1.3 d B and 0.8 d B respectively compared with the existing polar decoding and forwarding and network polar coding cooperation(NPCC)schemes at the BER is-310.Moreover,the proposed scheme can adaptively adjust the code rate according to the channel quality condition to obtain better BER performance;The polar coding cooperative transmission studied in this paper optimizes the Polar code and improves the cooperative transmission performance.Moreover,the proposed scheme is very suitable for communication transmission applications such as the new generation 5G Internet of Things due to its advantages such as good performance,low complexity and small calculation delay. |
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