The Research Of Network Coding Based On Systematic Polar Code In Cooperative Communication

Polar code is the first kind of channel coding technique that can be theoretically proved to achieve the capacity of binary symmetric channel.Diversity gain can be achieved by sharing antennas among users in cooperative communication systems.Network coding can improve network throughput.Based on this,network coding based on systematic polar code in cooperative communication system can not only ensure the reliable transmission of the system,but also improve the throughput of the system.On the basis of consulting the existing literature,three transmission mechanisms commonly used in cooperative communication are summarized and compared.The common application model of network coding in cooperative communication system is given,and its achievable transmission rate is analyzed.Successive cancellation decoding algorithm is adopted when polar code is proposed,which can not be combined with other soft detection algorithms for iterative decoding.The decoding algorithm based on belief propagation is also applicable to polar code.In this paper,the extrinsic information part of the interaction between BP decoding algorithm and other soft detection algorithms in joint iterative decoding is given.The simulation results show that the performance of polar code under SC decoding algorithm is similar to that of BP decoding algorithm.The initial polar code is presented in the form of a non-systematic code,but in essence,polar code is also linear block code,which exists a systematic code.Therefore,we further study the encoding and decoding algorithm of the systematic polar code.The simulation results show that the performance of the systematic polar code is better than that of the non-systematic polar code under SC decoding and BP decoding.Currently,in a multi-user wireless scenario,the polar code is mostly applied to a traditional three-node relay network,but generally there are a large number of mobile users in the cell coverage area covered by the base station.In order to improve the throughput and robustness of the network,polar code is applied to network coding in multi-source and multi-relay scenarios,and an adaptive mapping from multi-source and multi-relay network topology to encoding architecture of systematic polar code is realized.According to this mapping relationship,we can meet any arbitrary trade-off requirements between network throughputs and system reliability by adjusting the number of source nodes and relay nodes participating in the network coding in the relay network.Furthermore,we also adopt a joint iterative decoding algorithm at the destination node to achieve deep joint detection between channel coding at a single node and overall network coding based on systematic polar code.The simulation results show that the proposed method achieves a strong error correction capability under the premise of satisfying the dynamic adaptive network topology change.Since the code length of the polar code must be an integer power of 2,the sum of the number of bits sent by all source nodes and that sent by all relay nodes must be 2~n.In order to remove this constraint to achieve a rate compatible network coding.In view of the specific situation of our multi-source and multi-relay network coding model,based on the existing quasi uniform puncturing algorithm,a new puncturing algorithm based on modified QUP is proposed.Then,by studying the selection method of information bits of polar code,a puncturing algorithm based on Bhattacharyya parameter ordering is proposed.The simulations show that both algorithms have good performance,and the puncturing algorithm based on Bhattacharyya parameter ordering has a slightly lower performance,but its computational complexity is low.The rate compatible network coding based on systematic polar code is realized by these two puncturing algorithms.