Joint Design Of Phvsical-Laver Network Coding And LDPC Code In Multi-Relay Wireless Communication System

In the field of wireless communication technology,the schemes of Relay-cooperative-communication which due to long-distance constraints,complex channel condition constraints and other factors have alwavs been one of the central issues in the communication field.How to ensure that the excellent communication efficiency and transmission accuracy of information when it was transmitted over a long distance has attracted more and more scholars' attention.Since Rudolf.Ahlswede et al.proposed that Network Coding(NC)and Shengli Zhang et al.hereafter proposed Physical Layer Network Coding(PNC),NC and PNC have been highly favored for their superiority to significantly increase the Throughput Rate of communication system.Compared with other channel coding,LDPC code has the advantages of convenient description,simple form,simple coding decoding and close performance to Shannon bound.Therefore,it has stronger practicability when combined with network coding and phy'sical layer network coding.The main work of this paper can be briefly explained as follows:1.This thesis first introduces the historical development,research status and future development direction of network coding and physical layer network coding.It clearly describes the basic principles,transmission modes and their advantages and disadvantages ofNC and PNC.and analyzes their reduction.The principle ofinformation exchange slot number and system throughput rate improvement;the basic theory of LDPC code.Tanner graph representation and the LDPC code check matrix construction method and codec scheme involved in this paper are briefly integrated,which is the following joint scheme.The design provides theoretical support.2.Then the systerm model of QPSK-LDPC-NC,QPSK-PNC and QPSK-LDPC-PNC based on QPSK modulation is designed.The Relay mapping scheme and system decoding algorithm are given,and the system performance simulation analysis is carried out.The simulation results show that the PNC technology can deteriorate the system Bit Error Rate while improving the system throughput.This paper introduces the LDPC code technology to improve the system bit error rate performance.In addition,the performance of the QPSK-LDPC-NC and QPSK-LDPC-PNC joint system is optimized to further improve the system BER performance and shorten the decoding operation time.3.For the more complex relay cooperative transmission model,we research four classical transmission models on Traditional One-way Transmission,Two-way NC Cooperative Transmission,One-way PNC Cooperative Transmission and Two-way PNC Cooperative Transmission.The experimental simulation comparison shows that the Two-way PNC Cooperative Transmission model can greatly reduce the system information exchange time and improve the system throughput.Then the system model of 3R relay communication system(3R-QPSK-PNC-LDPC)based on QPSK modulation combined PNC technology and LDPC code is given.The design and Bit error rate performance simulation show that the introduction of PNC technology and LDPC code in the MR-QPSK-PNC-LDPC joint system can improve the system throughput rate.and also ensure good bit error rate performance and reduce the performance loss due to Multi-relay transmission and PNC technology,improve the reliability and efficiency of Multi-relay transmission systems.