Research On Cooperative Communication And Network Coding Technology In Satellite-terrestrial Network

Nowadays the satellite network,terrestrial mobile network are developing maturely in their respective fields,and each has its advantages.To be up to the higher communication standard and meet the communication needs of the next generation of networks,scientific research institutions proposed satellite-terrestrial communication system.In satellite-terrestrial communication system,the channels between satellites and ground terminals fade seriously and relative to the terrestrial users,satellites move at high speed,resulting in the communication reliability lacking of guarantee.Therefore,the cooperative communication technology is often applied in satellite-terrestrial communication networks,and until now the representative systems like DVB-SH,XM and other systems have been successfully established.However,taking into account the high laying cost of ground assistant communication equipment in these systems,researchers have proposed a prospective satellite-terrestrial interuser cooperative communication system,allowing ground terminals cooperating to achieve high spatial diversity as a kind of virtual MIMO.According to the connection between relay technology,cooperative communication technology and network coding,multicast,this paper will combine the digital field and complex field network coding with cooperative communication in satellite-terrestrial communication system to reduce the system's bit error rate and achievet he more reliable communication.This paper first analyzes the origin and background of satellite-terrestrial communication network,introduces the meaning and necessity of the combination of cooperative communication and network coding technology in satellite-terrestrial communication network,and according to the existing research situation at home and abroad,we summarizes the future direction of technological development.Later in this paper,we study the basic theory of combination the cooperative communication and the network coding in satellite-terrestrial communication system,and introduce the existing classical cooperative communication system models and their combination with the network coding.For the complex link,we establish the three states channel fading model for suburb and city scenes,which is more realistic.In addition,the application of network coding technology is studied,and it is found that network coding has great advantages on delay,energy efficiency,reliability,robustness,bit error rate and information security.Combining network coding and cooperation technology,this paper proposes three cooperative network coding transmission protocols.According to the the instability and fading of the channels between satellites and ground terminals as long as the application limitation of binary network coding in satellite-terrestrial communication network,and combining the RS code construction method,the high diversity gain network coding scheme on high-order Galois domain is proposed,named RS-DNC.In the case of ineffective cooperation and ineffective network coding under high SNR condition and satellite-terrestrial network's requirement for delay,a cooperative automatic retransmission network coding cooperative transmission protocol(CARQ-NC)based on feedback is proposed,and the simulation analysis of bit error rate and transmission efficiency is carried out.Finally,this paper addresses the problem that digital domain networcoding's reliability of cooperative channel between users and the bad performance of bit error rate under low signal-to-noise ratio,we proposed to apply the complex field network coding,to ensure the high communication reliability of satellite-terrestrial communication system even under low SNR or with poor interuser cooperation channel.