Research On Coded Cooperation Technology In Wireless Communication Systems

In the wireless communication system,fading channel is still the main facter to influence system performance, the main method to solve it is multi- antenna spatial diversity techniques.However, in a wireless communication network, we can not install multiple antenna in terminal equipmentsdue to various limitations,whichgreatly restrictsthe application of multi- antenna technology. Cooperative diversity technology is to collaborate and share the antenna each other,by the wireless communication terminalswith a single antenna inwireless communication network, whichsimulates multiple antenna diversity as a result.Hunter and someone else first proposed the channel coding technology combined with cooperative diversity technology, it enables the system to obtain diversity gain and coding gain as well. After that,the domestic and foreign scholars have proposed collaborative communication scheme using RCPC code and LDPC code different channel coding methods,And proved its excellentperformance. But these channel coding schemes are channel coding methodin fixed rate,thus greatly limits its application in cooperative communication system.Fountain code is a kind of channel coding scheme in no rate, which can be well applicated in cooperative communication system. So this paper proposed a collaborative communication scheme based on fountain codes, first optimizedecoding algorithmusing fountain codes under wireless channel, thenproposed serial BP decoding (ESD-SBP) algorithm based on the information symbols outside.Secondly, proposed collaboration solutions based on hybrid forwarding fountain codes to solve the problem that, the system is unable to obtain diversity gain when the partner can not be correctly decoded.The main work and results are as follows :For the problemthat, when using fountain codes for transmission over the wireless channel with BP iterative decoding algorithm, which results largedecoding iterations and the lack of effective mechanisms to stop the iteration. Firstly, improvethe BP iterative decoding,applyBP decoding algorithm to the serial code decoding using fountain codes,which doubles the decoding speed using fountain codes. Thenanalysisextrinsic information transfer curve (EXIT) chart duringdecoding process using fountain codes.Proposed ESD-SBP decoding algorithmwith iteration stop signsfrom the difference after a full iteration nodes using external information symbols. The simulation results show:The algorithm can effectively reducing the number of decoding iterations and improve system performance under the premise of excellent performance fountain codes.For the problem that, we can not get the gain of diversitywhen the relaynode can not correctly decode the information from source nodein collaborative communication,this paper firstly proposed a cooperativecodingschemebased on fountain codes and amplification forwarding scheme,theoretical analysis shows that:cooperative communications system can obtain a full diversity gain of degree twoin case of correct decoding of the information fronthe source node by the relay node, but wecan not get anydiversity gainwhendecoding is failed.Amplification forwarding can get diversity gain whatever correct decoding of the information fron the source node by the relay node,But the effect is limited.So this paper proposed a hybrid forward (HF) scheme, the simulation results show that :HF collaboration solutions are more excellent in the performance of the bit error rate, compared with other collaboration.