Research On Channel Decoding Algorithm And ARQ Technology Based On Relay Cooperation

At present,the requirements of information transmission performance in wireless communication systems have become increasingly stringent.Therefore,to improve the communication quality of cell edge users and extend the coverage of the cell,relay cooperation technology is introduced to the wireless communication system to improve the transmission performance of wireless communication by obtaining the diversity and reuse gain.Channel coding technology and ARQ?Automatic Repeat reQuest?technology have significant advantages in resisting interference and reducing bit error rate.Applying them to relay cooperative communication systems can effectively improve the reliability of the transmission system.Basing on the relay cooperative network scenario,this paper makes intensive research on the ARQ technology as well as Turbo code and LDPC code whose performance are approaching the Shannon limit,the research contents are as follows:?1?For the single-source single-relay transmission network,basing on the decoding principle of Turbo codes,this paper uses the correlation estimation between source information and relay information,and proposes a Turbo decoding algorithm based on bit flipping probability.In this algorithm,the relay node adopts a low-complexity demodulating and forwarding method.The base station performs correlation estimation based on the received source information and relay information,and estimates the bit flipping probability.Finally,based on the bit flipping probability,the update of the external information between the two component decoders is realized,so as to realize the design of Turbo code iterative decoding algorithm.The research shows that,compared with the traditional relay cooperative decoding scheme,the proposed Turbo decoding algorithm has obvious performance advantages under AWGN?Additive White Gaussian Noise?channel and Rayleigh channel conditions.?2?For the single-source single-relay transmission network,combing the BP?Belief Propagation?decoding algorithm and ARQ technology,an adaptive LDPC decoding algorithm is designed.In this algorithm,the relay node determines whether to forward low-complexity demodulation information according to the automatic retransmission request information sent by the base station.Secondly,the base station uses the bit flip probability to design a joint iterative decoding algorithm between the source LDPC decoder and the relay LDPC decoder.In each iteration of the decoding process,the update of the external information is implemented by the bit flip probability.The simulation results show that,compared with the traditional relay scheme,the designed adaptive LDPC decoding algorithm improves 4.0dB and 5.8dB,respectively,under the condition that the source-relaylink is better than the source-base link 5dB and 10dB,when the bit error rate is 10^-4.?3?For the multiple access relay transmission network,an adaptive joint LDPC-network coding transmission scheme based on ARQ technology is designed.According to the estimation of the received multiple direct link source information,the base station sends the ARQ information of source node factor set to the relay node through the feedback channel.The relay performs adaptive network coding according to the received ARQ information and forwards it.Finally,a joint LDPC iterative decoding design is performed based on the direct-transmitted link information and adaptively-forwarded information of relay.The simulation results show that the proposed transmission scheme has greater performance improvement than the relay XOR schem.In addition,the relay decoding scheme has better performance gain than the demodulating scheme.