Study On Joint Channel-network Encoding And Decoding For Underwater Acoustic Cooperative Networks

The research of underwater acoustic communication(UAC)is changing from point-to-point data transmission technology to network because of its widespread applications such as marine ecological protection,resource exploration,disaster forecasting,national defense and security.Cooperative communication technology can achieve diversity gain through the cooperation of nodes which is an effective way to combat multipath fading.It has been studied extensively as a promising technique for improving the performance of wireless networks.Due to the harsh underwater environment,designing a tansmission protocol that is suitable for the doubly selective underwater acoustic channel and has reduced power consumptionis very challenging in underwater acoustic cooperative networks.The performance of UAC is limited by the characteristics of narrowband,high noise and multi-path fading of underwater acoustic channel.Based on the concept of cross-layer design and iterative processing,we propose joint channel-network encoding and decoding scheme with LDPC(Low Density Parity Check)codes,as well as the joint iterative decoding algorithm.We investigate the optimal design of joint the physical and network layer,through the cooperation of nodes,to reduce the bit error rate(BER)of the UAC and it can improve the reliability of UAC system.The major work of this dissertation is as the following:1.The research status in the field of underwater acoustic cooperative networks in domestic and abroad is summarized.We introduce the performance of LDPC codes and network coding.In the dissertation,the XOR network coding is adopted in the relay.2.In underwater acoustic cooperative networks,we propose joint channel-network encoding and decoding scheme with LDPC codes and joint iterative decoding algorithm.The relay node adopts the XOR network coding for cooperative data transmission,and the destination node adopts joint iterative decoding for received data.The simulation results show that the proposed scheme can effectively reduce the BER and improve the throughput of the UAC system compared with the channel coding scheme and the decode and forward cooperative scheme.3.Based on the two-source single-relay UAC cooperative network model,we study the joint decoding iterations and the power allocation among nodes for the proposed scheme.The experiment results show that it can improve the BER performance of UAC system by choosing the appropriate number of iterations and power allocation factor.4.The joint channel-network encoding and decoding scheme is further applied to the underwater acoustic multi-hop cooperative networks.Based on the energy consumption model of UAC,the energy consumption of the number of hops and transmissions in each hop is derived.The number of hops and the number of transmissions in each hop are analyzed by numerical simulation.5.In thewater tank experiment,the feasibility and reliability of the proposed scheme are verified.And the analytical results show that the BER of decoding can be reduced by optimizing the received signal-to-noise ratio estimation,and the performance of the joint iterative decoding can be also improved.