The Performance Research Of Digital Fountain Codes In Underwater Acoustic Sensor Networks

Underwater acoustic sensor networks(UASNs)could manage and transfer messages within a specific area,making it an important tool in implementing underwater applications like ocean pollution monitoring and ocean data acquisition.However,acoustic link is in poor reliability with large propagation delay,presenting a great challenge in realizing reliable data transfer for time-critical applications in an energy-efficient way.Digital fountain codes(DFC)based data transmission scheme exempts the need for ordered data sequence and consequently simplifies the data delivery pattern,making DFC a kind of efficient coding techniques in UASNs.With the background of UASNs,the encoding/decoding algorithms of DFC and its relative transport protocols are deeply investigated in this paper,includingFirstly,the basic theory of DFC encoding and decoding algorithm are given out and analyzed.Then the paper analyzes the major factors that may have impress on the decoding performance of DFC and discusses the problems in applying DFC to UASNs.Secondly,joint encoding/ decoding algorithms of DFC based on stopping sets avoidance for UASNs are put forward and the performances of proposed algorithms are tested with the help of Visual C++ 6.0 simulation software.Thirdly,several mainstream transmission protocols are studied,especially for the DFC based HARQ transport protocols and the disadvantage in transmission redundancy of which is discussed.To solve this problem,the paper proposes a DFC correlation chain abstraction based HARQ transmission protocol(CCA-HARQ)to promote the protocol transmission efficiency effectively.Finally,a UASN model and its affiliated models such as node models,process models and channel models are established with the help of OPNET modeler.The proposed CCA-HARQ protocol is compared with the representative UASN HARQ protocol,UW-HARQ protocol on the established multi-hop network from the perspective of throughput and redundancy,energy efficiency,etc.Simulation results demonstrate that CCA-HARQ protocol performs better than UW-HARQ protocol.