Research Of FEC Codes Based Under Unstable Network

Forward Error Correction (FEC) is an effective method to improve reliability inNetwork transmission. FEC is quite suitable for Internet Broadcasting and real-timetransmission because it has relatively low delay and requires no feedback. It iscurrently widely applied in the fields of Digital Video Broadcasting and InternetCommunication. Based on studies of RS code and Digital Fountain Code, decodingperformances are simulated under high loss rate. Later a multi-channel transmissionscheme that combines ARQ and Digital Fountain Code is studied.Firstly, algorithm of Reed-Solomon code is introduced. RS code is easy todecode, and is fit to be used in Internet or3G network. Reconstruction of RS codebased on BEC channel is studied. Then Convolutional Interleaving is introduced tominimize data damage caused by a single UDP package loss. Encoding and decodingprocesses of Digital Fountain Code are also studied. Digital Fountain Code is arateless code, so it is efficient to adapt itself to complicated environment. As the keytechnology of the network FEC scheme, Digital Fountain Coding is currently widelyapplied in the fields of Digital Video Broadcasting and Internet Communication.Secondly, decoding performance of RS code and Raptor code are simulatedbased on UDP transmission. The simulation shows that under very high loss rate,while RS code can hardly restore data loss from transmission, Raptor code canachieve high performance with reasonable overhead.Thirdly, ARQ-Raptor transmission scheme combining ARQ and Digital FountainCode is proposed based on minimum feedback. Compared to HARQ, ARQ-Raptordoes not require decoding100%of data. Instead, it improves the reliability ofreal-time transmission by introducing ARQ, making it suitable for transmittingstreaming media and IP telephones.Finally, a scheme for multi-channel transmission is proposed based onARQ-Raptor Algorithm. Multi-channel transmission is able to improve performanceand reliability compared to single-channel method, especially on3G network. ARQ-Raptor multi-channel scheme is supposed to make full use of plural channelsand achieve very high reliability. Parameters of components are deeply discussedbased on the situations of transmission. The simulation proves that this scheme showsbetter performance than Raptor Code for the purpose of streaming transmission. In theend, the use of ARQ-Raptor for file transmission is discussed, and some issues to beimproved in the future are prospected.