Distributed Soft-decision Decoding Of Reed-Solomon Codes Based On Cooperative Network

Reed-Solomon (RS) codes have the rigorous algebraic structure and powerful error correction ability. It's widely applied in the satellite communication, the data storage and other fields. Its decoding algorithms, especially the soft decision decoding algorithms interest large number of researchers. But because of the high complexity and power of decoding, the RS code is difficulty used in mobile cellular network, ad hoc collaboration, and other energy-sensitive communication system. Reducing the complexity of decoding is the problem which needs to solve urgently for RS codes.By taking advantage of cyclic property of RS codes, Jiang and Narayanan proposed SSID algorithm, which is belief propagation (BP) algorithm with a stochastic shifting schedule. The iterative has a good performance; however the complexity is also high. In the existing cooperation communications system, the relay node mainly has two kinds of forward, AF and DF. It is proved that with the same total iterative times invariable situation, system's decoding performance may be greatly improved by assigning the iterative times between relay node and destination node reasonably. After studying the characteristic of AF and DF, we proposed a new forward model ~ partial decoding forward (PDF). This scheme uses SSID algorithm on relay node decoding. The algorithm is implemented as the following modifications. While the relay nodes decoding reach the outer and inner iteration stop conditions, other than announcing failure, the likelihood ratio (LLR) of each bit is judged. The bit with reliable LLR are determined to 0 or 1, others are set up to erasion. Relay nodes transmit the codes with 0, 1 and erasion to the destination node. The destination decodes with both the information from source node and relay node. It is proved that as a result of diversity and erasion the performance of PDF is better than non-relay, AF and DF.Lifetime is another important target in cooperative network, which is relative with total power and power balance. After discussing the impact of the SSID algorithm complexity in detail, the improvement of SSID algorithm—BP energy adaptive algorithm (energy adapted BP, EABP) is proposed in this paper. The outer and inner iteration stop conditions are changed from the original fixed value in SSID, and become to variables related to energy. This scheme compromises between performance and energy. The decoding complexity was greatly reduced, while the decline in decoding performance is kept in an acceptable range. As EABP according to the nodes' own energy, the algorithm in cooperative network can dynamically control the decoding power, so that the entire energy of network can reach a balanced distribution.It is proved by the experimental result that the decoding performance of PDF surpasses the non-relay system, AF and DF. PDF with EABP algorithm reduces the decoding complexity and the decoding power, balances various nodes' energy and lengthened the network lifetime.