Research And Application Of Two Weighted Iterative Decoding Algorithm

Error control coding is the main method to achieve the data reliability incommunication. Error control coding have gone through Hamming codes, convolutionalcodes, BCH codes, RS codes, LDPC(Low Density Parity Check, LDPC) codes andTurbo codes, since Shannon published his paper “A mathematical theory ofcommunication”. Now, the performance of error control coding is increasingly close toShannon theory limit, especially for latter several kinds of efficient techniques forchannel coding. The key for efficient channel coding involves random long codes anditerative decoding. This thesis emphasizes on the iterative decoding algorithm and itsapplications.Firstly, the iterative decoding algorithm of LDPC, named Belief Propagation (BP),was investigated. Providing the original application scenes and fundamental of BPalgorithm, this thesis tries to apply BP algorithm to data fusion in distributed spectrumsensing of cognitive radio. Through verification by simulation, we find BP algorithmcould obtain higher detection probability than that of conventional Major Voting. At thesame time, for the scene with a node in deep fading or a vicious node, this thesisproposes a weighted BP algorithm which can effectively improve the detectiveprobability of spectrum sensing. Also, this algorithm’s correctness has been proved bysimulation.Next, this thesis has researched hard decision decoding algorithm of Turbo productcodes (Turbo Product Codes, TPC) and then we obtain a weighted hard input hardoutput iterative decoding algorithm by modifying the previous algorithm. The main ideaof our algorithm is to set the weighted value of every bits in a codeword by means offour hard decision decoding results, then judge whether a bit should be flippedaccording to weighted value, and on this account iterative decoding will go on. Thebasic idea of setting weighted value is trying to avoid error propagation. This algorithmis able to enhance the performance of error control of codeword effectively bysimulation verification. The weighted iterative hard decision algorithm can be applied insubmarine cable transmission system and wireless sensor network. This thesis studied these two kinds of effective iterative decoding algorithms, andan improvement was made for the both, the modified algorithms can be applied todifferent scenes.