Performance enhancement of soft output viterbi algorithm for mimo of DM wireless systems

Abstract

The growth of the turbo codes is tremendous that it has transformed from the paper to commercialization in the present newlinetelecommunication industry, particularly in 3G and 4G mobile standards. The newlineultimate aim in any Turbo coder design is to find practical decoding newlinealgorithms for effective implementation. The Maximum a Posteriori newlineProbability (MAP) decoding algorithm is computationally intense and hence newlinethey cannot be implemented in real-time systems. So, simplified and suboptimal newlineversion of the algorithm, like the Soft Output Viterbi Algorithm newline(SOVA), has been used for practical implementation. newlineSOVA is deliberated as the best algorithm for decoding turbo newlinecodes due to its easy implementation for wireless applications. However, the newlinemain drawback of SOVA is that it suffers from two distortions: newline1. Reliability values are too optimistic newline2. Correlation between intrinsic and extrinsic information. newlineBoth these distortions result in the sub-optimal performance of the newlineSOVA algorithm. Either of these distortions have been discussed newlineindependently, but there has been no cohesive solution available in the newlineliterature. The main aim of this work is to suggest a solution that will newlineeliminate these errors in cohesion. Also, most of the approaches developed newlineearlier employed offline computation of scaling factors to remove either of newlinethese distortions. But, to get exact soft outputs, scaling factor values should be newlinerecalculated online whenever the turbo decoder outputs new extrinsic newlineinformation. newline