Faculty Publications
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Item Soft decision decoding of Davydov-Tombak codes using a parity check tree(2010) Prashantha Kumar, H.; Sripati, U.; Rajesh Shetty, K.; Shankarananda, B.Davydov and Tombak have designed an excellent single error correction-double error detection (SEC-DED) code that appears to be more capable of detecting triple and quadruple errors than the conventional Hamming SEC-DED codes. These codes have been applied to memory subsystems and digital storage devices in order to achieve efficient and reliable data processing and storage. A new approach to soft decision decoding of Davydov-Tombak codes using a parity check tree associated with the Tanner graph is presented. For the AWGN channel, gains in excess of 1.6dB at reasonable bit error rates with respect to conventional hard decision decoding are demonstrated for the (40, 33), (37, 30), (35, 28) and (72, 64) Davydov-Tombak codes. ©2010 IEEE.Item Soft decision Fano decoding of block codes over discrete memoryless channel using tree diagram(2012) Prashantha Kumar, H.; Sripati, U.; Rajesh Shetty, K.; Setty Shankarananda, B.A novel low complexity soft decision technique which allows the decoding of block codes with tree structure is proposed. These codes are shown to have a convenient tree structure that allows Fano decoding techniques to be used to decode them. The Fano algorithm searches through the tree structure of the block code for a path which has the optimal value of the Fano metric function. When a new candidate codeword is found, an optimality check is performed on it by using the threshold. If checked successfully, the candidate codeword is the most likely codeword and the search stops. The basic idea of this approach is to achieve a good error performance progressively in a minimum number of steps. For each decoding step, the error performance is tightly bounded and the decoding is terminated at the stage where either optimum or near optimum error performance is achieved. As a result, more flexibility in the trade off between performance and decoding complexity is provided. Some examples of the tree construction and the soft decision Fano decoding procedure are discussed. © 2012 FEI STU.Item Performance analysis of stack decoding on block coded modulation schemes using tree diagram(2012) Prashantha, K.H.; Vineeth, U.K.; Sripati, U.; Rajesh, Sh.K.The channel encoder adds redundancy in a structured way to provide error control capability. Modulator converts the symbol sequences from the channel encoder into waveforms which are then transmitted over the channel. Usually channel coder and modulator are implemented independently one after the other. But in a band limited channel better coding gains without sacrificing signal power are achieved when coding is combined with modulation. Block Coded Modulation (BCM) is such a scheme that results from the combination of linear block codes and modulation. In this paper we are proposing a stack decoding of rate 2/3 and rate 1/2 BCM schemes using tree structure and performance is compared with the Viterbi decoding that uses trellis representation. Simulation result shows that at reasonable bit error rate stack decoder performance is just 0.2 to 0.5 dB inferior to that of Viterbi decoding. Since stack decoding is a near optimum decoding scheme and whose decoding procedure is adaptable to noise level, we can consider this method in place of Viterbi decoding which is optimum and its decoding complexity grows exponentially with large code lengths. © K.H. Prashantha, U.K. Vineeth, U. Sripati, Sh.K. Rajesh, 2012.