An Adaptive Joint Viterbi Detector Decoder (AJVDD)

The Joint Viterbi Detector Decoder (JVDD) is a novel detection/decoding algorithm that can functionally replace the iterative detector/decoder in the channel. The algorithm performs detection and decoding on a single trellis structure and is conditionally optimal over an ISI/AWGN channel. Preliminary analysis of the algorithm indicates better performance at shorter codeword lengths when compared to an iterative detector, but the latter catches up and surpasses it at longer codeword lengths due to the high complexity the JVDD. The commercial viability of channel decoders for real-time systems is dependent on two important parameters — performance and computational complexity. In this paper, a novel algorithm called the Adaptive Joint Viterbi Detector Decoder (AJVDD) is proposed that enhances the performance and reduces the computational complexity of the JVDD algorithm. The proposed algorithm reduces the average number of survivors per frame by applying varying metric threshold values across different states of the trellis at each time index. It improves the chances of the Minimum Metric Legal Codeword (MMLC) surviving until the end of the frame while filtering out survivors with the least chance of being the MMLC. Extensive simulations are used to verify the improved performance and reduced computational requirements of the proposed algorithm.