Soft output Viterbi decoder using hybrid register exchange

Abstract

There are two types of decoding techniques, trace back method (TBM) and register exchange method (REM). In trace back method, memory requirement is high. TBM is the preferred method used in Viterbi decoders (VD) having large constraint length and high performance. However, the TBM has drawbacks, which requires last-in-first-out (LIFO) buffer and has to use multiple read operations for high speed operation. This multiple operation results in complex control logic In register exchange method, the no. of switching activities is high. So total power dissipation is high. Using Hybrid register exchange, no. of switching activities is reduced and so the total power dissipation is reduced. So we concentrate more on REM. There are two types of decision outputs, hard output and soft output. In hard decision output, error correcting capability is less as compared to soft output decision. So to increase the accuracy as compared with hard decision outputs, soft output viterbi algorithm is used.. In this paper, we propose a new approache hybrid register exchange method (HREM). The simulation model is ready. The main advantage of the proposed method is that it reduces the number of decoding operation and memory read operations, less switching activity and fewer requirements on additional control logic.