Implementation of a smart and power efficient Turbo Decoder using SDR algorithm

Turbo coding is one of the great achievement in the field of communication systems and signal processing. It is embedded in most of the European standardizations for the radio access networks of start-of-art cellular radio technologies. A Turbo-Decoder consists of two soft-in soft-out component decoders, which exchange information (soft-values) in an iterative process. Turbo-Decoder can be implemented using different algorithm, but Maximum A Posteriori decoding algorithm (MAP) is high Bit Error Rate (BER) performance, nearer to Shannon limit. However, decoding with a fixed number of iterations may lead to excessive processing, penalizing battery operated terminals while fewer iterations are sometimes sufficient. It is necessary to stop the decoding process at an appropriate moment to reduce the computational time, latency and power dissipation. Sign difference ratio (SDR) presents a simple and efficient criterion for stopping the iteration process in turbo-decoding with a negligible degradation of the error performance. In this paper MATLAB simulated results of turbo decoder are implemented using MAP decoder and its performance are presented.