Simulation of the Memory-Efficient Scan Decoder of Polar Codes

Abstract

The low-complexity soft-output version of the Successive Cancellation (SC) decoder is the Soft Cancellation (SCAN) decoder that produces reliable information for both the coded and message bits. Methods/Analysis: In polar codes the Belief Propagation (BP) soft-output decoding is a message-passing   algorithm, which performs well, at the cost of high processing and storage requirements. In this paper, The SCAN decoder offers better performance than BP decoder which significantly reduces processing and storage requirements. Findings: In this paper the SCAN decoder outperforms the SC decoder both in FER and BER performance with only two and one iteration. Additionally, the SCAN decoder exhibits larger gain in BER performance as compared to FER performance. The SCAN decoder requires only two iterations compared to 60 iterations of the BP decoder to achieve the same FER performance over a dicode channel and outperforms then the BP decoder with further increase in the number of iterations. In the SCAN decoder the normalized memory requirement decreases with the increasing the block length n. Novelty /Improvement: Polar codes outperform Low-Density Parity-Check (LDPC) codes if concatenated with very simple codes in AWGN channel. In this respect, The SCAN decoder used in polar codes has potential applications because of their ability to provide soft outputs.