Early stopping criterion for belief propagation polar decoder based on frozen bits

Abstract

In this Letter, a new criterion based on frozen BER (FBER) is proposed to early stop belief propagation (BP) decoding of polar codes. The authors first verify that the behaviour of FBER along with the iteration is almost the same as the information BER. Based on this phenomenon, the authors propose a new criterion by detecting the status of FBER to determine whether the BP decoding is successful or not. To reduce the complexity, only a part of frozen bits transmitted in most reliable frozen sub-channels are considered. Simulation results show that the proposed criterion is more hardware friendly than the existing criteria.

Area-Efficient Early-Termination Technique for Belief-Propagation Polar Decoders

“…In addition, References [16,17] propose area-efficient windowing methods that check the changes on the bit channels within the consecutive iteration numbers, known as the window size.…”

“…In Figure 3, the threshold-based earlytermination method requires 4-bit 8 adders, 8 abstractors, and 8 comparators for (8,4) polar codes [15]. In addition, References [16,17] propose area-efficient windowing methods that check the changes on the bit channels within the consecutive iteration numbers, known as the window size. In addition, References [16,17] propose area-efficient windowing methods that check the changes on the bit channels within the consecutive iteration numbers, known as the window size.…”

“…In addition, References [16,17] propose area-efficient windowing methods that check the changes on the bit channels within the consecutive iteration numbers, known as the window size. In addition, References [16,17] propose area-efficient windowing methods that check the changes on the bit channels within the consecutive iteration numbers, known as the window size. Algorithm 2 and Algorithm 3 depict information-BER-based [16] and frozen-BER-based [17] early-termination processes, respectively.…”

“…The conventional BP decoder passes reliable information over graphical models for performing inference until the maximum iteration number (max-iteration) [8]. In general, an early-termination technique [15][16][17][18] is widely adopted in BP decoders [8] to improve the average throughput. Although previous early terminations including threshold-based [15], information-BER-based [16], and frozen-BER-based [17] criteria succeeded in reducing decoding latency, they suffered from high hardware complexities to check the termination condition.…”

“…Therefore, this letter presents an area-efficient early-termination method by simplifying the previous early-termination criterion. The proposed method achieves area-efficiency by using only part of the log-likelihood ratio (LLR) values on information bit channels rather than entire bit channels in [15], and introduces no performance degradation incurred in References [16,17] by prohibiting the use of the windowing method. Experimental results show that the proposed method always provides the smallest hardware complexity, while maintaining error-correction capability and the average number of decoding iterations.…”