Low-Latency Successive-Cancellation Polar Decoder Architectures Using 2-Bit Decoding

Polar codes have emerged as important error correction codes due to their capacity-achieving property. Successive cancellation (SC) algorithm is viewed as a good candidate for hardware design of polar decoders due to its low complexity. However, for (n, k) polar codes, the long latency of SC algorithm of (2n-2) is a bottleneck for designing high-throughput polar decoder. In this paper, we present a novel reformulation for the last stage of SC decoding. The proposed reformulation leads to two benefits. First, critical path and hardware complexity in the last stage of SC algorithm is significantly reduced. Second, 2 bits can be decoded simultaneously instead of 1 bit. As a result, this new decoder, referred to as 2b-SC decoder, reduces latency from (2n-2) to (1.5n-2) without performance loss. Additionally, overlapped-scheduling, precomputation and look-ahead techniques are used to design two additional decoders referred to as 2b-SC-Overlapped-scheduling decoder and 2b-SC-Precomputation decoder, respectively. All three architectures offer significant advantages with respect to throughput and hardware efficiency. Compared to known prior least-latency SC decoder, the 2b-SC-Precomputation decoder has 25% less latency. Synthesis results show that the proposed (1024, 512) 2b-SC-Precomputation decoder can achieve at least 4 times increase in throughput and 40% increase in hardware efficiency.