A Node-Based Polar List Decoder with Frame Interleaving and Ensemble Decoding Support

TL;DR

This paper introduces a hardware architecture for node-based SCL decoders that enables simultaneous decoding of two frames, significantly improving throughput and error performance for 5G NR polar codes.

Contribution

It proposes a frame-interleaving architecture and dynamic strategies to eliminate stalls, enhancing throughput and flexibility in node-based SCL decoding.

Findings

Nearly 2x throughput improvement over baseline decoders

Achieves 3.34 Gbps throughput on 28nm ASIC

Compatible with all 5G NR polar codes

Abstract

Node-based successive cancellation list (SCL) decoding has received considerable attention in wireless communications for its significant reduction in decoding latency, particularly with 5G New Radio (NR) polar codes. However, the existing node-based SCL decoders are constrained by sequential processing, leading to complicated and data-dependent computational units that introduce unavoidable stalls, reducing hardware efficiency. In this paper, we present a frame-interleaving hardware architecture for a generalized node-based SCL decoder. By efficiently reusing otherwise idle computational units, two independent frames can be decoded simultaneously, resulting in a significant throughput gain. Based on this new architecture, we further exploit graph ensembles to diversify the decoding space, thus enhancing the error-correcting performance with a limited list size. Two dynamic strategies are proposed to eliminate the residual stalls in the decoding schedule, which eventually results in nearly 2x throughput compared to the state-of-the-art baseline node-based SCL decoder. To impart the decoder rate flexibility, we develop a novel online instruction generator to identify the generalized nodes and produce instructions on-the-fly. The corresponding 28nm FD-SOI ASIC SCL decoder with a list size of 8 has a core area of 1.28 mm2 and operates at 692 MHz. It is compatible with all 5G NR polar codes and achieves a throughput of 3.34 Gbps and an area efficiency of 2.62 Gbps/mm2 for uplink (1024, 512) codes, which is 1.41x and 1.69x better than the state-of-the-art node-based SCL decoders.