Offset and Normalized Min-Sum Algorithms for ATSC 3.0 LDPC Decoder

Offset min-sum algorithm (OMSA) and normalized min-sum algorithm (NMSA) are widely used in commercial LDPC decoders due to low complexity and reasonable performance. In this paper, we provide optimized offset and scaling values for those LDPC decoders based on Advanced Television Systems Committee (ATSC) 3.0 LDPC codes. Furthermore, according to extensive computer simulations, it is shown that the performance of the OMSA and NMSA with the obtained values is close to that of sum-product algorithm, even though the NMSA-based decoder may show a serious error floor due to a channel mismatch effect. Consequently, we recommend that the ATSC 3.0 transmitters use a concatenation of BCH outer code and LDPC inner code as channel coding, considering the use of NMSA for LDPC decoder in ATSC 3.0 receivers.

I. Introduction

The next generation digital broadcasting standard, known as Advanced Television Systems Committee (ATSC) 3.0, has been developed with distinct features and capabilities over the existing standards [1]. In the physical layer protocol standard of ATSC 3.0, different broadcasters’ needs and requirements have been taken into account, and as a result, this new standard provides delivery of high data rate services (e.g., ultra-high definition), robustness under mobile or indoor environments, and flexibility according to variety of parameter choices [2], [3]. The ATSC 3.0 physical layer protocol standard includes the following technology features: Given orthogonal frequency division multiplexing, bit-interleaved coded modulation (BICM) that consists of forward error correction codes, bit interleavers, and symbol mappers provides efficiency and channel error mitigation of transmitted broadcasting signals [4]. The latest BICM technologies of low-density parity-check (LDPC) codes and non-uniform constellations allow to further reach the Shannon limit in performance, and moreover, wide ranges of code rates and constellations provide flexible choices of broadcasting parameters [5], [6]. The standard also adopts the latest physical layer technologies such as signaling and framing, layered division multiplexing, channel bonding, enhanced multiple-input single-output and multiple-input multiple-output [7]–[14]. As these distinct features and capabilities are integrated in the ATSC 3.0 physical layer protocol, the overall physical layer system provides good robustness under both mobile and indoor environments, efficiency in multiple services configuration, and flexibility given broadcasters’ intention of service scenarios.