Guessing Random Additive Noise Decoding in Coded Multiple-Input Multiple-Output Systems

Abstract

Multiple-Input Multiple-Output (MIMO) wireless communication systems incorporate forward error correction (FEC) to achieve high reliability under fading and interference. In this thesis, we explore the emerging FEC paradigm of Guessing Random Additive Noise Decoding (GRAND) in a point-to-point MIMO system. Treating GRAND as an FEC decoder disjoint from the MIMO detector, we compare the soft-decision Ordered Reliability Bits GRAND (ORBGRAND) to CRC-Assisted Successive Cancellation List (CA-SCL) decoding of the CRC-Assisted Polar (CA-Polar) [105, 128] code found in the 5G New Radio standard. For this code, we find that ORBGRAND outperforms CA-SCL (list size 16) by 1 dB E_b/N₀ at block error rate of 10⁻³, under 16-QAM and Linear Minimum Mean Square Error detection, with two transmit antennas and four receive antennas. We also show that ORBGRAND, when paired with other moderate redundancy linear codes, can yield substantial savings in the range of 0.5 − 2 dB in E_b/N₀ over CA-SCL decoding (list size 16) of CA-Polar codes with the same code parameters, for a block error rate of 10⁻³. We provide extensive benchmarks comparing ORBGRAND to CA-SCL and other soft-decision GRAND variants. We also integrate a GRAND decoder producing soft output into a MIMO iterative detection and decoding (IDD) receiver. Specifically, we apply an established technique which utilizes soft-output GRAND as the component decoder for the block turbo decoding of product codes. This block turbo decoder is evaluated as a soft output decoder within a MIMO IDD receiver. We demonstrate competitive or superior performance relative to Belief Propagation (BP) decoding of 5G Low-Density Parity Check (LDPC) codes. This approach also marks a use of GRAND for low-rate, high-redundancy FEC in a MIMO system. With GRAND in MIMO still being an emerging area of research, this work is an exploratory evaluation of GRAND for FEC in MIMO, and highlights GRAND’s potential as a versatile and performant decoder in different MIMO receiver architectures.