Spatiotemporal 2-D Polar Codes over Non-Uniform MIMO Channels: A Reliability-Aware Construction Approach

TL;DR

This paper introduces a reliability-aware 2-D polar coding scheme for non-uniform MIMO channels, improving URLLC performance by effectively exploiting spatial and temporal polarization.

Contribution

It proposes a reciprocal channel approximation-based framework that accurately models heterogeneous SNRs in non-uniform MIMO channels for 2-D polar coding.

Findings

Achieves performance gains over traditional schemes in simulations.

Demonstrates robustness in practical MIMO channel conditions.

Effectively exploits spatial and temporal polarization for URLLC.

Abstract

With the increasing demand for ultra-reliable and low-latency communication (URLLC), spatiotemporal two-dimensional (2-D) channel coding has received growing interest. By leveraging the spatial degrees of freedom in massive multiple-input multiple-output (MIMO) systems, it shortens the time-domain blocklength, thereby reducing latency and enhancing reliability. However, existing spatiotemporal coding schemes typically assume uniform reliability across spatial streams. This assumption does not hold in practical MIMO channels, where the underlying propagation environment generally leads to unequal spatial-eigenmode gains and reliabilities, making the conventional Gaussian-approximation-based construction for 2-D polar codes less effective. This paper investigates spatiotemporal 2-D polar coding over non-uniform MIMO channels, where the spatial domain exhibits inherently heterogeneous signal-to-noise ratios (SNRs). We propose a reciprocal channel approximation (RCA)-based reliability-aware 2-D polar coding framework that accurately characterizes such heterogeneous SNRs without relying on log-likelihood-ratio distribution assumptions. Simulation results demonstrate that the proposed RCA-based spatiotemporal 2-D polar coding scheme achieves clear performance gains and strong robustness, confirming its effectiveness in jointly exploiting temporal and spatial polarization for URLLC in practical MIMO systems.