Performance Analysis of Spatiotemporal 2-D Polar Codes for Massive MIMO with MMSE Receivers

TL;DR

This paper introduces a novel 2-D polar coding scheme for massive MIMO systems that exploits spatial and temporal dimensions to reduce latency and improve reliability in 6G URLLC scenarios.

Contribution

It proposes a unified theoretical framework and a 2-D polar coding scheme that jointly encodes over space and time, enhancing performance in massive MIMO systems with MMSE receivers.

Findings

Significantly reduces latency compared to traditional polar codes.

Guarantees reliability while maintaining low latency in massive MIMO systems.

Proves capacity-achieving property under finite blocklength and large spatial DoF.

Abstract

With the evolution from 5G to 6G, ultra-reliable low-latency communication (URLLC) faces increasingly stringent performance requirements. Lower latency constraints demand shorter channel coding lengths, which can severely degrade decoding performance. The massive multiple-input multiple-output (MIMO) system is considered a crucial technology to address this challenge due to its abundant spatial degrees of freedom (DoF). While polar codes are theoretically capacity-achieving in the limit of infinite code length, their practical applicability is limited by significant decoding latency. In this paper, we establish a unified theoretical framework and propose a novel spatiotemporal two-dimensional (2-D) polar coding scheme for massive MIMO systems employing minimum mean square error (MMSE) receivers. The polar transform is jointly applied over both spatial and temporal dimensions to fully exploit the large spatial DoF. By leveraging the near-deterministic signal-to-interference-plus-noise ratio (SINR) property of MMSE detection, the spatial domain is modeled as a set of parallel Gaussian sub-channels. Within this framework, we perform a theoretical analysis of the 2-D polarization behavior using the Gaussian approximation method, and the capacity-achieving property of the proposed scheme is proved under finite blocklength constraints and large spatial DoF. Simulation results further demonstrate that, compared to traditional time-domain polar codes, the proposed 2-D scheme can significantly reduce latency while guaranteeing reliability, or alternatively improve reliability under the same latency constraint -- offering a capacity-achieving and latency-efficient channel coding solution for massive MIMO systems in future 6G URLLC scenarios.