Uplink Multiple Access with Heterogeneous Blocklength and Reliability Constraints: Discrete Signaling with Treating Interference as Noise

TL;DR

This paper proposes a novel uplink multiple access scheme for heterogeneous users with different reliability and latency constraints, using discrete signaling and treating interference as noise, achieving near-benchmark performance without SIC.

Contribution

It introduces a new multiple access method employing discrete signaling and TIN decoding for heterogeneous uplink users, avoiding SIC and maintaining low complexity.

Findings

Scheme performs close to Gaussian signaling with perfect SIC.

Discrete signaling can sometimes outperform traditional schemes.

Method handles heterogeneous interference effectively.

Abstract

We consider the uplink multiple access of heterogeneous users, e.g., ultra-reliable low-latency communications (URLLC) and enhanced mobile broadband (eMBB) users. Each user has its own reliability requirement and blocklength constraint, and users transmitting longer blocks suffer from heterogeneous interference. On top of that, the decoding of URLLC messages cannot leverage successive interference cancellation (SIC) owing to the stringent latency requirements. This can significantly degrade the spectral efficiency of all URLLC users when the interference is strong. To overcome this issue, we propose a new multiple access scheme employing discrete signaling and treating interference as noise (TIN) decoding, i.e., without SIC. Specifically, to handle heterogeneous interference while maintaining the single-user encoding and decoding complexities, each user uses a single channel code and maps its coded bits onto sub-blocks of symbols, where the underlying constellations can be different. We demonstrate theoretically and numerically that the proposed scheme employing quadrature amplitude modulations and TIN decoding can perform very close to the benchmark scheme based on Gaussian signaling with perfect SIC decoding. Interestingly, we show that the proposed scheme does not need to use all the transmit power budget, but also can sometimes even outperform the benchmark scheme.