Low-Latency Hybrid NOMA-TDMA: QoS-Driven Design Framework

TL;DR

This paper proposes a hybrid NOMA-TDMA scheme optimized for ultra-reliable, low-latency wireless communication, balancing physical and link-layer QoS through joint resource allocation in the finite blocklength regime.

Contribution

It introduces a novel joint optimization framework for blocklength and power allocation in hybrid NOMA-TDMA schemes tailored for different QoS scenarios in the finite blocklength regime.

Findings

The proposed schemes outperform existing methods in reliability and capacity.

Convexity and duality properties are validated through analysis.

Simulation results confirm the effectiveness of the optimization approaches.

Abstract

Enabling ultra-reliable and low-latency communication services while providing massive connectivity is one of the major goals to be accomplished in future wireless communication networks. In this paper, we investigate the performance of a hybrid multi-access scheme in the finite blocklength (FBL) regime that combines the advantages of both non-orthogonal multiple access (NOMA) and time-division multiple access (TDMA) schemes. Two latency-sensitive application scenarios are studied, distinguished by whether the queuing behaviour has an influence on the transmission performance or not. In particular, for the latency-critical case with one-shot transmission, we aim at a certain physical-layer quality-of-service (QoS) performance, namely the optimization of the reliability. And for the case in which queuing behaviour plays a role, we focus on the link-layer QoS performance and provide a design that maximizes the effective capacity. For both designs, we leverage the characterizations in the FBL regime to provide the optimal framework by jointly allocating the blocklength and transmit power of each user. In particular, for the reliability-oriented design, the original problem is decomposed and the joint convexity of sub-problems is shown via a variable substitution method. For the effective-capacity-oriented design, we exploit the method of Lagrange multipliers to formulate a solvable dual problem with strong duality to the original problem. Via simulations, we validate our analytical results of convexity/concavity and show the advantage of our proposed approaches compared to other existing schemes.