Design of Adaptive Hybrid Downlink NOMA-TDMA for Visible Light Communications Networks

TL;DR

This paper introduces an adaptive hybrid NOMA-TDMA scheme for VLC networks that intelligently pairs users for NOMA based on channel gain differences, improving sum-rate performance with low complexity.

Contribution

It develops an adaptive user pairing method for hybrid NOMA-TDMA in VLC, optimizing channel gain ratios to enhance network throughput.

Findings

Outperforms conventional hybrid NOMA-TDMA in simulations.

Effectively determines user pairs for NOMA based on channel gain ratios.

Achieves higher sum-rate performance with low complexity.

Abstract

This paper proposes an adaptive hybrid non-orthogonal multiple access (NOMA)-time division multiple access (TDMA) scheme for multi-user visible light communication (VLC) networks, aiming to enhance users' sum-rate performance while maintaining low complexity. In the proposed scheme, users are divided into groups where each group is served in a different time slot using TDMA. Within each group, up to two users can be served simultaneously using NOMA. A central challenge lies in determining which users should be paired together for NOMA, as the effectiveness of successive interference cancellation (SIC) employed by NOMA depends on the difference between users' channel gains. To address this, for a pair of users, we determine the range of their channel gain ratio within which the pair benefits more from NOMA or TDMA. Identifying the lower and upper bounds of this range is formulated as two optimization problems which are solved efficiently using the Successive Convex Approximation (SCA) method. Simulation results demonstrate that the proposed scheme outperforms the conventional hybrid NOMA-TDMA method under different numbers of users and transmit LED powers.