Joint LED Selection and Precoding Optimization for Multiple-User Multiple-Cell VLC Systems

TL;DR

This paper introduces a joint LED selection and precoding optimization scheme for multi-user, multi-cell VLC systems, enhancing sum-rate performance while satisfying illumination constraints through iterative problem-solving methods.

Contribution

It proposes a novel hybrid dimming scheme (TASP-HD) that dynamically optimizes LED selection and precoding, addressing a complex non-convex problem in VLC systems.

Findings

TASP-HD achieves 4.8-7.13 bit/s/Hz higher bandwidth efficiency than existing schemes.

The iterative solution converges effectively in indoor VLC scenarios.

Simulation confirms improved sum-rate performance under dimming constraints.

Abstract

This paper proposes a hybrid dimming scheme based on joint LED selection and precoding design (TASP-HD) for multiple-user (MU) multiple-cell (MC) visible light communications (VLC) systems. In TASP-HD, both the LED selection and the precoding of each cell can be dynamically adjusted to reduce the intra- and inter-cell interferences while satisfying illumination constraints. First, a MU-MC-VLC system model is established, and then a sum-rate maximization problem under dimming level and illumination uniformity constraints is formulated. In this studied problem, the indices of activated LEDs and precoding matrices are optimized, which result in a complex non-convex mixed integer problem. To solve this problem, the original problem is separated into two subproblems. The first subproblem, which maximizes the sum-rate of users via optimizing the LED selection with a given precoding matrix, is a mixed integer problem solved by the penalty method. With the optimized LED selection matrix, the second subproblem which focuses on the maximization of the sum-rate via optimizing the precoding matrix is solved by the Lagrangian dual method. Finally, these two subproblems are iteratively solved to obtain a convergent solution. Simulation results verify that in a typical indoor scenario under a dimming level of 70%, the mean bandwidth efficiency of TASP-HD is 4.8 bit/s/Hz and 7.13 bit/s/Hz greater than AD and DD, respectively.