Channel-Adaptive Space-Collaborative Constellation Design for MIMO VLC With Fast Maximum Likelihood Detection

Abstract

Multi-input multi-output (MIMO) holds great potential in the high-speed transmission of visible light communication (VLC). However, as for the current MIMO-VLC techniques, the error performance is improved by wasting spatial resources, which just drops the core advantage within an MIMO structure. Moreover, they cannot change over the channel, which greatly limits their application range. In this paper, a general design criterion of the channel-adaptive space-collaborative constellation (CASCC) is established for MIMO-VLC systems. Specifically, we not only consider the channel into our criterion, but also build relations among the light-emitting diodes to exploit the spatial resources instead of wasting. Under the criterion, a regular CASCC is particularly designed for $2\times 2$ MIMO-VLC in terms of the basic four-point constellation and the high-order constellation. Correspondingly, a fast maximum likelihood (ML) detection algorithm for CASCC is proposed. Simulation results show that our proposed CASCC obtains better error performance and wider application range compared with the conventional MIMO-VLC schemes. Moreover, the fast ML algorithm reduces the computational complexity without any performance loss.