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Graph-Based Scheduling for Cooperative Transmission in Indoor VLC Systems

In indoor visible light communication (VLC) systems, multiple access points are densely deployed to achieve seamless coverage and meet high throughput demand. However, the reuse of resources in adjacent cells may cause severe inter-cell interference (ICI), which degrades the user signal quality and limits the system throughput. Hence, an effective scheduling scheme based on interference mitigation is needed. In this paper, the concept of cooperative transmission (CT) is adopted to improve signal quality, where a group of transmitters send commonly shared message in a manner that allows all data to simultaneously arrive at the receiver. Two interference graph-based scheduling approaches and a bipartite graph-based scheduling approach are proposed to coordinate the interference and optimize the system performance for two types of CT-VLC systems. Simulation results illustrate that the CT approaches significantly enhance the signal to interference plus noise ratio over the non-CT approach with no loss in terms of the overall throughput. Moreover, the proposed scheduling approaches outperform other benchmarks in terms of the system throughput while ensuring a good fairness in the VLC system.