Abstract
Indoor visible light communications (VLC) combines illumination and communication by utilizing the high-modulation-speed of LEDs. VLC is anticipated to be complementary to radio frequency communications and an important part of next generation heterogeneous networks. In order to make the maximum use of VLC technology in a networking environment, we need to expand existing research from studies of traditional point-to-point links to encompass scheduling and resource allocation related to multi-user scenarios. This work aims to maximize the downlink throughput of an indoor VLC network, while taking both user fairness and time latency into consideration. Inter-user interference is eliminated by appropriately allocating LEDs to users with the aid of graph theory. A three-term priority factor model is derived and is shown to improve the throughput performance of the network scheduling scheme over those previously reported. Simulations of VLC downlink scheduling have been performed under proportional fairness scheduling principles where our newly formulated priority factor model has been applied. The downlink throughput is improved by 19.6% compared to previous two-term priority models, while achieving similar fairness and latency performance. When the number of users grows larger, the three-term priority model indicates an improvement in Fairness performance compared to two-term priority model scheduling.
Highlights
Ever since Nakagawa and his group proposed the combination of illumination and communication functions based on fast modulated LEDs [1,2], Visible Light Communications (VLC) have been extensively studied for use in generation wide band wireless communication networks
We have studied multi-user scheduling and resource allocations in visible light communications (VLC) downlink networks
By application of the interference graph, the inter-channel interference (ICI)-avoiding scheduling and allocation is performed by finding the Maximum Weighted Independent Set (MWIS) of the graph
Summary
Ever since Nakagawa and his group proposed the combination of illumination and communication functions based on fast modulated LEDs [1,2], Visible Light Communications (VLC) have been extensively studied for use in generation wide band wireless communication networks. Quality-of-service (QoS) oriented scheduling and allocation should achieve high capacity and low time latency This topic has been the subject of several articles [9,10,11,12] where frequency reuse and cell formation technology have been studied. In [17] an interference graph was introduced to describe the inter-user interference and a carrier scheduling scheme based on a PF principle for a centrally controlled VLC system which outperformed the maximum-rate scheduling policy in terms of balancing the achievable throughput against the fairness experienced by the users. Simulation shows that the scheduling and allocation algorithm with the three-term model achieves a notable increase in throughput, while maintaining similar fairness and time latency performance compared to existing models.
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