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The ever-increasing number of vehicles at a global level signifies the need for communications between vehicles and the surrounding environment. Visible light communications (VLC) is a viable complementary technology to the congested radio frequency-based wireless systems. In order to increase the reliability of the VLC link, in this paper we propose two novel algorithms based on (i) channel inversion (CI), and (ii) frame subtraction and CI (FSCI) schemes are proposed to successfully extract the data in a non-line-ofsight multiple-input multiple-output spatial division multiplexing optical camera communications system. We have adopted differential modulation and frame subtraction schemes and proposed a unique packet structure to mark the packet and the position of the footprint of transmitters (Txs) in the image frame. We show that, the FSCI scheme with much simpler receiver structures can offer almost the same bit error rate (BER) performance compared with the hybrid selection/equal gain combining (HS/EGC) technique at lower transmit power (illumination) levels of < 13 dBm for a single transmitter(Tx) and improved performance at higher illumination levels of > 20 dBm for multiple Txs. Compared with HS/EGC, CI schemes have a higher tolerance to the spacing between Txs, where the payload threshold level can be set to a fixed value of 0.5.

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This paper proposes a novel architecture of multiunmanned aerial vehicle (UAV)-enabled cloud radio access network (CRAN). In particular, we propose to deploy the UAVs as flying remote radio heads (RRHs) to serve ground user equipments (UEs). The baseband unit (BBU) is equipped with a large-scale antenna array to serve the flying RRHs and affords all the baseband signal processing. To optimize the proposed architecture, we consider the maximization of the minimum rate of UEs by jointly optimizing UAVs placement, quantization noise variance, and power control. The corresponding optimization problem is not convex and to solve it we devise an efficient iterative algorithm combining the block coordinate descent and successive convex optimization methods. Numerical results demonstrate the superior performance of the proposed algorithm compared to two benchmark schemes.

No abstract