Non-Orthogonal Multiple Access for Mobile VLC Networks with Random Receiver Orientation
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Visible light communications (VLC) is an emerging technology with a promise of viable solution to spectrum crunch problem in conventional radio frequency bands. In this work, we consider a VLC system where mobile users are randomly changing their horizontal location and vertical orientation. The non-orthogonal multiple access (NOMA) strategy with full channel state information (CSI) feedback is adopted to serve these users with improved spectral efficiency. To reduce computational burden and overhead due to tracking and feeding back the full CSI, we consider various limited feedback schemes where users are ordered based on their distance and vertical angle information instead of full CSI. Comprehensive numerical results verify the superiority of NOMA as compared to orthogonal multiple access while compensating the loss in user rates due to the random receiver orientation. In addition, vertical angle information based limited feedback schemes are observed to achieve satisfactory performance as compared to full CSI feedback, while conventional distance feedback scheme shows poor performance in this realistic VLC scenario.
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