Non-Orthogonal Multiple Access for Hybrid VLC-RF Networks with Imperfect Channel State Information

This paper proposes a general framework for the energy efficiency analysis of a hybrid visible light communication (VLC) and Radio Frequency (RF) wireless system, in which both VLC and RF subsystems utilize non-orthogonal multiple access (NOMA) technology. The proposed framework is based on realistic communication scenarios as it takes into account the mobility of users and assumes imperfect channel-state information (CSI). In this context, tractable closed-form expressions are derived for the corresponding average sum-rate of NOMA-VLC and orthogonal frequency division multiple access (OFDMA)- VLC. It is shown extensively that incurred CSI errors have a considerable impact on the average energy efficiency of both NOMA-VLC and OFDMA-VLC systems. Hence, they should be taken into detailed account in the design of practical systems. We further demonstrate that the average energy efficiency of the hybrid NOMA-VLC-RF system outperforms the NOMA-VLC system under imperfect CSI. Respective computer simulations corroborate the derived analytic results, and interesting theoret- ical and practical insights are provided, which will be useful in the effective design and deployment of conventional VLC and hybrid VLC-RF systems