Design and Optimization of Scheduling and Non-orthogonal Multiple Access Algorithms with Imperfect Channel State Information

Non-orthogonal multiple access (NOMA) is a promising candidate technology for 5G cellular systems. In this paper, design and optimization of scheduling and NOMA algorithms is investigated. First, the impact of power allocation for NOMA systems with round-robin scheduling is analyzed. A statistic model is developed for network performance analysis of joint scheduling of spectrum resource and power for NOMA algorithms. Then, proportional fairness (PF) scheduling for NOMA algorithms is proposed with a two-step approach, with its objectives to ensure low computational complexity, high throughput, and user fairness. In the first step, an optimal power allocation strategy is developed with an objective maximizing weighted sum rate. In the second step, three fast and scalable scheduling and user pairing algorithms with QoS guarantee are proposed, in which only a few user pairs are checked for NOMA multiplex. The algorithms are extended to the cases with imperfect channel state estimation and more than two users being multiplexed over one resource block. Numerical results show that the proposed algorithms are significantly faster and more scalable than the existing algorithms, and can maintain a higher throughput gain than orthogonal multiple access

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

The present contribution 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 nonorthogonal 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 its orthogonal frequency division multiple access (OFDMA)-VLC counterparts. It is shown extensively that incurred CSI errors have a considerable impact on the average energy efficiency of both NOMA-VLC and OFDMAVLC systems and hence, they should not be neglected in practical designs and deployments. Interestingly, we further demonstrate that the average energy efficiency of the hybrid NOMA-VLCRF system outperforms NOMA-VLC system under imperfect CSI. Respective computer simulations corroborate the derived analytic results and interesting theoretical and practical insights are provided, which will be useful in the effective design and deployment of conventional VLC and hybrid VLC-RF systems