Joint user and power scheduling in downlink NOMA over fading channels
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Non-orthogonal multiple access (NOMA) has been considered one of the most promising radio access techniques for next-generation cellular networks. In this paper, we study a joint user and power scheduling problem in downlink NOMA over fading channels. Specifically, we focus on a stochastic optimization problem to maximize the average weighted sum rate while ensuring given minimum average data rates of users. To address this challenging problem, we first develop an opportunistic user and power scheduling algorithm (OUPS) based on the duality and stochastic optimization theory, which transforms our stochastic problem into a series of deterministic ones to maximize the instantaneous weighted sum rate for each time slot. As a good feature, OUPS is an online algorithm that can make decisions without requiring information on the underlying distribution of the fading channels, making it effectively applicable to a variety of practical applications. Afterward, we develop a simple heuristic algorithm with very low computational complexity, called user selection and power allocation algorithm (USPA), for the instantaneous weighted sum rate maximization problem that is embedded in OUPS. Through the numerical results, we demonstrate that USPA provides near-optimal performance despite very low computational complexity and OUPS ensures given minimum average data rates of users.
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