Hybrid energy supply (HES) wireless networks have recently emerged as a newparadigm to enable green networks, which are powered by both the electric gridand harvested renewable energy. In this paper, we will investigate two criticalbut conflicting design objectives of HES networks, i.e., the grid energyconsumption and quality of service (QoS). Minimizing grid energy consumption byutilizing the harvested energy will make the network environmentally friendly,but the achievable QoS may be degraded due to the intermittent nature of energyharvesting. To investigate the tradeoff between these two aspects, we introducethe total service cost as the performance metric, which is the weighted sum ofthe grid energy cost and the QoS degradation cost. Base station assignment andpower control is adopted as the main strategy to minimize the total servicecost, while both cases with non-causal and causal side information areconsidered. With non-causal side information, a Greedy Assignment algorithmwith low complexity and near-optimal performance is proposed. With causal sideinformation, the design problem is formulated as a discrete Markov decisionproblem. Interesting solution structures are derived, which shall help todevelop an efficient monotone backward induction algorithm. To further reducecomplexity, a Look-Ahead policy and a Threshold-based Heuristic policy are alsoproposed. Simulation results shall validate the effectiveness of the proposedalgorithms and demonstrate the unique grid energy consumption and QoS tradeoffin HES networks.
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