Joint Energy-Bandwidth Allocation in Multiple Broadcast Channels With Energy Harvesting

In this paper, we consider the energy-bandwidth allocation for a network with multiple broadcast channels, where the transmitters each powered by an energy harvester, access the network orthogonally on the assigned frequency band and each transmitter communicates with multiple receivers orthogonally or non-orthogonally. We assume that the energy harvesting state and channel gain of each transmitter can be predicted for K time slots a priori. To maximize the weighted throughput, we formulate an optimization problem with O(MK) constraints, where M is the total number of receivers, and optimize over the energy and bandwidth allocation variables. To solve the problem efficiently, an iterative algorithm is proposed that alternatively solves the two subproblems of energy allocation and bandwidth allocation in each iteration. We show that this algorithm converges to the optimal solution. Also, we propose efficient algorithms to solve the two subproblems, so that the optimal energy-bandwidth allocation can be obtained with an overall complexity of O(MK2), even though the problem is non-convex when the broadcast channel is non-orthogonal. Simulation results show that the proposed algorithms can make efficient use of the harvested energy and the available bandwidth, and achieve significantly better performance as compared to some heuristic policies for energy and bandwidth allocation. Moreover, it is seen that with energy-harvesting transmitters, the non-orthogonal broadcast channel offers limited gain over the orthogonal broadcast channel.