Optimal Transmission Policies for Multi-Hop Energy Harvesting Systems

In this paper, we consider a multi-hop energy harvesting (EH) communication system in a full-duplex mode, considering arrival data and harvested energy curves in the source and the relays. Our model covers all possible harvesting profiles by considering a general function (including both continuous and discrete functions). This model includes the EH system with discrete arrival processes as a special case. We investigate the throughput maximization problem considering least utilized energy in the source and relays and find the optimal offline algorithm. We propose a three-step algorithm: 1) solving a point-to-point throughput maximization problem at the source; 2) solving a point-to-point throughput maximization problem at the relay (after applying the solution of first step as the input of this second problem); and 3) minimizing utilized energy in the source. We show this algorithm gives the optimal throughput. In addition, we find the relation between the optimal algorithm for the completion time minimization problem and the proposed algorithm for the throughput maximization problem. Further, for the throughput maximization problem, we propose an online algorithm and show that it is more efficient than the benchmark one (which is a direct application of an existing point-to-point online algorithm to the multi-hop system).