Total transmission time minimization through relay selection for full-duplex wireless powered cooperative communication networks

Abstract

We consider a relay based full-duplex wireless powered cooperative communication network which consists of a hybrid access point (HAP), N users and K decode-and-forward relays with energy harvesting capability. We propose an optimization framework for relay selection with the objective of minimizing the total transmission time subject to energy causality and user traffic demand constraints. The formulated optimization problem is a mixed integer non-linear programming problem, which is difficult to solve for the global optimal solution in polynomial-time. As a solution strategy, we decompose the proposed optimization problem into two sub-problems: time allocation problem and relay selection problem. We derive the optimal solution of the time allocation problem by using convex optimization techniques. For the relay selection problem, based on the optimality analysis, we propose a polynomial-time heuristic algorithm, which minimizes the total transmission time by allocating the best relay to each user. Through simulations, we illustrate that the proposed algorithm outperforms the conventional predetermined relay allocation scheme and performs very close to the optimal solution for different network densities, HAP power values, and initial battery levels.