NOMA-based resource allocation algorithm for UAV-assisted backscatter communication system

Abstract

Aiming at the issue of how to improve system transmission rate in large-scale device communication, we propose a resource allocation algorithm for UAV-assisted backscatter communication (BC) system based on Non-orthogonal Multiple Access (NOMA), which divides multiple backscatter devices (BDs) into different clusters. Within each cluster, NOMA is adopted. The optimization problem to maximize the sum rate is established under practical constraints of energy causality and backscatter rate. Since the optimization problem is non-convex, the original problem is divided into UAV trajectory problem and resource allocation problem, in which the UAV trajectory problem can be solved by affinity propagation (AP) algorithm. For resource allocation problem, the iterative algorithm based on block coordinate descent (BCD) method can be adopted, which decomposes into two subproblems, UAV hovering time allocation problem and BDs' reflection coefficient problem, in which the time allocation problem is solved by dyadic simplex method. BDs' reflection coefficient problem can be regard as a convex difference problem, and an effective concave-convex process (CCCP) algorithm is adopted to derive the optimal solution. Simulation results show that system rate of the proposed algorithm is significantly better than other benchmark algorithms.