Resource Allocation Algorithm for OFDMA System based on Bidirectional Multi-Relay

Abstract

A novel approach to optimize power allocation and subcarrier pairing in a high signal-to-noise ratio (SNR) scenario within a two-way multi-relay orthogonal frequency division multiple access (OFDMA) system has been introduced. Unlike conventional methods where relays operate on individual subcarriers, our scheme allows all relays to transmit signals across each subcarrier pair, thereby leveraging significant space diversity. Operating under a constraint of total system power, our proposed scheme initially assigns power to each relay using Cauchy inequality under the assumption of fixed total relay power. Subsequently, employing a dichotomous approach, we determine the power allocation between the source node and the relay node by maximizing the equivalent channel gain across various subcarrier pairs. Finally, we employ convex programming to allocate power to different subcarrier pairs, while utilizing the Hungarian algorithm to pair subcarriers effectively, thereby maximizing system capacity. Given the inherent complexity of power allocation algorithms in two-way multi-relay networks, conventional methods lack optimal solutions with low complexity. However, our algorithm significantly mitigates the complexity associated with power allocation, particularly within a system comprising 40 subcarriers. Simulation results underscore the superiority of our proposed scheme over conventional relay selection approaches, particularly those wherein relays operate on individual subcarriers.