WSR Maximized Resource Allocation in Multiple DF Relays Aided OFDMA Downlink Transmission

TL;DR

This paper develops a two-step algorithm to optimize resource allocation for maximizing weighted sum rate in OFDMA downlink systems with multiple DF relays, considering power constraints and relay cooperation.

Contribution

It introduces a globally optimal resource allocation algorithm for relay-assisted OFDMA downlink systems, combining power assignment and relay selection with convex optimization.

Findings

The algorithm achieves optimal weighted sum rate performance.

Relay cooperation significantly improves system throughput.

High power regimes simplify the resource allocation process.

Abstract

This paper considers the weighted sum rate (WSR) maximized resource allocation (RA) constrained by a system sum power in an orthogonal frequency division multiple access (OFDMA) downlink transmission system assisted by multiple decode-and-forward (DF) relays. In particular, multiple relays may cooperate with the source for every relay-aided transmission. A two-step algorithm is proposed to find the globally optimum RA. In the first step, the optimum source/relay power and assisting relays that maximize the rate is found for every combination of subcarrier and destination, assuming a sum power is allocated to the transmission at that subcarrier to that destination in the relay-aided transmission mode and the direct mode, respectively. In the second step, a convex-optimization based algorithm is designed to find the globally optimum assignment of destination, transmission mode, and sum power for each subcarrier to maximize the WSR. Combining the RAs found in the two steps, the globally optimum RA can be found. In addition, we show that the optimum RA in the second step can readily be derived when the system sum power is very high. The effectiveness of the proposed algorithm is illustrated by numerical experiments.