The Subchannel-Allocation for OFDMA Relaying Downlink Systems with Total Power Constraint

This paper considers the subchannel-allocation problem to maximize the sum-rate in orthogonal frequency- division multiple-access (OFDMA) regenerative relaying downlink systems with a total power constraint. Based on the Lagrange dual decomposition and the optimal condition of the problem, this paper proposes three heuristic algorithms: an extended modified inverse subchannel signal-to-noise ratio algorithm, a bit accumulation algorithm, and a bit ratio algorithm. Simulation results show that relaying systems with proposed algorithms outperform optimally resource-allocated OFDMA systems without relay stations by almost 100% ~ 270% depending on the system power, which confirms that subchannel-allocation is a key factor in obtaining a huge performance gain.