Cooperation Strategies and Resource Allocations in Multiuser OFDMA Systems

Cooperative communication and orthogonal frequency-division multiplexing (OFDM) technology are both promising candidates for next-generation wireless communication systems. In this paper, we investigate cooperation strategies and resource-allocation algorithms for multiuser cooperative orthogonal frequency-division multiple-access (OFDMA) systems. There are two major contributions of this paper. First, we propose a novel cooperation strategy for the OFDMA system. When there are two users in the system, the strategy achieves the capacity region upper bound for decode-and-forward (DF) cooperation. When there are multiple users in the system, the strategy can achieve near upper-bound performance in certain network topologies. Moreover, the strategy always outperforms those that are previously proposed for cooperative OFDMA systems. The second contribution is that we develop novel centralized resource-allocation algorithms for cooperative OFDMA systems. The advantages of the algorithms are that they not only simultaneously solve relay, power, and subcarrier allocation but also have complexity that increases only linearly with the number of subcarriers in the systems.