Imperfect CSI-Based Joint Resource Allocation in Multirelay OFDMA Networks

Radio resource allocation is very important in relay orthogonal frequency-division multiple-access (OFDMA) networks. Since perfect channel state information (CSI) is hardly obtained, the robust design that takes into account the CSI imperfection plays a crucial role in the development of efficient resource-allocation schemes. As to the chunk-based resource-allocation scheme, this paper focuses on the imperfect CSI-based resource-allocation problem to jointly optimize the chunk assignment, transmission link selection (direct or relay link), and power allocation in multirelay OFDMA systems. The optimization formulation minimizes the total transmit power with transmission requirement constraints and is considered a mixed-integer optimization problem, and a dual-maximization-based joint resource-allocation algorithm is proposed. The proposed dual-maximization-based algorithm is shown to be optimal. We also develop a low-complexity but near-optimal resource-allocation algorithm. The numerical results validate the performance gains offered by the proposed joint resource-allocation algorithms. The results also show that the impact of imperfect CSI is nonnegligible, which highlights the importance of robust designs in practical wireless networks.