Optimal Joint Resource Allocation and Power Control in Bidirectional Relaying Networks

Cooperative relaying (CoR) and network coding (NC) are two promising techniques for improving the performance of next-generation mobile networks. In this paper, a dynamic joint resource allocation and power control scheme is proposed for bidirectional relaying in wireless mobile networks. We consider a bidirectional relaying network consisting of three nodes: user equipment (UE), base station or eNodeB (eNB), and an intermediate relay station (RS). We model the network by a two-way relay channel (TWRC) in which UE and eNB can choose between different transmission schemes: direct transmission, pure CoR (CoR scheme), or via the combination of NC and CoR (NC/CoR scheme). We first study the achievable rate regions for direct transmission, CoR, and NC/CoR and characterize them by a set of linear inequalities. We show that NC/CoR does not always achieve better performance than CoR or direct transmission in terms of achievable throughput. Therefore, we propose a hybrid transmission scheme with adaptive resource allocation to dynamically choose the best transmission strategy and the optimal resource allocation at each bidirectional transmission time frame. This is done on the basis of the system channel state information and the buffer occupancy of UE and eNB. The hybrid approach achieves the convex hull of the union of the rate regions of the direct, CoR, and NC/CoR schemes. Finally, we extend our hybrid approach by considering power control at the RS, and we use simulations to study the effect of power control in the hybrid scheme. It is shown that in both single-input-single-output and multiple-input-multiple-output systems, the hybrid scheme with joint power control and resource allocation improves the throughput and delay performance of the system considerably.