Opportunistic relaying in delay-constrained mobile relay systems with linear mobility

In mobile relay systems, the mobility of relay node can potentially bring more and better communication opportunities for the source and destination, while at the same time, it also incurs channel fading which may lead to serious system performance degradation. In this paper, we study a fundamental problem that how to balance the above two conflicting effects of mobility so as to get optimal system throughput under given delay constraint. In particular, a three-node mobile relay system where a relay node moves linearly from the source to the destination is considered. An opportunistic relaying strategy is proposed, which optimally schedules transmission between the source and relay so that the system throughput is maximized while satisfying the delay requirement. Furthermore, the performance of the proposed strategy is analyzed. Especially, the asymptotic throughput achieved by the strategy is derived in the high transmit power regime. Finally, numerical results are given to illustrate the performance of the proposed strategy. Simulation results show its obvious advantages, and well illustrate both the positive and negative effects brought by the relay mobility. This work sheds some light to the design of delay constrained mobile relay system.