On energy-efficient TCP traffic over wireless cooperative relaying networks

Cooperative relay is a promising technology to provide better end-to-end performance for wireless communication through spatial diversity. Most of previous study on relay networks concentrates on lower layer performance. However, how to design the relay network for standard transport control protocol (TCP), which is very important for application layer service, is rarely investigated. We focus on energy efficiency of TCP traffic which is determined by relay selection and transmission parameters in the lower layer, e.g., the length of frame, the modulation and the maximum retransmission time. The relay selection in the cooperative network is formulated as a restless bandits with switching cost (RBSC) system, in which the problem of optimal selection of cooperative relay is solved by using a linear programming relaxation and primal-dual index based heuristic algorithm. By this means, the relay selection is designed with "one step looka-head" policy so that the energy efficiency performance can be achieved in a time horizon. The simulations verify that the lower layer parameters affect the energy efficiency of TCP traffic in wireless cooperative networks environment, and demonstrate that the proposed relay selection scheme outperforms the memoryless schemes, e.g., greedy scheme that takes no consideration of the statistical characteristics of the channels.