Revisiting relay assignment in cooperative communications

Abstract

The performance gain of cooperative communications heavily depends on the selection of relay. Most of the existing relay selection methods for cooperative communications aim at maximizing cooperative gain by selecting appropriate relay, without taking into account the adverse effect brought by cooperative communications: extra interference introduced by relay transmission (called cooperation interference). Thus the derived performance gain could be inaccurate and/or the selected relay may be not optimal. In this paper, we address the assignment of relays for multiple communication sessions using cooperative communication mode in wireless networks. We first thoroughly investigate the adverse effect brought by using relays, and derive the cooperation gain with consideration of cooperation interference. Based on the insights of our investigation, we propose a method of assigning relays to individual transmission flows while taking into account cooperation interference. In order to tradeoff the advantage and adverse effect caused by relay transmissions, we use an auction approach to address relay assignment of cooperative communications. Specifically, we propose a single round double auction scheme (SAS) for centralized wireless network and a multiple rounds sequential auction scheme (MAS) for decentralized wireless network for relay assignment. We conduct extensive simulation experiments to validate the effectiveness of SAS and MAS. The significance of cooperation interference, the improvement of overall system throughput and energy efficiency of our proposed relay assignment schemes are demonstrated by numerical results.