Relay Assignment and Cooperation Maintenance in Wireless Networks

In this paper, we study the relay assignment problem in cooperative wireless networks with self-interested nodes. Such systems should be organized from the point of view of efficiency, stable and providing consistent incentives to all nodes. We propose a cooperation mechanism which includes the cooperative relationship formation stage and cooperation maintenance stage. The cooperative relationship among the nodes can be modeled as an exchange market game (a special coalitional game) where nodes trade transmission power between each other to get diversity gain. The exchange games have a basic assumption that each node conforms to trade agreement. So that, each agent has the option to trade its good in order to get a better one. In such game, \textit{strict core} is considered as individual rational, Pareto optimal and relationship-stable solution. A Cooperation Cycle Formation (CCF) algorithm is proposed to get the strict core solution. But, in networks, some deviated nodes may break the cooperation agreement to get more utility gain. Such deviated behaviors in the cooperation cycles can totally destroyed the cooperation relationship. However, the date transmissions in networks have the repeated element (e.g., the data of each user are transmitted in many time slots). Hence, based on the cooperative cycle formed by CCF, we introduce a repeated game model for cooperation maintenance in the second stage. A Dynamic Punishment and Recover (DPR) mechanism is proposed to punish the deviated behaviors and recover cooperation.