Distributed games for coordinated coalition formation in femtocell networks

For performance enhancement of indoor users, we consider a femtocell network consisting of densely deployed femto base stations (FBSs) which use a set of empty sub-channels to serve the end user. In this environment, users may still suffer from high inter-femtocell interference problem over downlink, which can be solved through cooperation among femto base stations. In this paper, we investigate a game-theoretic approach by which FBSs can form distributed and stable coalitions, which enhances the utility function that is defined as the ratio of obtained capacity to the cost of cooperation. Our proposed kernel-based algorithm for coalition formation is stable as well as Pareto-optimal in both closed and open access modes. In closed access mode, only registered users are able to access a FBS, whereas in open access mode, access is granted to any users. For both modes, we define two different kernel-stability criteria. Through simulation experiments, we confirm that our algorithm yields better utility for end users compared to non-cooperative transmission in both closed and open access modes. Our results further illustrate a tradeoff between the achieved utility and the overhead incurred by coalition members.