Coordinated coalition formation in throughput-efficient cognitive radio networks

In this paper, we consider the problem of joint coalition formation (CF) and bandwidth allocation in cognitive radio networks. We assume that the secondary links will be partitioned into disjoint coalitions, by which the available spectrum will be reused. On the other hand, we assume that the members of each coalition will transmit over orthogonal sub-bands with the available spectrum being optimally allocated among them. We formulate the problem as a coordinated CF game, where the optimization is held at a secondary coordinator that has all the required channel information. Given these assumptions, we derive a closed-form expression of the optimal bandwidth allocation for any given network partition, and we propose an efficient algorithm to reach a Nash-stable partition (coalition structure), with the objective of improving the network throughput. Furthermore, we provide a probabilistic analysis of the stability of a grand structure and a singleton structure, and we employ this to obtain a lower bound on the stability of a general coalition structure (other than grand and singleton). Performance analysis shows that the proposed CF algorithm with optimal bandwidth allocation provides a substantial gain in the network throughput over existing CF techniques as well as the simple cases of singleton and grand coalitions.