A greedy spectrum sharing algorithm for cognitive radio networks

In this paper, we propose a novel simple heuristic algorithm for scheduling the secondary link activation and provide a dynamic spectrum sharing in cognitive radio networks. This algorithm is presented for spectrum underlay where primary and secondary users transmit simultaneously on the same frequency bands in cognitive radio networks. The proposed algorithm is based on a graph-theoretical model. First, the cognitive radio network is modeled as a weighted graph. The spectrum sharing problem is then reduced to the one of finding a sensitive vertex coloring of the constructed graph. The spectrum sharing decisions are taken at the level of a spectrum server that coordinates the secondary transmissions in order to find the best transmission/spectrum pairs in terms of system sum rate. The spectrum server is also responsible for protecting the transmission of primary users from harmful interference via assigning appropriate transmitting power to the activated secondary transmissions. We show through simulations the gain that the proposed algorithm can extract in terms of system sum rate from the transmission selection diversity.