A token based control channel protocol for cognitive radio networks

In cognitive radio networks, the main purpose of medium access layer is to make optimum decisions for efficient usage of spectrum which is scarcely used by primary users. In addition to primary users (PUs), secondary users (SUs) have to share the spectrum with each other by exchanging information over a control channel. Therefore, control channel has vital importance on MAC layer. When there is a significant number of SUs in the network, this control channel becomes saturated because of the increasing number of channel requests and control information. In this paper, we propose a token ring based solution for the control channel to limit the response delay; thus prevent excess waiting time which happens with carrier sensing methods even though there are available licensed channels. The protocol proposed also improves the quality of the spectrum decision process, because the necessary global information about the state of channels is carried inside the token. The protocol was compared with a CSMA/CA protocol and gained better results in response delay and utilization.