CORHYS: Hybrid signaling for opportunistic distributed cognitive radio

Abstract

Opportunistic cognitive radio (CR) allows unlicensed wireless nodes to dynamically locate and access spectrum holes, i.e., licensed channels that are not being used by their incumbent users. In this context, sensing the spectrum is a key issue and performing it on a data frame basis maximizes the protection of incumbent users. Additionally, when the architecture of a CR network is distributed (i.e., ad hoc), there are no central entities that perform operations such as collecting and fusing data, and taking spectrum decisions. Therefore, CR users (i.e., secondary users) must take their own decisions and cooperate with each other in order to exchange relevant information and coordinate access to the vacant channels. To achieve this goal, the utilization of a dedicated common control channel (CCC) is a common approach since it makes implementation and cooperation easier. However, a CCC can also saturate and become a bottleneck to performance, especially when handshake is performed on a data frame basis. In this paper, we define an approach that performs signaling over the CCC and over the allocated data channels simultaneously, i.e., out-of-band signaling and in-band signaling, respectively. This medium control access-level approach, which we designate as CORHYS (Cognitive Radio Hybrid Signaling), still takes advantage of the strengths of out-of-band signaling, effectively limits the CCC saturation problem, and, therefore, has potential to improve the communication performance of secondary users in distributed CR scenarios, particularly when they perform handshake and sensing on a data frame basis, and utilize a dedicated CCC. Simulation results are conclusive.