An Effective Spectrum Handoff Scheme for Cognitive Radio Ad Hoc Networks

Cognitive Radio Networks (CRNs) is the key technology to overcome the disadvantages of static spectrum allocation and enhance spectrum utilization through Dynamic Spectrum Access (DSA) techniques. One important topic of the development of CRNs is spectrum handoff, which ensures the uninterrupted communication of Secondary Users (SUs). Two types of spectrum handoff approaches exist, namely the proactive and the reactive spectrum handoff. When the Primary User (PU) traffic is high the proactive spectrum handoff approach is more suitable whereas the reactive handoff on light PU traffic achieves better performance. In this paper we evaluate the use of proactive and reactive spectrum handoff policies in CRNs. Simulations are conducted using NS-3 simulator. To the extent of our knowledge, an extensive CRN simulation regarding spectrum handoff on NS-3 simulator has not been carried out. Furthermore, we implemented a hybrid spectrum handoff scheme that selectively uses either reactive or proactive handoffs, based on PU traffic intensity. Additionally our scheme adjusts dynamically the SU frame size throughout SU communications, to minimize collisions. Simulations show that the proposed hybrid scheme performs better than the proactive and reactive handoff types. Moreover, the dynamic adjustment of the frame size on cognitive nodes enhances performance noticeably in certain scenarios.