Hybrid Spectrum-handoff in Cognitive Radio Ad Hoc Networks

Cognitive Radio Network implements dynamic spectrum access and is a major solution to spectrum scarcity. Multiple operators can use a single spectrum band and can increase the utilization greatly. In order to enable spectrum sharing among users, the network must sense suitable channels, determine and decide the most appropriate channel, maintain communication and share spectrum with other users, and vacate the channel when a PU activity is detected. Spectrum mobility is an important part of the system, and a smooth and quick transfer of the channel is important so that the users suffer minimum performance loss and degradation. Continuous allocation of spectrum, as the available bands also change, and hence maintaining QoS in these channels still remains a major challenge. Spectrum handoff can be reactive or proactive. These techniques use spectrum sensing and spectrum prediction to perform handoff respectively. Various types of spectrum handoffs and the performance comparison of hybrid spectrum handoff with the traditional round-robin technique is discussed. The method proves effective in saving sensing time and in reducing the number of handoffs. The spectrum handoff techniques are carried out in NS3 which is a free and open-source network simulator.