A survey on spectrum handoff techniques in cognitive radio networks

The last decade has witnessed tremendous increase in the use of wireless applications in all walks of life. Consequently, the availability of treasurable and limited electromagnetic radio spectrum has emerged as a major challenge. The escalated demand of this limited natural resource puts a number of constraints on its usage. Because of inefficient spectrum usage and ineffective utilization, a new communication model, namely cognitive radios has been developed to exploit the available spectrum in an opportunistic manner. In order to use the vacant or underutilized frequency bands (called spectrum holes, henceforth) opportunistically, the cognitive radios may have to switch the frequency band quite often. This may lead to application discontinuity and performance degradation. Thus, it is desired to have efficient techniques to handle the spectrum handoff. In this paper, we present a survey of spectrum handoff techniques with a brief overview of cognitive radio technology. The cognitive user throughput and handoff delay are the two popular parameters of interest for comparing different handoff techniques.