Spectrum Handoff in Cognitive Radio Networks: Opportunistic and Negotiated Situations

Spectrum handoff is an indispensable component in cognitive radio networks to provide resilient service for the secondary users. In this paper, we explore the spectrum handoff procedure and then propose four metrics to characterize both short-term and long-term spectrum handoff performance: link maintenance probability, the number of spectrum handoff, switching delay, and non-completion probability. In particular, the probability mass function (pmf) and the average number of spectrum handoff are developed. The tele-traffic parameters are relaxed to follow a general distribution function, which will enable a wide applicability and theoretical significance of the derived formulae. Both opportunistic and negotiated spectrum access strategies are investigated. Results show that these two mechanisms will generate significantly different performance. Numerical examples are presented to demonstrate the performance trade-off and the interaction between the primary users and the secondary users. The impact of key parameters on spectrum handoff is also discussed. The techniques as well as the results are important for evaluating the primary and second users co-existence, and hence helpful for design and optimization of cognitive radio networks.