Spectrum handoff reduction for cognitive radio ad hoc networks

Spectrum handoff is one of the main challenges in cognitive radio ad hoc networks. Spectrum handoff occurs when the owner of the spectrum or the primary user (PU) appears in the same channel that is already occupied by a secondary user (SU). In this case, the SU should vacate this channel and determine another free one. This process may continue till SU finishes its transmission. Spectrum handoff has a negative impact on the performance of SU in terms of delay and link maintenance; therefore the number of handoffs should be reduced. Opportunistic Spectrum Access with Backup channels (OSAB) is a new spectrum access concept for managing and increasing the spectrum capacity for ad hoc networks. Reducing the number of spectrum handoffs is one of the main features of OSAB. This is achieved by utilizing the unlicensed channels as backup channels in case of the appearance of the PUs. In this paper, an extensive mathematical model is presented to evaluate the performance of the OSAB in terms of the link maintenance probability and the expected number of spectrum handoffs. Numerical results show that OSAB outperforms the classical opportunistic spectrum access concept in terms of the aforementioned performance metrics.