ABSTRACT
This chapter explains three handoff strategies in the context of cognitive radio networks. There are nonhandoff, reactive and proactive. In nonhandoff strategy, when a primary user (PU) reclaims its channel, the secondary users (SU) stops transmission, remains idle, and resumes transmission once the PU vacates the channel. This process may be repeated by the SU as necessary during a single session of data transmission. In proactive handoff, the handoff process is planned and performed before a handoff triggering event occurs. Hybrid Handoff strategy is a combination of reactive and proactive handoff strategies. The backup channel list is prepared proactively while the handoff action is done reactively. Mathematical models can provide insights into the performance of spectrum handoff. The need of frequent handoff can be reduced by using multiband cognitive radio networks. The chapter also provides a brief discussion of design requirements and current issues in spectrum mobility management.
