  Cognitive radio technology allows the secondary users to utilize the
spectrum, when it is not occupied by the primary users. Whenever a primary user
wants to utilize a channel which is occupied by a secondary user, the secondary
user should perform a proactive spectrum handoff to another channel and vacate
the selected channel before the primary user utilizes it. This scheme avoids
collision between the primary users and secondary users; moreover, increases
the throughput of the primary and secondary users. In this paper, a novel
proactive spectrum hand protocol based on the Greedy Channel Selection (GCS) is
proposed which avoids collision between secondary users, as well as, collision
between primary and secondary users. In the proposed scheme, proactive spectrum
handoff is based on the SRV (Single Rendezvous) coordination scheme; therefore,
the secondary users perform proactive spectrum handoff without using the common
control channel. Moreover, the channel selection is distributed which leads to
the higher throughput, and lower average service time. The proposed proactive
spectrum handoff protocol is compared with the other proactive spectrum handoff
protocols. Simulation results illustrate that the proposed protocol outperforms
the other protocols regarding higher average throughput and lower average
service time.
