On multiple handoff blocking-then-reaccess for opportunistic spectrum access

Opportunistic spectrum access (OSA), a promising technology to resolve radio spectrum scarcity, is still faced with some challenges, of which one is potentially frequent channel handoff (CH) even handoff blocking (HB) for secondary user (SU) to avoid primary user (PU). Reaccess is a direct way to resolve HB. However, multiple handoff blocking-then-reaccess (H-BTR) are time consuming. Whether it is worthwhile to make multiple H-BTR, is an interesting but hardly mentioned issue. To this end, the multiple H-BTR-based OSA are focused on here. Three key indices, the average transmission probability, handoff delay, and average reaccess times of SU in the H-BTR-based OSA, are deduced as close form first. Then, the effects of H-BTR frequency and service traffic rate of SU on OSA are discussed. Finally, the H-BTR-based OSA is compared to two other schemes, the handoff without BTR (HWBTR)-based OSA and the stop-and-waiting (SW)-based OSA. Theoretical and simulated results show that the H-BTR-based OSA performs best among three schemes. Making H-BTR in moderate frequency according to service traffic rate can increase transmission opportunity while additional delay of SU is tolerable, thus the performance of OSA can be well improved.