Abstract
In cognitive radio (CR), the secondary user (SU) needs to hand off its ongoing communication to an idle channel in order to avoid interference to the primary user (PU). Spectrum hand off issue becomes challenging in CR mobile ad hoc networks (CR-MANETs) because of the uncertainty in spectrum availability, broad range of spectrum bands and lack of central entity. The purpose of this study is to design a unified spectrum handoff (USH) scheme for CR-MANETs that considers the spectrum heterogeneity and its availability over time and space. A local flow hand off is performed when spectrum hand off cannot be carried out due to the SUs mobility. To improve further USH, preemptive unified spectrum handoff (PUSH) algorithm is proposed in which two different preemptive hand off threshold regions are defined. The PUSH algorithm also predicts the cognitive link availability considering the PU interference boundary. Although the PUSH scheme improves the hand off performance, the number of spectrum hand offs due to the PU activity should be reduced in this scheme. Therefore, the PC-PUSH (Power Controller-PUSH) scheme is proposed in which the fuzzy logic is used to improve the PUSH in terms of the number of spectrum handoffs because of the PU activity. The PC-PUSH decreases the interference to the PUs, while reducing the number of spectrum handoffs. The results show that the proposed scheme improves the link maintenance probability, decreases the hand off delay, and reduces the number of spectrum handoffs.
Highlights
Over the last few decades, the huge success of wireless applications has caused some spectrum bands being heavily used, especially unlicensed bands, such as ISM bands
The PC-preemptive unified spectrum handoff (PUSH) (Power Controller-PUSH) scheme is proposed in which the fuzzy logic is used to improve the performance of the PUSH in terms of the number of spectrum handoffs because of the primary user (PU) activity
The performance improvement achieved by the proposed method is demonstrated using four different versions of the handoff management schemes that are defined as the spectrum handoff (SH), the unified spectrum handoff (USH), the PUSH, and the PC-PUSH algorithm
Summary
Over the last few decades, the huge success of wireless applications has caused some spectrum bands being heavily used, especially unlicensed bands, such as ISM bands. This can be attributed to interference and poor network performance. Researchers have concluded that the traditional fixed spectrum allocation approach cannot continue to efficiently regulate the spectrum access. To address this situation, wireless devices operating in unlicensed bands can dynamically identify currently unused licensed spectrum bands for data communications and opportunistically access the unoccupied spectrum called spectrum holes or white spaces. PUs have been licensed to use the spectrum band and SUs must access the spectrum in a nonintrusive manner [2]
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