Cooperative Spectrum-Aware Opportunistic Routing in Cooperative Spectrum-Aware Opportunistic Routing in Cognitive Radio Ad Hoc NetworksCognitive Radio Ad Hoc Networks

Cuimei Cui*Cuimei Cui* † †, Hong Man, Hong Man†† , Yiming Wang* , Yiming Wang*

*School of Electronics and Information Engineering, Soochow University*School of Electronics and Information Engineering, Soochow University†† Dept. of Electrical and Computer Engineering, Stevens Institute of TechnologyDept. of Electrical and Computer Engineering, Stevens Institute of Technology

nicolec2008@126.com, Hong.man@stevens.edu, ymwang@suda.edu.cnnicolec2008@126.com, Hong.man@stevens.edu, ymwang@suda.edu.cn

I. Motivations & Contributions

MotivationsMotivations Cognitive radio (CR) technology has been recognized as an Cognitive radio (CR) technology has been recognized as an

viable solution to counteract both viable solution to counteract both spectrum inefficiency spectrum inefficiency andand spectrum scarcity spectrum scarcity problems.problems.

To fully unleash the potentials of CR Ad Hoc networks To fully unleash the potentials of CR Ad Hoc networks (CRAHNs), new challenges must be addressed at the network (CRAHNs), new challenges must be addressed at the network layer by tightly coupling with layer by tightly coupling with physical layer spectrum sensing physical layer spectrum sensing and and MAC layer spectrum sharingMAC layer spectrum sharing, taking into account the unique , taking into account the unique properties of the cognitive environment.properties of the cognitive environment.

How to extend opportunistic routing adopting cooperative How to extend opportunistic routing adopting cooperative spectrum sensing technology is still an open research issue.spectrum sensing technology is still an open research issue.

ContributionsContributions Propose a Dual-stage Collaborative Spectrum Sensing (DCSS) Propose a Dual-stage Collaborative Spectrum Sensing (DCSS)

routing protocol to discover the established routing opportunity.routing protocol to discover the established routing opportunity.

Metrics of cooperative spectrum-aware opportunistic routing Metrics of cooperative spectrum-aware opportunistic routing were defined and derivedwere defined and derived

Evaluate the performance of the proposed routing protocol in Evaluate the performance of the proposed routing protocol in CRAHNs. CRAHNs.

II. Opportunistic Cognitive Routing Protocol

Network ModelNetwork Model

Model the CRAHN with a direct temporal graph:Model the CRAHN with a direct temporal graph:

Vertex denotes an CR routing node or an CR sensing Vertex denotes an CR routing node or an CR sensing relay, and an edge denotes the routing link from CR relay, and an edge denotes the routing link from CR node Unode Uii to U to Uj j at t time . at t time .

If PU is not active, the route with the minimum hop count and If PU is not active, the route with the minimum hop count and the longest single-hop distance Uthe longest single-hop distance Uss-U-Uii-U-Ujj-U-Udd will be established. will be established.

Otherwise, the route with a higher hop count, as shown in Otherwise, the route with a higher hop count, as shown in dashed line, will be selected.dashed line, will be selected.

Channel SensingChannel Sensing The occupancy rate of PU at m-th channel,The occupancy rate of PU at m-th channel,

The transition probability after a duration of for Ui in The transition probability after a duration of for Ui in busy(ON) state,busy(ON) state,

(t) (U,E(t))G

, SRi iU U

( ) ( )ije t E t

The probability that a channel at UThe probability that a channel at Uii stays in busy state during stays in busy state during

the sensing period tthe sensing period tss adopting DCSS scheme, adopting DCSS scheme,

Path SelectionPath Selection The successful routing probability between UThe successful routing probability between U i i and Uand Ujj in the in the

channel m,channel m,

Select the optimal channel as routing path,Select the optimal channel as routing path,

The successful routing opportunity of the pathThe successful routing opportunity of the path

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III. Performance Evaluation

,

Simulations are presented to evaluate the performance of Simulations are presented to evaluate the performance of cooperative spectrum-aware opportunistic routing in terms of cooperative spectrum-aware opportunistic routing in terms of accuracy and optimality.accuracy and optimality. Fig.1 & Fig.2 illustrate the routing breakage probability of Fig.1 & Fig.2 illustrate the routing breakage probability of

DCSS is more closer to the practical result than these of DCSS is more closer to the practical result than these of SCSS and NCS when selecting optimal relay.SCSS and NCS when selecting optimal relay.

Fig.2 & Fig.3 show that the longer the average time of a PU Fig.2 & Fig.3 show that the longer the average time of a PU is in ON state, the higher is the breakage probability of is in ON state, the higher is the breakage probability of end-to-end routing, the less is the opportunity of routing.end-to-end routing, the less is the opportunity of routing.

Fig.4 presents that the successful end-to-end opportunity Fig.4 presents that the successful end-to-end opportunity routing probability using the DCSS increases as the routing probability using the DCSS increases as the number of usable channels increases, and decreases as number of usable channels increases, and decreases as the number of routing hops.the number of routing hops.

Fig.1

Fig.3

Fig.2

Fig.4

From accuracy and optimality of view, DCSS scheme is more From accuracy and optimality of view, DCSS scheme is more accuracy to find routing access opportunity than other accuracy to find routing access opportunity than other spectrum sensing approaches.spectrum sensing approaches.

Simulation results suggest the benefit of using DCSS in Simulation results suggest the benefit of using DCSS in CRAHNs is considerable.CRAHNs is considerable.

In the future work, we will investigate how to adapt metric to In the future work, we will investigate how to adapt metric to optimize the routing performance in dynamic CRAHNs.optimize the routing performance in dynamic CRAHNs.

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iv. Conclusions