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Analysis of Quiet Period Scheduling in QP-CSMA-CA Cognitive Radio MAC Protocol


In cognitive radio networks (CRN), the secondary network opportunistically access the wireless channels that are free from primary user (PU). Recently, the usage of quiet period (QP) scheduling mechanism to detect transmission opportunities for 802.11 secondary network has gained popularity.The QP-CSMA-CA is a 802.11 based CRN MAC protocol that uses DIFS-based QP scheduling mechanism. In this paper, we propose an analytical model for DIFS-based QP scheduling mechanism. We study the impact of number of secondary nodes on QP scheduling and on their throughput and delay. The access point of 802.11 secondary network can use our analytical model to map the optimal QP scheduling interval \(T_{QP}\) (in time units) to the number of DIFS occurrences \(N_{DIFS}\) which is required for QP-CSMA-CA MAC protocol to detect the reappearance of PU. We validate our mathematical model in finding the optimal \(N_{DIFS}\) through extensive MATLAB simulation.

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  1. The Decoupling approximation states that “From the view of tagged node, all other nodes can be seen attempting transmission with probability \(\tau\). Thus, the collision seen by tagged node is calculated as \(\gamma (\tau ) = 1-(1-\tau )^{N_u-1}\). The transmission attempt probability is also a function of collision probability, i.e. \(\tau (\gamma )\). This results in Fixed-point equation which has solution for back-off parameters mentioned in IEEE 802.11 DCF mechanism.”


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We would like to thank Chittabrata Ghosh, Wireless Systems Engineer at Intel Corporation, Santa Clara, California for clarifying our doubts on his work “QP-CSMA-CA MAC protocol” through e-mail conversation.

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Correspondence to S. Senthilmurugan.

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Senthilmurugan, S., Venkatesh, T.G. Analysis of Quiet Period Scheduling in QP-CSMA-CA Cognitive Radio MAC Protocol. Wireless Pers Commun 92, 1625–1637 (2017).

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