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Modeling and Analysis of Two Wireless Networks with Opportunistic and Primary Spectrum Access

Moradian, Masoumeh | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41033 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Ashtiani, Farid; Nasiri Kenari, Masoumeh
  7. Abstract:
  8. In this thesis, we propose an analytical model to evaluate the maximum stable throughput of a cognitive IEEE 802.11-based WLAN overlaid on a cellular network. In the considered scenario, the secondary nodes operate in uplink frequency band of primary network and transmit on their own idle detected primary channels using OFDM technique. The activity of primary nodes is modeled independently by ON-OFF alternating states with negative exponential distributed durations. The main feature of the proposed analytical model is to include different status of the secondary users, i.e., different spectrum opportunities for different cognitive users, as the result of dynamic nature of primary users as well as different locations of secondary users relative to primary ones. The proposed model has been founded on an open queueing network comprised of several queueing nodes equivalent to different states of a typical secondary user. The details of MAC scheme of the cognitive WLAN, dynamic nature of spectrum opportunities and primary users’ effect on secondary transmission are mapped onto suitable parameters of the proposed analytical model. In order to compute the service times and routing probabilities in the proposed queueing network, we have modeled the observation process of secondary nodes by a typical secondary node through a two-state Markov chain. Then, by writing the traffic equations of the queueing network, we are able to find the maximum stable throughput, i.e., the maximum rate of packet generation at the cognitive nodes guaranteeing the stability of all nodes. The comparison of maximum stable throughput of secondary network operating in uplink and downlink frequency bands of primary network shows that the spectrum opportunities due to spatial distribution of primary users can effectively increase the maximum stable throughput especially in heavy primary load. We also have computed the quality factors including quality loss in primary network as well as delay and packet loss probability in secondary network. We show the applicability of our approach in evaluating the effect of different parameters of the cognitive network scenario, e.g., the number of users, activity factors, etc., onto the maximum stable throughput. Simulation results confirm the validity of our analytical approach
  9. Keywords:
  10. Cognitive Radio ; Queueing Network ; Institiute Electrical and Electronic Engineers (IEEE)802.11 Standard ; Wireless Local Area Network ; Maximum Stable Throughput

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