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Performance and Analytical Discussion on OFDMA-Based Cognitive Radio Networks with Relaying Capabilities

Golrezaei-Khuzani, Sakineh | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39972 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Nasiri Kenar, Masoumeh
  7. Abstract:
  8. In this thesis, a novel OFDMA-based cognitive cooperative relaying scheme is proposed in which cognitive users not only try not to interfere with primary users but also assist them by relaying their information. Both primary users (PU) and cognitive users (CR) communicate to a common base station (BS). Bit error probability (BEP) of primary users and outage probability of primary users are investigated to evaluate performance of the primary users. In all parts of this thesis, we assume that data of users is not jointly encoded across subcarriers. So, the outage probability and BEP are investigated for each subcarrier independently. In the last part of the thesis, it is assumed that data is jointly encoded across all subcarriers. Thus, the outage probability for all subcarriers is jointly evaluated. We consider two different relay assignment schemes. In the first scheme, for each subcarrier of the primary user that exposes outage the best cognitive user is selected as a relay. In the second scheme, for all of the subcarriers which experience outage, one cognitive user is selected as a relay. Our evaluations show that the first relay selection scheme surpasses the second one. This issue is more obvious when data is not jointly encoded across subcarriers. The way that the cognitive users allocate power to relaying primary user can affect the primary and cognitive users performance. Two different power allocations are considered. While in the first scheme, the total power dedicated to the relaying unsuccessful subcarriers of the PU is fixed, in the second scheme, the power allocated to relaying each subcarrier is fixed. Our analyses show that the second power allocation scheme outperforms the first one. Outage probability of cognitive users is investigated to study effects of cooperation on the performance of cognitive users. Our analyses show substantial improvements in BEP and outage probability of primary users while the outage probability of the cognitive users does not change significantly.

  9. Keywords:
  10. Cognitive Radio ; Outage Probability ; Bit Error Rate ; Orthogonal Frequency Division Multiplexing (OFDM) ; Cooperation Communication

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