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On the Capacity of Information Networks Utilizing Cognition and Cooperative Strategies

Mirmohseni, Mahtab | 2012

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 42750 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Aref, Mohammad Reza
  7. Abstract:
  8. Interference management is one of the key issues in wireless networks wherein multiple source-destination pairs share the same medium and frequency band and interfere with each other. The exponentially growth in the number of wireless systems and services results in the spectrum shortage which has emerged the technologies that increase the spectral efficiency. Providing the users with cognition equipments in these networks enables them to sense the medium and use the obtained data to adapt their transmissions to cooperate with other users and improve their own rates as well as the others which results in the cognitive radio technology. In order to access the full potential of this technology, it is important to understand its fundamental limits and tradeoffs.In this thesis, we investigate the effect of cognition in the interference channels from an information theoretical prospective, where the problem is to determine the capacity region of the cognitive radio channel, i.e., the set of all rates that can be simultaneously sustained by all users in the network with arbitrarily low probabil-ity of error. Moreover, we consider different strategies and try to determine the optimum schemes under specific conditions by comparing their performances. For this purpose, we first introduce a new information theoretical model for the cog-nitive radio channel, which includes the previous ones as special cases. Then, we derive several inner and outer bounds on the capacity region of the proposed model. Our coding schemes make use of collaborative strategy, cooperative strategy, and interference mitigating techniques, such as: rate splitting, Gel’fand-Pinsker binning, generalized block Markov and superposition codings, decode-and-forward strategy, compress-and-forward strategy, instantaneous relaying and Marton coding. The de-rived achievable rate regions under special conditions reduce to several previously known results. We also compare the performances of different strategies and inves-tigate the rate gain of the cognitive link in different cases. Moreover, we show that the coding strategies which we use to derive the achievable rate regions achieve ca-pacity for some classes of the proposed model. Finally, we consider the cognitive radio channels with more than two-user pair and investigate their performances by introducing reasonable scenarios. In addition to derive the inner and outer bounds on the capacity region for these scenarios, we obtain the capacity region in different interference regimes
  9. Keywords:
  10. Interference Channel ; Capacity Region ; Cognitive Radio ; Compress-and-Forward ; Decode and Forward ; Instantaneous Relaying

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