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Security and Cooperation in Multi-User Information Theory

Yassaee Maybodi, Mohammad Hossein | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40653 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Aref, Mohammad Reza
  7. Abstract:
  8. In this thesis, we study the role of cooperation and security in multi-user channel from an information theoretic point of view. First, we review the wiretap channel as a fundamental model for the study of confidentiality in information theoretic security. To do this, we first introduce two measures for measuring the level of secrecy of confidential message, namely, average equivocation rate (AER) and equivocation rate in probability (ERP). By using a new proof, based on random covering, we show that the capacity-equivocation region of wiretap channel under AER and ERP is the same. To study cooperation in multi-user channel, we introduce the cooperative network in which each user can simultaneously encode, relay and decode. By generalizing the compress and forward strategy, we obtain an achievable rate region for this network. We observe that in deterministic cooperative network, this region and the cut-set region are partially matched. Also, in Gaussian cooperative network, we show that the cut-set region is achievable within a constant number of bits. In addition, we investigate the role of cooperation for providing of security in multi-user network. For this purpose, we study relay networks in the presence of a set of iretappers. First, with some simple examples, we show that how relays can cooperate to enhance security, even when cooperation does not provide more reliability. Finally, we drive an inner bound for rate-equivocation region, based on compress and forward strategy and wiretap coding over wire-tap multiple-access channel.
  9. Keywords:
  10. Multiple Access ; Capacity ; Relay Channel ; Wiretap Channel ; Broadcast Channel ; Cooperative Network ; Rate-Equivocation Region

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