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Yayın Design and optimization of multiuser cooperative protocols for wireless networks(Işık Üniversitesi, 2014-09-12) Edemen, Çağatay; Kaya, Onur; Işık Üniversitesi, Fen Bilimleri Enstitüsü, Elektronik Mühendisliği Doktora ProgramıRecently, the main trend in wireless communications has shifted from voice transmission to data communication. Naturally, this shift caused an increase in the data rate and bandwidth requirements. Being a limited and thus expensive resource, wireless spectrum needs to be used efficiently. For higher spectral and data rate efficiency, new spectrum allocation policies as well as new transmission techniques are needed. Cooperative and cognitive radios are promising emerging technologies, which can enable efficient spectrum resource utilization as well as high data rate transmission in the next generation wireless networks. This thesis addresses wireless relay networks consisting of multiple cooperative and/or cognitive nodes. The main contribution of this thesis is the extension of cooperative strategies from two users to three user settings, focusing on mutual cooperation. In the first part of this dissertation, we concentrate on a superposition block Markov encoding based three user cooperative communication scheme for a fading Gaussian multiple access channel. We consider all possible channel conditions between users and propose a channel adaptive block Markov encoding strategy. In the second part of this thesis, for the same three user MAC model we discuss a new channel non-adaptive superposition block Markov encoding structure which enables all three users to cooperate collectively as well as in pairs. The proposed cooperation models not only provide increased diversity to all participating users, but also contain as special cases the multiple relay channel and the multiple access relay channel. In the third part, we focus on the joint use of cognition and cooperation. In particular, we consider overlay and underlay cooperative-cognitive radio models with one primary and two secondary users. We extend the cooperative encoding models developed for the three user MAC to the cognitive set-up. In all three problems studied in this thesis, we obtain new and improved achievable rate regions, by cognition and/or cooperation.Yayın Channel adaptive user cooperation strategies for fading wireless channels(Işık Üniversitesi, 2006) Edemen, Çağatay; Kaya, Onur; Işık Üniversitesi, Fen Bilimleri Enstitüsü, Elektronik Mühendisliği Yüksek Lisans ProgramıIn this dissertation, a channel adaptive method is proposed for a two user halfduplex cooperative communication system under the assumption of perfect channel state information at the transmitters and the receiver. An achievable rate region for the proposed method is characterized, and evaluated by computer simulation.
