Non Commercial You may not use this work for commercial purposes. No Derivative Works - You may not alter, transform, or build upon this work. Any of these conditions can be waived if you receive permission from the author. Your fair dealings and other rights are in no way affected by the above. Take down policy If you believe that this document breaches copyright please contact xxxxxxxxxxx@xxx.xx.xx providing details, and we will remove access to the work immediately and investigate your claim. INTEREFERENCE MANAGEMNET IN COGNITIVE RADIO NETWORKS Xxxx Xxxxxxxxx-Xxxxxxxx Centre for Telecommunications Research School of Natural & Mathematical Sciences King’s College London Doctor of Philosophy June 2013 This thesis is dedicated to my parents for their love and endless support. Acknowledgements Completing my PhD degree was probably the most challenging part of my life. The best and worst moments of my doctoral journey have been shared with many people. It has been a great privilege to spend several years in the Centre for Telecommunications Research (CTR) at King’s College London, and its members will always remain dear to me. At the end of my thesis I would like to thank all those people who made this thesis possible and an unforgettable experience for me. The highest gratitude goes to my supervisor, Xx Xxxxxxxx Xxxx Nakhai, for his support, patience, and encouragement throughout my PhD studies. It is not often that one finds a supervisor that always finds the time for listening to the little problems and roadblocks that unavoidably crop up in the course of performing research. His technical and editorial advice was essential to the completion of this dissertation and has taught me innumer- able lessons and insights on the workings of academic research in general. I could not have imagined having a better advisor and mentor for my PhD study. I am grateful to to my beloved parents; Xx Xxxxxxxx Xxxxxxxxx-Esfahani and Xxx. Xxxxxx Xxxxxx. Their love provided my inspiration and was my driving force. I owe them everything and wish I could show them just how much I love and appreciate them. I wish also to thank my brothers; Xx Xxxxx Xxxxxxxxx-Esfahani and Xx Xxxxxxx Xxxxxxxxx-Esfahani for their endless love and encouragement. I would like to thank my former colleague, Xx Xxxx Xxx Xx for his valuable assistance and support through out my PhD. Last but not least, to those who indirectly contributed in this research, your kindness means a lot to me. Thank you very much. Xxxx Xxxxxxxxx-Xxxxxxxx London, U.K. May 2013. Abstract Radio spectrum is becoming increasingly scarce as more and more devices go wireless. Meanwhile, studies indicate that the assigned spectrum is not fully utilised. Cognitive radio technology is envisioned to be a promising solution to address the imbalance between spectrum scarcity and underutilisation. Cognitive radio enables the unlicensed (secondary) user to establish a communication link in licensed (primary) spectrum on the condition that there is no or minimal interference to the primary user. The interference management has become an important topic in cognitive radio in order to manage and fulfill the regulatory constraints. The management of interference is, unquestionably, required to treat and quantify all the interference produced by the cognitive transmission at the primary users. In order to manage this interference, the secondary users must be able to adjust their parameters to fulfill these constraints. In addition, the performance of contemporary multicell wireless networks is limited by intercell interference (ICI), due to cochannel transmission in other cells. This per- formance degradation is especially severe for users close to the cell-edge. As a solution, in this thesis different cognitive beamfomring techniques are proposed by deploying cognitive cells on the primacy cells boundaries to support the primary cell-edge users as well as servicing the secondary users. This thesis proposes interference management techniques based on cognitive beam- forming in a cellular network. We have identified conditions and proposed different techniques for optimal usage of radio spectrum, by allowing coexistence on the same spectrum resources between primary and cognitive users. Deploying cognitive cells on
