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 the primary cells borders results to ICI mitigation for primary cell-edge users within the cognitive cell and also leads to supporting cognitive users with the same allocated spectrum to the primary network. The aim is to minimise the total transmit power across the cognitive network while maintaining the required signal-to-interference-plus-noise ratio (SINK) for all primary cell-edge/cognitive users within the cognitive cell and to mitigate the interference caused by the cognitive system towards the primary users. It forms the fundamental basis for interference management in cognitive radio systems and consequently gives insights into the design and deployment of cognitive radio net¬works. At the end, we introduce robust cognitive beamforming based on imperfect channel state information for both primary and cognitive users’ channel. These different approaches to interference management at cognitive radio networks contribute to the increasing set of techniques that will make cognitive radio possible to deploy.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:634189 |
| Date | January 2013 |
| Creators | Zarrebini-Esfahani, Azar |
| Contributors | Nakhai, Mohammad Reza ; Said, Fatin |
| Publisher | King's College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://kclpure.kcl.ac.uk/portal/en/theses/intereference-management-in-cognitive-radio-networks(afcff86d-c4ee-4cfe-80e0-9e53aad01128).html |
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