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Title: Cross-layer design and optimization of OFDMA-based cognitive radio networks
Author: Saki, Hadi
ISNI:       0000 0004 5368 2623
Awarding Body: King's College London
Current Institution: King's College London (University of London)
Date of Award: 2014
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Increasing demand and sophistication of wireless applications require intelligent systems which, along with performing efficient and reliable adaptive operations, should be simple to implement. Cognitive radio (CR) is one such system which has the capability of adapting to its surroundings. In this thesis, the role of different layers of network in carrying out the functionalities of CR systems is investigated and cross-layer design strategies involving the physical (PHY), the media access control (MAC), and the application are proposed. This thesis makes several contributions. Firstly, we propose novel optimal radio resource allocation (RRA) algorithms under different scenarios with deterministic and probabilistic interference violation limits based on perfect and imperfect availability of cross-link channel state information (CSI). In particular, in contrast to the ‘average case’ and ‘worst case’ estimation error scenarios in the literature, we propose a probabilistic approach to mitigate the total imposed interference on the primary service under imperfect cross-link CSI. An expression for the cumulative density function (cdf) of the received signal-tointerference-plus-noise ratio (SINR) is developed to evaluate the average spectral efficiency. Through simulation results, we investigate the achievable performance and the impact of parameters uncertainty on the overall system performance. Secondly, we implement stochastic RRA algorithms in both hybrid- (i.e., mixed underlay and overlay) and opportunistic (i.e., overlay) access orthogonal frequencydivision multiple access (OFDMA)-based CR systems. The proposed solutions allocate power and subcarrier to cognitive users over wireless fading channels in order to maximize the total transmission rate based on the probabilities of channel availability obtained through spectrum sensing. In order to protect the primary service operation from harmful intervention, stochastic transmit and interference power constrains are imposed on the cognitive users. The performance of the proposed stochastic algorithms and their advantages over the conventional hard-decision-based approaches are assessed and demonstrated through simulation results. Finally a specific cross-layer design for multi scalable video application transmission in an interference-limited spectrum sharing system is proposed. The proposed design jointly considers the parameters from the PHY and the application layers in order to maximize the overall peak signal-to-noise ratio (PSNR). Results indicate that significant improvement in secondary receivers (SRxs) average video quality is achieved through our proposed algorithm over other state-of-the-art non-qualityaware (NQA) designs in the literature. The enhanced performance was obtained whilst guaranteeing SRx minimum quality and primary receiver (PRx) prescribed quality of service (QoS) constraints.
Supervisor: Shikh-Bahaei, Mohammad Reza ; Aghvami, Abdol-Hamid Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available