Browsing by Author "Fajemilehin, Temitope"
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Item Improved energy detection algorithm for cognitive radios in cooperative spectrum sensing(Published by Faculty of Communication and Information Science, University of Ilorin, Ilorin, Nigeria, 2019-05) Fajemilehin, Temitope; Olatunji, Samuel; Opadiji, JayeolaBackground: The performance of algorithms used in white space detection in cooperative spectrum sensing is largely dependent on the sensitivity of the cognitive radios used. The sensitivity of the radios is measured in terms of the probability of missed detections and probability of false alarms. Aim: This work is aimed at improving on the detection sensitivity of the Conventional Energy Detection (CED) algorithm while preserving its simplicity. Method: The detection performance of the CED was improved by avoiding the misdetections caused by instantaneous signal energy drops through the use Modified Energy Detection (MED) and Improved Energy Detection (IED) algorithms in cooperative spectrum sensing. Results: The IED scheme proposed reduces the false alarm ratio of the MED scheme while preserving the detection performance improvement attained with respect to the CED method. With a probability of false alarm at 0.1, the MED algorithm increases the CED detection probability from 0.2 to 0.4, while the IED algorithm increases the probability of detection to 0.8, in poor channel conditions where the CED performs unreliably. This fulfils the objective of improving the sensitivity of energy detection in cooperative spectrum sensingItem Optimizing Energy Utilization in Unequally Spaced Linear Array for Smart Antenna(Faculty of Engineering, University of Maiduguri, 2019) Fajemilehin, Temitope; Opadiji, Jayeola; Olatunji, SamuelRadiation in unwanted patterns, energy wastage and reduction are caused by high side lobe levels in a radiation pattern. This in turn affects the overall performance of the antenna. The purpose of this work is to improve the performance of a smart antenna by optimizing the radiation pattern using genetic algorithm. Optimal antenna parameters that would minimize side lobe level were obtained using genetic algorithm. Simulations were carried out to determine the impact of the increase in inter-element spacing on array factor and beamwidth using the optimal antenna parameters. The optimal arrangement of inter-element spacing and number of elements in unequally spaced antenna elements were then considered. The array factor model for a uniform linear array of elements was used with the aim of obtaining the optimum weights that would give a radiation pattern with reduced side lobe level. It was observed from the results for unequally spaced linear arrays, using all the possible configurations, that non-tapered arrangement gave the best improvement in the side lobe level. The outcome of this improvement is an optimized radiation pattern which is expected to aid the reduction of radiated power wasted in the side lobes of linear arrays in antenna systems.Item Performance evaluation of equally spaced linear array antenna by optimizing the radiation pattern using two optimization techniques(Published by IEEE Nigeria, Computer Science Section, 2019) Opadiji, Jayeola; Fajemilehin, Temitope; Olatunji, SamuelHigh side lobe levels in a radiation pattern often lead to unwanted patterns of radiation, energywastage 10 and reduction in the overall performance of the antenna. This research work aims to improve 11 theperformance of a smart antenna by optimizing the radiation pattern usingvarious approaches. This was 12 done by obtaining the optimum weights that givea radiation pattern with reduced side lobe level (SLL). 13 Least Mean Squares (LMS) Algorithm and Genetic Algorithm (GA) were used to determine the optimal 14 antenna parametersthat would minimize side lobe level. Simulations were carried out to determine the 15 effect ofincrease in inter-element spacing on array factor and beamwidth using the optimal 16 antennaparameters. It was observed from the results, that for the same number of elements, LMS gave the 17 better outcome in form of a more reduced beamwidth while GA performed better for the reduction of the 18 side lobe level. This translates to the reduction of radiated power wasted in side lobes for linear arrays in 19 antenna systems.Item Reduction of Computational Time for Cooperative Sensing Using Reinforcement Learning Algorithm(Published by IEEE Nigeria, Computer Science Section, 2019) Olatunji, Samuel; Fajemilehin, Temitope; Opadiji, JayeolaCooperative spectrum sensing in cognitive radio systems is characterized by high computational time for decision making due to the fusing of individual decisions of cognitive radios involved in the cooperative scheme. This increases the communication overhead of the network. In this paper, an adaptive cooperative spectrum sensing algorithm is developed with improved detection algorithm. Reinforcement learning is thenincorporated to improve the decision making efficiency of the cooperative spectrum sensing such that less time is required to make a decision at the fusion centre. Three temporal difference learning techniques were compared in order to select the most efficient to reduce sensing and decision delays. Appropriate learning rate was utilized in the sensing and decision making algorithm to enhance the performance ofthe adaptive cooperative spectrum sensing. Results reveal significant reduction in the computation time required in cooperative spectrum sensing and decisions. This permits greater efficiency in dynamic spectrum management as the limited electromagnetic spectrum is being utilized for telecommunication services.