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|Title||Spectrum Handoff Strategies in Cognitive Radio Networks|
Today, Cognitive Radio (CR) have a promising solution to both spectrum inefficiency and spectrum scarcity issues by enabling secondary users (SUs) to exploit the idle frequency bands temporarily in opportunistic manner as long as the primary users (PUs) do not occupy their spectrum. The SUs must vacate these frequency bands when the PUs come back and reuse them. This is one of challenge in CR technology. In this case, the communication links of the SUs must be finding another idle frequency bands to resume their communication links. This is called spectrum handoff which is affecting to the performance of system by main factors such as: link maintenance probability, the number of spectrum handoff, switching delay. Spectrum handoff may be happen more than once for a wide range of the spectrum available in CR. This switching change the characteristics of propagation transmission loss which is affects the overall system performance. Thus, in this thesis, the path loss and coverage area are essential factors studied to enhance the system performance and make it more immune to propagation losses. In this dissertation, we aim to overcome these issues by proposing a systematic selection method to select and assign new appropriate frequency channels efficiently to achieve a better transmission performance. Additionally, the adaptation power technique is applied in order to control base station transmitted power and estimate the appropriate coverage area to reduce and avoid interference and also to conserve power dissipation in the system. The combining of these approaches, selection method and power adaptation, is found to be helpful to achieve an efficient spectrum utilization, reduce power consumption, maintain the connectivity link, decrease the number of spectrum handoffs from failure which are very important to improve overall system performance. The simulation results show a comparison of the proposed strategy with other techniques by increasing the wide of frequency switching up to 70% and also studies the effect of the adaptation technique on the system performance.
|Publisher||الجامعة الإسلامية - غزة|
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