| Summary: | 碩士 === 國立交通大學 === 電信工程系所 === 95 === With the demand for additional bandwidth increasing due to existing and new services, both spectrum policy and communication technologists are seeking solutions for this apparent spectrum scarcity. The use of “cognitive radio” (CR) technology is viewed as the key technology to fully utilize the bandwidth. In this thesis, a CR-based dynamic spectrum access (DSA) algorithm is proposed for CR systems downlink transmission. The white space detection in WLAN spectrum and WCDMA spectrum, frequency bands switch between two spectrums and downlink radio resource allocation are controlled by CR-based DSA algorithm. The goals of CR-based DSA algorithm are throughput maximization in a fixed bandwidth. The proposed CR-based DSA algorithm dynamically decides CR systems to be active for periods of time and be quiet for another periods of time in WLAN spectrum and gives the holding time in WCDMA spectrum. In addition, it controlled the timing when CR systems shift their operational spectrum to another. Finally, a simple downlink radio resource allocation is presented to maximize the throughput of CR systems. From the simulation results, we can conclude that the CR-based DSA algorithm improve the overall throughput, reduce the idle time in WLAN spectrum and fully utilize the power resource in WCDMA spectrum.
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