隨著無線網路技術的不斷進步，人們對無線網路的需求與使用度大幅的增加，然而，可用的頻譜資源並沒有相對地增加，於是相對地，頻譜變得越來越稀少、珍貴。美國聯邦通訊委員會(FCC)和電機電子工程師學會(IEEE)有鑑於此問題的嚴重性與迫切性，均開始發展感知無線電網路技術並制定其規格，希望能藉此提高頻譜的使用效率，同時增加系統的總傳輸量。 感知無線電的使用者可以在不影響授權的使用者的情況下使用其頻譜。當授權的使用者要使用其頻譜時，感知無線電的使用者則需歸還此資源。為了繼續用無線網路傳輸資料，感知無線電的使用者會更換其傳輸的頻率，此頻率交遞的過程所花的時間會讓使用者的服務有所停頓。為了讓使用者的服務品質更好、達到更佳的無縫交遞，本論文提出一種頻譜管理和頻率交遞的機制，以降低頻率交遞所需的時間，達到更好的服務品質。As the developing of science and technology, the need of wireless network is becoming huger. However, the spectrum resources do not increase, therefore, the spectrum resources in contract become rarer. In considering of the seriousness and the urgency of this problem, FCC and IEEE start to develop Cognitive Radio Technology and make the standards, hoping to use this new technology to increase not only the utilization of spectrum but also the total throughput of the system. Cognitive Radio Users can use the spectrum under the circumstances that they do not influence Licensed Users. When Licensed Users need to use the spectrum, Cognitive Radio Users should release the resources. In order to continue wireless network transmission, Cognitive Radio Users would change their transmission frequency, the time spent in spectrum handoff would break the user’s transmission. In this thesis, a spectrum management and spectrum handoff scheme is proposed to reduce spectrum handoff time for better QoS.
