Power Control Technique in Cognitive Radio Networks Using Smart Antennas

對於頻帶主要使用者和感知無線電使用者共存，而且同時傳輸的主題，引起研究興趣，在無線環境中智慧型天線使用指向式的方法避免干擾不在指向範圍內的節點，並藉由智慧型天線的指向增益節省功率而改善通訊系統品質。在共存系統中，因為感知無線電傳輸對避免在互相干擾的區域中通訊，所以不同傳輸對間所產生的干擾低於可容忍的臨界值，不同的傳輸對可以互相通訊，而將互相干擾之區域稱之禁止傳輸區域。 功率控制在消除干擾上也是十分重要，本論文中結合功率控制與智慧型天線，可行性研究中指出在禁止傳輸區域和特定的拓樸外，頻帶主要使用者與感知無線電使用者可同時傳送，使用功率控制更可解決有些在禁止傳輸區域中，所面對到的問題，讓成功解碼律增加。在此研究中也談到了通道不對等和位置不確定性的所造成問題。The co-existence and simultaneous transmission for primary users and cognitive radio users in the cognitive network attract the researching interesting. The smart antenna technology has been widely adopted in wireless environment to prevent the interference outside the expected transmission direction together with advantage of power saving by antenna directional gain to improve the system communication quality. That is intuitively witness that the different transmission pairs can communicate once when those interference among transmission pairs below the tolerance threshold since cognitive radio users do not transmit in the mutual interfering area, called restricted area . Power control is another popular mechanism to reduce the interference. In this thesis we combine the concepts of smart antenna and power control. The feasibility study demonstrates the simultaneous transmission scenario among primary users and cognitive radio users when they locate at spectacular topology or not within the restricted area. Power control can further solve some problems which met in restrict area to increase the successful decodable rate. The channel mismatch and location uncertainty are also studied in this research