本篇論文之研究架構於覆蓋式(Overlay)感知無線電上的合作式通訊系統，此系統中擁有一組主用戶(Primary user)及多組次用戶(Secondary user)，次用戶的傳輸功率是來自於主用戶傳輸時所發送的訊號能量進行能量採集而獲取，且次用戶將扮演中繼點的角色，幫助主用戶傳輸訊號，同時也藉機傳送自身資料。在本篇論文的系統傳輸中，將會選擇一組最佳的次用戶幫忙主用戶進行資料的傳輸，其餘的次用戶持續將進行能量採集，而被選出的最佳次用戶則是以解碼後轉送(Decode-and-forward, DF)的方式幫助主用戶傳遞訊號，主用戶藉由次用戶幫忙可增加主用戶的空間分集(spatial diversity)，因而可降低其發生中斷的機率，提升傳輸可靠度。本論文的目的為在確保主用戶的傳輸品質(Quality of service, QoS)下，盡可能的為次用戶爭取最大傳輸率。本系統中，次用戶的傳輸功率，將取決於它持續累計之採集能量，而當施行合作傳輸時，我們將針對次用戶的傳輸將進行功率分配設計，選出得以滿足上述條件的最佳次用戶，被選出的最佳次用戶將成為主用戶的傳輸時的中繼端，並利用其相對應的功率分配值，協助主用戶進行傳輸，同時分享主用戶的頻譜資源傳送自身訊號，增進頻譜使用效率，也提升次用戶的傳輸率。最終，我們將以電腦模擬圖呈現，本論文所提出的系統能在確保主用戶的傳輸品質下，隨著次用戶數目的增加，主用戶發生中斷的機率降低，次用戶傳輸率也獲得提升。

This thesis investigate in overlay cognitive radio network with cooperative communication. In this system, we consider a pair of primary user and multiple secondary users. Secondary users of transmission power harvest from signal transmitted by primary user and then secondary user will plays the role of relay to help primary user transmission and transmits its own data. We select the best secondary user to help primary user transmission and the other secondary users will continue to harvest energy. The best secondary user adopts decode-and-forward to help primary user transmission message. When the best secondary user assist primary user transmission, it could increase the primary user's spatial diversity. Thus, the outage probability of primary user can be reduced and the transmission reliability can be increased. This thesis aims to ensure the primary user's transmission quality of service and then promote secondary user's transmission rate. In this system, secondary user's transmission power depend on the duration harvesting of energy. We propose the power-allocation scheme at the secondary transmitter to get the best secondary user. The best secondary transmitter which we choose act as primary user's relay at the cooperative transmission. We will use the corresponding power allocation value to assist primary user transmission and transmit own data; therefore, it can boosts spectrum utilization effectively and improves secondary user's transmission. Finally, we employ computer simulation to show the proposed scheme. When the secondary user be increased, the outage probability of primary user can be reduced and secondary user's data rate can be increased.

論文審定書 i
致謝 ii
摘要 iii
Abstract iv
目錄 vi
圖目錄 vii
第一章.簡介 1
第二章.相關背景 6
2.1 感知無線電 6
2.2 合作式通訊 8
2.3 前人的研究 10
第三章.系統模型 11
3.1 傳輸模式 12
3.2 主用戶的傳輸狀態良好 13
3.3 主用戶的傳輸狀態不佳 15
第四章.次用戶資料傳輸分析與功率分配設計 18
4.1　主用戶的傳輸狀態良好時之資料傳輸分析 18
4.2　主用戶的傳輸狀態不佳時之資料傳輸分析 19
4.2.1 次用戶扮演中繼點之功率分配設計 20
4.3　演算流程 26
第五章.模擬結果與討論 29
第六章.結論 36
參考文獻 .37

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