感知無線網路之動態頻譜接取與空閒資源偵測

Abstract

隨著既有與新興無線通訊服務的增加，對於頻寬的需求量也日漸提高，然而頻寬資源卻是有限的，對此問題大家已經開始尋求更有效的利用頻寬之方法。而感知無線電(Cognitive Radio)被視為一個可以有效的使用頻寬的重要技術。 在本篇論文中，我們提出了一個感知無線電式的動態頻譜接取(Cognitive Radio-Based Dynamic Spectrum Access)演算法來提供感知無線電系統之下鏈路資料傳送。此演算法控制了包含空閒頻譜資源偵測、頻譜切換與下鏈路無線通訊資源分配。其主要目的是在固定頻段中提升整體的傳輸量。在提出的演算法中，我們針對兩段頻譜來做空閒頻譜偵測，包含了以WLAN為現行運行系統的免執照頻譜與需要執照的WCDMA頻譜，根據這兩個系統的特性，我們設計了各自的空閒頻譜偵測演算法。此外，我們還控制感知無線電系統在此兩個頻段上做切換的控制機制。最後我們提供了一個簡單的下鏈路無線通訊資源分配方法來最有效的提升感知無線電系統的傳輸量。從模擬的結果可以顯示出來我們所提出的方法，可以減少閒置的頻譜資源，有效的提升整體傳輸量，得到最佳的頻譜使用效率。

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.