IEEE 802.16h 系統下使用乏晰有效週期調整之動態頻譜擷取

Abstract

由於科技的日益進步，無線通訊服務的需求量也逐漸增加，而其傳輸所需要頻寬也越來越珍貴，因此我們必須在這有限的頻寬資源中尋找出更有效的頻寬利用方法。近年來，隨著感知無線電(Cognitive Radio, CR)之提出，我們將其視為一個可以有效的使用頻寬的重要技術。 在本篇論文中，我們採用了IEEE 802.16h的機制來做空閒頻譜偵測，並且設計了一個乏晰有效週期調整器（Fuzzy Active Period Adaptor）來有效利用我們所偵測到的空閒頻譜。其主要目的是在固定頻段中提升系統整體的效能。在提出的演算法中，我們主要是以WLAN為現行運行系統的免執照頻譜(Unlicensed Band)為主要感測之頻譜，而WiMAX系統將使用感知無線電技術來作免執照頻段的動態頻譜擷取(Dynamic Spectrum Access)之動作。 從模擬的結果中，我們所提出的方法可以有效且合理的去使用所偵測到的空閒頻譜，在盡量減少干擾WLAN系統運作之前提下，有效的提升整體傳輸量並且減少頻譜的閒置資源。

With the development of communication technology, wireless communications become more important to provide convenient services. It triggers a huge demand for bandwidth for transmission. Because of the spectrum scarcity, how to use the spectrum dynamically and efficiently becomes an important issue. Dynamic spectrum access (DSA) is a promising approach to alleviate the spectrum scarcity that wireless communications face today. To provide the mechanism of DSA networks, 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) device named fuzzy active period adaptor (FAPA) is proposed in downlink transmission of IEEE 802.16h systems. FAPA decides the active period of CR system to efficiently coexist with WLAN system in 802.16h system. Simulation results show the fuzzy active period adaptation can improve the overall throughput and reduce the idle time of the spectrum with slightly interfering in the operation of the primary WLAN system.