動態頻譜存取之以序列為基礎的裝置偵測

Abstract

中文摘要 為了解決日益短缺的無線頻譜資源問題，美國聯邦通訊委員會（The US Federal Communications Commission）於西元2008年公布了非持照裝置可使用持照頻譜的一系列規則。根據此種新規則下的非持照裝置須使用所謂「動態頻譜存取」的新技術。此種新技術重點在於不干擾原有頻譜持照者正常使用的前提下，動態地使用原有持照者暫時不使用的頻道。由於原有頻譜持照者的動態難以掌握，很可能不預期地回到其所擁有的頻譜，導致非持照頻譜裝置間的連線可能隨時被中斷，因此在非持照頻譜裝置間建立連線並維持裝置間的連線並非如同傳統無線網路般容易。 在本論文中，我們針對非持照裝置間的裝置偵測及連線建立問題，設計了一套以序列為基礎的演算法，此演算法保證非持照裝置間的連線能快速地成功建立。根據此演算法，我們設計了一套分散式的媒體接取層通訊協定，用以提供非持照裝置間的連線建立以及頻譜存取能力。在此通訊協定中不需要任何居中協調的裝置，也不需要任何基地台。運作於此通訊協定下的非持照裝置，只要彼此之間存在至少一個共同可用的頻道，我們便能保證這些非持照裝置可以互相偵測到彼此的存在並且建立連線。最後，我們利用OPNET模擬所提出的演算法及通訊協定，並設計了多種網路環境去模擬裝置間實際的運作並分析其效能。 關鍵字：動態頻譜存取、感知型無線電、裝置偵測、連線初始化、媒體接取層通訊協定、多頻道媒體接取層通訊協定

In views of the shortage of the wireless spectrum, the US Federal Communications Commission (FCC) adopted the rules that allow unlicensed transmitters to operate in TV bands so as to more efficiently use the spectrum resource. To enable such a new type of communication, referred to as “Dynamic Spectrum Access” (DSA), unlicensed devices should avoid interfering with the licensed devices. In general, the communication between unlicensed devices is intermittent, due to unpredictable interruption from licensed devices. Therefore, establishing a communication link between unlicensed devices (i.e., neighbor discovery) and maintaining the link in the DSA-based network are not as easy in the conventional wireless networks. In this thesis, we focus on the neighbor discovery issue and propose a sequence-based algorithm to guarantee link establishment between unlicensed devices. We then design a distributed MAC protocol to realize the sequence-based neighbor discovery and the corresponding channel access. In this protocol, there is no coordinator or any other access point. The unlicensed devices are guaranteed to find each other as long as there exists one commonly available channel. We implement our protocol in the OPNET Modeler and show the performance of our protocol in various scenarios.