陳光禎臺灣大學:電信工程學研究所彭宇正Peng, Yu-ChengYu-ChengPeng2010-07-012018-07-052010-07-012018-07-052008U0001-1610200813452500http://ntur.lib.ntu.edu.tw//handle/246246/188209感知無線電已被視為未來無線通訊發展中，增進頻譜使用效率的重要技術。為了更進一步最佳化網路使用效率，整合感知無線電系統以及現存通訊系統的感知無線電網路於是被提出。由於鏈結在感知無線電網路具有暫時可得性和單向性，可能造成網路效能下降的路由的新問題因而產生而必須加以考慮。在這篇論文中，我們從三個方面來定義路由在感知無線電網路的新問題，分別是: 路徑探索、封包遞送以及路徑維持。考慮路徑探索時，路由訊息會因為暫時性單向鏈結而被延遲甚至丟失，進而延遲整個路徑探索的時間，甚至導致其失敗。考慮封包遞送，在路徑多樣性低時封包也會因暫時性單向鏈結的影響而被延遲甚至丟失。考慮路徑維持，由於感知無線網路的鏈結有單向性，一條路徑上的每一個鏈結都必須至少有一條從下游節點往上游節點的反向路徑。由於暫時性單向鏈結造成反向路徑上封包的延遲和丟失，鏈結狀況的判斷與確認會被延遲甚至導致誤判，進而降低網路效能。在這篇論文我們定義以上三個問題並加以驗證。接著針對這些問題我們歸納出原因並提出兩個演算法來減輕問題：多重相交路徑探索演算法以及局部主動反向路徑維持演算法。Cognitive radio has been considered as a promising technology for improving spectrum utilization. To further enhance the efficiency of packets/messages transportation (i.e. network utilization), cognitive radio networks (CRN) has been proposed to integrate existing communication system/networks with cognitive radios systems/networks. Due to the temporarily availability and unidirectional properties of links in CRN, new routing problems that degrade network efficiency need to be considered. In this thesis, we define these problems from three perspectives: route discovery, packet forwarding and route maintenance. When discovering routes in CRN, the routing messages can be delayed and/or dropped by the temporarily unidirectional links, which can delay or even fail the route discovery procedure. Similar situations occur in packet forwarding when route diversity is low. When maintaining a route, the unidirectional property of CRN links makes the reverse route(s) from the downstream node to the upstream node for each link on the route necessary. Due to the delay and/or loss of feedback information on the reverse routes, the confirmation of link status can often be delayed and misled, which can degrade the routing performance. All problems are defined and verified in this thesis. Then we propose two solutions to alleviate these problems – non-disjoint multipath discovery algorithm and local proactive reverse route maintenance algorithm.誌謝………………………………………………………………………I要……………………………………………………………………IIIbstract…………………………………………………………………Vist of Figures………………………………………………………IXist of Tables………………………………………………………XIhapter 1 Introduction………………………………………………1.1 Cognitive Radio Networks…………………………………1.2 Temporarily Unidirectional Links in CRN………………8.3 Organization…………………………………………………10hapter 2 Preliminaries……………………………………………11.1 Dynamic Source Routing (DSR)……………………………11.1.1 Basic Route Discovery……………………………………12.1.2 Basic Route Maintenance…………………………………15.1.3 Properties of DSR…………………………………………18.2 Ad-hoc On-demand Distance Vector (AODV)……………23.2.1 Basic Route Discovery……………………………………24.2.2 Basic Route Maintenance…………………………………27.2.3 Properties of DSR…………………………………………27hapter 3 Challenges of Applying Ad Hoc Routing Protocols in Cognitive Radio Networks………………………………………31.1 Assumptions…………………………………………………32.2 Route Discovery Delay and Loss…………………………33.2.1 Problem Description………………………………………33.2.2 Problem Verification………………………………………36.3 Inevitable Delay of Packets Forwarding on Node-Disjoint Routes…………………………………………………45.3.1 Problem Description………………………………………45.3.2 Problem Verification………………………………………46.4 High Link Status Confirmation Delay…………………49.4.1 Problem Description………………………………………49.4.2 Problem Verification………………………………………52hapter 4 Proposed Solutions………………………………………55.1 Non-disjoint Multipath Discovery Algorithm…………55.2 Local Proactive Reverse Route Maintenance Algorithm………………………………………………………………64hapter 5 Conclusions and Future Works…………………………67ibliography……………………………………………………………69736620 bytesapplication/pdfen-US感知無線電網路網路使用效率路徑探索封包遞送路徑維持Cognitive radio networksNetwork efficiencyRoute discoveryPacket forwardingRoute maintenancethesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/188209/1/ntu-97-R95942089-1.pdf