在NCTUns 網路模擬器上支援IEEE 802.11 無線感知網路並進行效能評估

Abstract

隨著無線網路愈來愈深入的研究與探討，目前可為人所用的無線網路傳輸之協定與其所使用之頻譜也隨之增加。根據現有的頻段用途與其分配方式，部份頻段需要經過申請執照的程序後才可使用。但在目前現有的研究就指出，並非所有頻段皆被充份的使用，這種情況在需要頻段使用執照的頻段更為明顯。因此，在近年來開始發展出一套稱作無線感知網路的技術，透過這種技術，無線感知網路的使用者可以在不干擾其他頻段的主要使用者來進行該頻段的使用；而當該位主要使用者欲使用此頻段時，無線感知網路的使用者便會主動退讓，使主要使用者在頻段的使用上不受干擾。 然而，在現階段對於無線感知網路的研究中所擁有的測詴工具並不多，而且對於更高層的網路通訊協定之應用程式的支援也相當的有限，使得研究人員在驗證上難以利用更為複雜的情境來進行效能的評比。因此，本篇論文主要將透過NCTUns 這套網路模擬器來進行平台的開發，並從目前既有的無線感測網路的相關研究進行實作，以提供給研究人員一套完整的無線感測網路之模擬環境，藉此能夠在沒有實體設備的狀況下進行通訊協定的開發。此外，本文也將基於該無線感測網路之通訊協定，從隱匿終端機問題的角度進行分析，並且對此通訊協定進行改善，期望能藉此使其效能提升。

According to a report about the utilization of spectrum, not all the range of spectrum is fully utilized, especially in licensed bands. In order to solve this problem, the concept of cognitive radio is proposed. Cognitive Radio is a technique which allows cognitive radio users to use channels that are not owned by them without interfering the primary users of channels. In other words, when a cognitive radio user is using a channel without any authorization, it should switch to other channels immediately if a licensed user wants to use this channel so that the licensed user will not be interfered by the cognitive radio users. Nowadays, simulators that can support the research of cognitive radio networks are very rare. In addition, most of them can only simulate the physical and MAC layers of a cognitive radio network and lack the ability to simulate a cognitive network with high-layer protocols such as TCP/IP. In this thesis, we implement an IEEE 802.11 cognitive radio module on the NCTUns network simulator so that researchers can use it as a base to test their novel ideas. We also study the effects of hidden-terminal scenarios on the performances of cognitive radio networks and propose several enhancements to the basic scheme to improve its performances under hidden-terminal conditions.