在802.11無線網路下感知網路中同步感測頻道與使用之研究

Abstract

有許多新的議題在感知網路中被討論，其中一項就是頻道感測與頻道存取。在本篇論文中，我們提出了一套在802.11 無線網路環境下感知網路中的同步頻道感測與存取。此套機制包含了兩種階段：快速頻道感測及主動釋放頻道。快速頻道感測是針對一對感知網路使用者找尋可使用的頻道；主動釋放頻道是讓感知網路使用者察覺主要使用者要使用頻道時，能快速的釋放頻道給主要使用者，避免干擾。我們更利用頻道跳躍序以減少平均頻道感測時間。我們更進一步利用二維馬克夫鍊去分析且評估感測網路之效能。經由理論值與模擬值的結果，我們所提出的方法，可以有效的利用頻道及減少主要使用者的等待時間。

One of the most challenging issues in cognitive radio systems is channel sensing and channel accessing. In this paper, a synchronized channel-sensing and accessing for cognitive radio users in IEEE 802.11 wireless networks is proposed. The mechanism consists of two phases: fast channel sensing and proactive channel vacating. Fast channel sensing is for a pair of cognitive radio users to search an available channel time-efficiently; proactive channel vacating is for the pair of cognitive radio users to be aware of the presence of primary users and vacate the occupied channel as quick as possible. We utilize the concept of channel hopping to reduce the average channel sensing time of cognitive radio users. Besides, through the designed interruption mechanism, cognitive radio users can create opportunities for primary users to claim the spectrum and thus minimize the caused interference to primary users. We further analyze and evaluate the performance of a considered cognitive radio network through a two-dimensional Markov chain and simulations. From the analytical and simulation results, our proposed protocol can efficiently balance the tradeoff between throughput performance of a cognitive radio network and waiting time of primary users to claim channels.