因為近年來無線網路使用者大幅增加的緣故, 導致頻譜資源嚴重缺乏。
為了解決這個問題, 感知無線電(cognitive radio, CR)受到許多關注, 用於提升頻譜(spectrum)使用率。
為了改善靜態頻譜分配所造成的頻譜使用率低落的問題, 感知無線電引進了次要使用者(secondary user, SU), 在不影響到主要使用者(primary user, PU)
的情況下使用頻譜, 藉以達到提升頻譜使用率的目的。
為了不干擾到主要使用者, 一般來說次要使用者需要進行感測(sensing)來得知主要使用者的使用情形,
因此感測的所需時間及正確性變成感知無線網路研究的重要課題。
本論文為了使次要使用者獲得較高的服務品質 (Quality of Service, QoS),
設計了一些基於IEEE 802.11標準, 能使次要使用者在不進行感測的情況下, 獲得各使用者使用頻譜時間的機制。
並且能夠在只針對主要使用者增加一點干擾的情況下, 延長次要使用者使用頻譜的時間。
透過模擬結果顯示, 本論文所提出的機制能降低次要使用者傳輸時被中斷的可能性, 達到提升次要使用者服務品質之目的。

Because of number of wireless network users increase in recent year, spectrum source become lack.
To solve this problem, Cognitive Radio which got much attention could enhance the spectrum utilization.
In order to improve the low spectrum utilization problem which caused by static spectrum allocation,
Secondary Users come to system which use spectrum without affecting Primary Users,
In this way it can upgrade spectrum utilization .In order not affect Primary Users,
Secondary Users should sense the state of Primary Users in general.
Therefore, sensing time and sensing accuracy become the important issue of cognitive radio network.
In this paper, in order to upgrade higher QoS of Secondary Users,
we design a mechanism without sensing to know the transmission time of users based on IEEE 802.11.
Our scheme can extend the transmission time of Secondary Users which increase a few interference to Primary Users.
Simulation results show that our scheme can decrease the probability of Secondary User's interruption and
increase the QoS of Secondary User.

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