802.11e無線區域網路下之跨階層VoIP應用程式控制系統

Abstract

近幾年來VoIP服務深受到人們的喜愛，成為重要的應用服務。而由於無線網路的行動特性，人們在無線網路上使用VoIP服務更為方便。在目前常見的無線區域網路中，IEEE 802.11e無線區域網路可以提供VoIP較為良好的服務品質，但未考慮到無線頻道狀況改變帶來的影響，它需要一個調變機制來補足這一點。因此，在本篇論文中，我們實作出一個可隨著無線網路頻道訊號的狀況調變的VoIP應用程式。除此之外，我們也實作出一個具管理策略的802.11e無線區域網路，以保證有申請服務之使用者權益。最後的實驗結果顯示使用可調變的VoIP應用程式會比傳統的固定式VoIP應用程式擁有更好的效能。

In the recent years, Voice over Internet Protocol (VoIP) is the most popular technology and will be a kind of killer application. Since Wireless Local Area network (WLAN) has a characteristic of mobility, people who use VoIP over WLAN can be more convenient. In the WLAN, IEEE 802.11e can support VoIP with better Quality of Service (QoS). However, 802.11e doesn’t consider the time-varying condition of wireless channel. It needs an adaptive mechanism to complement it. Thus, in this thesis, we implement a cross-layer adaptive VoIP application which can use a suitable codec according to current channel condition. Besides, we also implement a policy-based 802.11e WLAN to protect the right of user who has applied real-time services. The experiment results show the proposed cross-layer adaptive VoIP application can archive better performance than the fixed one.