透過無線區域網路提供語音服務已成為一個相當重要的網路服務，相較於傳統公眾電信交換網路(Public Swhiched Telephone Network, PSTN)，利用IP網路提供語音服務(Voice over Internet Protocol, VoIP)可以大幅地降低通訊成本。然而現有的IEEE 802.11b無線網路所能提供的話務量(voice calls)極為有限，因此如何讓IEEE 802.11b無線網路在不影響數據服務之下提供更多的話務量，是一個相當重要的議題。
本篇論文中，我們延續多重存取資源預留(Packet Reservation Multiple Access, PRMA)的方法，提出『非集中式多重存取資源預留』(Decentralized Coordination Packet Reservation Multiple Access, DC-PRMA)的機制，將無線網路的資源以時間為依據，劃分成許多的超訊框(superframe)，而每一個超訊框又劃分成語音與資料兩個部分，語音部分提供語音的資源預留，資料部分則依循IEEE 802.11的分散式資源存取(Distributed Coordinator Function, DCF)方式。DC-PRMA除了致力於提供更多的話務量外，我們也考慮到無線網路現存的問題與特性，如：行動台(mobile nodes)因地域不同的關係，產生隱藏點的問題(hidden terminal problem)、行動台因通訊品質的差異性而使用多種傳輸率(multi-rate characteristic)。經由模擬的結果，相較於IEEE 802.11b的資源存取機制，我們可以看出本機制能提供較多的話務量(voice calls)與較好的語音品質，因此DC-PRMA比IEEE 802.11b的資源存取方式更適合於無線區域網路中提供語音服務。

Voice over Internet Protocol (VoIP) in wireless local area network (WLAN) is an emerging Internet application. VoIP services provide lower cost than Public Swhiched Telephone Network (PSTN).
This thesis proposes the Decentralized Coordination Packet Reservation Multiple Access (DC-PRMA) scheme to increase the number of voice calls that can be supported in WLAN. DC-PRMA extends the concept of the Packet Reservation Multiple Access (PRMA) in WLANs. In DC-PRMA, wireless channel is divided into superframes. A superframe is the composite of voice phase and data phase. Voice phase provides reservation resources for voice users. Users in data phase access channel by the Distributed Coordinator Function (DCF) mechanism. Consider the potential hidden terminal problem and multi-rate characteristic in WLAN, an adaptive slot reservation is employed in DC-PRMA. The performance of DC-PRMA is investigated by computer simulations in comparison with legacy IEEE 802.11. The results show that the DC-PRMA scheme can indeed provide more voice calls than legacy IEEE 802.11 while the QoS requirements of voice calls are guaranteed.

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