雙網手機於無線網路之品質服務保證之設計與實作

Abstract

近年來由於無線網路佈建的普及化以及網路電話如skype等的蓬勃發展，內建Wi-Fi晶片的雙網手機不再只是利用無線網路來上網，一項殺手級的應用正逐漸受到大眾的青睞，這個殺手級的應用即是”利用無線網路撥打網路電話”。 利用無線網路撥打網路電話主要的好處如下： 1.節省電話資費 2.擴展電信網路的涵蓋範圍 3.設備費用較為低廉 基於上述理由，學界以及業界對於這項新的應用十分感興趣。然而這項應用仍有許多的技術瓶頸需要克服，其中最迫切的一項就是”語音品質的保證”。 相對於行動電話系統的語音封包擁有特定的頻道，無線網路的語音封包必須與其他封包例如資料封包以及視訊封包一同競爭頻寬，因此在無線網路中語音的品質遠差於行動電話系統的語音品質。在這篇論文中我們提出一個機制來解決這個問題，同時我們將這個機制加以實作並驗證這個機制的成效。在驗證的結果中，我們證明了這個機制不但有效並且易於實作。

Owing to the rapid growth of Wireless Local Area Network (WLAN) and Voice over Internet Protocol (VoIP), dual-mode handheld which is embedded with Wi-Fi chip is not only used for accessing the Internet via WLAN. A new killer application which is Voice over WLAN (VoWLAN) is gradually favored by people. The major advantages of VoWLAN are as follows. 1.Save telecommunication bills 2.Expand the coverage of telecommunication 3.Save the cost of telecommunication deployment For the above reasons, this application has attracted much interest from academia and industry. However, there are still many constrains in this application. Among these constrains, the provision of Quality of Service (QoS) is considered as the most emergent one. Unlike cellular networks where dedicated channels are assigned to voice traffic, voice packets in WLANs are multiplexed with best effort traffic. Therefore, quality of voice in WLANs is much worse than cellular networks. In this thesis, we proposed a mechanism to solve this problem. The mechanism is implemented and verified practicable at the same time. We also proved that this mechanism is simple and easy for implementation by the result of verification.