以競爭方式傳送資料之無線網路的通道使用效能之改善

Abstract

近年來無線網路技術的快速成長，進而帶動了無線網路使用者的大幅增加。而現今最成熟的無線網路技術就是IEEE 802.11，它已經可以提供足夠的頻寬去傳送即時的多媒體資料。另外一種新的無線網路技術(IEEE 802.15.4)逐漸變得成熟，IEEE 802.15.4是一種無線個人網路傳送技術，它能供提供短距離、低功率、低成本的傳輸方式。 IEEE 802.11是使用載波檢測多重存取/碰撞避免(CSMA/CA)的方式來傳送資料， 而IEEE 802.15.4是去修改原來的載波檢測多重存取/碰撞避免技術來傳送資料， 讓IEEE 802.15.4可以符合省電的要求。它們都是屬於利用競爭式的方法來傳送資料。使用競爭式的方法來傳送資料它的優點是簡單、而且公平，但是它們使用無線頻寬是沒有效率的，進而會降低無線網路系統的效能。因此我們在本篇論文中將提出數個方法去改善利用競爭式的方法去傳送資料的無線網路效能(IEEE 802.11跟IEEE 802.15.4)。另外，我們提出分析及實驗的模型去驗證在本論文中我們所提出方法的效能。我們可以從實驗結果中得知我們所提出的方法確實相對於IEEE 802.11及IEEE 802.15.4有更好的效能。

With the explosive growth of wireless subscribers, wireless communication technologies play an increasingly important role in recent years. With the development of IEEE 802.11 WLAN techniques, wireless network bandwidth has gradually become su±cient for many multimedia applications. Furthermore, the emergence of short-transmission- range wireless devices further boosts the development of wireless personal area networks (WPANs). When low cost and low power-consumption are considered, IEEE 802.15.4 emerges as a good alternative WPAN. To transmit data frames, both of wireless communication technologies (i.e., IEEE 802.11 and 802.15.4) utilize contention scheme to access channel. The carrier sense multiple access/collision avoidance (CSMA/CA) and modify CSMA/CA mechanism are utilized in contention-based of IEEE 802.11 and IEEE 802.15.4 for access channel, re- spectively. However, the contention-based wireless networks encounter some problems and result in pretty bad channel performance. This dissertation proposes some schemes to improve the channel performance of contention-based wireless networks. Our schemes can solve the bottleneck of contention-based wireless networks under di®erent wireless communication technologies. Furthermore, we develop the analytical model and simula- tion model to investigate the performance of our schemes. The numerical results indicate that performance of our schemes is superior to IEEE 802.11/IEEE 802.15.4 standard.