一個WiFi群播串流之QoS回饋與改良機制研究

Abstract

隨著網路技術的日新月異，無線網路的使用者越來越多，近幾年無線區域網路也變得非常熱門。隨著越來越多手持裝置的需求，我們可以藉由無線區網網路擷取各種不同的服務，而此種服務也很廣泛的運用在大學校園、機場、車站或是一些觀光景點。 當我們要傳送相同的資訊給眾多的使用者時，考慮到資料傳輸的效率，群播服務是一個適當的選擇。但由於群播服務的封包並不會被回報給發送端，發送端無法準確的掌握各個使用者的情況。因此當有些使用者遠離了無線區域網路的傳輸範圍時，發送端也無法得知。 在本篇論文中，我們一開始介紹第二層無線網路下的群播服務。再者我們會提出幾個問題與提供解決方式，我們提出的架構有下列特色:(1) 實作回饋機制服務。(2) 增進發送端對於群播服務的整體感知。(3) 藉由群播回報的傳送功率動態調整發送端的傳送功率。(4) 尋找合適的群播接收者的收訊範圍。在這篇論文中，我們在無線區域網路中提出新的群播搭配回饋技術以及相關的運作媒體存取控制(MAC)層訊息，然後比對一般傳統方式和討論可適當增加的接收範圍與其效能改進。

The Internet access through wireless network becomes more and more popular. In recent years, wireless local-area network (WLAN) users are also growing quickly due to the rapid development of the mobile devices. With this development of wireless network, we can enjoy various advanced services using our mobile device. These services are common in the area of university campus, airport, transportation stations, or tourist sites. The use of the wireless local-area network service has been spread extensively. However, to send the same media stream to multiple receivers, we need to consider the efficiency of the data transmission, and multicast is a candidate solution. Since the multicast packets will not be acknowledged, there is no way to evaluate the efficiency of the data delivery service in the wireless network. Furthermore, if some of the users are leaving the coverage area of the WLAN, the sender would not be noticed. In this thesis, we first review wireless layer-2 multicast communications, then we raise several issues and propose solutions to these problems. Our proposed architecture features the following characteristics: It (1) implements acknowledgement for multicast communications, (2) improves overall network awareness on WLAN multicast, (3) find member transmission power and do server power-adjustment, (4) increases the coverage for all members. We also show and compare the traditional methods and discuss the appropriate techniques as much as possible. Consequently, we propose new method based on X-beacon mechanism and corresponding MAC management messages, we then applies the proposed method to Wireless-LAN network and evaluate their performance improvement.