IEEE 802.11 無線區域網路 MAC 層上可靠群播協定之設計與分析

在IEEE 802.11無線區域網路(Wireless LAN)中，並沒有提供可靠的群播(multicast)機制。然而隨著無線區域網路的日益發達，群播的應用也愈顯重要。因此，提供無線網路使用者良好且可靠的群播服務將是當務之急。群播指的是由發送端將資料一次傳給多個使用者。無線區域網路本身即是運用廣播(broadcast)的特性來傳送資料給特定的使用者，所以群播特別適用於無線區域網路上。然而，當發送端傳送群播資料時，如果每一個接收端都回傳確認訊息(ACK)給發送端的話，則會在發送端產生碰撞(collision)，因此發送端就無法確認群播接收者是否已成它洧鼽禤ヾC所以在無線區域網路中，群播接收者是不必回傳確認訊息的，意即無線區域網路對群播資料沒有提供任何可靠度(reliability)的保障。在這篇論文中，我們提出了三種可靠的群播協定，使得無線區域網路的群播可靠度受到了保障。這三種協定分別是(1)以確認為基礎的群播協定(ACK-based Multicast Protocol, AMP)。(2)以領導者為基礎的增強型群播協定(Enhanced Leader-Based Protocol, ELBP)。(3)以負確認為基礎的群播協定(NAK-based Multicast Protocol, NMP)。這三種協定不僅提供可靠的群播服務，而且可解決隱藏性節點問題(hidden terminal problem)。我們也分析了這三種協定在無線網路存取點(Access Point, AP)的群播訊框停留時間(frame holding time)。經由模擬的驗證，可得知我們的分析方法適當且精確地描述了群播系統的運作。

關鍵字

可靠群播； IEEE 802.11無線區域網路

並列摘要

There is no reliable MAC-layer multicast in IEEE 802.11 wireless LANs (WLANs). In recent years, WLAN has been a popular architecture, and thus providing reliable multicast to wireless users is an important issue. Multicast refers to the mechanism that a sender transmits data to multiple receivers. In nature, stations transmit data by means of broadcasting in WLANs. Therefore applying multicast to WLANs is proper and efficient. However, a collision will occur if each multicast receiver immediately sends an ACK to the sender; so that the sender cannot recognize whether each receiver has received the data successfully. As a result, each multicast receiver will not send an ACK in reply, i.e., no reliability is guaranteed to multicast data in WLANs. In this thesis, we propose three reliable MAC-layer multicast protocols to guarantee multicast reliability for IEEE 802.11 WLANs. They are: (1) ACK-based Multicast Protocol (AMP), (2) Enhanced Leader-Based Protocol (ELBP), and (3) NAK-based Multicast Protocol (NMP). These three protocols not only provide reliable multicast but also solve the hidden terminal problem. We further analyze these three protocols in terms of the frame holding time at AP. The simulation results show that our analytical methods are proper and provide a good description for the proposed mechanisms.

並列關鍵字

IEEE 802.11 Wireless LAN ； reliable multicast

參考文獻

[1] IEEE 802.11 Working Group, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, ANSI/IEEE Std 802.11, 1999.

[3] D. F. Towsley, J. Kurose and S. Pingali, “A Comparison of Sender-Initiated and Receiver-Initiated Reliable Multicast Protocols,” IEEE Journal on Selected Areas in Communications, vol. 15, no.3, pp. 398-406, Apr. 1997.

[4] G. Bianchi, “Performance Analysis of the IEEE802.11 Distributed Coordination Function,” IEEE Journal on Selected Areas in Communications, vol. 18, no. 3, pp. 535-547, Mar. 2000.

[6] B. Whetten and G.Taskale, "An Overview of Reliable Multicast Transport Protocol II," IEEE Network magazine, vol. 14, no. 1, pp.37-47, Jan./Feb. 2000.

[8] E. M. Royer and C. E. Perkins, “Multicast Operation of the Ad hoc On-Demand Distance Vector Routing Protocol,” Proc. of MobiCom, pp. 207-218, Aug. 1999.

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IEEE 802.11 無線區域網路 MAC 層上可靠群播協定之設計與分析

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