臺灣博碩士論文加值系統

載波感測多重擷取 (CSMA) 被廣泛的應用在無線行動隨建即連網路上。IEEE 802.11亦使用載波感測多重擷取及衝撞避免 (CSMA/CA) 的支術。但傳統的IEEE 802.11 基本的分散協調式功能 (Distributed Coordination Function，DCF) 並不支援即時多媒體的傳送。換句話說，IEEE 802.11 媒介存取控制的基本擷取方法無法保證即時資料的時限性，儘管是具有時限性的資料封包，一樣必須和一般的資料封包進入競爭視窗 (Contention Windows，CW) 來競爭頻道的使用權。
在這一篇論文中，我們提出了一個分散式的媒介存取協定。它能提供以優先權為主的多媒體存取協定。首先，每個網路成員若有資料要傳送須競爭頻道時，會先進入一個優先權機制來決定出相對最大的優先權。在此之後具有相同最大的成員們會再進入獲得傳送順序數字的機制，來得到唯一的順序號碼。一旦有了這個傳送順序，便可輪流來傳送資料。而具時限性封包要傳送的網路成員，則可依據此順序號碼來持續傳送封包，來限制資料封包的延遲時間。最後模擬的結果可是驗證我們定的協定可以有較佳的使用率和較少的平均封包延遲時間。

Carrier sense multiple access and its variants have been widely used in mobile ad hoc networks (MANET). However, it cannot guarantee the quality of real-time traffics. This thesis presents a distributed medium access control (MAC) protocol that provides priority based multimedia access to wireless ad-hoc networks. With this protocol, it has two phases to proceed. First, each station that wants to contend for access to the channel proceed the priority scheme, higher-priority packets (like real-time packets) have access priority over the lower-priority packets (like data packets). Second, after the priority scheme, the stations that have the same priority packets are assigned an unique ID (identity number) respectively in the contention period, and then (after the contention period) all stations that want to transmit packets depend on their ID sequence to access channel in turn. The simulation result used to verify this protocol, it can bounded real-time packet delay and has the high channel utilization.

1 Introduction 1
2 Preliminary 6
3 Our MAC protocol 10
3.1 A priority classication scheme . . . . . . . . . . . . . . . . . . . . 10
3.2 An InitialID scheme . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.3 Transmission scheme . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.4 Our MAC protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4 Analysis and Simulation Results 21
4.1 Simulation Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.2 Performance Measurements . . . . . . . . . . . . . . . . . . . . . . 22
4.3 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5 Conclusion 27
A Comparison 30

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