無線網路下新媒體存取控制協定

Abstract

於本論文中，我們評估在無線網路環境下一個新的媒體存取控制協定的效能表現。這個控制協定稱為是統計表徵媒體存取控制協定 (ST-MAC)。我們也為這個協定加了一個省電機制。從頻道的使用率來看，ST-MAC 使用了一個不均勻的隨機數產生器，使得在無線網路頻道的時槽競爭上呈現出一個普松分佈的狀態。ST-MAC 在較高的資料流量情況下，其表現是很穩定的。藉由一個簡單的省電機制的加入，ST-MAC能源使用效率增進了約60%至70%之間。CSMA/CA在無線區域網路上是一個很好的媒體存取控制協定，但是從ST-MAC的效能評估結果來看，在較低的競爭程度上(例如， )，ST-MAC 較 CSMA/CA提升了將近150%的頻道效能。這是由於統計表徵的特色使得系統下的每一個使用者知道該在什麼時間傳送它們的封包而避免因競爭頻道使用權而造成的碰撞現象。由於碰撞的次數與封包重新傳送的時間延遲都可以被減到最少，ST-MAC在長距離的通訊系統與車間通訊上是一個很適用的媒體存取控制協定。

In this thesis, we evaluate the performance of a novel MAC protocol for wireless networks. This protocol is called Statistic Token Medium Access Control (ST-MAC). We have enhanced the protocol with a power saving strategy. From a point view of channel utilization, ST-MAC uses a non-uniform distributed random number generator which performs a Poisson distribution on competing time slots of a wireless channel. ST-MAC is stable at an extreme end of high traffic load. By incorporating a simple power saving strategy, 60% to 70% of power efficiency improvement has been achieved. CSMA/CA is an emerging MAC protocol in wireless local area networks. Performance evaluation has shown that ST-MAC has 150% higher throughput than CSMA/CA under low contention degree ( ). This is due to the characteristic of statistic token that each station knows when to transmit a packet without encountering collision. ST-MAC is suited for long range communications and inter-vehicle communications, where the number of collisions and retransmission delay can both be minimized.