一個多重範圍行動無基礎無線網路(MANET)，是由多個具一定限制範圍通訊的獨立行動主機(MHs)或設備所組成。在此一特殊的網路環境中，當有兩個行動主機間無法直接的通訊，卻需要交換資料封包時，就需要有某種網路繞徑通訊協定來達成。因此，在多重範圍MANET中，如何來設計一個有效率的網路繞徑協定是一個重要的課題。許多無基礎網路繞徑協定利用廣播的方式，來交換及更新他們的路由資訊。然而在現今的無線通訊中，例如IEEE 802.11無線區域網路(WLAN)，並沒有提供任何廣播及群播訊框的答覆機制。此一缺點將造成在MANET中，不確定性的廣播/群播問題，並且將降低繞徑通訊協定的效能。 最近有多種具多重傳輸的技術，被廣泛地研究用來改進無線通訊的傳輸效能。其中的一項技術就是使用多重速率的正交振幅調幅法(QAM)。依據調變方法的特性，無線通訊傳送的速率會隨無線電訊號傳送距離(範圍)成反比。因此，如何設計一個高效率的媒介存取控制(MAC)及繞徑通訊協定，來提供在多重範圍MANET環境中，多速率/多距離的傳輸是另一個重要的議題。 根據以上所提的問題，我們在本篇論文中，提出一個可靠的廣播機制，來解決在MANET中不確定性的廣播/群播問題。並進而提出一個具多速率及多距離的繞徑通訊協定(M2RP)來支援多速率傳輸(例如，1/2/5.5/11 Mb/sec)。由於這些特性，使得傳統以最少跳躍的最短路徑選擇法，將不再適用於多速率/多距離及多重範圍的無基礎網路(M3AN)。因此透過對IEEE 802.11通訊協定的MAC延遲研究，所提出的M2RP能夠預測出所有路徑的傳送延遲，並從中找出自來源端到目的地端最小傳輸延遲的最佳路徑。模擬結果顯示，M2RP在處理負載平衡及快速找尋路徑的表現非常好，且其通訊阻礙機率亦明顯地較傳統的最短路徑且固定速率的方法來得小。 A multi-hop mobile ad hoc network (MANET) is formed with several independent mobile hosts (MHs) or devices in a limited communication range. Some form of routing protocol is in general necessary in such an environment, since two MHs that may wish to exchange packets might not be able to communicate directly. Therefore, how to design an efficient routing protocol is an important issue in such multi-hop MANET. Many ad hoc routing protocols exchange and update their routing information by using broadcast scheme. However, in current wireless communications such as IEEE 802.11 wireless local area network (WLAN), there is no acknowledgment reply mechanism for broadcast and multicast frames. This shortcoming leads to an uncertain broadcast/multicast problem in MANET and will degrade the performance of routing protocols. Recently, adaptive transmission techniques have been extensively investigated for improvement of transmission performance in wireless communications. One of these techniques is the variable-rate quadrature amplitude modulation (QAM) scheme. With the characteristics of modulation schemes, the data rate of wireless communication is inversely proportional with the transmission distance (range). Therefore, how to design an efficient medium access control (MAC) and routing protocol for supporting multi-rate/multi-range transmission in multi-hop MANET environment is another important issue. According to above-mentioned problems, we propose a reliable broadcast mechanism to solve the uncertain broadcast/multicast problem in MANET, and then propose a multi-rate/multi-range routing protocol (M2RP) for multi-rate transmissions (e.g., 1/2/5.5/11 Mb/sec) in this dissertation. With the characteristics of these issues, the conventional shortest path of minimum-hops approach will be no longer suitable for the multi-rate/multi-range multi-hop ad hoc networks (M3AN). Thus, by analyzing the MAC delay of the IEEE 802.11 MAC protocol, the proposed M2RP is capable of predicting the transfer delay of a routing path and finding the best one, which has the minimum transfer delay from source to destination. The proposed M2RP can maximize the channel utilization as well as to minimize the network transfer delay from source to destination. Simulation results show that M2RP performs the load balancing and fast routing very well, and its call blocking probability is obviously lower than that of conventional minimum-hops approach with fixed transmission rate.
