High Availability Ad Hoc Networks

The Mobile Ad Hoc network (MANET) is a dynamic and self-organized network system with temporary network topology, which is composed of mobile stations with wireless transceivers. Each mobile station can serve not only as a communication terminal but also as a router; moreover, the data packet is relayed hop-by-hop between two adjacent nodes, without any supports of infrastructure. The MANET is deployed broadly in military area, civil area and commercial area such as battle communication, disaster relief, emergency rescue, temporary meeting, intelligent transport, exploration and so on. Nowadays, MANET is a hot research area at home and abroad and has broad prospect.With the increasing applications of the Ad Hoc network, the demanding for providing service availability in the network arises, but the feature of sharing media, multi-hop, distributed, asymmetric channel, limited resources and dynamic topology etc, make it difficult to achieve our objects in MANET. The distributed access manner makes the nodes sharing the same wireless media utilize the channel alternately in time domain, and the different access categories can be differentiated by the contention parameters pre-defined, so the soft priority is realized. To analyze the contention procedure is the premise for designing admission and control mechanism, even for providing the service availability; on the other hand, the backoff procedure must be executed in the distributed contention access process, the utilization of network resources can be enhanced by the backoff algorithm; data flows are transmitted on the end-to-end path, and the intermediate nodes forward the data packets, so the wireless media within these nodes' carrier sensing range are influenced by these flows, according to the monitoring results of the utilization of wireless media, to predict the availability can make the node aware of the current network status; the network overload should be prevented in the MANET with limited resources, the new arrival flows should be admitted by the nodes based on the network residual capacity; at last, the nodes moving randomly will make the network topology changing dynamically, the stable end-to-end path is needed for the real time service to ensure that the content can be playback smoothly.Focusing on the above problems and the hot research subjects, at the same time, with the progress of the National Natural Science Fund of China, the network layer and MAC layer are studied carefully and systematically in this dissertation, the main content and innovation are summarized as follows:1. The three-dimensional time discrete Markov model is constructed to analyze the EDCA service differentiation mechanism defined in the IEEE802.11e standard.2. The contention aware combination adjusting scheme is proposed, and the contention parameters are tuned actively and passively, the utilization of network resources is enhanced.3. Analyzing the factors that influencing the channel utilization and the available bandwidth estimating mechanism with retransmitting predicting method proposed in MANET.4. Based on the bandwidth estimating results, the distributed admission control technology is evaluated to balance the network capacity and load.5. The link lifetime estimating method is proposed; moreover, the routing scheme is proposed to establish the stable end-to-end path, in order to decrease the route discovery times and the corresponding control overhead.Through the research above, the aim of this dissertation is to provide a complete service availability solution mechanism for Mobile Ad Hoc networks.