Research Of Reliable Mobile Ad Hoc Networks With Awareness Ability

Mobile Ad hoc network (MANET) is a fully distributed network, where the mobile nodes have limited energy and storage space, while the network topology and the quality of wireless channel are time-varying. The nodes within the network are highly mobile, which can join or leave the network dynamically. The nodes of MANET have both the functions of terminals and routers. The main purpose of MANET technology is to set up temporary network with a group of mobile terminals in the absence of base stations. Real-time multimedia services are popular MANET applications nowadays.With the rapid development of MANET technology, the requirements of multimedia services over MANET have been increased gradually. However, some characters of MANET, such as dynamic and fully distributed character, the competition of multiple nodes within the same wireless media and the unstable wireless channel, all affect the quality of service (QoS) of multimedia services. Although we cannot overcome the limitation of the physical layer technology and the unstable wireless channel of MANET, we still can design some mechanisms appropriate for MANET against these characters above to enhance the quality of service of the multimedia services. For the dynamic characters of MANET, if the nodes have the awareness of their own status, such as the available bandwidth and the path lifetime, they can choose the forwarding paths with higher reliability; for the infrastructureless character, the distributed routing and call admission control mechanisms are needed; and for the unstable wireless channel, we can utilize multipath routing mechanism to enhance the end-to-end path reliability and use the opportunistic routing mechanism which can adapt to the time-varying wireless channel, and change the way of forwarding data packets profoundly and finally enhance the quality of service of the multimedia services.Focusing on the above problems and from the practical point of view, I studied the node awareness abilities, the distributed control mechanisms and the mechanisms for enhancing the reliability of network carefully and systematically, and I achieved some innovative research results, which are:1. The analysis of the relationship between the application layer bandwidth and the Medium Access Control (MAC) layer bandwidth of voice and video services under the non-saturation condition;2. A link residual lifetime aware mechanism based on the signal strength of the received messages, and this mechanism can be applied to multiple mobility models and wireless propagation models without the aid of extra control messages and positioning equipment;3. A flow detection mechanism based on the usage of Bloom filter, the load of node is measured as the amount of data flows;4. A distributed call admission control mechanism which combined with the route discovery process, and proper forwarding path is calculated by this mechanism for the incoming data flows without affecting the QoS of the existing flows;5. An adaptive partial multipath routing mechanism for the scenario with small node density, the end-to-end path is divided into several shorter segments, and multipath can be built at some segments;6. A parallel redundancy mechanism based on the adaptive partial multipath, the redundant data packets are sent according to the predicted path breakage time in order to reduce the redundant data packets.7. An opportunistic routing mechanism, where the data packets are not forwarded along the predefined path but dynamic forwarding nodes to adapt to the unstable wireless channel.Through the researches above, the QoS of the multimedia services of MANET can be supported well.