Mobile Ad Hoc Networks, Broadcasting And Routing Technology Research

Wireless networks provide users with the capability of ubiquitous communicating and access to information at anytime and keeping connections valid in continuous movement. Users are frequently connected to the network via base stations in traditional mobile communication systems and a wired backbone is often utilized to carry the information transferred among base stations. A mobile ad hoc network (MANET) is a special wireless network that is self-organized by mobile nodes communicating with distributed protocols. Such a network can function in absence of fixed routing infrastructures, e.g. base stations. When the wireline network is not available, as in battlefield communications and emergency search-and-rescue operations, mobile ad hoc networks provide a feasible means for ground communications and information access.The topology of a MANET can change frequently since all communicating nodes can move with unlimited mobility. Traditional routing techniques are designed with implicit assumption of a comparatively stable network topology, and their performances degrade in mobile environments. New routing techniques are demanded for mobile ad hoc networks. Routing is a challenging problem in multi-hop wireless networks. There are three basic routing problems: point-to-point (or unicast) routing, broadcast and multicast routing. In this dissertation, broadcast and unicast routing are studied in MANETs with flat structure.Broadcast is an important operation in MANETs. It is not only an important communication pattern in many MANET applications, but also the basic means for route discovery in unicast routing and a useful tool to maintain the multicast membership and multicast tree in some multicast routing protocols. The characteristics of MANAETs distinguish the broadcast problem from those in wireline networks and traditional mobile communication systems. With the assumption of omni-directional antenna, broadcast in MANETs can be reduced as the minimal connected dominating set (MCDS) problem in graph theory. Because the MCDS problem is NP-complete, only approximation 昦lgorithms are proposed in this dissertation. They include the genetic algorithm for MCDS problem, the distributed broadcast tree algorithm, the virtual backbone algorithm and the broadcast algorithm utilizing redundancy information. Rebroadcasting nodes are limited within the connected dominating sets obtained by the algorithms and the broadcast efficiency is improved greatly. With different characteristics, these algorithms possess different application value or theoretic value. Their performances are compared throughsimulation and the size of the resultant connected dominating set is evaluated.Reasonable tradeoffs must be made among the design objectives, including routing overhead, reliability, simplicity, and so on. Flooding is an widely-used way for broadcasting. However, it can result in broadcast storm problem in MANETs. The redundancy-reduced broadcast protocol (RRBP) is presented in this dissertation. It is designed based on the broadcast algorithm utilizing redundancy information. The protocol can avoid many unnecessary rebroadcasts by collecting the information of duplicates and utilizing the local topology information. Many redundant rebroadcast operations are saved and the broadcast efficiency is improved greatly. Besides, the broadcast protocols based on flooding and multi-point relaying are studied. Using the network simulator ns-2, we study the protocol performance with different parameter settings so that the impact of protocol parameters can be evaluated. The protocol performances are compared with respect to different network size, different mobility and different network payload.Routing information is time-effective in networks with dynamic topology. As the topology of a MANET can change frequently, efficient route maintenance operations are required. In order to reduce the routing overhead, the technique of redundant routing is proposed to localize the influence of the changing of network topology. Meanwhile, it provid...