Research On Key Technologies Of Mobile Ad Hoc Network Protocols

Wireless networks provide users with the capability of ubiquitous communication and information access, as well as connection maintenance in continuous movement. Users are frequently connected to the network via base stations in traditional mobile communication systems where 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. MANET 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 scenarios, mobile ad hoc networks provide a feasible means for ground communications and information access.The dynamic topology, variable link state, low-power-consuming equipments and distributed features of MANET result in many new problems and challenges for its protocol design. The dissertation studies thoroughly the key technologies on designing MAC and network layer protocols of MANET, including MAC protocol unfairness problem, topology control problem, broadcast problem and energy-conserving routing problem, and presents some efficient proposals.IEEE802.11 DCF protocol has been widely used in various simulators and testbeds for MANET, which makes it the defacto MANET MAC specification. We find there exists severe unfairness when applying DCF protocol into multihop MANET environment, which falls into three categories according to their causations: LSP unfairness, MAP unfairness and LIP unfairness. The dissertation gives thoroughly simulative and theoretic analysis for each category of unfairness, explains its causation and quantifies its relation to the MAC parameters. Then we propose three schemes to solve these unfairness problems and verify their effectiveness by simulation. Considering the complexity of the practical network, we integrate the three schemes and propose a DCF fairness improvement algorithm FDCF, extensive simulation results show it is effective to solve the DCF protocol unfairness problem in multihop mobile ad hoc networks.Topology control has significant impact on the performance of MANET protocols. The dissertation first studies the flat energy-conserving topology control problem, proposes the KC algorithm for homogenous MANET and MINS algorithm for heterogenous MANET respectively. KC algorithm not only guarantees the k-connectivity of the network topology while reducing the node's average transmission power, but also ensures there exists an upper bound for each node's degree in the final topology. By introducing the ingress neighbor...