Extend The Performance Of The Aodv Routing Protocol In Ad Hoc Network Subnet Interconnect Structure

Mobile Ad Hoc Network (MANET) is a kind of complicated distributed network composed of wireless mobile nodes, which can form temporary network topology and thus communicate in the circumstances without pre-existing infrastructure. MANET is frequently used in the environment such as military communication, catastrophe recovery and searching and aid action.MANET always takes flat or clustered structure as networking architecture, which sometimes doesn't meet the specific demands, such as building up Ad Hoc network in accordance to army architecture. This thesis presents architecture of Ad Hoc subnets connected by wireless gateway. Each node has its own belonging level of hierarchy and nodes with same level form the independent subnet which is then connected with other ones by gateway. Gateway belongs to both levels of subnets connected to its interfaces. The advantage of this architecture is not only keeping interdependence and performance of each subnet, but also forming much bigger Ad Hoc network. Each subnet can run its own characteristic routing protocol. With right gateway setting, inter-subnet traffic could get through Ad Hoc subnets even with varying formations and communication mechanisms.This thesis introduces three kinds of gateway discovery protocol in order that nodes within different subnets find the route to the gateway before communicating with each other. These gateway discovery protocols, including Proactive Gateway Discovery, Reactive Gateway Discovery and Hybrid Gateway Discovery, can separately combined with the modified and extended AODV routing protocol, implementing inter-subnet communication.After describing details of network architecture and routing protocol, a simulation model is constructed by Network Simulator 2 to conclude protocol performance and provide reference to the designing of practical systems.