Designing Cooperative Communication Protocols for Improving Reliability in Wireless Ad Hoc Networks

Ad-hoc networking is the process by which users create a temporary network without the supervision of a central administrator. Each node in the network functions as both a host and a router, therefore it must be willing to send packets to other nodes. A routing protocol is necessary to accomplish this task. Ad hoc networks have unique properties that throw additional demands on the routing system. The most important property is the dynamic topology produced by node mobility. Because nodes move so frequently, routing systems must respond fast to topology changes. Ad-hoc networks often use laptops and personal digital assistants with limited resources such as CPU, storage, battery life, and bandwidth. The routing protocol should minimize control traffic, which includes periodic update messages. The routing protocol should be reactive, determining routes only after receiving specific requests. Simulations show that a specific ad-hoc routing technique will be required when mobility grows. When there is a high degree of mobility, classical routing protocols like DSDV perform much poorer. The proposed protocols include DSR and AODV. They thrive in high-mobility settings. However, relying entirely on IP-level communications for routing does not provide optimal performance. Lower-layer support, such as connection failure detection and neighbor search, is required for high performance. DSR, as well as other source routing algorithms, are affected by network size and traffic demand. A large network with many mobile nodes and a high load considerably increases DSR's overhead. In these instances, a hop-by-hop routing system, such as AODV, is preferred.