| The desire to be untethered and yet be connected has resulted in the popularity of an array of wireless enabled devices such as PDAs (Personal Digital Assistants), palm-tops, web-enabled cellphones and laptops. Two complementary technologies have evolved for interconnecting these devices, namely, the cellular data networks, which connects these devices to the Internet using a base station network, and the ad hoc networks, which connects these devices to other such devices through a multi-hop wireless network without using base stations. Various properties of these networks, such as mobility, frequent disconnections and varying channel conditions have made it a challenging task to design networking protocols for these technologies. In this thesis we focus on the design of routing and transport layers for providing mechanisms for fast data delivery that avoids creating congestion in the network.; The current routing protocols used for ad hoc networks incur very high route computation overheads as they are based on flooding the network with a route query, as the nodes do not have a notion of fixed location and the destination could be anywhere in the network. We design and implement the CEDAR (Core Enhanced Distributed Ad hoc Routing) routing infrastructure for ad hoc networks on the ns-2 simulator. We demonstrate its capability to improve flooding based routing protocols by enhancing two prominent protocols, namely, DSR and AODV.; We study the performance limitations of TCP's (Transmission Control Protocol) congestion control mechanism on Wide Area Wireless Networks (WWANs) and also on ad hoc networks. We identify the properties of typical WWANs based on studies on the CDPD (Cellular Digital Packet Data) network, simulate (ns-2) the environment and design our protocol (WTCP) in this simulation environment to compare it with TCP-NewReno, TCP-Vegas, and Snoop-TCP. We also evaluated an implementation of the protocol in the CDPD network and found substantial performance improvements over an off-the-shelf TCP. For ad hoc networks, we propose and evaluate (using ns-2 simulator) a congestion control mechanism which uses hop-by-hop rate control with back-pressure. We show that our protocol has improved fairness properties compared to TCP based protocols. |
