Browsing by Author "Saha, Amit Kumar"
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Item Design and Performance of PRAN: A System for Physical Implementation ofAd Hoc Network Routing Protocols(2005-02-28) Du, Shu; Johnson, David B.; PalChaudhuri, Santashil; Saha, Amit Kumar; To, KhoaSimulation and physical implementation are both valuable tools in evaluating ad hoc network routing protocols, but neither alone is sufficient. In this paper, we present the design and performance of PRAN, a new system for implementation of ad hoc network routing protocols that merges these two types of evaluation tools. PRAN (Physical Realization of Ad Hoc Networks) allows existing simulation models of ad hoc network routing protocols to be used—without modification—to create a physical implementation of the same protocol. We have evaluated the simplicity and portability of our approach across multiple protocols and multiple operating systems through example implementations in PRAN of the DSR and AODV routing protocols in FreeBSD and Linux using the existing, unmodified ns-2 simulation models. We illustrate the ability of the resulting protocol implementations to handle real, demanding applications by describing a demonstration with this DSR implementation transmitting real-time video over a multi hop mobile ad hoc network; the demonstration features mobile robots being remotely operated based on the video stream transmitted over the network. We also present a detailed performance evaluation of PRAN to show the feasibility of our architecture.Item Energy saving and partition bridging using directional antennas in mobile ad hoc networks(2003) Saha, Amit Kumar; Johnson, David B.In this thesis, I present the design and evaluation of new techniques for using directional antennas to save energy and to bridge network partitions in a mobile ad hoc network. This thesis advocates close but simple collaboration between the routing layer and the Medium Access Control (MAC) layer and shows through simulations, the effectiveness of this design by modifying the Dynamic Source Routing (DSR) protocol, an on-demand ad hoc network routing protocol based on source routing. First, in order to save energy, Route Requests and data packets are transmitted directionally. Extensive simulations show that without affecting the behavior of the routing protocol noticeably, energy savings of up to 75% is achieved. Second, in order to bridge network partitions, the routing protocol is modified to use the ability of a directional antenna to transmit directionally over longer distance as compared to an omnidirectional antenna, both antennas using the same power. Again, through simulations, the protocol is shown to be able to bridge network partitions. Also, when no partitions are present, the protocol is otherwise equivalent to the version without the partition bridging modifications.Item Throughput and coverage improvement in wireless mesh networks(2007) Saha, Amit Kumar; Johnson, David B.In a wireless mesh network, nodes known as transit access points (TAPs) cooperatively forward traffic from users that may be multiple wireless hops apart. A limited number of TAPs also have a connection directly to the Internet, serving as gateway nodes that provide Internet connectivity to the entire mesh network. Wireless mesh networks are gaining in importance as an alternative to cable and DSL and are envisioned to provide fixed, nomadic, portable, and---eventually mobile---wireless broadband connectivity. In this thesis, I provide solutions to two important problems in wireless mesh networks and evaluate these solutions through simulation experiments. The two solutions, improving throughput and coverage, can simultaneously coexist and can complement each other in a single mesh network. Nevertheless, both the techniques can also exist independent of each other in a wireless mesh network and can individually prove advantageous. First, I present two novel traffic-aware routing metrics that take into account existing user traffic flows in the network. Previous routing metrics have been traffic-unaware, often causing routes with poor throughput to be selected when other better routes are available. These new traffic-aware metrics use information captured through measurements at the medium access control (MAC) layer, which is then exposed to the routing layer. I compare these traffic-aware metrics with existing traffic-unaware metrics under different network scenarios. Second, I present the design and analysis of a new technique for increasing the coverage of a wireless mesh network through deployment of small, low-cost booster TAPs (bTAPs). These bTAPs are strategically deployed and controlled by the system operator to wirelessly forward traffic between users and TAP nodes. This deployment model is especially suitable for wide area wireless access networks that use centralized management of radio resources. I analyze the use of bTAPs across different frequency reuse patterns typical of those used in multi-cell wireless environments for efficient management of costly radio spectrum. The bTAP architecture provides dramatic improvements in outage performance and a sufficient capacity gain to compensate for the radio resources required for forwarding user traffic via bTAPs.