Amit Kumar Saha

Modeling mobility for vehicular ad-hoc networks

Without realistic modeling of node mobility, simulation evaluation of performance of mobile ad hoc networks may not correlate well with performance in a real deployment. In this work, we present a new, realistic model of node motion based on the movement of vehicles on real street maps. Our model can be used with the ns-2 network simulator. We compare our model with the Random Waypoint mobility model, the most widely used mobility model. Results show that, in many ways, the Random Waypoint mobility model is a good approximation for simulating the motion of vehicles on a road, but there are situations in which our new model is better suited.

RMAC: A Routing-Enhanced Duty-Cycle MAC Protocol for Wireless Sensor Networks

Duty-cycle MAC protocols have been proposed to meet the demanding energy requirements of wireless sensor networks. Although existing duty-cycle MAC protocols such as S-MAC are power efficient, they introduce significant end-to-end delivery latency and provide poor traffic contention handling. In this paper, we present a new duty-cycle MAC protocol, called RMAC (the routing enhanced MAC protocol), that exploits cross-layer routing information in order to avoid these problems without sacrificing energy efficiency. In RMAC, a setup control frame can travel across multiple hops and schedule the upcoming data packet delivery along that route. Each intermediate relaying node for the data packet along these hops sleeps and intelligently wakes up at a scheduled time, so that its upstream node can send the data packet to it and it can immediately forward the data packet to its downstream node. When wireless medium contention occurs, RMAC moves contention traffic away from the busy area by delivering data packets over multiple hops in a single cycle, helping to reduce the contention in the area quickly. Our simulation results in ns-2 show that RMAC achieves significant improvement in end-to-end delivery latency over S-MAC and can handle traffic contention much more efficiently than S-MAC, without sacrificing energy efficiency or network throughput.

Routing improvement using directional antennas in mobile ad hoc networks

In this paper, we present the initial design and evaluation of two techniques for routing improvement using directional antennas in mobile ad hoc networks. First, we use directional antennas to bridge permanent network partitions by adaptively transmitting selected packets over a longer distance, still transmitting most packets a shorter distance. Second, in a network without permanent partitions, we use directional antennas to repair routes in use, when an intermediate node moves out of wireless transmission range along the route; by using the capability of a directional antenna to transmit packets over a longer distance, we bridge the route breakage caused by the intermediate nodes movement, thus reducing packet delivery latency. Through simulations, we demonstrate the effectiveness of our design in the context of the dynamic source routing protocol (DSR).

TreeCast: a stateless addressing and routing architecture for sensor networks

Summary form only given. Recent advances in technology have made low-cost, low-power wireless sensors a reality. A network of such nodes can coordinate among themselves for distributed sensing and processing of certain phenomena. We propose an architecture to provide a stateless solution in sensor networks for efficient addressing and routing. We name our architecture TreeCast. We propose a unique method of address allocation, building up multiple disjoint trees which are geographically inter-twined and rooted at the data sink. Using these trees, routing messages to and from the sink node without maintaining any routing state in the sensor nodes is possible. Next, we use this address allocation method for scoped addressing, through which sensor nodes of a particular type or in a particular region can be targeted. Evaluation of our protocol using ns-2 simulations shows how well our addressing and routing schemes perform.

Safari: A self-organizing, hierarchical architecture for scalable ad hoc networking

As wireless devices become more pervasive, mobile ad hoc networks are gaining importance, motivating the development of highly scalable ad hoc networking techniques. In this paper, we give an overview of the Safari architecture for highly scalable ad hoc network routing, and we present the design and evaluation of a specific realization of the Safari architecture, which we call Masai. We focus in this work on the scalability of learning and maintaining the routing state necessary for a large ad hoc network. The Safari architecture provides scalable ad hoc network routing, the seamless integration of infrastructure networks when and where they are available, and the support of self-organizing, decentralized network applications. Safaris architecture is based on (1) a self-organizing network hierarchy that recursively groups participating nodes into an adaptive, locality-based hierarchy of cells; (2) a routing protocol that uses a hybrid of proactive and reactive routing information in the cells and scales to much larger numbers of nodes than previous ad hoc network routing protocols; and (3) a distributed hash table grounded in the network hierarchy, which supports decentralized network services on top of Safari. We evaluate the Masai realization of the Safari architecture through analysis and simulations, under varying network sizes, fraction of mobile nodes, and offered traffic loads. Compared to both the DSR and the L+ routing protocols, our results show that the Masai realization of the Safari architecture is significantly more scalable, with much higher packet delivery ratio and lower overhead.

Design and Performance of PRAN: A System for Physical Implementation of Ad Hoc Network Routing Protocols

Simulation 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 the physical implementation of ad hoc network routing protocols that unifies these two types of evaluation methodologies. 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 standard existing, unmodified ns-2 simulation model of each. 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 streams over a multihop mobile ad hoc network; the demonstration features mobile robots being remotely operated based on the real-time video stream transmitted from the robot over the network. We also present a detailed performance evaluation of PRAN to show the feasibility of our architecture

Conferences - Mobile computing at the beach

The Fifth IEEE Workshop on Mobile Computing Systems and Applications descended on the Beach Resort in Monterey, California, for a series of technical discussions of new research in pervasive and mobile computing.