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Today's communication techniques for mobile ad hoc networks take a connection-oriented approach.Mobile nodes need to discover routes and establish a connection before they can communicate. This strategy is not robust as it cannot adhpt to frequent unpredictable topologv changes due to high mobility. Constant reconnections incur signijcant overhead making these schemes unsuitable for applications such as voice and video. To address these issues, we explore a connectionless paradigm in this paper. We leverage technologv such as GPS (Global Positioning System) to allow a source node to discover a grid path to the destination node. Data packets are relayed along this path toward the destination using different intermediate nodes at different times without having to first establish connections between them.The performance of this new solution is essentially unaffecfed by node mobility. As a result, it is suitable for a wide range of mobile applications.

SUMMARYNext-generation ad hoc networks need to be able to handle high mobility in order to support a wide range of emerging applications such as vehicular networks. Maintaining communication links of an established communication path that extends between source and destination nodes is a significant challenge in mobile ad hoc networks due to the movement of the mobile nodes. In particular, such communication links are often broken under a high mobility environment. Although a new communication route can be established when a break in the communication path occurs, repeatedly reestablishing new routes incurs delay and substantial overhead. To address this limitation, we introduce the Virtual Router abstraction in this paper. A virtual router is a dynamically created logical router that is associated with a particular geographical area. Its routing functionality is provided by the physical nodes (i.e. mobile devices) currently within the geographical region served by the virtual router. These physical nodes take turns in forwarding data packets for the virtual router. In this environment, data packets are transmitted from a source node to a destination node over a series of virtual routers. Since virtual routers do not move, this scheme is much less susceptible to node mobility. We give simulation results to demonstrate the effectiveness of this technique in handling high mobility. They show that the Virtual Router approach can achieve several times better performance than the traditional approach based on physical routers (i.e. relay nodes).

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Contemporary terrorists have made public transportation a new theater of operations. Specifically, attacks on the urban transportation system can cause great disruption and alarm, which are the traditional goals of terrorism.The unexpected and stochastic character of terrorist attacks poses unique challenges to those responsible for security. Since the threat of terrorism is obscure and security measures are costly, it is hard to justify the expenditures before an attack. Security against terrorism therefore tends to be reactive. In this paper we propose new ITS technologies to enhance the surface transportation aspects of homeland security, by providing more efficient and safer evacuation for general public in case of terrorist attacks or other human caused disasters. In particular, we extend our existing work on developing a Smart Traffic Evacuation Management System (STEMS), by enhancing it with capabilities to adapt to the dynamics of the traffic environment, by leveraging real-time information obtained from sensors or other surveillance technologies. STEMS handles the unexpected aspect of terrorist attacks or other unpredictable disasters, by generating evacuation plans dynamically, when given an incident location and scope. To handle traffic dynamics, STEMS will continue to revise the initially generated plan, during the evacuation operation, to keep it consistent with the continuously changing traffic conditions. The advantages of this revision process are twofold: first, it ensures that traffic will not be directed towards congested areas; and secondly, it decreases congestion by spreading the traffic from currently congested segments to alternative routes. Our simulation studies show that employing real-time information greatly improves STEMS performance and therefore, evacuation efficiency.G.L. Hamza-Lup is with the

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Broadcasting in ad hoc networks is required for many routing and other network-layer protocols to request information like routes or locations about destination nodes. Most of these routing protocols use a simple flooding mechanism that can cause broadcast storms, particularly in high density environments. Although many techniques have been proposed to address the problem of broadcast storms, they require additional periodic location beacons or do not satisfactorily reduce transmission redundancy in high density environments.We propose Cell Broadcast, a broadcast protocol that significantly reduces redundancy without the use of beaconing and while maintaining complete reachability in a high density environment. The proposed technique divides a terrain into cells. These cells help a node to determine its geographic relationship with a broadcasting node. This geographic relationship can eliminate rebroadcasts not only from nodes close to a broadcasting node but also from a majority of nodes near the transmission edge of the broadcasting node. The effect is that, in a high density environment, only a few nodes located near the 4 diagonal corners of a transmission range need to rebroadcast to maintain 100% reachability. To the best of our knowledge, this technique is not present in any existing techniques that do not use location beaconing.