VCAST: A Distance-Sensitive Scalable Information Dissemination Protocol

The future of intelligent transportation systems lies in dealing with safety and navigation of vehicles. Building a technology that provides the real-time information about the state of other vehicles like its location, speed and direction would help in developing a system that ensures safety along with navigation. However, the network limitations pose difficulty in obtaining the state information over multiple-hops, because of the bandwidth limitations and congestion in the shared wireless channel. Overcoming this challenge would yield an intelligent transportation system which gives information regarding the collisions, lane changes and merges, emergency vehicle approaching alerts, stopped vehicle alerts, etc., over larger distances. In my thesis I developed an algorithm VCAST that addresses this challenge by considering the grounds that the response time needed by vehicles at farther distances is more than that of at the smaller distances. This fact exploits the notion of distance sensitivity in information propagation, in which information is forwarded at a rate that decreases linearly with distance from source. The algorithm outputs traffic information with staleness, a measure of error in traffic information, bounded by O(dh 2), where dh is the single communication hop range. Also the communication rate per vehicle per unit time depends on the area of consideration but not on the density or number of vehicles in the region, which can be further reduced by considering the aggregated information over smaller regions. Thus, this technique would be able to supply timely information over large distances without compromising on data rates at smaller distances. Also, VCAST doesn\u27t need any special hardware or changes to the vehicular transmission standards. We evaluate the performance of VCAST by simulating a 4-lane highway of 5Kms occupied by 800 vehicles, wherein we vary the densities with and without fading apart from aggregated information propagation using the IEEE 802.11p communication model on NS-3

Anti-Jamming Schedules for Wireless Broadcast Systems

Modern society is heavily dependent on wireless networks for providing voice and data communications. Wireless data broadcast has recently emerged as an attractive way to disseminate data to a large number of clients. In data broadcast systems, the server proactively transmits the information on a downlink channel; the clients access the data by listening to the channel. Wireless data broadcast systems can serve a large number of heterogeneous clients, minimizing power consumption as well as protecting the privacy of the clients' locations. The availability and relatively low cost of antennas resulted in a number of potential threats to the integrity of the wireless infrastructure. The existing solutions and schedules for wireless data broadcast are vulnerable to jamming, i.e., the use of active signals to prevent data distribution. The goal of jammers is to disrupt the normal operation of the broadcast system, which results in high waiting time and excessive power consumption for the clients. In this paper we investigate efficient schedules for wireless data broadcast that perform well in the presence of a jammer. We show that the waiting time of client can be efficiently reduced by adding redundancy to the schedule. The main challenge in the design of redundant broadcast schedules is to ensure that the transmitted information is always up-to-date. Accordingly, we present schedules that guarantee low waiting time and low staleness of data in the presence of a jammer. We prove that our schedules are optimal if the jamming signal has certain energy limitations

Beaconless Packet Forwarding Approach for Vehicular Urban Environment

Existing wireless technologies provide communication and information services to all fields of life. The one of the emerging and popular field is vehicular ad hoc networks, with its unique characteristics and highly mobile environment. Different types of routing protocols have been proposed to address the routing issues in network and one of the most efficient types is geographical routing. In this type of protocols, the beacon messages are using to update the node locations and positions. However, these protoocls have been suffered with high channel congestion issue in the network. To this end, we propose a beaconless packet forwarding strategy based on modified handshake messages mechanism. The protocol uses some realistic metrics to select the next forwarder node such as forward progresss and link quality. The protocol performance is evaluated with existing beacon and beaconless geographical routing protocols. The simulation results showed the better performance of the proposed protocol in terms of packet delay and data delivery ratio in realistic wireless channel conditions

Beaconless Packet Forwarding Approach for Vehicular Urban Environment

Existing wireless technologies provide communication and information services to all fields of life. The one of the emerging and popular field is vehicular ad hoc networks, with its unique characteristics and highly mobile environment. Different types of routing protocols have been proposed to address the routing issues in network and one of the most efficient types is geographical routing. In this type of protocols, the beacon messages are using to update the node locations and positions. However, these protoocls have been suffered with high channel congestion issue in the network. To this end, we propose a beaconless packet forwarding strategy based on modified handshake messages mechanism. The protocol uses some realistic metrics to select the next forwarder node such as forward progresss and link quality. The protocol performance is evaluated with existing beacon and beaconless geographical routing protocols. The simulation results showed the better performance of the proposed protocol in terms of packet delay and data delivery ratio in realistic wireless channel conditions

A Logically Centralized Approach for Control and Management of Large Computer Networks

Management of large enterprise and Internet Service Provider networks is a complex, error-prone, and costly challenge. It is widely accepted that the key contributors to this complexity are the bundling of control and data forwarding in traditional routers and the use of fully distributed protocols for network control. To address these limitations, the networking research community has been pursuing the vision of simplifying the functional role of a router to its primary task of packet forwarding. This enables centralizing network control at a decision plane where network-wide state can be maintained, and network control can be centrally and consistently enforced. However, scalability and fault-tolerance concerns with physical centralization motivate the need for a more flexible and customizable approach. This dissertation is an attempt at bridging the gap between the extremes of distribution and centralization of network control. We present a logically centralized approach for the design of network decision plane that can be realized by using a set of physically distributed controllers in a network. This approach is aimed at giving network designers the ability to customize the level of control and management centralization according to the scalability, fault-tolerance, and responsiveness requirements of their networks. Our thesis is that logical centralization provides a robust, reliable, and efficient paradigm for management of large networks and we present several contributions to prove this thesis. For network planning, we describe techniques for optimizing the placement of network controllers and provide guidance on the physical design of logically centralized networks. For network operation, algorithms for maintaining dynamic associations between the decision plane and network devices are presented, along with a protocol that allows a set of network controllers to coordinate their decisions, and present a unified interface to the managed network devices. Furthermore, we study the trade-offs in decision plane application design and provide guidance on application state and logic distribution. Finally, we present results of extensive numerical and simulative analysis of the feasibility and performance of our approach. The results show that logical centralization can provide better scalability and fault-tolerance while maintaining performance similarity with traditional distributed approach

Age of Information for Actuation Update in Real-Time Wireless Control Systems

In this paper, we introduce a generalized definition of age of information (AoI) for actuation update in real-time wireless control systems. In such a system, a general queueing model, i.e., M/M/1/1 queueing model, is used to describe the actuation update, in which the sampling packets arrive at the remote controller following the Poisson process, the process from the controller to the actuator follows the exponential distribution, and the actuation intends to update at the actuator at the predictive time. Then, the initial time of the AoI for the new actuation update is the predictive time for the latest update, which is significantly different from the traditional calculation in status update. By the relationship between communication time from the controller to the actuator and predictive time, the AoI calculation falls into two cases, where the conventional AoI in status update is a specific case in this paper. Simulation results show the performance of our method