(1987). Applied Probability and Queues. Journal of the Operational Research Society: Vol. 38, No. 11, pp. 1095-1096.

https://link.springer.com/content/pdf/10.1057%2Fjors.1987.184.pdf

Applied Probability and Queues

/pdf/reversibility-and-stochastic-networks-17kl9p5ino.pdf

Reversibility and Stochastic Networks

We study a sensor node with an energy harvesting source. The generated energy can be stored in a buffer. The sensor node periodically senses a random field and generates a packet. These packets are stored in a queue and transmitted using the energy available at that time. We obtain energy management policies that are throughput optimal, i.e., the data queue stays stable for the largest possible data rate. Next we obtain energy management policies which minimize the mean delay in the queue. We also compare performance of several easily implementable sub-optimal energy management policies. A greedy policy is identified which, in low SNR regime, is throughput optimal and also minimizes mean delay.

Optimal energy management policies for energy harvesting sensor nodes

By broadcasting messages about traffic status to vehicles wirelessly, a vehicular ad hoc network (VANET) can improve traffic safety and efficiency. To guarantee secure communication in VANETs, security and privacy issues must be addressed before their deployment. The conditional privacy-preserving authentication (CPPA) scheme is suitable for solving security and privacy-preserving problems in VANETs, because it supports both mutual authentication and privacy protection simultaneously. Many identity-based CPPA schemes for VANETs using bilinear pairings have been proposed over the last few years to enhance security or to improve performance. However, it is well known that the bilinear pairing operation is one of the most complex operations in modern cryptography. To achieve better performance and reduce computational complexity of information processing in VANET, the design of a CPPA scheme for the VANET environment that does not use bilinear paring becomes a challenge. To address this challenge, we propose a CPPA scheme for VANETs that does not use bilinear paring and we demonstrate that it could supports both the mutual authentication and the privacy protection simultaneously. Our proposed CPPA scheme retains most of the benefits obtained with the previously proposed CPPA schemes. Moreover, the proposed CPPA scheme yields a better performance in terms of computation cost and communication cost making it be suitable for use by the VANET safety-related applications.

An Efficient Identity-Based Conditional Privacy-Preserving Authentication Scheme for Vehicular Ad Hoc Networks

VANet security challenges and solutions: A survey

We study an adaptive window protocol (AWP) with a general increase and decrease profile in the presence of window dependent random losses. We derive a steady-state Kolmogorov equation and obtain its solution in analytic form. We obtain some stochastic ordering relations for a protocol with different bounds on window. A closed form necessary and sufficient stability condition using the stochastic ordering for the window process is established. Finally, we apply the general results to particular TCP versions such as NEW Reno TCP, scalable TCP and Highspeed TCP. We observe that Highspeed TCP can be used to approximate almost any kind of window behavior by varying only one design parameter.

/pdf/performance-analysis-and-stochastic-stability-of-congestion-1oydcc8abo.pdf

Performance analysis and stochastic stability of congestion control protocols

A method for improving the reliability and performance of Vehicle-to-Vehicle (V2V) networks where digital certificates are necessary for message authentication and some messages may be lost in transmission. The method uses Forward Error Correcting (FEC) codes to encode a digital certificate into multiple segments, and attaches one or more segment to each message transmitted. Nodes receiving the messages can reconstruct the certificate as long as they successfully receive a minimum number of the transmitted messages, where the minimum number is less than the total number of messages transmitted. This allows message authentication to continue uninterrupted, even in a network environment where some messages are lost in transmission. Two different types of FEC codes are described, and adaptive schemes are included to optimize message throughput based on such network conditions as node density.

Adaptive certificate distribution mechanism in vehicular networks using forward error correcting codes

We consider the problem of optimal next-hop selection in a route between two vehicles, for a simple scenario of Vehicular ad hoc networks (VANETs) on a highway. For a given approximation of the optimal number of hops, we seek the optimal choice of next-hop based on its speed and inter-node distances, so as to maximize the expected route lifetime. Under a Markovian assumption on the process of speed of nodes, we show that the optimal choice of speeds attempts to equalize the lifetimes of adjacent links. A monotone variation property of the speed of relay nodes under the optimal policy is proved. These properties have been confirmed with simulations. The optimal policies and their structures can assist in enhancing the performance of existing VANET routing protocols.

/pdf/route-lifetime-based-optimal-hop-selection-in-vanets-on-m9evvi9d56.pdf

Route lifetime based optimal hop selection in VANETs on highway: an analytical viewpoint

We consider a mobile ad hoc network consisting of three types of nodes: source, destination, and relay nodes. All the nodes are moving over a bounded region with possibly different mobility patterns. We introduce and study the notion of relay throughput, i.e. the maximum rate at which a node can relay data from the source to the destination. Our findings include the results that the relay throughput depends on the node mobility pattern only via its (stationary) node position distribution and that a node mobility pattern that results in a uniform steady-state distribution for all nodes achieves the lowest relay throughput. Random Waypoint and Random Direction mobility models in both one and in two dimensions are studied and approximate simple expressions for the relay throughput are provided. Finally, the behavior of the relay buffer occupancy is examined for the one-dimensional Random Walk, and an explicit form of its mean value is provided in the heavy-traffic case.

/pdf/impact-of-mobility-on-the-performance-of-relaying-in-ad-hoc-3khhohqwd2.pdf

Impact of Mobility on the Performance of Relaying in Ad Hoc Networks

Safety applications aim to avoid vehicular accidents, by providing advisories to the driver, by using secure broadcast vehicle-to-vehicle (V2V) communications. However, any security mechanism used for authenticating broadcast V2V messages, comes with overheads in terms of computation, storage and communications. Further due to the resource-constrained computing platforms used in the automotive domain, these overheads could translate into performance bottlenecks. Prior works related to performance modeling of secure V2V communications do not consider the computational overheads of security, since traditionally packet transmission rather than packet processing is taken to be the bottleneck. This paper provides an evaluation of the performance of secure V2V communications, while explicitly modeling the computational and storage overheads due to security. We observe that there is a complex coupling between the security and the communication layers, and that the performance bottlenecks could shift from one to the other depending on the system parameters. In order to explain these observations, we propose a fixed point based approach which essentially assumes the two layers at a given node independent from each other and from those at other nodes, and uses the inherent consistency relationships to yield fixed point equations for performance metrics such as blocking or collision probability. Our results indicate that this is a promising approach which works quite accurately.

Arzad A. Kherani

Papers

Performance analysis and stochastic stability of congestion control protocols

Adaptive certificate distribution mechanism in vehicular networks using forward error correcting codes

Route lifetime based optimal hop selection in VANETs on highway: an analytical viewpoint

Impact of Mobility on the Performance of Relaying in Ad Hoc Networks

Secure V2V communications: Performance impact of computational overheads