Ratul K. Guha

A survey and challenges in routing and data dissemination in vehicular ad hoc networks

In this paper, we survey recent results in VANET data dissemination. We structure the survey into three broad categories: geocast/broadcast, multicast, and unicast approaches; and describe key ideas of representative technologies in each category. In addition, we consider location service and security issues that are crucial for data dissemination in VANET. We conclude by sharing our thoughts on further challenges.

A survey and challenges in routing and data dissemination in vehicular ad-hoc networks

In this paper, we survey recent results in VANET data dissemination. We structure the survey into three broad categories: geocast/broadcast, multicast, and unicast approaches; and describe key ideas of representative technologies in each category. In addition, we consider location service and security issues that are crucial for data dissemination in VANET. We conclude by sharing our thoughts on further challenges.

A distributed traffic navigation system using vehicular communication

Traffic congestion leads to significant cost in terms of time, money and influence on the environment. To alleviate the effect through situational awareness, various traffic service providers aggregate traffic information using a variety of inputs such as probes, toll collection etc. This aggregated information is fed back to the drivers to achieve congestion avoidance and provide arrival-time estimates. In this paper, we outline a framework for a distributed vehicle traffic navigation system. The proposed system leverages a multi-hop vehicular network to gather local information. Such information can be elusive to traffic service providers in terms of timeliness and accuracy. Based on the gathered information, a distributed scheme is proposed that locally determines the shortest time travel paths. The proposed system can function independently or can complement an existing infrastructure-based system and can capture the dependence between route decisions of different vehicles in a given area. Based on performance evaluations, we observe that the proposed protocol can significantly enhance local route decisions leading to better traffic flow and road utilization.

Achieving High-Rate Multi-Hop Data Delivery in Vehicular Networks

A method for high rate data delivery in a multi-hop vehicular network comprises at each source vehicle, initiating a packet having a flow tag, assigning an identifier of the content and the current location to the flow tag, and forwarding the packet; at each destination vehicle, setting a flow request and broadcasting at the current intersection; further on movement, setting the flow request at the new intersection, and at each intersection, selecting a header vehicle at the intersection, computing backlog and congestion indicators and listening for broadcasts with a matrix and the flow requests at the header vehicle, determining if the matrix is present, updating the matrix in accordance with the backlog and congestion indicators if the matrix is present, initializing the matrix and estimating the delay on the outgoing road segments if the matrix is not present, forwarding the packet flow, and broadcasting the matrix from the header vehicle.

A multi-antenna switched links based inter-vehicular network architecture

In recent years, there have been significant research efforts related to vehicle-to-vehicle (V2V) communication. The major demand of the V2V communication is originally from safety-related applications; other possible application areas including communication support for traffic management have increased. In this paper, we propose an architectural framework for achieving a vehicle network that employs dynamically switched directional links. This serves to address channel contention associated with omni-directional antenna based network architecture and leads to a simple protocol specification for V2V communication. We propose new data dissemination methods that leverage the unique characteristics of the dynamic switched directional links based architecture. The tradeoffs of the proposed framework and dissemination methods are also discussed.

Context-driven disruption tolerant networking for vehicular applications

In this paper, we describe how a context-driven disruption tolerant network may be utilized for vehicular applications. The key concept involves utilizing contextual information pertaining to space and time settings of applications to drive networking functions. As a result, the performance characteristics may be better attuned to the time-scale of relevant vehicular applications. We discuss the protocol highlights and present a compact grid-based method for performance evaluation of such systems. Novel metrics such as information freshness demonstrate the discrete nature of information dissemination. Additionally, we observe that asymptotic evaluation of metrics such as packet delivery ratio do not provide a realistic picture of application performance. As a consequence, the time-scale of interest for the applications becomes crucial.

Evaluation of a multi-antenna switched link-based network architecture for quasi-stationary vehicle network

In recent years, there have been significant research efforts related to vehicle to vehicle (V2V) communication. V2V communication was originally targeted for safety-related applications but interest in other possible application areas including communication support for traffic management has increased. This paper describes a system architecture that can provide high throughput and rapid data dissemination in vehicular networks. While vehicle mobility results in frequent routing changes, we expect that in a highway scenario vehicles will maintain relative positions and speeds for some time resulting in a quasi-stationary network configuration. The proposed approach system is intended to be robust and work with a very simple protocol specification taking advantage of the quasi-stationary behavior of vehicle networks. It also addresses some of the major concerns facing multi-hop vehicular communication. We previously proposed an architectural framework for achieving a vehicle network that employs dynamically switched directional links [30]. In this article we provide preliminary simulations results that highlight the scalability, reliability and latency benefits provided by the switched directional links for a given baseline vehicle configuration emulating a quasi-stationary network. A significant improvement in metrics such as PDR and latency is observed.

A fast and distributed algorithm for vehicular network coding

It is significant to discover an efficient method to construct network codes such as a linear multicast or broadcast. It is valuable if we find a practical way to apply the technique to a vehicular ad hoc network (VANET) to improve the throughput to broadcast large data. It would be essential to discover a fast and distributed coding scheme since VANETs are well-known to change their topology quickly. In this paper, we present such a network coding algorithm suitable to a VANET. It will be guaranteed that the obtained code forms a two-dimensional linear multicast over a network that meets natural restrictions for a VANET on a multi-lane road. Due to the completely decentralized process, it is non-trivial to prove the correctness of construction even for the dimension 2. We will also discuss additional practical performance enhancement for the basic algorithm.

A Light-weight Location-aware Position Update Scheme for High Mobility Networks

In a mobile networking environment, constant node motion result in drastic changes in spatial distribution of nodes which in turn causes changes in network topology. Blind position information updates could comprise a significant fraction of the network traffic. Consequently, maintaining accurate position information in such situations could become prohibitively expensive. In addition, the reference of information decreases as the distance increase, i.e., interest in position information could be highly localized and distant nodes do not require precise position description. In this paper, we propose a grid-based update mechanism that establishes the relationship between the grid-size and the frequency of position update. Such an association has two salient features: Firstly, only relevant updates based on location are transmitted avoiding redundant position updates. Secondly, it provides a guidance for adjusting the frequency of position updates in connection with the required positional accuracy and mobility pattern. We present an analysis of the performance of the proposed approach under the random walk mobility model, and proposes a fully distributed grid-based Markov model to capture the impact of mobility pattern on the frequency of position updates. We show in the simulation experiment that the proposed grid-based position update mechanism can reduce the network overhead for position updates by more than 65% while affecting the positional accuracy by less than 3%.

Optimal On-demand Mobile Sensor Allocation

In many practical applications of sensor networks, the level of sensor coverage needed at different locations varies with time. Pre-computation of sensor deployment in such cases is inadequate; on-the-fly redistribution of nodes in the network, as the system evolves, becomes necessary. Reallocation of sensors consumes resources (e.g., energy). Thus it is desirable to do so while minimizing a global metric of cost. The contribution of this paper is a distributed sensor reallocation algorithm superior to existing algorithms that computes the set of sensor movement that satisfies the demand of sensors at each part of the network, if it is at all feasible, while optimizing a given metric of interest, such as the total distance traveled. In general such discrete problems are NP-hard. However, the proposed algorithm is polynomial-time computable as it exploits a special structure of the problem. We numerically establish its superiority over previous algorithms.