Elsevier

Ad Hoc Networks

Volume 14, March 2014, Pages 118-129
Ad Hoc Networks

Review Article
A probabilistic routing by using multi-hop retransmission forecast with packet collision-aware constraints in vehicular networks

https://doi.org/10.1016/j.adhoc.2013.11.012Get rights and content

Abstract

In this paper, we introduce a novel reliable and low-collision packet-forwarding scheme for vehicular ad hoc networks, based on a probabilistic rebroadcasting. Our proposed scheme, called Collision-Aware REliable FORwarding (CAREFOR), works in a distributed fashion where each vehicle receiving a packet, rebroadcasts it based on a predefined probability. This probability is manipulated by different physical factors derived from the vehicular environment, including density of the vehicles in the vicinity, distance between transmitting and receiving vehicles, and finally, transmission range of the next-hop. All these factors are combined into one probability that enables each vehicle to evaluate whether there is another vehicle that ought to be receiving this message and could be feasible if the message is rebroadcasted. The success of rebroadcast is determined based on allowing the message to travel the furthest possible distance with the least amount of packet rebroadcast collision.

CAREFOR is different from other existing techniques as it accounts for the effect of the next-hop transmission in the rebroadcast decision. Simulation results show the effectiveness of our approach in terms of limited number of rebroadcasts needed with low collision probability as compared to existing techniques. Two and three-hops message retransmissions are also considered.

Introduction

In the past few years, Vehicular Ad hoc NETworks (VANETs) have emerged as a critical component of Intelligent Transportation System (ITS), which can be considered to be a special kind of Mobile Ad hoc NETworks (MANETs), where mobile nodes are the vehicles. Due to the nature of the vehicles, node mobility in a VANET is constrained by certain paths (i.e., highways and rural/urban roads), and with certain speed limits. Communication in a VANET can be carried in one of the two fashions [1]. The first is Vehicle-to-Vehicle (V2V) communication paradigm, where the vehicles communicate in an ad hoc multi-hop method. The second is Vehicle-to-Infrastructure (V2I), where vehicles communicate to a Road Side Unit (RSU) or an Access Point (AP) on the sides of a road or a highway. The main objective of the VANET design is to provide different categories of applications including Internet access, as well as safety and traffic congestion to vehicles, operators, and passengers.

V2V protocol provides vehicular communications through a Dedicated Short-Range Communication (DSRC) in multi-hop mode that exploits flooding of information for vehicular data applications [2]. With an increasing number of vehicles equipped with on-board wireless devices, (e.g., UMTS, IEEE 802.11p, GPS, Bluetooth, etc.) and sensors (e.g., radar, lidar, camera, etc.), efficient transport and management applications are helping in optimizing the flows of vehicles by reducing the travel time and avoiding any traffic congestion. On the other hand, non-safety applications are expected to create new commercial opportunities by increasing the market penetration of the technology and enhancing its cost-effectiveness. Comfort and infotainment applications aim to support road travelers with needed information and entertainment to make the journey enjoyable. Such applications are numerous and range from traditional IP-based applications (e.g., media streaming, voice over IP, web browsing, etc.) to unique requirements for the vehicular environment (e.g., point of interest advertisements, maps download, parking payments, automatic toll services, etc.) [1].

Besides the nature of a VANET, the characteristics of a vehicular network are different from that of a traditional MANET. This is due to difference in the node mobility between the two types of networks. Although in MANET, the nodes are mobile, however, their speeds traditionally do not exceed 5 [m/s], which is different than VANETs where the node mobility reaches up to 40 [m/s]. This variation in speed and mobility causes the topology of VANETs to be highly dynamic, which in turn, causes disruptions in established connections and frequent link failure.

The study of connectivity in VANETs is not only important to evaluate the network performance and to understand packet exchange among vehicles, and between vehicles and RSUs; both modeling and prediction are crucial in enabling network designers to effectively improve the network deployment planning and resource management in order to meet applications’ requirements [3].

Frequent topological changes of a VANET makes it not very efficient to rely on existing MANET protocols. Rebroadcasting packets by multiple vehicles causes an increase in redundant data, which leads to wasted bandwidth and misuse of radio channels in the network. One of the main objectives of packet rebroadcasting in a VANET is to minimize this redundancy while still guaranteeing packet delivery to all relevant vehicles.

Due to these unique features of a VANET, several types of routing protocols have been introduced in the literature [4]. These protocols are mainly defined taking certain attributes of the VANET into account, such as (i) connectivity-based, (ii) mobility-based, (iii) infrastructure-based, (iv) location-based, and (v) probability-based routing protocols. Later on, many techniques are used to exploit probability theory in system’s dynamics, representing the likelihood of certain events such as the probability of link breakage at a given transmission power. Many such routing protocols utilize a probability model to indicate the state of a wireless communication link between two adjacent nodes, while using many different parameters (e.g., link lifetime in the network) as a major routing parameter.

In this paper, we propose a probability-based multi-hop broadcast protocol, called Collision-Aware REliable FORwarding (CAREFOR) with an objective of reducing the number of rebroadcasts in the network. This minimizes the number of packets in the system, which leads to a lower collision probability and eventually improved throughput. CAREFOR achieves this by allowing the vehicles to compute the probability of their successful transmission in case they are selected to rebroadcast the packet if there exists no better candidate for rebroadcast. A better candidate would be a vehicle that has a chance of delivering the packet for a larger number of uncovered vehicles with fewer number of retransmissions and with minimum packet collisions. Hence, the CAREFOR algorithm relies both on collision avoidance and on a reliable forwarding mechanism. By using both, CAREFOR is able to limit the number of retransmissions while maintaining lower collision value.

The rest of the paper is organized as follows. Section 2 discusses some recent research on routing protocols for VANETs. We mainly highlight the work of [5], which is the foundation of our CAREFOR technique. In Section 3, we describe CAREFOR technique with details mainly covering the theoretical analysis of the next-hop vehicle election probability, and the collision probability estimation. Section 4 describes the main phases of CAREFOR algorithm. The simulation results demonstrate the effectiveness of our technique and are presented in Section 5, also supported by considerations on the use of two versus three hops forward prediction. Finally, conclusion and future work are drawn at the end of the paper.

Section snippets

Related work

Many categories of routing protocols in VANETs have been described in the literature over the past few years. One of these schemes is the probability-based routing protocol that avoids flooding of the network with duplicates of the same packet, by assessing availability of the links and reachability of the packet to the destination, through a given multi-hop route. Clearly, the advantage of such technique is to reduce the overall required number of packets in the system that improves the

Collision-aware REliable FORwarding

In this section, we introduce the CAREFOR technique, and discuss the main rationale behind it, such as reliable forwarding and collision probability. The CAREFOR protocol particularly exploits twofold probabilistic analysis, aiming (i) to limit the number of packet collisions, and (ii) to select potential vehicle forwarder.

CAREFOR takes into consideration reduction in the packet collision probability by estimating and selecting the next-hop forwarder for every single transmission as a method

CAREFOR algorithm

In this section, we present the details of how the CAREFOR protocol can actually work in a VANET environment. As mentioned earlier, the protocol includes two main phases (i) Collision probability estimation, and (ii) Reliable forwarding.

CAREFOR considers a contention resolution procedure necessary for each vehicle to estimate the collision threshold associated with the vehicle density and the actual transmission ranges. The procedure follows in several steps, which can be described as follows:

Simulation results

In this section, we present results of extensive simulation to illustrate the performance and the advantage of the CAREFOR, working in (i) two, and (ii) three hops, over the previous IF algorithm. We used our own simulator that we have developed before for our previous work [23]. For comparison purpose with IF approach, we assume each vehicle is equipped with a GPS device, as well as an IEEE 802.11b network interface card [24], [25].

Vehicles move at a constant speed of 20 m/s along a highway,

Conclusions

In this paper, we presented a novel algorithm, Collision-Aware REliable FORwarding (CAREFOR), which is probabilistic rebroadcast scheme for VANETs. CAREFOR aims to improve the overall performance of the VANET system by minimizing the number of rebroadcasts required in order for a packet to reach a destination. It also relies on reducing the number of collisions using a distributed algorithm. CAREFOR is composed of two phases, a collision probability estimation phase, followed by a reliable

Ahmad Mostafa is a Ph.D. candidate at the Center for Distributed and Mobile Computing at the University of Cincinnati. He obtained a M.Sc. in Industrial engineering from the University of Cincinnati, and B.Sc. in Electrical Engineering from Cairo University. His research interests include QoS in vehicular networks as well as heterogeneous networks, routing, energy conservation and localization in wireless sensor networks, VoIP and physical implementation over wireless mesh network.

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  • Cited by (0)

    Ahmad Mostafa is a Ph.D. candidate at the Center for Distributed and Mobile Computing at the University of Cincinnati. He obtained a M.Sc. in Industrial engineering from the University of Cincinnati, and B.Sc. in Electrical Engineering from Cairo University. His research interests include QoS in vehicular networks as well as heterogeneous networks, routing, energy conservation and localization in wireless sensor networks, VoIP and physical implementation over wireless mesh network.

    Anna Maria Vegni is Assistant Professor in Telecommunications at the Department of Applied Electronics, University of Roma Tre, Rome, Italy. She received the Ph.D. degree in Biomedical Engineering, Electromagnetics and Telecommunications from the University of Roma TRE, in March 2010. During her last year of doctoral studies she joined the MCL (Multimedia Communications Laboratory) at Boston University in Boston, MA, USA under the supervision of Prof. Little. Her research activity focuses on wireless and vehicular communications, heterogeneous networks, and interconnectivity.

    Dr. Agrawal is the Ohio Board of Regents Distinguished Professor at University of Cincinnati, OH. He received B.E. in Electrical Engineering from Ravishanker University, Raipur, India, in 1966, M.E. (Honors) in Electronics and Communication Engineering from the University of Roorkee, Roorkee (now IIT Roorkee), India, in 1968, and the D. Sc. in Electrical Engineering from EPFL Lausanne, Switzerland, in 1975. His recent research interests include resource allocation and security in mesh networks, efficient deployment and security in sensor networks, use of Femto cells, and heterogeneous wireless networks. He has six approved patents, two personal pending patents and twenty four patent filings in the area of wireless cellular networks. His recent contribution in the form of a co-authored introductory text book on Wireless and Mobile Computing has been widely accepted throughout the world and a third edition has just been published. The book has been has been reprinted both in China and India and translated in to Korean and Chinese languages. His co-authored book on Ad hoc and Sensor Networks, second edition published in spring of 2011, is called the best seller by the publisher. He has delivered keynote speech at 26 different international conferences. He has published 624 papers, given 42 different tutorials and extensive training courses in various conferences in USA, and numerous institutions in Taiwan, Korea, Jordan, UAE, Malaysia, and India in the areas of Ad hoc and Sensor Networks and Mesh Networks, including security issues. He has been appointed as the founding Editor-in-Chief of the Central European Journal of Computer Science, Versita. He has graduated 63 PhDs and 55 MS students. He has also been named as an ISI Highly Cited Researcher in Computer Science. He is a winner of 2008 Harry Goode Memorial award from the IEEE Computer Society and 2011 Award for Excellence in Mentoring of Doctoral Students, University of Cincinnati.

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