Spring 2005 Graduate Seminar on Vehicular Computing


Networking 1
Networking 2

This seminar will explore the principles, state of the art, research challenges and trends in vehicular computing and networking. Vehicle-to-vehicle ad-hoc networks are becoming an area of explosive growth. The goal is to provide new driver assistance systems, which can contribute to safer and more efficient roads. This field has an abundance of unsolved problems and will become an increasingly important and active research area in the following years. We will approach these problems from several perspectives: systems, mobile networking, distributed computing, applications, security, social, etc. The seminar is based on research papers and will require students to develop a research-quality project.

The target audience is graduate students with solid background both in operating systems and networking.

Expected Work
Students will be required to:
read and present research papers
complete a research-oriented project (likely related to TrafficView ) .

Project: 80%. In-class presentations and discussions: 20%.

Internet on the Road via Inter-Vehicle Communications (FLEETNET)
  Authors Walter Franz, Hannes Hartenstein, Bernd Bochow
  Conference Unknown.
  Abstract FleetNet aims at the development and demonstration of a wireless ad hoc network for inter-vehicle communications. Key design requirements for FleetNet are the capability to distribute locally relevant data where generated and needed and to satisfy the vehicle drivers’ and passengers’ needs for location-dependent information and services. Location awareness and position data play a crucial role not only for FleetNet applications but also for the communication protocols deployed. This paper provides an overview of the FleetNet project: we describe FleetNet applications and services as well as Fleetnet’s technical challenges together with our current design choices.
      (Presented by Andrew Tjang)

CarNet: A Scalable Ad Hoc Wireless Network System
  Authors Robert Morris John Jannotti Frans Kaashoek Jinyang Li Douglas Decouto (MIT LCS)
  Conference 9th ACM SIGOPS European Workshop, 2000
  Abstract CarNet is an application for a large ad hoc mobile network system that scales well without requiring a fixed network infrastructure to route messages. Car-Net places radio nodes in cars, which communicate using Grid, a novel scalable routing system. Grid uses geographic forwarding and a scalable distributed location service to route packets from car to car without flooding the network. CarNet will support IP connectivity as well as applications such as cooperative highway congestion monitoring, fleet tracking, and discovery of nearby points of interest.
      (Presented by Saif Iqbal)

Inter-vehicle communication: Recent Developments at Ohio State University
  Authors Ozguner, U., Ozguner, F., Fitz, M., Takeshita, O., Redmill, K., Zhu, W. and Dogan, A. (Dept. of Electr. Eng., Ohio State Univ., Columbus, OH, USA)
  Conference 9th ACM SIGOPS European Workshop, 2000
  Abstract In this paper an overview of recent developments on inter-vehicle communication at the Ohio State University is presented. This activity addresses different aspects of human-vehicle, vehicle-vehicle and vehicle-base station-vehicle connections. In this paper, we review the utility of, and concentrate on vehicle-vehicle communication.
      (Presented by Andrew Tjang)

Network 1
Broadcast reception rates and effects of priority access in 802.11-based vehicular ad-hoc networks
  Authors Marc Torrent-Moreno, University of Karlsruhe; Daniel Jiang, DaimlerChrysler RTNA, Inc.; Hannes Hartenstein, University of Karlsruhe;
  Conference VANET 2004
  Abstract One key usage of VANET is to support vehicle safety applications. This use case is characterized by the prominence of broadcasts in scaled settings. In this context, we try to answer the following questions: i) what is the probability of reception of a broadcast message by another car depending on its distance to the sender, ii) how to give priority access and an improved reception rate for important warnings, e.g., sent out in an emergency situation, and iii) how are the above two results affected by signal strength fluctuations caused by radio channel fading? We quantify via simulation the probability of reception for the two-ray-ground propagation model as well as for the Nakagami distribution in saturated environments. By making use of some IEEE 802.11e EDCA mechanisms for priority access, we do not only quantify how channel access times can be reduced but also demonstrate how improved reception rates can be achieved. Our results show that the mechanisms for priority access are successful under the two-way-ground model. However, with a non-deterministic radio propagation model like Nakagami's distribution the benefit is still obvious but the general level of probability of reception is much smaller compared to two-ray-ground model. The results indicate that -- particularly for safety-critical and sensor network type of applications -- the proper design of repetition or multi-hop retransmission strategies represents an important aspect of future work for robustness and network stability of vehicular ad hoc networks.
      (Presented by Nishkam Ravi)

Wireless LAN performance under varied stress conditions in vehicular traffic scenarios
  Authors Singh, J.P., Bambos, N., Srinivasan, B. and Clawin, D.
  Conference Unknown
  Abstract Mobile ad-hoc networking with wireless LAN infrastructure can be employed to build inter-vehicle communication based applications. The associated high velocities and hostile driving environments pose a challenge to the performance of a wireless LAN. This paper assesses the performance of a wireless Local Area Network in different vehicular traffic and mobility scenarios. The network throughput and the quality of the wireless communication channel, measured on IEEE 802.11b compliant equipment, are observed to degrade with increasingly stressful communication scenarios. The test scenarios are varied by conducting the experiments under different vehicular mobility, peer-distance and driving environment conditions. We present results that can facilitate development of efficient applications for inter-vehicular communication. We also suggest optimization measures through aggression control via variations in packet size.
      (Presented by Pravin Shankar)

A Receiver-Centric Transport Protocol for Mobile Hosts With Heterogeneous Wireless Interfaces
  Authors Hung-Yun Hsieh, Kyu-Han Kim, Yujie Zhu, Raghupathy Sivakumar
  Conference MobiCom 2003
  Abstract Numerous transport protocols have been proposed in related work for use by mobile hosts over wireless environments. A common theme among the design of such protocols is that they specifically address the distinct characteristics of the last-hop wireless link, such as random wireless errors, round-trip time variations, blackouts, handoffs, etc. In this paper, we argue that due to the defining role played by the wireless link on a connection’s performance, locating the intelligence of a transport protocol at the mobile host that is adjacent to the wireless link can result in distinct performance advantages. To this end, we present a receiver-centric transport protocol called RCP (Reception Control Protocol) that is a TCP clone in its general behavior, but allows for better congestion control, loss recovery, and power management mechanisms compared to sender-centric approaches. More importantly, in the context of recent trends where mobile hosts are increasingly being equipped with multiple interfaces providing access to heterogeneous wireless networks, we show that a receiver-centric protocol such as RCP can enable a powerful and comprehensive transport layer solution for such multi-homed hosts. Specifically, we describe how RCP can be used to provide: (i) a scalable solution to support interface specific congestion control for a single active connection; (ii) seamless server migration capability during handoffs; and (iii) effective bandwidth aggregation when receiving data through multiple interfaces, either from one server, or from multiple replicated servers. We use both packet level simulations, and real Internet experiments to evaluate the proposed protocol.
      (Presented by Nishkam Ravi)

ATP: Autonomous Transport Protocol
  Authors Tamer Elsayed, Mohamed Hussein, Moustafa Youssef, Tamer Nadeem, Adel Youssef, Liviu Iftode
  Conference IEEE Midwest Symposium on Circuits and Systems, December 2003
  Abstract In this report we present the design of the Autonomous Transport Protocol (ATP). The basic service provided by ATP is a reliable transport connection between two endpoints (identified by content identifiers) independent of their physical location. Autonomy allows dynamic endpoints relocation on different end hosts without disrupting the transport connection between them. ATP depends on the existence of an underlying Instance-Based Network (IBN) to achieve its goals. An IBN provides the flexibility of having different instances of the same content. It is up to the user of the IBN network to define the relation between these instances. An IBN allows its user to to map a content to a particular node. Application endpoints can send messages to other content-identified endpoints. Routing in the IBN is instance-based; the IBN can route a message to a specific content instance or to the nearest instance, if no exact match is found for the destination content instance. Moreover, the IBN replicates the stored contents in order to provide fault tolerance and IBN nodes along the query path can cache a content to provide fast answers to future queries. The ATP layer in the intermediate nodes between the source and destination endpoints can actively participate in the connection, for example, to buffer data for the destination endpoints during periods of unavailability. Data is transferred by a combination of active and passive operations, where the ATP layer of a node can decide whether to actively push the data to the destination or to passively wait for the destination endpoint to pull the data. The decision to whether to use the active or passive modes can be taken by a local policy on the node running the ATP protocol
      (Presented by Arati Baliga)

Internet Indirection Infrastructure
  Authors Ion Stoica, Daniel Adkins, Shelley Zhuang, Scott Shenker, Sonesh Surana
  Conference SIGCOMM 2002
  Abstract Attempts to generalize the Internet’s point-to-point communication abstraction to provide services like multicast, anycast, and mobility have faced challenging technical problems and deployment barriers. To ease the deployment of such services, this paper proposes an overlay-based Internet Indirection Infrastructure that offers a rendezvous-based communication abstraction. Instead of explicitly sending a packet to a destination, each packet is associated with an identifier; this identifier is then used by the receiver to obtain delivery of the packet. This level of indirection decouples the act of sending from the act of receiving, and allows to efficiently support a wide variety of fundamental communication services. To demonstrate the feasibility of this approach, we have designed and built a prototype based on the Chord lookup protocol.
      (Presented by Arati Baliga)

Improving TCP/IP Performance over Wireless Networks
  Authors Hari Balakrishnan, Srinivasan Seshan, Elan Amir and Randy H. Katz
  Conference Mobicom 1995
  Abstract TCP is a reliable transport protocol tuned to perform well in traditional networks made up of links with low bit-error rates. Networks with higher bit-error rates, such as those with wireless links and mobile hosts, violate many of the assumptions made by TCP, causing degraded end-to-end performance. In this paper, we describe the design and implementation of a simple protocol, called the snoop protocol, that improves TCP performance in wireless networks. The protocol modifies network-layer software mainly at a base station and preserves end-to-end TCP semantics. The main idea of the protocol is to cache packets at the base station and perform local retransmissions across the wireless link. We have implemented the snoop protocol on a wireless testbed consisting of IBM ThinkPad laptops and i486 base stations communicating over an AT&T Wavelan. Our experiments show that it is significantly more robust at dealing with unreliable wireless links as compared to normal TCP; we have achieved throughput speedups of up to 20 times over regular TCP in our experiments with the protocol.
      (Presented by Martin Constantine)

I-TCP: Indirect TCP for Mobile Hosts
  Authors Ajay Bakre, B.R. Badrinath
  Conference ICDCS 1994
  Abstract IP-based solutions to accommodate mobile hosts within existing internetworks donot address the distinctive features of wireless mobile computing. IP-based transport protocols thussuffer from poor performance when a mobile host communicates with a host on the fixed network.This is caused by frequent disruptions in network layer connectivity due to — i) mobility and ii)unreliable nature of the wireless link. We describe the design and implementation of I-TCP, whichis an indirect transport layer protocol for mobile hosts. I-TCP utilizes the resources of MobilitySupport Routers (MSRs) to provide transport layer communication between mobile hosts and hostson the fixed network. With I-TCP, the problems related to mobility and the unreliability of wirelesslink are handled entirely within the wireless link; the TCP/IP software on the fixed hosts is notmodified. Using I-TCP on our testbed, the throughput between a fixed host and a mobile host improved substantially in comparison to regular TCP.
      (Presented by Martin Constantine)

Improving the Performance of Reliable Transport Protocols in Mobile Computing Environments
  Authors Ramón Caceres, Liviu Iftode
  Conference IEEE Journal of Selected Areas in Communications
  Abstract We explore the performance of reliable data communication in mobile computing environments. Motion across wireless cell boundaries causes increased delays and packet losses while the network learns how to route data to a host's new location. Reliable transport protocols like TCP interpret these delays and losses as signs of network congestion. They consequently throttle their transmissions, further degrading performance. We quantify this degradation through measurements of protocol behavior in a wireless networking testbed. We show how current TCP implementations introduce unacceptably long pauses in communication during cellular handoffs (800 milliseconds and longer), and propose an end-to-end fast retransmission scheme that can reduce these pauses to levels more suitable for human interaction (200 milliseconds). Our work makes clear the need for reliable transport protocols to differentiate between motion-related and congestion-related packet losses, and suggests how to adapt these protocols to perform better in mobile computing environments.
      (Presented by Martin Constantine)

ATP: A Reliable Transport Protocol for Ad-hoc Networks
  Authors Karthikeyan Sundaresan, Vaidyanathan Anantharaman, Hung-Yun Hsieh, and Raghupathy Sivakumar
  Conference SPECTS02
  Abstract Existing works have approached the problem of reliable transport in ad-hoc networks by proposing mechanisms to improve TCP’s performance over such networks. In this paper we show through detailed arguments and simulations that several of the design elements in TCP are fundamentally inappropriate for the unique characteristics of ad-hoc networks. Given that ad-hoc networks are typically stand-alone, we approach the problem of reliable transport from the perspective that it is justifiable to develop an entirely new transport protocol that is not a variant of TCP. Toward this end, we present a new reliable transport layer protocol for ad-hoc networks called ATP (ad-hoc transport protocol). We show through ns2 based simulations that ATP outperforms both default TCP and TCP-ELFN.
      (Presented by Nishkam Ravi)

Performance of a Medium Access Scheme for Inter-Vehicle Communication (FLEETNET)
  Authors Lott M.
  Conference SPECTS02
  Abstract Bluetooth™ is a promising wireless technology designed for short-range ad hoc connections, which has many potentially useful applications. One such use is the transfer of data between two fast-moving vehicles such as automobiles. In this paper we explore the suitability of Bluetooth to make connections in highly mobile environments. In particular, we have developed a hardware testbed to make an empirical analysis of the time it takes to establish Bluetooth connections and the range at which those connections can be established. We also explore, by means of simulation, ways in which to improve connection setup times and the impact this will have on any potential data transfer.
      (Presented by Pravin Shankar)

Dedicated Short Range Communications (DSRC) for AHS (Advanced Highway Systems) Services
  Authors Inoue, H. Osawa, S. Yashiki, A. Makino, H.
  Conference IEEE Intelligent Vehicles Symposium 2004
  Abstract The Japanese advanced cruise-assist highway system (AHS) provides driving support services through collaboration between the system and vehicle. AHS uses dedicated short-range communications (DSRC) for road-to-vehicle dialog that requires real-time and high-reliability operation. AHS-DSRC constitutes a small radio zone that provides driving support information in a cycle of 0.1 seconds. DSRC incorporates a marker beacon and an information beacon that are successively positioned at the roadside. This paper describes the AHS-DSRC was verified by experiment to provide a safety level of 99.1% or better.
      (Presented by Andrew Tjang)

A Survey of Inter-Vehicle Communication
  Authors Jun Luo, Jean-Pierre Hubaux
  Conference EPFL Technical report, IC/2004/04
  Abstract The paper surveys IVC with respect to key enabling technologies ranging from physical radio frequency to group communication primitives and security issues. The mobility models used to evaluate the feasibility of these technologies are also briefly described. There is also a discussion of various MAC protocols that seem to be indispensable components in the network protocol stack of IVC. The paper shows that the design of communication protocols in the framework of IVC is extremely challenging due to the variety of application requirements and the tight coupling between an application and its supporting protocols.
      (Presented by Saif Iqbal)

Network 2
Design and Implementation of a Peer-to-Peer Data Dissemination and Prefetching Tool for Mobile Users
  Authors Maria Papadopouli, Henning Schulzrinne
  Conference Vanet 2004
  Abstract This paper presents 7DS, a novel peer-to-peer data sharingsystem. Peers can be either mobile or stationary (such as info-stations). 7DS is an architecture, a set of protocols and animplementation enabling the exchange of data among peersthat are not necessarily connected to the Internet. Communi-cation is typically, but not necessarily, wireless. 7DS runs asan applicationand communicates with other 7DS participantsvia a LAN. It operates in two modes, namely prefetch andon-demand. In the prefetch mode, it anticipates informationneeds of users and the system queries other peers for thesedata. In the on-demand mode, the user can directly searchfor information among peers. 7DS can work complementaryto other data access methods. 7DS enhances the collabora-tion by allowing users to create on-the-fly an ad-hoc networkand browse the content of the cache of peers that have beenmade accessible to it. It can be used to spread informationand for data access, particularly, for location-dependent data(such as weather or traffic reports, news, tourist guides, cam-pus events or news) and popular data (music files, news, videogames) that do not change very rapidly. We discuss the designand an implementation of 7DS.
      (Presented by Steve Smaldone)

Moving Objects Information Management: The Database Challenge
  Authors Ouri Wolfson (Affil: DCS, University of Illinois Mobitrac Inc, Chicago IL )
  Conference Unknown
  Abstract Miniaturization of computing devices, and advances in wireless communication and sensor technology are some of the forces that are propagating computing from the stationary desktop to the mobile outdoors. Some important classes of new applications that will be enabled by this revolutionary development include location-based services, tourist services, mobile electronic commerce, and digital battlefield. Some existing application classes that will benefit from the development include transportation and air traffic control, weather forecasting, emergency response, mobile resource management, and mobile workforce. Location management, i.e. the management of transient location information, is an enabling technology for all these applications. Location management is also a fundamental component of other technologies such as fly-through visualization, context awareness, augmented reality, cellular communication, and dynamic resource discovery. In this paper we present our view of the important research issues in location management. These include modeling of location information, uncertainty management, spatio-temporal data access languages, indexing and scalability issues, data mining (including traffic and location prediction), location dissemination, privacy and security, location fusion and synchronization.
      (Presented by John Austen)

Seven Degrees of Separation in Mobile and Ad Hoc Networks
  Authors Maria Papadopouli and Henning Schulzrinne
  Conference GLOBECOM 2000
  Abstract We present an architecture that enables the sharing of information among mobile, wireless, collaborating hosts that are intermittently connected to the Internet. Participants in the system obtain data objects from Internet-connected servers, cache them and exchange them with others who are interested in them. The system exploits the fact that there is a high locality of information access within a geographic area. It aims to increase the data availability to participants with lost connectivity to the Internet. We investigate how user mobility and query patterns affect data dissemination in such an environment. We discuss the main components of the system and possible applications. Finally, we present simulation results that show that the ad hoc networks can be very effective in distributing popular information.
      (Presented by Himanshu Gupta)

Vehicle-to-Vehicle Safety Messaging in DSRC
  Authors Qing Xu (University of California at Berkeley), Tony Mak, Jeff Ko, Raja Sengupta
  Conference VANET 2004
  Abstract This paper studies the design of layer-2 protocols for a vehicle to send safety messages to other vehicles. The target is to send vehicle safety messages with high reliability and low delay. The communication is one-to-many, local, and geo-significant. The vehicular communication network is ad-hoc, highly mobile, and with large numbers of contending nodes. The messages are very short, have a brief useful lifetime, but must be received with high probability. For this environment, this paper explores the efficacy of rapid repetition of broadcast messages. This paper proposes several random access protocols for medium access control. The protocols are compatible with the Dedicated Short Range Communications (DSRC) multi-channel architecture. Analytical bounds on performance of the proposed protocols are derived. Simulations are conducted to assess the reception reliability and channel usage of the protocols. The sensitivity of the protocol performance is evaluated under various offered traffic and vehicular traffic flows. The results show our approach is feasible for vehicle safety messages in DSRC.

Efficient Attribute Authentication with Applications to Ad Hoc Networks
  Authors Markus Jakobsson (RSA Security), Susanne Wetzel
  Conference VANET 2004
  Abstract We present a family of certification methods with applications to attribute certification, which in turn has ample applications to ad hoc networks by way of the use of centrally managed recommendation mechanisms. Our construction is based on a Merkle tree consisting of subtrees, each of which corresponds to some aspect of an attribute. We study how the ordering of these subtrees can impact the cost of representing, maintaining, and verifying attribute certificates. We describe the applicability of our construction to vehicle ad hoc networks, detail our proposed methods, and evaluate their suitability to the proposed settings.

Stealth Attacks on Vehicular Wireless Networks
  Authors M. Jakobsson, X. Wang, S. Wetzel (Invited Paper)
  Conference Proceedings of IEEE Vehicular Technology Conference 2004-Fall "Wireless Technologies for Global Security"
  Abstract In this position paper we discuss various issues related to so-called stealth attacks. We elaborate on stealth attacks in the context of three common types of wireless networks, namely ad hoc networks, hybrid networks, and sensor networks. We consider the relevance of these settings to various vehicular environments; e.g., emergency and rescue operations, military operations, and theft recovery. Along with this, we discuss adversarial models. We furthermore explore the level of threat in a set of example situations and discuss potential tools that could be used to reduce the severity of stealth attacks in these contexts.

The Security and Privacy of Smart Vehicles
  Authors Jean-Pierre Hubaux, Srdjan Capkun and Jun Luo
  Conference IEEE Security & Privacy Magazine, Vol. 2, No. 3, pp 49--55, May-June 2004
  Abstract An important evolution for the automotive industry is the one toward context awareness, meaning that a vehicle is aware of its neighborhood (including the presence and location of other vehicles). Modern cars now possess a network of processors connected to a central computing platform that provides Ethernet, USB, Bluetooth, and IEEE 802.11 interfaces. To allow the wireless authentication of vehicles, these authorities must provide each vehicle with a private/public key pair, along with a shared symmetric key, and a digital certificate of its identity and public key. An important task is to devise appropriate privacy preserving protocols, which are typically based on anonymity schemes, relying on temporary pseudonyms.
      (Presented by Yan Nuriyev)

Self-Organized Public-Key Management for MANETS
  Authors Srdjan Capkun, Levente Buttyan, and Jean-Pierre Hubaux
  Conference IEEE Transactions on Mobile Computing, Jan-Mar 2003
  Abstract In contrast to conventional networks, mobile ad hoc networks usually do not provide on-line access to trusted authorities or to centralized servers and they exhibit frequent partitioning due to link and node failures and to node mobility. For these reasons, traditional security solutions that require on-line trusted authorities or certificate repositories are not well suited for securing ad hoc networks. The paper proposes a fully self-organized public-key management system that allows users to generate their public-private key pairs, to issue certificates, and to perform authentication regardless of the network partitions and without any centralized services. Furthermore, the paper’s approach does not require any trusted authority, not even in the system initialization phase.
      (Presented by Pandurang Kamat)

Mobility Helps Security in Ad Hoc Networks
  Authors Srdjan Capkun, Jean-Pierre Hubaux, and Levente Buttyan
  Conference MobiHoc, June 2003
  Abstract Contrary to the common belief that mobility makes security more difficult to achieve, the paper shows that node mobility can, in fact, be useful to provide security in ad hoc networks. A technique is proposed in which security associations between nodes are established, when they are in the vicinity of each other, by exchanging appropriate cryptographic material. Also proposed is an extension of this basic mechanism, in which a security association can be established with the help of a “friend”. The mechanism can work in any network configuration and that the time necessary to set up the security associations is strongly influenced by several factors, including the size of the deployment area, the mobility patterns, and the number of friends; we provide a detailed investigation of this influence.

Detecting and Correcting Malicious Data in VANETS
  Authors Philippe Golle Dan Greene , Jessica Staddon (PARC)
  Conference Proceedings of the First ACM Workshop on Vehicular Ad Hoc Networks; 2004
  Abstract In order to meet performance goals, it is widely agreed that VANETs (vehicular ad hoc networks) must rely heavily on node-to-node communication, thus allowing for malicious data traffic. At the same time, the easy access to information afforded by VANETs potentially enables the difficult security goal of data validation. We propose a general approach to evaluating the validity of VANET data. In our approach a node searches for possible explanations for the data it has collected based on the fact that malicious nodes may be present. Explanations that are consistent with the node’s model of the VANET are scored and the node accepts the data as dictated by the highest scoring explanations. Our techniques for generating and scoring explanations rely on two assumptions: 1) nodes can tell "at least some" other nodes apart from one another and 2) a parsimony argument accurately reflects adversary behavior in a VANET. We justify both assumptions and demonstrate our approach on specific VANETs.

Security Analysis of a Cryptographically-Enabled RFID Device
  Authors Steve Bono, Matthew Green, Adam Stubblefield, and Avi Rubin (Johns Hopkins University) Ari Juels and Michael Szydlo (RSA Labs)
  Conference Unpublished draft
  Abstract We describe our success in defeating the security of an RFID device known as a Digital Signature Transponder (DST). Manufactured by Texas Instruments, DST (and variant) devices help secure millions of SpeedPassTM payment transponders and automobile ignition keys. Our analysis of the DST involved three phases: 1. Reverse engineering: Starting from a rough published schematic, we determined the complete functional details of the cipher underpinning the challenge-response protocol in the DST. We accomplished this with only “oracle” or “black-box” access to an ordinary DST, that is, by experimental observation of responses output by the device. 2. Key cracking: The key length for the DST is only 40 bits. With an array of of sixteen FPGAs operating in parallel, we can recover a DST key in under an hour using two responses to arbitrary challenges. 3. Simulation: Given the key (and serial number) of a DST, we are able to simulate its RF output so as to spoof a reader. As validation of our results, we purchased gasoline at a service station and started an automobile using simulated DST devices. We accomplished all of these steps using inexpensive o -the-shelf equipment, and with minimal RF expertise. This suggests that an attacker with modest resources can emulate a target DST after brief short-range scanning or long-range eavesdropping across several authentication sessions. We conclude that the cryptographic protection a orded by the DST device is relatively weak.
      (Presented by Pandurang Kamat)

Urban Multi-Hop Broadcast Protocol for Inter-Vehicle Communication Systems
  Authors Gokhan Korkmaz (The Ohio State University), Eylem Ekici, Fusun Ozguner, Umit Ozguner
  Conference VANET 2004
  Abstract Inter-Vehicle Communication Systems rely on multi-hop broad- cast to disseminate information to locations beyond the trans- mission range of individual nodes. Message dissemination is especially dicult in urban areas crowded with tall buildings because of the line-of-sight problem. In this paper, we pro- pose a new ecient IEEE 802.11 based multi-hop broadcast protocol (UMB) which is designed to address the broadcast storm, hidden node, and reliability problems of multi-hop broadcast in urban areas. This protocol assigns the duty of forwarding and acknowledging the broadcast packet to only one vehicle by dividing the road portion inside the trans- mission range into segments and choosing the vehicle in the furthest non-empty segment without apriori topology infor- mation. When there is an intersection in the path of the message dissemination, new directional broadcasts are initi- ated by the repeaters located at the intersections. We have shown through simulations that our protocol has a very high success rate and efficient channel utilization when compared with other ooding based protocols.

Location-Aided Routing (LAR) in mobile ad hoc networks
  Authors Young-Bae Ko
Nitin H. Vaidya (DCS, Texas A&M University)
  Conference Wireless Networks (Journal) Vol 6, Issue 4 2000
  Abstract A mobile ad hoc network consists of wireless hosts that may move often. Movement of hosts results in a change in routes, requiring some mechanism for determining new routes. Several routing protocols have already been proposed for ad hoc networks. This paper suggests an approach to utilize location information (for instance, obtained using the global positioning system) to improve performance of routing protocols for ad hoc networks. By using location information, the proposed Location-Aided Routing (LAR) protocols limit the search for a new route to a smaller “request zone” of the ad hoc network. This results in a significant reduction in the number of routing messages. We present two algorithms to determine the request zone, and also suggest potential optimizations to our algorithms.
      (Presented by Nishkam Ravi)

Contention-Based Forwarding for Street Scenarios
  Authors Holger Füßler, Hannes Hartenstein, Jörg Widmer, Martin Mauve, Wolfgang Effelsberg
  Conference 1st International Workshop in Intelligent Transportation (WIT 2004)
  Abstract Existing position-based unicast routing algorithms which forward packets in the geographic direction of the destination require that the forwarding node knows the positions of all neighbors in its transmission range. This information on direct neighbors is gained by observing beacon messages each node sends out periodically. Due to mobility, the information that a node receives about its neighbors becomes outdated, leading either to a significant decrease in the packet delivery rate or to a steep increase in load on the wireless channel as node mobility increases. In this paper, we propose a mechanism to perform position-based unicast forwarding without the help of beacons. In our contention-based forwarding scheme (CBF) the next hop is selected through a distributed contention process based on the actual positions of all current neighbors. For the contention process, CBF makes use of biased timers. To avoid packet duplication, the first node that is selected suppresses the selection of further nodes. We propose three suppression strategies which vary with respect to forwarding efficiency and suppression characteristics. We analyze the behavior of CBF with all three suppression strategies and compare it to an existing greedy position-based routing approach by means of simulation with ns-2. Our results show that CBF significantly reduces the load on the wireless channel required to achieve a specific delivery rate compared to the load a beacon-based greedy forwarding strategy generates.
      (Presented by Saif Iqbal)