CS 672 Paper Presentation

1. CS 672 Paper Presentation “A Survey of Inter-Vehicle Communication” Jun Luo, Jean-Pierre Hubuax EPFL, Switzerland Technical Report IC/2004/24 Presented By Saif Iqbal

2. IVC - The Big Picture • About • Component of Intelligent Transportation System (ITS) • One of the concrete applications of MANETS • Attracted research attention in US, EU, and Japan • Motivation • Improves road safety and efficiency by increasing the horizon of drivers • and on-board devices • Transmission of road-side information about emergencies, congestion, • etc. • Ability for inter-driver communication • Existing ad hoc networks protocols and experiences can actually be put • to practice

3. IVC - The Big Picture • Groups & Applications • Association of Electronic Technology for Automobile Traffic and • Driving (JSK), Japan - early 1980’s • CarTALK, EU - 2000 • FleetNet, Germany - 2000 • PATH, California • Chauffeur, EU • DEMO 2000, Japan

4. IVC – Main Applications Information and Warning Functions Dissemination of road information to distant vehicles Communication-based Longitudinal Control Exploiting “look-through” capacity to avoid accidents, platooning vehicles, etc. Co-operative Assistance Systems Coordinating vehicles at critical points Added-value Applications Internet access, Location-based services, Multiplayer games

5. Paper • Surveys IVC with respect to key-enabling technologies • Focuses the discussion on the various MAC protocols that are really • important for IVC • Analyzes application requirements and protocols and comes up with • suggestions with regards to the direction of future work • Does not describe applications, but mentions them when their enabling • mechanisms are discussed

6. Radio Frequency Spectrum • Both infrared and radio waves have been studied and employed • Radio waves: VHF, micro, and millimeter waves • VHF and microwaves are of broadcast type • Dedicated Short Range Communication (DSRC) spans 75MHz of • spectrum in the 5.9 GHz band • DEMO 2000, Chauffeur used 5.8 GHz DSRC • CarTALK, FleetNet use ULTRA TDD • JSK, PATH, CarTALK have used infrared, typically for cooperative • driving

7. MAC/PHY Layer • WLAN approach • 802.11, Bluetooth • Plus: inherent support for distributed coordination in ad hoc mode • Minus: low flexibility in radio resource assignment and transmission rate • control • 3G approach • CDMA • Plus: high granularity for data transmission and flexible assignment of • radio resources • Minus: complexity in designing the the coordination function in ad hoc • mode

8. WLAN • Can directly use WLAN standards for RVC, but does not work as well • for IVC • For migrating to IVC the following problems need to be tackled • -Resistance to more severe multipath effects • -Time synchronization between rapidly moving nodes • -Distributed resource allocation • Token Ring Protocol - PATH • Mechanism to construct, recover, join, and leave a ring • Token circulation, recovery, and multiple token resolution • Solves contention for radio resources • Need further experiments to see if this suitable for IVC

9. WLAN • Location-based Channel Access (LCA) • Divides the geographical area into cellular structure • Each cell has a unique channel associated with it • Any multiple access scheme like CSMA, CDMA, TDMA can be used • within the cell • Adaptability to high mobility in IVC is a question mark • Non-Persistent CSMA – DOLPHIN/DEMO 2000 • DOLPHIN – Dedicated Omni-purpose inter-vehicle communication • Linkage Protocol for Highway Automation • Non-persistent CSMA outperforms p-persistent one with respect to • packet loss in IVC

10. 3G • Cannot directly employ it as it is meant for centralized cellular networks • For extending to IVC the following problems need to be addressed • -Distributed radio resource management • -Power control algorithms • -Time synchronization • Solution should rely on distributed media access control • Reservation ALOHA – CarTALK/FleetNet • Use R-ALOHA for distributed channel assignment • High throughput, as a node which catches a slot can use it in subsequent • frames as long as it has packets to send • Frequent reservation attempts due to short packet trains • Due to hidden terminal problem, destructive interference with • established channels may occur • Reliable R-ALOHA lets all nodes know the status of the slots

11. 3G • Random Access CDMA • Combines CDMA with random channel access – start transmission • immediately irrespective of the state of the channel • Can avoid primary collisions (two nodes with the same code try to • access the channel together) using code assignment, spread-coding • schemes • Multi-access interference (MAI) results in secondary collisions (near-far • problem) at the receiver • Controlled Access CDMA • Uses a modified RTS/CTS mechanism to solve the problem • Split the channel for control and data – RTS/CTS is transferred over • control channels to let the interfering nodes be aware of the status • Use knowledge of power levels to alleviate the near-far problem

12. MAC/PHY Layer • Summary • Number of MAC protocols proposed, but not all of them are put into • practice • 802.11b is used for demonstration (FleetNet) • 802.11a is chosen by ASTM (American Society for Testing and • Materials) as the basis for DSRC • MAC Protocol based on ULTRA TDD, used in CarTALK, could be • another solution especially in the EU

13. Network Layer • Any existing position-based routing protocol for ad hoc networks can be • applied to IVC • Can optimize by using location and surrounding awareness information • Mostly group-oriented communications rather than pair-wise • Unicast Routing • Contention-Based Forwarding • Proposes a forwarding scheme avoiding the use of beacons and hence • higher efficiency • Reactive Location Service - FleetNet • Reactive routing protocol by requesting the location of the destination • when sending a packet • Afterwards, a greedy geographical forwarding technique is used

14. Network Layer • Broadcast Routing • Used to disseminate traffic information • Can be made adaptive – change the inter-transmission interval • Use a randomized interval • Multi-resolution data structure to express information in the message • Summary • Unicast routing is superfluous in most cases • Broadcast routing seems to be a necessary supporting mechanism of • IVC applications • Broadcast routing could also be optimized in various ways

15. Group Communication • Group communication primitives are important as reliability required for • critical situations, where group information dissemination may not work • Required by two important applications – platooning and cooperative • driving • Localized Group Membership Service (LGMS) • Reduce the group membership service to the local environment of a • node • Only tracks memberships of neighbors and installs a local view at each • node • Works for congestion area detection • Does not support any functions with reliability requirement due to lack • of a global view of the group

16. Group Communication • Event-based middleware • Supports cooperative mobile applications • Underlying membership service is costly and not really needed • Implemented only on RVC scenarios • The Driving Philosopher Problem • Sharing resources among a group of vehicles • Proposed algorithm solves the model in a synchronous model • Impossible to achieve fairness and concurrency at the same time • Impossible to solve the problem in an asynchronous model • Summary • Important component of IVC • Build the system directly upon the MAC layer • Lightweight membership tracking instead of doing it globally

17. Security • Driver Ad Hoc Networking Infrastructure (DAHNI) • System mounted on each vehicle which includes both processing and • wireless communication facilities • Each car constitutes a local communication network around itself • Come to the conclusion that no confidentiality is needed, and ignore • privacy concerns • To securely estimate the distance between vehicles, establishment of • symmetric keys is required • Electronic License Plates • Certified identity that a vehicle provides via a wireless link • Usage: Dynamic toll charge, identify culprits, distance estimation • Attacks: Disable system, impersonation, denial of service • Supports cooperative driving

18. Security • Summary • Security of IVC has been ignored so far by the research community • Some ideas proposed but not followed through and implemented • Emerging and potentially important research topic

19. Mobility Model • Mobility pattern in IVC is quite different from the “random waypoint” • model used for ad hoc networks simulation • Simulations for MAC protocols should also take mobility into account • which is not necessarily the case with traditional MAC • There are proposed tools for traffic simulation to help extend the • network simulators • Application context has to be taken into account before choosing a • mobility model to evaluate certain protocols • Mathematical Modeling for Traffic • Microscopic – suitable for simulating group communications • Macroscopic – for routing protocols discussion • Statistical – real mobility pattern is in 2-d or 3-d space, approach based • on Markov chain theory

20. Conclusion • Design of communication protocols in IVC is extremely challenging • Ad hoc routing protocols, and group communication primitives • migrated from wired networks might not be efficient • Most of the proposed work is in routing algorithms and MAC • Routing protocols are unnecessary in most cases • Local distributed coordination functions sitting directly upon the • MAC would be more efficient • As vehicles become “smarter”, security and privacy gain importance • Mathematical models for road traffic are important for simulations