challenge: peers on wheels a road to new traffic information systems jedrzej rybicki, bjrn...
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Challenge: Peers on Wheels – A Road to New TrafficInformation Systems
Jedrzej Rybicki, Björn Scheuermann, Wolfgang KiessChristian Lochert, Pezhman Fallahi, Martin Mauve
Computer Networks Research GroupHeinrich Heine University
Düsseldorf, Germany
MobiCom 2007
presenter: James
Agenda• Introduction• P2P networks• A First System – Traffic Information Sharing
– Challenges• Conclusion
– Key points & contribution– Pros & Cons– Relevance to our research
Introduction• Vehicular ad-hoc networks (VANETs)
– Community: Public authorities, academia, car manufacturers – Applications: reduction of road casualties
• brake warning, intersection assistance, collision avoidance system• Parking lots, route plan, coordinating car flow
• Technology– Infrastructure-based: 3G, GPRS, WiMax, WiFi
• Internet connection• DHT (distributed Hash Table), P2P• Multiple hops vs. over long distances
P2P networks• Overlay virtual network
– Locate the resource? DHT: Chord, CAN, Tapestry• Resources mapped to peers by “Hash function”
– Peer knows a subset of the other peers– Lookup can be routed– Logarithmic complexity
Traffic Information Sharing
• Basic: road segment ID in DHT• System load and scalability issue
– Update/query rate? (think close-by segments)• Independent vs. adjacent support (shortcuts)• N-dimensional ID space (CAN), road ID vs. position
• Fairness and reliability issue– High update/query rate? (In a node responsible for
highway intersection)• Load balancing & redundancy group concept
Traffic Information Sharing• Bootstrapping (Join) issue
– DHT provides a well-known always on nodes• Non-cars peers on the internet
• In-network aggregation issue– Query for a whole possible route
• Query each segment separately (traffic) vs. one node responsible for aggregation (computation)
• Distributed caching, local storage space vs. reduced reoccurring queries traffic
• Trustworthiness & privacy issue– Abnormal data will be easy to notice.– Cryptography and decentralized approach protects user’s privacy
• Route plan, IDs?
Traffic Information Sharing• Connectivity issue
– Abrupt loss & disconnect voluntarily• The level of required redundancy in the overlay• Delay of restructuring
• Publish/Subscribe TIS issue– Query the system periodically? Ex. All possible route?
•Detection of changes•History of observations & bring it to respective peers.
•Manage subscriptions•Car’s route is stored and indexed!
•Dissemination service•Burden of sending msg to each subscriber multicast, redundancy•Acceptable delay for changing alternative route.
Traffic Information Sharing
• Further think into car-to-car info exchange– Processing specific requests
• Ex. Sunny road (sensors in car)?– Allows to query relevant sensor readings on demand.– System as a broker
– Traffic coordination & distributed computation• Ex. Rush hour. All has its good route by themselves.
– Cooperate for route planning and information sharing • Ex. Query optimal route may travel through the
network and get final answer.
Conclusion• Key points & contribution
– Present a traffic information system using an infrastructure-based p2p network made up of vehicles.
– Describe the technical challenges from this approach. • Pros
– Easy to understand. It Leverages DHT concept in VANET• Cons
– Not address current problems in VANET/C2C TIS• Relevance to our research
– P2P/Sensor network in VANET/C2C TIS
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