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Mobile Ad Hoc Networks and Automotive Applications

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  1. Mobile Ad Hoc Networks and Automotive Applications Luiz A. DaSilva, Jeff H. Reed, William Newhall Mobile and Portable Radio Group Virginia Polytechnic Institute and State University © Luiz DaSilva, 2002

  2. Agenda • Fundaments of Mobile Ad Hoc Networks (MANETs) • Advances in MANET • Research on MANET at Virginia Tech • Automotive applications Ad Hoc Networks and Automotive Applications

  3. Fundaments of Mobile Ad Hoc Networks (MANETs) Definition and applications Challenges Standardization Ad Hoc Networks and Automotive Applications

  4. Mobile Ad Hoc Networks (MANET) Backbone Mobile nodes Access points MANET Wireless Mobile Network Ad Hoc Networks and Automotive Applications

  5. Fundamental Concepts • Ad hoc networks are autonomous networks operating either in isolation or as “stub networks” connecting to a fixed network • Do not necessarily rely on existing infrastructure • No “access point” • Each node serves as a router and forwards packets for other nodes in the network • Topology of the network continuously changes Ad Hoc Networks and Automotive Applications

  6. Motivation • Battlefield survivability • Must support mobility • Avoid single point of failure typical of centralized systems • Often unable to rely on existing communications infrastructure • Desire for a rapidly deployable, self-organizing network • Multi-hop packet routing used to exchange messages between users who are not within LOS of each other Ad Hoc Networks and Automotive Applications

  7. Applications • Military • Rapidly deployable battle-site networks • Sensor fields • Unmanned aerial vehicles • Disaster management • Disaster relief teams that cannot rely on existing infrastructure • Neighborhood area networks (NANs) • Shareable Internet access in high density urban settings • Impromptu communications among groups of people • Meetings/conferences • Wearable computing • Automobile communications (more on this later) Ad Hoc Networks and Automotive Applications

  8. Characteristics • Dynamic topology • Heterogeneity • Bandwidth-constrained variable-capacity links • Limited physical security • Nodes with limited battery life and storage capabilities Ad Hoc Networks and Automotive Applications

  9. Standardization • Internet Engineering Task Force (IETF) MANET working group (http://www.ietf.org/html.charters/manet-charter.html) “The primary focus of the working group is to develop and evolve MANET routing specification(s) and introduce them to the Internet Standards track. The goal is to support networks scaling up to hundreds of routers. (…) The working group will also serve as a meeting place and forum for those developing and experimenting with MANET approaches.” Ad Hoc Networks and Automotive Applications

  10. Advances in MANET Areas of current research Routing Cluster management Ad Hoc Networks and Automotive Applications

  11. Research focus to date • Routing protocols • Reactive, proactive, hybrid • Cluster management • To reduce overhead, to facilitate network management, to enable QoS, etc. • Quality of service (QoS) • Differentiating among different types of applications • Medium access • Closing the link, recognizing neighbors, scheduling transmission, etc. • Other • TCP performance in MANETs, etc. Ad Hoc Networks and Automotive Applications

  12. Routing in MANETs • Why is it different from routing in other types of network? • Because both end nodes and routers are mobile • Rate of link failure can be high if mobility is high • Unicast and multicast routing problems are being treated • No protocol has been standardized yet (but several under consideration as Internet Drafts at the IETF) • Need new metrics to assess the effectiveness of the protocol • Route stability • Control overhead • Data rebroadcast overhead (for multicast) Ad Hoc Networks and Automotive Applications

  13. MANET Routing Protocols • Proactive • Establish routes in advance • Example: Optimized Link State Routing Protocol (OLSR) • Reactive • Establish routes as needed • Example: Dynamic Source Routing (DSR) • Less routing overhead, but higher latency in establishing the path • Hybrid • Proactive within a restricted geographic area, reactive if a packet must traverse several of these areas • Example: Zone Routing Protocol (ZRP) Ad Hoc Networks and Automotive Applications

  14. Routing Example denotes neighbors A B Ad Hoc Networks and Automotive Applications

  15. Dynamic Source Routing -- DSR (1) • Suppose node A wishes to send a packet to node B, but does not currently have a valid route to the destination • Need for route discovery • Node A broadcasts a ROUTE_REQUEST packet • Each node forwards the packet to its neighbors unless they are the destination or have a valid route to the destination • As the packet traverses the network, each intermediate node adds its address to the header, establishing the reverse route • The destination, node B, sends a ROUTE_REPLY packet to node A • If the links are not bi-directional, node B must perform its own route discovery to respond to node A Ad Hoc Networks and Automotive Applications

  16. A DSR (2) ROUTE_REQUEST packets B Ad Hoc Networks and Automotive Applications

  17. A DSR (3) ROUTE_REPLY packets B Ad Hoc Networks and Automotive Applications

  18. DSR (4) • Intermediate nodes may cache accumulated route record contained in the ROUTE_REQUEST packet headers in order to reduce routing overhead • Security concerns with this type of snooping • Confirmation of the receipt of a packet can be done by passive acknowledgement • Node overhears a downstream node forwarding the packet • DSR also contains provisions to avoid route reply storms Ad Hoc Networks and Automotive Applications

  19. Optimized Link State Routing Protocol (OLSR) • Unlike DSR, a proactive routing scheme • Routers maintain awareness of current network topology by exchanging beacons (“HELLO messages”) • Each node tells the entire network about its immediate neighbors • So each node forms a picture of the entire network topology • Each node can then calculate the best route to any destination • Flooding the network with HELLO messages incurs too much overhead • OLSR uses multi-point relay (MPR) nodes to decrease the number of unnecessary broadcasts (only selected nodes broadcast HELLO) Ad Hoc Networks and Automotive Applications

  20. Other routing protocols • Zone Routing Protocol (ZRP) • Proactive within the node’s local neighborhood, reactive for inter-zone routing • Temporally Ordered Routing Algorithm (TORA) • Structured reaction to link failures by temporally ordered sequence of searches for alternative routes • Multicast routing protocols • Protocol Independent Multicast (PIM) • Multicast Zone Routing (MZR) • Multicast Optimized Link State Routing (MOLSR) • On-demand Multicast Routing Protocol (OMRP) And many more… Ad Hoc Networks and Automotive Applications

  21. Clustering • Transforms the physical network into a virtual network of interconnected node clusters • Cluster controllers act on behalf of other members of the cluster to make control decisions • Gateways establish communication between clusters • The objective is to improve efficiency of resource use by • Reducing channel contention • Forming routing backbones to reduce network diameter • Abstracting network state information to reduce its quantity and variability Ad Hoc Networks and Automotive Applications

  22. Link-Clustered Architecture (1) gateway cluster cluster head ordinary node Ad Hoc Networks and Automotive Applications

  23. Link-Clustered Architecture (2) • Must have a protocol for electing clusterheads, choosing gateways • Provides a natural routing backbone consisting of clusterheads and gateways • However, may reduce throughput and network robustness (single point of failure) • Another option is to use the clusterhead for control purposes but not for routing • Each node distributes and collects routing information and chooses routes • Neither inter-cluster nor intra-cluster routing requires clusterhead traversal Ad Hoc Networks and Automotive Applications

  24. Clustering for backbone formation Gateway and Head the Same(1) cluster cluster head ordinary node backbone Ad Hoc Networks and Automotive Applications

  25. Clustering for backbone formation (2) • May create a backbone, reducing delay related to multiple hops • Long distance backbone links may be provided by increased transmit power for the clusterheads • Need a protocol to elect clusterheads, decide cluster affiliation • For fault-tolerant connectivity and load balancing, may create multiple disjoint routing backbones • Virtual Subnet Architecture Ad Hoc Networks and Automotive Applications

  26. Research on MANET at Virginia Tech Smart antennas in ad hoc networks Policy-based management for ad hoc mobile networks Game Theory Adaptive MACs Ad Hoc Networks and Automotive Applications

  27. Smart antennas in ad hoc networks • Potential benefits in closing the link, reaching distant notes through a direct link, directional multicasting, etc. • Simulation of smart antenna controller, with dynamic beam forming and null steering • Development of an integrated Matlab™/OPNET Modeler™ simulation including layers 1 (signal degradation and attenuation, optimum assignment of antenna weights), 2 (medium access) and 3 (routing) considerations • Application of directed beams to increase the efficiency of medium access algorithms in ad-hoc environments • Multi-hop request-to-send/request-to-orient Ad Hoc Networks and Automotive Applications

  28. Simulation snapshot • Node 1 & Node 3 transmit packets to Node 0 using circular array antenna containing 8 elements. • Node 2 orients the receive antenna towards the Node 1. • Node 0 uses null forming algorithm to receive packets only from Node 1. Ad Hoc Networks and Automotive Applications

  29. Policy-based Management • Policy-based Networking (PBN) • Automating network management • Abstraction of complex low-level policies to simple high-level policies • Multiple policy disciplines • QoS, network security, IP address allocation etc. • QoS policy • QoS means incentive to steal resources?! • Need for Authentication, Authorization, Accounting • Policy-based Admission Control (PAC) • Not just based on available resources (bandwidth) • IETF/DMTF Standardization • Common Open Policy Service (COPS) protocol etc. Ad Hoc Networks and Automotive Applications

  30. Management of Ad Hoc Networks • Autonomous networks operating in isolation or as ‘stub networks’ • Extremely challenging • Severe bandwidth constraints • Limited battery life • Dynamic topology • Heterogeneity • Limited survivability • Need a robust, adaptive, and efficient management framework • Are wireless mobile networks another venue for policy-based management? Ad Hoc Networks and Automotive Applications

  31. Goals (QoS Specification) Dynamic Policies, Feasibility Analysis, etc. Adaptation Logic Policy Specification Battery life, link bandwidth, role discovery, etc. Policy Distribution Capabilities Discovery Topology Discovery PEPs, PDPs, etc. Protocol(s) Policy Provisioning Policy-based Routing Architecture Policy Monitoring Framework Ad Hoc Networks and Automotive Applications

  32. Testbed Ad Hoc Networks and Automotive Applications

  33. Automotive Communications Issues and applications Performance and feasibility assessment Ad Hoc Networks and Automotive Applications

  34. Automotive communications • In-vehicle devices • Under the hood (brakes, transmission, engine, …) • Passenger cabin (dashboard, seatbelt, air bags, …) • Mobile devices • Palmtop, laptop, Blackberry, pager, … • External communications • Satellite radio, AM/FM radio • Positioning information, directions, road assistance • Notification of traffic information, general Internet access Diversity of needs implies multiple communications solutions Ad Hoc Networks and Automotive Applications

  35. Communications solutions IEEE 802.11 Bluetooth Cellular (2G/2.5G/3G) Infrared Ad hoc networks IEEE 1394 CAN IN VEHICLE EXTERNAL Ad Hoc Networks and Automotive Applications

  36. Existing initiatives • Several projects dealing with automobile communications (primarily in Europe) • Project COMCAR (Communication and Mobility by Cellular Advanced Radio) • Dynamic Radio for IP Services in Vehicular Environments (DRiVE) • Multimedia Car Platform (MCP) • Note that all rely on infrastructure-based wireless systems (not ad hoc) Ad Hoc Networks and Automotive Applications

  37. Project COMCAR • www.comcar.de • Communication and Mobility by Cellular Advanced Radio • Asymmetrical, interactive, high quality IP multimedia services • Application to automobiles and trains • Uses cellular infrastructure • W-CDMA, OFDM, GPRS • Project developed in Germany • Ericsson, Daimler Chrysler, Sony Ad Hoc Networks and Automotive Applications

  38. DRiVE • www.ist-drive.org • Dynamic Radio for IP-Services in Vehicular Environments • Uses cellular infrastructure • Dynamic frequency allocation and coexistence of different radio technologies (GSM, GPRS, UMTS, etc.) • Cooperation among network elements and applications • European IST (Information Society Technologies) program started in 2000 Ad Hoc Networks and Automotive Applications

  39. Multimedia Car Platform (MCP) • http://mcp.fantastic.ch • IP-based, using GSM/GPRS • Project partners include BMW, Volkswagen, France Telecom, Nokia and others Ad Hoc Networks and Automotive Applications

  40. Ad hoc automotive network • Each automobile participating in the network would contain a low power data transceiver • Enable communications with other automobiles in the vicinity • Each vehicle serves as both an end point (to receive/transmit data) and a router (to relay data to/from other vehicles) • Some fixed sites serve as gateways to the Internet • Vehicle dealerships, other partners • Feasibility • Use unlicensed frequency bands – low cost deployment • Must determine achievable performance as a function of density of vehicles Ad Hoc Networks and Automotive Applications

  41. Applications • Weather and hazard alerts • Safety and security • Travel information and m-commerce (car is your credit card) • Interactive navigation • Diagnostic data • Maintenance support • Instant messaging • Data mining • General Internet access Ad Hoc Networks and Automotive Applications

  42. Performance Assessment • Factors deal primarily with very dynamic nature of the topology… • Latency of transmissions • Probability of success • Throughput • Control traffic overhead • Route stability • … and impairments due to the wireless medium • Error rate • Spectrum utilization Ad Hoc Networks and Automotive Applications

  43. Network architecture • Mobile nodes (vehicles) • Transceiver • In-vehicle devices, mobile consumer devices • Existing infrastructure • Cellular/PCS, public data network, etc. • New infrastructure • Car dealerships • Gas and service stations • Drive-through windows • Fixed points along highways Ad Hoc Networks and Automotive Applications

  44. Network components • Radio • Power requirements and power control • Bandwidth • Memory requirements • Programmability • Antenna requirements • Backhaul strategies • Wireline, fixed wireless, satellite • IP-based, PSTN, … • Protocols • Physical, MAC and transport layers • Ad-hoc routing protocols for unicast and multicast Ad Hoc Networks and Automotive Applications

  45. Evolutionary path • Migration to new standards and technologies • Compatibility with existing standards • Challenges • Development and product life cycle is very different for automobiles versus communications devices • Market penetration of proposed new technology in new vehicles and existing vehicles will impact network density and therefore performance Ad Hoc Networks and Automotive Applications

  46. Technology assessment • Analysis and simulation • Network capacity • Network performance as a function of node density • Demonstrations • Experimental statistics • Application demonstration Ad Hoc Networks and Automotive Applications

  47. Benefits of Research • Benefits to GM • Clear understanding of feasibility of vehicular ad-hoc network and performance of such a network • Fill a gap in vehicular communications research on external networking and communications • Future research to provide more detailed descriptions of realizing the network on a broad scale • Future work could include prototypes to be demonstrated Ad Hoc Networks and Automotive Applications

  48. Readings and References (1) • Books on MANET • C. K. Toh, Ad Hoc Mobile Wireless Networks: Protocols and Systems, Prentice Hall, 2001. • C. E. Perkins, Ad Hoc Networking, Addison Wesley, 2000. • IETF MANET working group for RFCs with details of proposed routing protocols • http://www.ietf.org/html.charters/manet-charter.html Ad Hoc Networks and Automotive Applications

  49. Readings and References (2) • For a summary of unicast and multicast routing protocols • M. Christman, “Extensions for Multicast in Mobile Ad-hoc Networks (XMMAN): the Reduction of Data Overhead in Wireless Multicast Trees,” M.S. Thesis, Virginia Tech, July 2002. • For a discussion of automotive communications • W. Kellerer et al., “(Auto) Mobile Communication in a Heterogeneous and Converged World,” IEEE Personal Communications, December 2001. Ad Hoc Networks and Automotive Applications