Post on 05-Apr-2018
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Mobile Ad Hoc Networks andAutomotive Applications
Luiz A. DaSilva, Jeff H. Reed, William Newhall
Mobile and Portable Radio Group
Virginia Polytechnic Institute and State University
Luiz DaSilva, 2002
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Agenda Fundaments of Mobile Ad Hoc Networks (MANETs)
Advances in MANET
Research on MANET at Virginia Tech
Automotive applications
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Fundaments of Mobile Ad HocNetworks (MANETs)
Definition and applications
Challenges
Standardization
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Mobile Ad Hoc Networks (MANET)
Mobile nodes
Access points
Backbone
Wireless Mobile Network
MANET
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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 forother nodes in the network
Topology of the network continuously changes
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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 betweenusers who are not within LOS of each other
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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)
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Characteristics Dynamic topology
Heterogeneity
Bandwidth-constrained variable-capacity links
Limited physical security
Nodes with limited battery life and storage capabilities
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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 introducethem 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 andforum for those developing and experimenting with
MANET approaches.
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Advances in MANET
Areas of current research
Routing
Cluster management
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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.
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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)
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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 packetmust traverse several of these areas
Example: Zone Routing Protocol (ZRP)
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Routing ExampleA
B
denotes neighbors
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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 destinationAs 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
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DSR (2)A
B
ROUTE_REQUEST
packets
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DSR (3)A
B
ROUTE_REPLY
packets
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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
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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)
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Other routing protocols Zone Routing Protocol (ZRP)
Proactive within the nodes 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
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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 andvariability
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Link-Clustered Architecture (1)gateway
ordinary node
cluster head
cluster
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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 andchooses routes
Neither inter-cluster nor intra-cluster routing requires clusterhead
traversal
Cl t i f b kb f ti
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Clustering for backbone formation
Gateway and Head the Same(1)
ordinary node
cluster head
cluster
backbone
Cl t i f b kb f ti
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Clustering for backbone formation
(2) May create a backbone, reducing delay related to
multiple hops
Long distance backbone links may be provided by increasedtransmit 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
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Research on MANET at Virginia
Tech
Smart antennas in ad hoc networks
Policy-based management for ad hoc
mobile networks
Game Theory
Adaptive MACs
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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
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Policy-based Management Policy-based Networking (PBN)
Automating network management
Abstraction of complex low-level policies to simple high-levelpolicies
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.
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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?
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Testbed A R INetw ork Virg in ia AT M
Campus ne twork
Linux router
CISCO router 3660
Linux router
CISCO router 3660
Linux router
CISCO router 3660
Linux router
CISCO router 3660
H ubSwitch
P C PC PC PC802.11b
Laptop
Laptop
H ub
CISCO router 3620
100 Mbps
Sniffer
OC3c
100 Mbps
PC
K VM
Patch panel
H ub
Switch
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Automotive Communications
Issues and applications
Performance and feasibility assessment
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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
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Communications solutions
IEEE 802.11
Bluetooth Cellular
(2G/2.5G/3G)
Infrared
IN VEHICLE EXTERNAL
Ad hoc networks
CANIEEE 1394
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Existing initiatives
Several projects dealing with automobile communications
(primarily in Europe)
Project COMCAR (Communication and Mobility by CellularAdvanced 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)
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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
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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
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Multimedia Car Platform (MCP)
http://mcp.fantastic.ch
IP-based, using GSM/GPRS
Project partners include BMW, Volkswagen, France
Telecom, Nokia and others
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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
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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
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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
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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
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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
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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 vehiclesand existing vehicles will impact network density and therefore
performance
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Technology assessment
Analysis and simulation
Network capacity
Network performance as a function of node density
Demonstrations
Experimental statistics
Application demonstration
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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
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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
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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 WirelessMulticast Trees, M.S. Thesis, Virginia Tech, July 2002.
For a discussion of automotive communications
W. Kellereret al., (Auto) Mobile Communication in a
Heterogeneous and Converged World, IEEE Personal
Communications, December 2001.