1 nato-arw, suceava, romania, september 4-8, 2006 1 a survey of wireless communications professor s....
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NATO-ARW, Suceava, Romania, September 4-8, 2006 11
A Survey of Wireless Communications
Professor S. Olariu
Department of Computer ScienceOld Dominion University
Norfolk, VA 23529U.S.A.
[email protected]://www.cs.odu.edu/~olariu
NATO-ARW, Suceava, Romania, September 4-8, 2006 22
In case you haven’t noticed…
Tethered communication does not scale End-user mobility is becoming the norm rather
than the exception Anytime/anywhere communication is here to
stay Paradigm shift – the way we view
communication and computation must change if we want to remain competitive
Are we ready for it??
NATO-ARW, Suceava, Romania, September 4-8, 2006 33
Recent trends
One billion wireless communication devices in use worldwide (2005)
400 million wireless telephone handsets (purchased annually)
Users want (need?) anytime/anywhere communications Emerging PCS services, multimedia, mobile
commerce, etc.
NATO-ARW, Suceava, Romania, September 4-8, 2006 44
Networks 101
Wired networks static: no mobility e.g. LAN, MAN, WAN, and Internet
Wireless networks mobility is becoming the norm name of the game: Hide mobility from the application!
NATO-ARW, Suceava, Romania, September 4-8, 2006 55
Wireless networks 101
Infrastructure-based networks cellular networks satellite networks HALO-type networks
Infrastructure-free networks Mobile Ad hoc Networks (MANET) wireless sensor networks other rapidly-deployable networks
Hybrid networks Wireless Internet
NATO-ARW, Suceava, Romania, September 4-8, 2006 66
The vision: an integrated global communication system
Portable terminals
Stationary terminals
Mobile terminals Nomadic business users
Individual multimedia communication
Local and group multicast services
High speed provider link
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Hybrid wireless networks
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Mobility management addressing and routing location tracking: GPS, E-911
Network management virtual infrastructure
Resource management network resource allocation energy management
QoS management dynamic resource reservation and adaptive error
control techniques
Major issues (1)
NATO-ARW, Suceava, Romania, September 4-8, 2006 99
MAC protocols contention control and resolution
Middleware measurement and experimentation
Security authentication, encryption, anonymity, and intrusion
detection Error control and fault tolerance
error correction and retransmission management deployment of back-up systems
Major issues (2)
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Cellular networks
• A Mobile Host (MH) communicates with
• A Base Station (BS) that controls
• A Cell - the BS’s area of coverage
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Channel assignment
Co-channel interference between frequencies used in neighboring cells
Fixed assignment poor for hotspots good in uniformly high loads
Dynamic assignment complex
Hybrid assignment fixed assignment plus dynamic pool
NATO-ARW, Suceava, Romania, September 4-8, 2006 1212
Increasing system capacity
B: Channels used at reduced power
A3
B
A1
BA2
B
A: Channels used at full power
NATO-ARW, Suceava, Romania, September 4-8, 2006 1313
Handoff
A B
NATO-ARW, Suceava, Romania, September 4-8, 2006 1414
Wireless QoS
QoS in wireless networks difficult due to user mobility, limited bandwidth, various impairments, etc.
Demand for new services yields multi-class traffic with different resource and QoS requirements:
telephony web e-mail video
NATO-ARW, Suceava, Romania, September 4-8, 2006 1515
Classification of QoS parameters
Packet level: packet delay jitter packet dropping probability
Call level: call dropping probability (CDP) call blocking probability (CBP) supplied bandwidth
Session level
NATO-ARW, Suceava, Romania, September 4-8, 2006 1616
LEO satellites
Description: Low Earth Orbit: 500km-2000km high, constant, velocity deployed in constellations of multiple satellites
Benefits low power requirements at the end-user level low signal propagation delay global coverage
NATO-ARW, Suceava, Romania, September 4-8, 2006 1717
LEO satellites
Satellite footprint coverage area on the
surface of the surface of the Earth
Footprint divided into
spotbeams, forming a pattern of overlapping circles, similar to a cellular network
NATO-ARW, Suceava, Romania, September 4-8, 2006 1818
The HALO network
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Multi-hop self-organized networks
Peer to peer networks Ad hoc networks Sensor networks
Rapidly deployable networks (1)
NATO-ARW, Suceava, Romania, September 4-8, 2006 2020
Wireless mesh
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Brief history of rapid deployment
The concept of rapidly-deployable networks dated back to 1970s
DARPA packet radio networks Development languished in 1980s
due to the lack of low cost CPU and memory for ad hoc routing
Rekindled about 1995 DARPA vision – late 1990s – Smart Dust
consisting of mm3 devices
NATO-ARW, Suceava, Romania, September 4-8, 2006 2222
MANET: an intro
MANET consist of mobile nodes that form a network in an ad hoc manner
The nodes intercommunicate using single or multi-hop wireless links
Each node in MANET can operate as a host as well as a router
The topology, locations, connectivity, transmission quality are variable
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Self-organizing: no central control Scarce resources: bandwidth and batteries Dynamic network topology
Characteristics of MANET
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MANET applications
Civilian Wireless LANs/WANs – mobile and stationary Remote data collection and analysis Taxi cabs Disaster recovery Vehicular ad hoc network (VANET)
Defense Battlefield communications and data transfer Surveillance Early warning systems
NATO-ARW, Suceava, Romania, September 4-8, 2006 2525
MANET issues and challenges
Operating in presence of unpredictable mobility Operating in an error-prone media Low bandwidth channels Low power devices with limited resources Maintaining and retaining connectivity and state
info Security: infrastructure and communication
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MAC for MANET
Special requirements Avoid interferences among simultaneous transmissions
Yet, enable as many non-interfering transmissions as possible Fairness among transmissions
No centralized coordinators, should function in full distributed manner
No clock synchronization, asynchronous operations
NATO-ARW, Suceava, Romania, September 4-8, 2006 2727
Carrier-sensing in MANET
Problems Hidden terminal problem Exposed terminal problem
Possible solution: Busy tone
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Hidden terminal problem
A
B
XNode X finds that the mediumis free, and transmits a packet
No carrier does not imply OK to transmit!
A is transmitting a packet to B
NATO-ARW, Suceava, Romania, September 4-8, 2006 2929
Exposed terminal problem
A is transmitting a packet to B
X will not transmit to Y, eventhough it will not interfere at B
A
B
XY
Presence of carrier does not imply to hold off transmission!
NATO-ARW, Suceava, Romania, September 4-8, 2006 3030
Busy tone
A
B
XA
B
XY
X OK to transmit X not OK to transmit
1. Receiver transmits busy tone when receiving data2. All nodes hearing busy tone keep silent3. Requires a separate channel for busy tone
B is receiving a packet from A
NATO-ARW, Suceava, Romania, September 4-8, 2006 3131
Neighbor discovery Network organization
choosing transmission radii choosing neighbors
Scheduling node activity Clustering
Select cluster-heads assign nodes to clusters
Dominating sets: each node in set or neighbor of some node in the set Bluetooth scatternet formation
Topology control
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Routing: find a path from source to destination Location update: maintain destination information Broadcasting: send from source to all nodes Multicasting: send from source to some nodes Geocasting: send from source to all nodes inside a region Network partitioning: data/service replication IP-based addressing and routing
Data communication
NATO-ARW, Suceava, Romania, September 4-8, 2006 3333
MANET – Effect of dynamic topology
S
X
Y
D
S
D
Z
X
NATO-ARW, Suceava, Romania, September 4-8, 2006 3434
Dominating sets
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Wireless Sensor Networks
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How it all started …
SmartDust program sponsored by DARPA defined sensor networks as:
A sensor network is a deployment of massive numbers of small, inexpensive, self-powered devices that can sense, compute, and communicate with other devices for the purpose of gathering local information to make global decisions about a physical environment
NATO-ARW, Suceava, Romania, September 4-8, 2006 3737
SmartDust – the vision
An airplane traverses a battlefield and deploys massive numbers of tiny sensors
The sensors randomly scatter spatially as they land
They self-organize into an ad hoc network such that information can be transmitted multi-hop to a collection point
The sensors monitor and report on troop movements, armaments, mine fields, etc
NATO-ARW, Suceava, Romania, September 4-8, 2006 3838
Miniature devices with modest capabilities linked by some wireless medium (e.g. radio, ultrasound, laser)
Non-renewable energy budget Disposable: tiny, mass-produced, dust cheap! Mass production implies:
testing is not an option anonymity: no fabrication-time IDs
What are sensors?
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Typical sensor diagram
Transceiver
Embedded
Processor
Sensor
Battery
Memory
Transceiver
Embedded
Processor
Sensor
Battery
Memory
1Kbps-10Kbs-transmission
range3-10m
4bit, 5-10 MHz
Slow processor
Non-renewable
4-8Kb
-Limited storage
Low-power special-purpose
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Types of sensors
Pressure Temperature Light Biological Chemical Strain, fatigue Tilt Acceleration Seismic Metal detectors
Sensors you can buy off-the-shelf
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Distance to an object Direction of object Ambient temperature Presence of
chemicals Light intensity Vibrations Motion Seismic tremors Noise (acoustic data)
Thus, sensors can measure…
NATO-ARW, Suceava, Romania, September 4-8, 2006 4242
Must work unattended Modest non-renewable energy budget Name of the game – prolong longevity of
network sleep a lot, wake up periodically work locally, communicate sparingly optimize transmission radius when communicating!
Supplement modest energy budget by scavenging
Hopefully, energy will not be a major problem
Sensors – modus operandi
NATO-ARW, Suceava, Romania, September 4-8, 2006 4343
Sensor networks
Distributed systems with no central control Massive number of tiny sensors densely
deployed in the area of interest Random deployment: individual sensor
positions cannot be engineered Main goal: produce globally-meaningful
information from locally-collected data Only as good as the information produced
information quality information security
NATO-ARW, Suceava, Romania, September 4-8, 2006 4444
Battlefield surveillance - monitoring critical terrain, routes, bridges and straits for enemy activity
Battle damage assessment - field reports from attached sensors afford real-time assessment
Early detection of biological, chemical, or nuclear attack
Early warning systems Containment of terrorist attacks - in metropolitan
areas guide public and first aid providers
Homeland security applications
NATO-ARW, Suceava, Romania, September 4-8, 2006 4545
Early warning systems
Networked sensors make monitoring and early warning systems more accurate and affordable
NATO-ARW, Suceava, Romania, September 4-8, 2006 4646
Traffic control
Can networked sensors control traffic flow better than a loose network of people?
NATO-ARW, Suceava, Romania, September 4-8, 2006 4747
Securing US ports
Only 2% of the containers entering our ports are checked!
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Securing container transit
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… and handling
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Two views of sensor networks
Centrally controlled the user pushes queries/interests sensor network provides answers does not scale well prone to creation of energy holes
Autonomous assumes a pervasive instrumentation organized ad hoc in service-centric fashion scales well less prone to the creation of energy holes
NATO-ARW, Suceava, Romania, September 4-8, 2006 5151
Centrally-controlled network
Sink
End user
Internet
EventSatellite
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Autonomous sensor network
Command Node
Command Node
Command Node
Remote security monitoring station
Sensor nodes
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Conquering scale: the virtual infrastructure
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How do we conquer scale?
Golden Rule: Divide and Conquer!
Graft a virtual infrastructure on top of physical network
Infrastructure leveraged by many protocols!
NATO-ARW, Suceava, Romania, September 4-8, 2006 5555
Components of the virtual infrastructure
Dynamic coordinate system location-based identifiers coarse-grain location awareness
Clustering scheme cheap scalability
Work model hierarchical specification of work and QoS
Task-based management model low-level implementation of work model
NATO-ARW, Suceava, Romania, September 4-8, 2006 5656
The dynamic coordinate system
Components:Components: coronascoronas wedgeswedges
Individual sensors Individual sensors
acquireacquire corona numbercorona number wedge numberwedge number
Coordinate system is Coordinate system is
dynamic and does not dynamic and does not
require sensor IDsrequire sensor IDs
Works perfectly well in Works perfectly well in
autonomous settingautonomous setting
My My coordinates coordinates are (4,2)are (4,2)
Mine too!Mine too!
NATO-ARW, Suceava, Romania, September 4-8, 2006 5757
The cluster structure
Cluster: locus of all sensors having the same coordinates
Clustering -- free once coordinate system available
Accommodates sensors w/o IDs In our model, smallest unit of work!
NATO-ARW, Suceava, Romania, September 4-8, 2006 5858
A multi-sink sensor network
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Routing to closest sink
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ANSWER
AutoNomouS Wireless sEnsor netwoRk capable of performing sophisticated analyses detecting trends and identifying unexpected, coherent and emergent behavior
Primary goal of ANSWER: provide in-situ users with information services, for example enhancing their location awareness
ANSWER finds immediate applications to tactical battlefield surveillance, crisis management and homeland security
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Providing mission-oriented security
Patrol Search and Rescue (PSAR) vehicle
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Initiating interaction
Authenticate PSAR before entering ANSWER Establishment of trust relationship PSAR is issued seeds from PCC – passed on to sensors Upon entering, PSAR organizes sensors in its vicinity
AFN
AFN
AFN
AFN
AFN
AFN
AFN
AFN
AFN
AFN
AFN
PSAR
AFNAggregate & forward node
Patrol, search, rescue vehicle
Miniaturized sensor node
PSAR
B
A
PSAR
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When the task has been completed the aggregated data will be routed to the specified cluster in order to be available to the PSAR in a timely fashion
As the PSAR reaches the cluster, it will interact with the sensors in its immediate neighborhood and collect the aggregated data
Routing aggregated data to PSAR
AFN
AFN
AFN
AFN
AFN
AFN
AFN
AFN
AFN
AFN
AFN
PSAR
AFNAggregate & forward node
Patrol, search, rescue vehicle
Miniaturized sensor node
PSAR
B
AAFN
PSAR
NATO-ARW, Suceava, Romania, September 4-8, 2006 6464
Biomedical applications
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Habitat monitoring
NATO-ARW, Suceava, Romania, September 4-8, 2006 6666
Ecosystem monitoring
Primary node
Secondary nodes
•Dense network of physical, chemical sensors in soil and
canopy
•Measure and characterize previously unobservable
ecosystem processes
NATO-ARW, Suceava, Romania, September 4-8, 2006 6767
Supply chain management
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Homeland security applications monitoring friendly forces equipment and ammunition
(via attached sensors) battlefield surveillance (monitoring critical terrain,
routes, and straits for enemy activity) battle damage assessment (field reports from
attached sensors give reports in real-time) biological, chemical, or nuclear attack detection and
containment (sensors deployed across metropolitan areas to guide public and first responders)
Homeland security applications