Download Ad Hoc Networks: Overview

Ad Hoc Networks: Overview
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Textbook
C. Siva Ram Murthy and B. S. Manoj, Ad Hoc Wireless
Networks: Architectures and Protocols, Prentice Hall
PTR, 2004.
References
Carlos de Morais Cordeiro and Dharma Prakash
Agrawal, Ad Hoc & Sensor Networks: Theory and
Applications, World Scientific Publishing Co., 2006.
Feng Zhao and Leonidas Guibas, Wireless Sensor
Networks: An Information Processing Approach,
Elsevier, 2004.
Edgar H. Callaway, Jr., Wireless Sensor Netwoks:
Architectures and Protocols, Auerbach, 2004.
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Related Sites
 Advanced Network Technologies Division, NIST,
 Wireless Ad Hoc Networks,
http://w3.antd.nist.gov/wahn_home.shtml
 Autonomous Networks Research Group, USC
 WSN bibliography, http://ceng.usc.edu/~anrg/SensorNetBib.html
 IETF MANET WG
 http://www.ietf.org/html.charters/manet-charter.html
 IEEE 802 WG
 http://grouper.ieee.org/groups/802/dots.html
 Zigbee
 http://www.zigbee.org
 TinyOS
 http://www.tinyos.net/
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Wireless Network Technology
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Wireless Networks
 Wireless Networks
 Infrastructured Network
• Cellular Network (3GPP or 3GPP2)
• Wireless LAN (IEEE 802.11)
 Infrastructureless Network
• Ad Hoc Network
Internet
WLAN
Cellular
[Mobile/Wireless] Ad Hoc Networks
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Ad Hoc Networks vs. …
 Ad hoc networks vs. Wireless mobile networks
Infrastructureless vs. Infrastructured Network
All devices of an ad hoc network are likely to have similar
constraints
 Ad hoc networks vs. Peer-to-peer networks
P2P devices use existing networked structures such as
Internet
All P2P networks are not ad hoc network
• Because NOT all ad hoc network utilize an existing structure for
the communication among devices
 Ad hoc computing vs. Pervasive computing
The devices for pervasive computing are usually very small
and can be embedded in any type of objects
• Users are sometimes not even aware of the existence of the
embedded electronic chips
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Ad hoc networks (1)
 Temporary network composed of mobile nodes
without preexisting communication infrastructure,
such as Access Point (AP) and Base Station (BS).
 Each node plays the role of router for multi-hop routing.
 Self-organizing network without infrastructure
networks
 Started from DARPA PRNet in 1970
 Cooperative nodes (wireless)
 Each node decode-and-forward packets for other nodes
 Multi-hop packet forwarding through wireless
links
 Proactive/reactive/hybrid routing protocols
 Most works based on CSMA/CA to solve the
interference problem
 IEEE 802.11 MAC
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Ad hoc networks (2)
 But, there is no links
 Nodes simply radiate energy
 Nodes can be cooperative in many other ways (complex)
 Amplify and forward
 interference cancellation to increase SINR
 There may be many things out there that we can take
advantage of across layers for improvement!
A
F
C
D
B
E
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Ad Hoc Network (3)
Ad hoc networks
Mobile ad hoc networks
(MANETs)
Wirelss Mesh Networks
(WMN)
Wireless
sensor networks
 The application areas, the security requirements and the
constraints of the single devices differ …
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Cellular Net vs. Ad Hoc Net (1)
Cellular Net
Ad Hoc Net
Fixed infrastructure-based
Infrastruxture-less
1-hop wireless links
Multi-hop wireless links
Guaranteed bandwidth
Shared radio channel
Centralized routing
Distributed routing
Frequency reuse through
geographical channel reuse
Frequent path breaks due to
mobility
Quick and cost-effective
deployment
Dynamic frequency reuse based
on CSMA
Time sync: easier to achieve.
Difficult and consume BW
Seamless connectivity
High cost and time of deployment
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Cellular Net vs. Ad Hoc Net (2)
Cellular Net
Ad Hoc Net
BW reservation: easier
Requires complex MAC
App. Domain: civilian and
commercial sector
Battlefields, emergency operations,
collaborative computing
Self-organization and maintenance
is built into net
High cost of net maintenance
MHs: low complexity
More intelligence
Find paths with min overhead,
quick reconfiguration of broken
paths
Several issues are to be addressed
for commercial deployment,
Widespread use in defense
Major goal of routing: max call
acceptance, min call drop
Widely deployed
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Major Applications
Demands for
group
communications
Military
Emergency Service
Collaborative and Distributed Computing
Wireless Mesh Network
Wireless Sensor Network
Telematics
Wireless Personal Area Network
Home Network
Ad Hoc Relay for Cellular Network
Networks for ubiquitous computing
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Military
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Emergency Service
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MANET – Research Target
 MANET
 Issues in MANET
 No infrastructure
 Self organizing networks
 Communications via mobile
nodes
 Dynamic topology
 Heterogeneity bandwidthconstrained variablecapacity links
 Limited physical security
 Nodes with limited battery
life and storage capabilities
 Ad Hoc Unicast Routing
 Ad Hoc Multicast/Broadcast
Routing
 Power Saving
 Global Connectivity for
MANET
 Addressing & DNS Service
 Automatic Support of
Networking in MANET
• MANET Autoconfiguration
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Wireless Mesh Networks
Mesh network implemented over WLAN
Industrial standards Activities
IEEE 802.11, IEEE 802.15, IEEE 801.16 have
established sub-working groups to focus on new
standards for WMNs
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WMN Architecture
 WMNs (Wireless Mesh Networks) consist of:
mesh routers and mesh clients
 Mesh routers
 Conventional wireless AP (Access Point) functions
 Additional mesh routing functions to support multi-hop
communications
 Usually multiple wireless interfaces built on either the same or
different radio technologies
 Mesh clients
 Can also work as a router for client WMN
 Usually one wireless interface
 Classification of WMN architecture
 Infrastructure/Backbone WMNs
 Client WMNs
 Hybrid WMNs
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Infrastructure/backbone WMNs
Internet
Wireless Mesh
Backbone
Mesh Router
with Gateway
Mesh Router
Wired Clients
Mesh Router
with Gateway
Mesh Router
with Gateway/Bridge
Mesh Router
with Gateway/Bridge
Wireless Clients
Mesh Router
with Gateway/Bridge
Mesh Router
with Gateway/Bridge
Sensor
Access Point
Wi-Fi
Networks
Sink node
Sensor
Networks
Base Station
Base Station
Cellular
Networks
WiMAX
Networks
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Client WMNs
Mesh Client
Mesh Client
Mesh Client
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Hybrid WMNs
Internet
Wireless Mesh
Backbone
Mesh Router
with Gateway
Mesh Router
Mesh Router
with Gateway
Mesh Router
with Gateway/Bridge
Mesh Router
with Gateway/Bridge
Mesh Router
Mesh Router
Wi-Fi, Wi-MAX,
Sensor Networks,
Cellular Networks, etc.
Mesh Router
Conventional Clients
Wireless Mesh Clients
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Sensor Network Model
Sink
Stimulus
Sink
Source
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Wireless Sensor Networks
 A sort of ad-hoc networks
Ad Hoc
 A network of low cost,
densely deployed,
Wireless
untethered sensor nodes
Sensor
 Application areas:
Network
heath, military, and home
 Placed in inaccessible terrains or disaster areas
Net
 It may be impossible to recharge batteries
 Different Node Characteristics from Traditional nodes
 # of nodes in a sensor network can be several orders of magnitude
higher than the nodes in an Ad Hoc network (100s to 1000s nodes)
 Densely deployed (20 nodes/m3)
 Prone to failures
 Topology changes very frequently
 Mainly use a broadcast communication, whereas most Ad Hoc
networks are based on point-to-point
 Limited in power, computing capacities, and memory
 May not have global ID because of the large amount of overhead and
large number of sensors
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Existing Wireless Net vs. Sensor Net
Cellular system
Bluetooth, MANET
Sensor Network
Single Hop
Multi-hop
Multi-hop
High QOS
Bandwidth
efficiency
High QOS
Power conservation
Limited bandwidth
Large number of
node
Narrow radio range
Frequent topology
change
Station to Base
station
Peer to peer
Peer to multi node
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Peer to multi node
Sensor Networks Architecture
 Sensor node
 Made up of four basic components
• Sensing unit, Processing unit, Transceiver unit, and Power
unit
 Additional application-dependent components
• Location finding system, power generator, and mobilizer
 Scattered in a sensor field
 Collect data and route data back to the sink
 Sink
 Communicate with the task manager node (user) via
Internet or satellite
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Challenges in Ad Hoc Networks
Limited wireless transmission range
Broadcast nature of the wireless medium
Packet losses due to transmission errors
Mobility-induced route changes
Mobility-induced packet losses
Battery constraints
Potentially frequent network partitions
Ease of snooping on wireless
transmissions (security hazard)
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Issues in Ad Hoc Networks
Medium access scheme
Routing
Multicasting
Transport layer protocol
Pricing shceme
QoS provisioning
Security
Energy management
Addressing and service discovery
Scalability
Deployment considerations
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Medium Access Scheme
 Distributed operation
 Synchronization
 Hidden terminal problem
 Exposed terminal problem
 Throughput
 Access delay
 Fairness: especially for relaying nodes
 Real-time traffic support
 Resource reservation
 Ability to measure resource availability
 Capability for power control
 Adaptive rate control
 Use of directional antennas
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Routing (1)
Challenges
Mobility
• results in path breaks, packet collisions, transient loops, stale
routing information, and difficulty in resource reservation
BW constraints
Error-prone and shred channel
• BER: 10-5 ~ 10-3 wireless vs. 10-12 ~ 10-9 wired
Location-dependent contention
• Distribute load uniformly
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Routing (2)
Requirements
Minimum route acquisition delay
Quick route reconfiguration
Loop-free routing
Distributed routing approach
Minimum control overhead
Scalability
QoS provisioning
Support for time-sensitive traffic
Security and privacy
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Multicasting
Robusteness
recover and reconfigure quickly from potential
mobility-induced link breaks
Efficiency
Min control overhead
QoS support
Efficient group management
Scalability
security
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Transport Layer Protocols
 UDP
 No congestion control  congestion  increase contention 
degrade throughput
 TCP: major performance degradation due to
 Frequent path break
•  route reconfiguration  RTO  ReTx/CC  low throughput
 Stale routing information
• Increase out-of-order packets  dup ACKs  CC
 High channel error rate
• Loss of data/ACK  ACK is delayed  RTO  CC
 Frequent network partition
• All the packets dropped  RTO/multiple ReTx  increase RTO/CC
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Security
DoS attack
Resource consumption
Energy depletion
Buffer overflow
Host impersonation
Information disclosure
Interference
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Energy Management
Tx power mgmt
MAC: sleep mode
Routing: consider battery life time: load balancing
Transport: reduce ReTx
App
Battery energy mgmt
Extend battery life by taking adv of chemical
properties, discharge patterns, and by the selection of
a battery from a set of batteries
Processor power mgmt
Device power mgmt
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Deployment Consideration (1)
Adv. in ad hoc net
Low cont of deployment
Incremental deplyment
Short deplyment time
Reconfigurablity
Scenario of deployment
Military deployment: data-centric or user-centric
Emergency operation deployment: hend-held,
voice/data, < 100 nodes
Commercial wide-area deployment: e.g. WMN
Home network deplyment
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Deployment Consideration (2)
 Required longevity of network
 Area of coverage
 Service availability: redundancy
 Operational integration with other infrastructure
 Satellite network, UAV(unmanned aerial vehicles), GPS
 Cellular network
 Choice of protocols
 TDMA or CSMA-based MAC?
 Geographical routing (using GPS)
 Power-saving routing ?
 TCP extension ?
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