INTRODUCTION TO AD HOC WIRELESS NETWORKS

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INTRODUCTION TO AD HOC WIRELESS NETWORKS
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contents

• Taxonomy of networks
• Categoies of wireless network
• Ad-hoc network
• Characteristics of ad-hoc network
• Application of ad-hoc network
• Sensor networks
• Characteristics of sensor network
• Application of sensor network
• Lmitation of ad-hoc and sensor networks

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What is network?

• Network
• Network is series of points or nodes
• Interconnected by communication paths
• Network can interconnect with other netowrks
  contains subnetworks

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Taxonomy of wireless networks

• wireless networks
  
• fixed mobile access ad hoc
• networks networks networks
  
• 
  
• cellular random wireless
  sensor networks access
  internets networks networks

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Categories of wireless networks

• Cellular (one hop) networks
• Wireless ad hoc (multi hop)networks.
• Wireless Sensor Networks

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Cellular Networks

• Cellular Networks
• Networking Wireless Hosts
• Infrastructure dependent
• High setup costs
• Large setup time
• Reliable

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What is Ad-hoc?

• A local area network, or some small networks,
  parts are time-limited, and only usable for the
  duration of a communication session
• The routers are free to move randomly, organize
  themselves arbitrarily
• The wireless topology vary rapidly and
  unpredictably

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A wireless ad hoc network
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IEEE 802.11 in OSI Model
Wireless
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802.11 Architecture of an ad-hoc network
Direct communication within a limited range
Station (STA) terminal with access mechanisms to
the wireless medium Independent Basic Service
Set group of stations using the same radio
frequency You may use SDM or FDM to establish
several BSS
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Dynamic network topology

• The mobile nodes are free to move randomly and
  organize themselves arbitrarily thus, the
  network's wireless topology may change rapidl
• and unpredictably.

Seminar on Wireless Ad hoc Sensor Networks
move
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What are ad hoc/sensor networks?

• Sometimes there is no coverages
• remote areas, ad hoc meetings, disaster areas
• cost can also be an argument against an
  infrastructure
• Sometimes not every station can hear every other
  station
• Data needs to be forwarded in a multihop
  manner

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Advent of Ad hoc Wireless Networks(Cont)
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Comparisons between Cellular and Ad Hoc Wireless
Networks (I)
Cellular Networks Ad Hoc Wireless Networks
Fixed infrastructure-based Infrastructureless
Guaranteed bandwidth (designed for voice traffic) Shared radio channel (more suitable for best-effort data traffic)
Centralized routing Distributed routing
Circuit-switched (evolving toward packet switching) Packet-switched (evolving toward emulation of circuit switching)
Seamless connectivity (low call drops during handoffs) Frequent path breaks due to mobility
High cost and time of deployment Quick and cost-effective deployment
Reuse of frequency spectrum through geographical channel reuse Dynamic frequency reuse based on carrier sense mechanism
Easier to employ bandwidth reservation Bandwidth reservation requires complex medium access control protocols
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Comparisons between Cellular and Ad Hoc Wireless
Networks (II)
Cellular Networks Ad Hoc Wireless Networks
Application domains include mainly civilian and commercial sectors Application domains include battlefields, emergency search and rescue operations, and collaborative computing
High cost of network maintenance (backup power source, staffing, etc.) Self-organization and maintenance properties are built into the network
Mobile hosts are of relatively low complexity Mobile hosts require more intelligence (should have a transceiver as well as routing/switching capability)
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Mobile Ad hoc Networks

• mobile hosts
• multi-hop routes between nodes
• may not use infrastructure

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Motivation

• Ad-hoc nodes are typically battery powered and
  may not support energy scavenging
• Node and network lifetime must be prolonged
• Most energy consumption is at the nodes
  transceiver
• Minimum transmit power decreases contention
• Higher number of simultaneous transmissions can
  be allowed
• Increase in Capacity

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Motivation (Cont)

• wireless networks
• have special limitations and properties such as
  limited bandwidth,
• highly dynamic topology, link interference,
  limited range of links,
• and broadcast.

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Characteristics and tradeoffs

• Characteristics
• Self-organized
• Self-deployed
• Decentralized
• Dynamic network topology
• Tradeoffs
• Limited Bandwidth
• Need Multi-hop router
• Energy consumption problem
• Security problem

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Characteristics of MANETs

• Dynamic topology
• links formed and broken with mobility
• Possibly uni-directional links
• Constrained resources
• battery power
• wireless transmitter range
• Network partitions

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Limitations of MANET

• Power network life limited by battery life
• Short radio range
• Packet Collisions
• Network topology changes
• Address allocation

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Mobile Ad Hoc Networks (MANET)
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Broadcasting

• Unlike wired network, every hop is broadcasting
• Every packet can reach every node in the radio
  range of the sender
• Flooding messages make the problem even worse
• Wasted bandwidth
• High collision rate

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Applications

• Personal area networking
• Cell phone, laptop, PDA , tablet pc
• Meeting room/conference
• Emergency operations
• Search and rescue(Disaster Relief)
• Policing and fire fighting
• Civilian environments
• Taxi cab network
• Boats, aircrafts
• Military use
• On the battle field

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Wireless Ad Hoc Sensor Networks
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Layers in Use

• Ad-hoc networks
• link layer medium access control
• network layer routing
• transport layer TCP/IP

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NETWORK LAYETRS
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Ad-hoc routing protocols
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functional diagram of a wireless sensor
communication node. 
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IEEE 802.11 in OSI Model
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CHARACTERISTICS OF WIRELESS SENSOR NODES AND
NETWORKS

• Batteries in an ad hod network can be recharged,
  while they are not replaceable in wireless sensor
  networks.
• The goal of a wireless sensor network is to
  prolong battery life at the expense of QoS and
  bandwidth utilization 7, whereas the objective
  of an ad hoc network is to provide QoS.

Seminar on Wireless Ad hoc Sensor Networks
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Applications

• Structural, seismic
• Bridges, highways, buildings

• Smart roads
• Traffic monitoring, accident detection, recovery
  assistance

highway
camera
microphone

• Contaminants detection

4/10/08
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One day Workshop on Wireless Ad Hoc Networks
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Wireless Ad Hoc Sensor Networks
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Wireless Sensor Networks (WSN)
New technologies have reduced the cost, size and
power of micro-sensors and wireless interfaces
Circulatory Net
Environmental Monitoring

• Benefits from 3 technologies
• digital circuitry
• wireless communication
• silicon micro-machining

4/10/08
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One day Workshop on Wireless Ad Hoc Networks
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7 Comparisons between Cellular and Ad Hoc
Wireless Networks (I)
Cellular Networks Ad Hoc Wireless Networks
Fixed infrastructure-based Infrastructureless
Guaranteed bandwidth (designed for voice traffic) Shared radio channel (more suitable for best-effort data traffic)
Centralized routing Distributed routing
Circuit-switched (evolving toward packet switching) Packet-switched (evolving toward emulation of circuit switching)
Seamless connectivity (low call drops during handoffs) Frequent path breaks due to mobility
High cost and time of deployment Quick and cost-effective deployment
Reuse of frequency spectrum through geographical channel reuse Dynamic frequency reuse based on carrier sense mechanism
Easier to employ bandwidth reservation Bandwidth reservation requires complex medium access control protocols
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on Wireless Ad Hoc Networks
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Comparisons between Cellular and Ad Hoc Wireless
Networks (II)
Cellular Networks Ad Hoc Wireless Networks
Application domains include mainly civilian and commercial sectors Application domains include battlefields, emergency search and rescue operations, and collaborative computing
High cost of network maintenance (backup power source, staffing, etc.) Self-organization and maintenance properties are built into the network
Mobile hosts are of relatively low complexity Mobile hosts require more intelligence (should have a transceiver as well as routing/switching capability)
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Seminar on Wireless Ad Hoc Networks
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CONCLUSION
Ad-hoc and sensor network is everywhere
. The development of Ad-hoc wireless networks
senior networks provides tremendous
opportunities in many areas including
industrial environments.
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FUTURE?

• Ad hoc Wireless Network
• Everywhere

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• Thanks