Overview of Wireless Networks:
Cellular
Mobile Ad hoc
Sensor
Wireless networking
 Digital connection through radio waves
 Justification:
– Convenience
– Cost!
 It is always more efficient to go wired (especially optical)
– No interference
– You need more bandwidth: just add a bunch more of fibers!
– As fiber is cheaper than digging and resurfacing streets, many
companies put in more fiber than they would ever need (dark
fiber – look it up!)
Wireless networking types
 Cellular
– With a big emphasis on voice communication
 Satelite
 WiFi
– Local networks over wireless, with infrastructure
– 801.11a,b,g,n
– Thrash frequencies
 WiMAX
– Internet provider last mile replacement
 Ad Hoc Networking
– Local networks over wireless, without infrastructure
 Sensor networks
 RFID
Cellular Architecture
- Infrastructure-based networks
- All units are fixed in location except mobile units
- BS and MSC are connected via wirelines
- Communication between BS and mobile unit is wireless
WIRELINE
Cell
Base Station (BS)
Mobile unit
Wireless Links
Wired Links
Mobile Switching Center (MSC)
NETWORK
Mobile Ad hoc Networks
Characteristics
- Infrastructureless
- All nodes are potentially mobile
- Network topology is dynamic
- All nodes act as individual routers
Examples
- Disaster recovery situations
- Battle field communications
- Law enforcement operations
- Civilian applications
Objectives
- Maintain connectivity between mobile devices
- Provide congestion-free routing for multimedia traffic
- Support scalability
- Minimize memory, bandwidth and energy consumption
Mobile Ad hoc Networks (MANET)
transmission
range
Sensor Networks
Wireless sensor networks consists of group of sensor nodes
to perform distributed sensing task using wireless medium.
Characteristics
- low-cost, low-power, lightweight
- densely deployed
- prone to failures
- two ways of deployment: randomly, pre-determined or engineered
Objectives
- Monitor activities
- Gather and fuse information
- Communicate with global data processing unit
Sensor Networks
Application Areas [Akyildiz+ 2002]
1. Military:
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Monitoring equipment and ammunition
Battlefield surveillance and damage assessment
Nuclear, biological, chemical attack detection and reconnaissance
2. Environmental:
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Forest fire / flood detection
3. Health:
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Tracking and monitoring doctors and patients inside a hospital
Drug administration in hospitals
Sensor Networks
Application Areas [Akyildiz+ 2002]
4. Home:

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Home automation
Smart environment
5. Other Commercial Applications:
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Environmental control in office buildings
Detecting and monitoring car thefts
Managing inventory control
Vehicle tracking and detection
Sensor Networks vs. Traditional
Wireless Networks (Cellular, MANET)
– Higher number of sensor nodes (several orders of magnitude)
– Dense deployment
– Prone to failures
– Limited in power, computation and memory
– May not have global identification (ID) due to high overhead and
the total number of sensors
– Optimization on the energy consumption vs. QoS and high
bandwidth constraints
– Stationary vs. mobile
– Data flow: unidirectional vs. bi-directional
– Date rates
Sensor Networks Preliminaries
– For large scale environment monitoring applications, dense
sensor networks are mainly used
– Sensing capabilities should be distributed and coordinated
amongst the sensor nodes
– Algorithms deployed should be localized since transmissions
between large distances are expensive and lowers networks life
time
– These networks should be self-configuring, scalable, redundant
and robust during topology changes
Current Challenges
 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)
Research Problems in Ad hoc and
Sensor Networks
 Clustering
– Partitioning of the network
– Identification of vital nodes (clusterheads)
 Routing
– Discovering routes from source to destination
– Maintaining the routes
– Rediscovery and repair of routes
 Topology management
– Maintain the links
– Minimize the changes in underlying graph
 Security
Research Problems in Ad hoc and
Sensor Networks
 Medium Access Control Protocols
 Sensor data management
 Power conservation/energy consumption
 Data fusion and dissemination of sensor data
 New applications for ad hoc and sensor networks
References
[Akyildiz+ 2002] I. F. Akyildiz, W. Su, Y. Sankarasubramaniam, and E. Cayirci, A Survey
on Sensor Networks, IEEE Communications Magazine, Vol. 40, No. 8, pp. 102-114,
August 2002.