1. Overview of Wireless Networks:
Cellular
Mobile Ad hoc
Sensor

2. 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
WIRE-LINE
NETWORK
Base Station (BS)
Cell
Wireless Links
Wired Links
Mobile Switching Center (MSC)
Mobile unit

3. Why Mobile Ad hoc Networks?
Characteristics - Infrastructure-less - 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

4. Mobile Ad hoc Networks (MANET)
transmission
range

5. Hybrid Environments Use infrastructure when convenient
Use ad hoc connectivity when necessary or superior
infrastructure
BS1
BS2 E A Z
Ad hoc connectivity X
© 2001 Nitin Vaidya

6. Variations Symmetric environments Asymmetric capabilities
Nodes having identical capabilities and responsibilities
Asymmetric capabilities
Transmission ranges
Processing power
Battery lifetime
Mobility speed
Asymmetric responsibilities
Some nodes may forward route packages
Leaders vs. ordinary nodes
May co-exist (and collaborate) with an infrastructure-based network

7. Variations Traffic characteristics Mobility Patterns
Bit rate
Timeliness constraints
Reliability requirements
Mobility Patterns
Students on campus
Passengers on airports
Taxi cabs
Mobility Characteristics
Speed / Direction / Pattern of movement

8. 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

9. Sensor Networks Military: Environmental: Health:
Application Areas [Akyildiz+ 2002]
Military:
Monitoring equipment and ammunition
Battlefield surveillance and damage assessment
Nuclear, biological, chemical attack detection and reconnaissance
Environmental:
Forest fire / flood detection
Health:
Tracking and monitoring doctors and patients inside a hospital
Drug administration in hospitals

10. Sensor Networks Home: Other Commercial Applications:
Application Areas [Akyildiz+ 2002]
Home:
Home automation
Smart environment
Other Commercial Applications:
Environmental control in office buildings
Detecting and monitoring car thefts
Managing inventory control
Vehicle tracking and detection

11. 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

12. 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

13. 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)

14. 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

15. 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

16. 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 , August 2002.