1. Introduction to Wireless Networking
ECE/CSC 575 – Section 1
Introduction to Wireless Networking
Lecture 23 Dr. Xinbing Wang

2. Overview of the Course
Part 1: Wireless communication systems (Chapter 1)
Flexibility to support roaming
Limitations: Geographical coverage, transmission rate, and transmission errors
Part 2: Wireless communication technology
Radio propagation (Chapter 5)
Spread spectrum (Chapter 7)
Part 3: Current wireless systems
Cellular network architecture (Chapter 10)
Mobile IP (Chapter 12)
Wireless LAN (Chapter 11/13/14)
Part 4: Other wireless networks
Ad hoc networks (Reading materials)
Sensor networks (Reading materials)
Wireless PAN (Chapter 15)
Satellite systems (Chapter 9)
Part 5: Wireless Security
In our daily lives, wireless communication technology is used everywhere, from VCR remote control, to satellite weather forecast. The common characteristics of wireless communication systems is that there is no physical (visible) lines between two communication parties.
Therefore, a wireless system is able to support user roaming. For example, we do not have to use a remote control in a particular position to.., we can use our cellular phones almost everywhere.
However, there are many impairments to a wireless channel, causing a lot of limitations to wireless communications system such as geographical.. (signal fading, additional noise, cochannel interference. Wireless systems also suffers from limit usable spectral width, so that the transmission rate is relatively low.
Specifically, wireless cellular systems based on radio propagation has been evolving from narrow band (1G, late 170s) to wide-band(3G).
With their geographical coverage limitation, wireless systems need a backbone network to extend their geographical coverage to enable global communications.
The interoworking of a wireless network as the front-end and the Internet as the backbone has received much attention in recent years.
So we will first take a look at the network architecture of current wireless systems,…, Then we will talk about the evolution from 2G to 3G systems.
Dr. Xinbing Wang

3. Wireless Sensor Networks
Architecture
Hardware and examples
Applications
Design issues: hardware, fault tolerance, energy conservation and so on.
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4. Architecture Internet, Satellite, etc Several thousand nodes Sink
Task
Manager
Several thousand nodes
Nodes are tens of feet of each other
Densities as high as 20 nodes/m3
I.F.Akyildiz, W.Su, Y. Sankarasubramaniam, E. Cayirci, “Wireless Sensor Networks: A Survey”, Computer Networks (Elsevier) Journal, March 2002.
Dr. Xinbing Wang

5. Key technologies that enable sensor networks:
Micro electro-mechanical systems (MEMS)
Wireless communications
Digital electronics
Dr. Xinbing Wang

6. Sensor Network Concepts
Sensors nodes are very close to each other
Sensor nodes have local processing capability
Sensor nodes can be randomly and rapidly deployed even in places inaccessible for humans
Sensor nodes can organize themselves to communicate with an access point
Sensor nodes can collaboratively work
Dr. Xinbing Wang

7. Location Finding System
Sensor Node Hardware
Power Unit
Power Generator
Sensor ADC
Processor
Memory
Transceiver
Location Finding System
Mobilizer
Small
Low power
Low bit rate
High density
Low cost (dispensable)
Autonomous
Adaptive
SENSING UNIT
PROCESSING UNIT
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8. Berkeley Motes
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9. Specifications of the Mote
Processor/Radio Board
MPR300CB
Remarks
Speed
4 MHz
Flash
128K bytes
SRAM
4K bytes
EEPROM
Radio Frequency
916MHz or 433MHz
ISM Band
Data Rate
40 Kbits/Sec
Max
Power
0.75 mW
Radio Range
100 feet
Programmable
2 x AA batteries
Dr. Xinbing Wang

10. Examples of Sensors UCLA: WINS Rockwell: WINS UC Berkeley: Smart Dust
UC Berkeley: COTS Dust
UC Berkeley:
Smart Dust
UCLA: WINS
JPL: Sensor Webs
Rockwell: WINS
Dr. Xinbing Wang

11. Sensor Networks Applications
Sensors can monitor ambient conditions including:
Temperature
Humidity
Vehicular movement
Lightning condition
Pressure
Soil makeup
Noise levels
The presence or absence of certain kinds of objects
Mechanical stress levels on attached objects, and
Current characteristics (speed, direction, size) of an object
Dr. Xinbing Wang

12. Sensor Networks Applications (2)
Sensors can also be used for :
Sensing
Event detection
Event identification
Location sensing
Local control of actuators
Dr. Xinbing Wang

13. Sensor Networks Military Applications
Command, control, communications, computing, intelligence, surveillance, reconnaissance, targeting (C4SRT)
Monitoring friendly forces, equipment and ammunition
Battlefield surveillance
Reconnaissance of opposing forces and terrain
Targeting
Battle damage assessment
Nuclear, biological and chemical (NBC)
attack detection and reconnaissance
Dr. Xinbing Wang

14. Sensor Networks Applications (2)
Sensors can also be used for :
Sensing
Event detection
Event identification
Location sensing
Local control of actuators
Dr. Xinbing Wang

15. Factors Influencing Sensor Network Design
A. Fault Tolerance (Reliability)
B. Scalability
C. Production Costs
D. Hardware Constraints
E. Sensor Network Topology
F. Operating Environment
G. Transmission Media
H. Power Consumption
Dr. Xinbing Wang

16. A. Fault Tolerance (Reliability)
Sensor nodes may fail or be blocked due to lack of power have physical damage, or environmental interference.
The failure of sensor nodes should not affect the overall task of the sensor network.
This is called RELIABILITY or FAULT TOLERANCE, i.e., ability to sustain sensor network functionality without any interruption
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17. Reliability (Fault Tolerance) of a sensor node is modeled:
i.e., by Poisson distribution, to capture the probability of not having a failure within the time interval (0,t) with lambda_k is the failure rate of the sensor node k and t is the time period.
G. Hoblos, M. Staroswiecki, and A. Aitouche, “Optimal Design of Fault Tolerant Sensor Networks,” IEEE International Conference on Control Applications, pp , Anchorage, AK, September 2000.
Dr. Xinbing Wang

18. Fault Tolerance (3)
Reliability (Fault Tolerance) of a broadcast range with N sensor nodes is calculated from:
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19. Fault Tolerance (4)
EXAMPLE: How many sensor nodes are needed within a broadcast radius (range) to have 99% fault tolerated network?
Assuming all sensors within the radio range have same reliability, prev. equation becomes
Drop t and substitute f = (1 – R).
o.99 = 1 – fN  N = 2
Dr. Xinbing Wang

20. Fault Tolerance (5) REMARK:
1. Protocols and algorithms may be designed to address the level of fault tolerance required by sensor networks.
2. If the environment has little interference, then the requirements can be more relaxed.
Dr. Xinbing Wang

21. Factors Influencing Sensor Network Design
A. Fault Tolerance (Reliability)
B. Scalability
C. Production Costs
D. Hardware Constraints
E. Sensor Network Topology
F. Operating Environment
G. Transmission Media
H. Power Consumption 
Dr. Xinbing Wang

22. B. Scalability
The number of sensor nodes may reach millions in studying a field/application
The density of sensor nodes can range from few to several hundreds in a region (cluster) which can be less than 10m in diameter.
Dr. Xinbing Wang

23. Scalability (2)
The Sensor Node Density: i.e., the number of expected nodes within the radio range R
where N is the number of scattered sensor nodes in region A and R is the radio transmission range.
Basically:  is the number of sensor nodes within the
transmission radius of each sensor node in region A.
The number of sensor nodes in a region is used to indicate the node density depends on the application.
Dr. Xinbing Wang

24. EXAMPLE: Scalability (3) Use the eq. on the previous slide
Assume sensor nodes are evenly distributed in the sensor
field, determine the node density if 200 sensor nodes
are deployed in a 50x50 m2 region where each sensor
node has a broadcast radius of 5 m.
Use the eq. on the previous slide
 (R) = (200 * * 52 )/(50*50) = 2 * 
Dr. Xinbing Wang

25. Example -- Node Distribution
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26. Scalability (4) -- Network Configuration
dnei  Expected distance to the nearest neighbor, may or may not be communicating neighbor.
dhop  Expected distance to the next hop, i.e., distance to communicating neighbor. dhop>=dnei
Assuming that connection establishment is equally likely with any node within the radio range R of the given node, the expected hop distance is:
Sink node
dhop = 2R/3
Radio Range R
e.g., R=20m  13.33m
dnei
dhop
Sensor nodes
Dr. Xinbing Wang

27. Scalability (5) -- Examples
Machine Diagnosis Application: less than 300 sensor nodes in a 5 m x 5 m region.
Vehicle Tracking Application: Around 10 sensor nodes per cluster/region.
Home Application: 2 dozens or more.
Habitat Monitoring Application: Range from 25 to 100 nodes/cluster
Personal Applications: Ranges from 100s to 1000s, e.g., clothing, eye glasses, shoes, watch, jewelry.
Dr. Xinbing Wang

28. Factors Influencing Sensor Network Design
A. Fault Tolerance (Reliability)
B. Scalability
C. Production Costs
D. Hardware Constraints
E. Sensor Network Topology
F. Operating Environment
G. Transmission Media
H. Power Consumption  
Dr. Xinbing Wang