1.
DILLA UNIVERSITY
COLLEGE OF ENGINEERING & TECHNOLOGY
School of Computing & Informatics
M. Sc in Computer Science & Networking
By
Chapter-04
COET, Dilla University 1
Course Number CN6117
Course Title Mobile Computing

2.
Mobile Computing
CHAPTER-04
• Radio frequency identification(RFID)
• Location based services
COET, Dilla University 2

3.
Radio Frequency Identification(RFID)
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4.
Overview
• What is RFID?
• How RFID Works
• Applications
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What is RFID?
• Radio Frequency Identification
• The use of radio frequency tags to identify
real objects.
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6.
RFID
 Radio-frequency identification (RFID) uses
electromagnetic fields to automatically identify
and track tags attached to objects.
 An RFID system consists of a tiny radio
transponder; a radio receiver and transmitter.
 When triggered by an electromagnetic
interrogation pulse from a nearby RFID reader
device, the tag transmits digital data, usually an
identifying inventory number, back to the reader.
 This number can be used to track inventory
goods.
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Identification
• Assign IDs to objects
• Link the ID to additional information about
the object
• Link the ID to complementary info
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Identification Examples
• Bar Codes
• License Plates
• Social Security Numbers
• Student ID
• Serial Numbers
• Car Keys
• Database Keys
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How Does RFID Work?
• 3 Components
– Transceiver – Tag Reader
– Transponder – RFID tag
– Antenna
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10.
RFID Hardware
Magnetic / Inductive Coupling
Transceiver
Tag Reader
antenna
RFID
Tag
IC or microprocessor
antenna
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11.
RFID Hardware
Propagation Coupling
Transceiver
Tag Reader
antenna
RFID
Tag
IC or microprocessor
antenna
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12.
Types of Tags
• Passive Tags
– No battery
– Low cost
• Active Tags
– On-board transceiver
– Battery – must be replaced
– Longer range
– High cost
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Passive tags & Active tags
There are two types of RFID tags:
Passive tags are powered by energy from the
RFID reader's interrogating radio waves.
Active tags are powered by a battery and thus
can be read at a greater range from the RFID
reader; up to hundreds of meters.
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Readers
RFID systems can be classified by the type of
tag and reader.
 A Passive Reader Active Tag (PRAT)
 Active Reader Passive Tag (ARPT)
 Active Reader Active Tag (ARAT)
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Readers
RFID systems can be classified by the type of tag and reader.
 A Passive Reader Active Tag (PRAT)
• A Passive Reader Active Tag (PRAT) system has a
passive reader which only receives radio signals from active
tags (battery operated, transmit only).
• The reception range of a PRAT system reader can be
adjusted from 1– 2,000 feet (0 – 600 m) , allowing flexibility
in applications such as asset protection and supervision.
 Active Reader Passive Tag (ARPT)
• An Active Reader Passive Tag (ARPT) system has an
active reader, which transmits interrogator signals and also
receives authentication replies from passive tags.
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Cont..
Active Reader Active Tag (ARAT)
• An Active Reader Active Tag (ARAT) system
uses active tags awoken with an interrogator
signal from the active reader.
• A variation of this system could also use a
Battery-Assisted Passive (BAP) tag which acts
like a passive tag but has a small battery to
power the tag's return reporting signal.
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Types of Tags
• Read Only
– factory programmed
– usually chipless
• Read / Write
– on-board memory
– can save data
– can change ID
– higher cost
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18.
Real Tags
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Data Transfer
• Amplitude Modulation (AM)
• Frequency Shift Keying (FSK)
• Phase Shift Keying (PSK)
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Amplitude Modulation (AM)
 Amplitude modulation is a modulation
technique used in electronic communication,
most commonly for transmitting messages
with a radio carrier wave.
 In amplitude modulation, the amplitude of
the carrier wave is varied in proportion to that
of the message signal, such as an audio signal.
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Frequency Shift Keying
 Frequency-shift keying (FSK) is a frequency
modulation scheme in which digital information is
transmitted through discrete frequency changes of a
carrier signal.
 The technology is used for communication systems
such as telemetry, weather balloon radiosondes, caller
ID, garage door openers, and low frequency radio
transmission in the VLF(Very low frequency) and
ELF(Extremely Low Frequency) bands. The simplest FSK
is binary FSK (BFSK).
 BFSK uses a pair of discrete frequencies to transmit
binary (0s and 1s) information.
 With this scheme, the 1 is called the mark
frequency and the 0 is called the space frequency.
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Cont..
• Fc/8/10
– 0’s are the carrier divided by 8
– 1’s are the carrier divided by 10
• Count clock cycles between changes in
frequency
• Slows the data rate
• Provides for a simple reader design
• Fair noise immunity
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23.
Phase Shift Keying
 Phase-shift keying (PSK) is a digital
modulation process which conveys data by
changing (modulating) the phase of a constant
frequency reference signal (the carrier wave).
 The modulation is accomplished by varying
the sine and cosine inputs at a precise time.
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Cont..
• One frequency
– Change the phase on the transition between a 0
to 1 or 1 to 0
• Faster data rate than FSK
• Noise immunity
• Slightly more difficult to build a reader than
FSK
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Multiple Tags?
• What happens when multiple tags are in
range of the transceiver?
• All the tags will be excited at the same time.
• Makes it very difficult to distinguish between
the tags.
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Collision Avoidance
• Similar to network collision avoidance
• Probabilistic
– Tags return at random times
• Deterministic
– Reader searches for specific tags
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Frequency Ranges
• Low – 100-500 kHz
– short range, low data rate, cost, & power
• Intermediate – 10-16 MHz
– medium range and data rate
• High – 850-950 MHz & 2.4-5.8GHz
– large range, high cost, high data rate
• 8 total ranges around the world
• No standards … yet
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Frequency Trade-Offs
Frequency
 Power
 Cost
 Bandwidth
 Line of Sight
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RFID can be used in a variety of
applications such as:
o Electronic key for RFID based lock system
o Access management
o Tracking of goods
o Tracking of persons and animals
o Toll collection and contactless payment
o Machine readable travel documents
o Smart dust (for massively distributed sensor
networks)
o Locating lost airport baggage
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30.
Cont..
o Timing sporting events
o Tracking and billing processes
o Monitoring the physical state of perishable
goods
o Passive / Secure Entry
o Airline Baggage Tracking
o Postal Package Tracking
o Time and Attendance
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31.
Who’s got an RFID tag with them
right now?
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32.
Security
• RFID used to grant entry to secure areas
• Tracks time and movement of people
• Dynamically change access codes
• Provide automated entry
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33.
Livestock Tagging
Meet Bobby the Cow
Bobby has an old
fashioned ear tag
for identification.
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Tracking Penguins
http://www.beitec.com/penguin.htm 34
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Automated Toll Collection
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Package Tracking
Picture courtesy Texas Instruments
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Potential Applications
• Smart Grocery Store
• Smart Kitchen
• Smart Sitterson
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Smart Grocery Store
• Every item in the store already has a bar code.
• Why not use an RFID tag?
• Speed up checkouts
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Smart Grocery Store
• Several carts this full
in early evening could
seriously slow down
the checkout process.
• How much do
cashiers cost?
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Smart Grocery Store
• Add an RFID tag to all
items in the grocery.
• As the cart leaves the
store, it passes
through an RFID
transceiver
• The cart is rung up in
seconds.
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Smart Groceries Enhanced
• Track products
through their
entire lifetime.
Diagram courtesy How Stuff Works
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Smart Fridge
• Recognizes what’s been put in it
• Recognizes when things are removed
• Creates automatic shopping lists
• Notifies you when things are past their
expiration
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RFID Chef
• Uses RFID tags to recognize food in your
kitchen
• Shows you the recipes that most closely
match what is available
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Smart Sitterson
• Tag locations throughout Sitterson
• User walks around with handheld and
transceiver
• RFID tags point the handheld to a webpage
with more information about their location or
the object of interest
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45.
RFID’s Advantages
• Passive
– wireless
• Store data on a tag
• Can be hidden
• Work in harsh environments
• Low cost
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46.
RFID’s Disadvantages
• Lack of standards
• Short range
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References
RFID Chef
http://www.inf.ethz.ch/vs/res/proj/rfidchef/
AIM Global Network
http://www.aimglobal.org/technologies/rfid/what_is_rfid.htm
Texas Instruments RFID Solutions
http://www.ti.com/tiris/default.htm
Interaction Design Institute
RFID Whitepaper
http://people.interaction-ivrea.it/natasha/rf/RFID_research.pdf
Auto-ID Center
http://www.autoidcenter.org/
Cow Jewelry – or – Revolution http://www.cs.unc.edu/~sparkst
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48.
Thank you
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