Transcript Location Sensing technologies for context

Politecnico di Milano
V facoltà di ingegneria – Ingegneria informatica
II anno di laurea specialistica
Anno accademico 2004-05
Location Sensing technologies
for context-aware Software Systems
Corso: Argomenti avanzati di sistemi informativi
Docente: Stefano Ceri
Alunno: Nadia Castiglioni
Matricola: 667001
Definition of “context”
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Schmidt:
“knowledge about the user’s and IT device’s state, including
surroundings, situation, and to a less extent, location”.
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Dey:
“any information that can be used to characterize the situation of
an entity. An entity is a person, place, or object that is considered
relevant to the interaction between a user and an application,
including the user and applications themselves”
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Chen and Kotz:
“Context is the set of environmental states and settings that either
determines an application’s behavior or in which an application
even occurs and is interesting to the user.”
Differences from desktop computing:
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Multimodal interaction
Physically embodied interaction
Dynamic set of devices
Lack of single focal point
Multiple simultaneous users
Location Sensing Technique
• Geometric techniques:
– Lateration
• Direct (Probing)
• Time-of-Flight
• Attenuation
– Angulation
• Scene Analysis
• Proximity
– Physical contact
– Wireless cellular access point
– Automatic ID Systems
• Statistical Methods
Properties
• Approaches: Type of information systems
– The computation is made by the device
– The computation is made by the net
• Type of information provided
– Physical / Semantical
– Absolute / Relative
• Accuracy
• Precision
• Coverage
Outdoor technologies: GPS & Galileo
• Global Positioning System
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The Global Positioning System, usually called GPS, is a
satellite navigation system used for determining one's precise
location and providing a highly accurate time reference almost
anywhere on Earth or in Earth orbit.
It uses an intermediate circular orbit (ICO) satellite constellation of
at least 24 satellites in 6 orbits.
The GPS system is divided into three segments:
– space,
– control,
– user,
Characteristics:
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It calculates its position by trilateration.
Precision: 3 meters
Physical absolute position
• Galileo
Indoor systems: RFID & Bluetooth
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RFID
– It is a method of remotely storing and retrieving data using devices called
RFID tags or transponders.
– An RFID tag is a small object, that can be attached to or incorporated into a
product. RFID tags contain antennas to enable them to receive and
respond to radio frequency queries from an RFID tranceivers.
– The RFID Tags can be Active or Passive
– A typical RFID tag consists of a microchip attached to a radio antenna
mounted on a substrate; the chip can store as much as 2 kilobytes of data
– Systems: Verichip
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Landmark
SpotON
Bluetooth
– Bluetooth is a standard
– Bluetooth is a method for data communication that uses short-range radio
links to replace cables between computers and their connected units
– It uses a fast acknowledgement and frequency-hopping scheme to make
the link robust, even in noisy radio environments.
– It is based on a Master Slave architecture, with time slots, 2.4 GHz
frequency.
– It maintains the information updated throught PageScan and InquiryScan
– It can transfer voice and data
Indoor technologies: IrDA
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Infrared Data Association
– The Infrared Data Association defines physical specifications
communications protocol standards for the short range exchange of
data over infrared light, for uses such as personal area networks
(PANs).
– IrDA is a very short-range example of free-space optical
communication.
– IrDA interfaces are used in palmtop computers and mobile phones.
– Speeds for IrDA v. 1.0 range from 2400 to 115200 kbps.
– IrDA specifications include IrPHY, IrLAP, IrLMP, IrCOMM, Tiny TP,
IrOBEX, and IrLAN. IrDA has now produced another standard, IrFM, for
Infrared financial messaging also known as "Point & Pay".
– For the devices to communicate via IrDA they must have a direct line
of sight
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Applications
– Active Bat
– ParcTab
Indoor technologies: Wi-Fi & UMTS
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Wi-Fi networks use radio technologies called IEEE 802.11b or
802.11a to connect computers to each other, to the Internet, and to
wired networks.
Wi-Fi is a radio technology, on the frequency 2,4 GHz in an area
covered by an antenna, called hat spots.
The main wireless technologies are two:
– Narrowband:.
– Spread
Application: RADAR
UMTS is one of the main mobile system of the third generation,
defined by the ITU (International, Telecommunication Union)
inside the IMT 2000.
It is the combination of the W-CDMA air interface, GSM's Mobile
Application Part (MAP) core, and the GSM family of speech
codecs
Key technologies:
– UTRA
– Multimode second generation terminals
– Satellite Systems
– USIM cards
Hybrid Systems
• Active Bat ultrasonic system
– Using bats that spread ultrasonic in order to
localize them according to a grid posed on the
ceiling
• Smart floor
– Using footsteps to provide localization
• Cricket location-support system
– Radio and ultrasonic signals together to
support a proximity algorithm
Comparisons
The application goals and services will guide you
at the correct technology
Conclusions
• The main challenges are privacy
issues, security, autentication and
interoperability between these
different tecnologies
• But, throught these tecnologies, we
can realize all that our fantasy
suggests!