Location Sensing technologies for context-aware Software Systems Corso: Argomenti avanzati di sistemi informativi Docente: Stefano Ceri Alunno: Nadia Castiglioni Matricola: Politecnico di Milano V facoltà di ingegneria – Ingegneria informatica II anno di laurea specialistica Anno accademico

Definition of “context” Schmidt: “knowledge about the user’s and IT device’s state, including surroundings, situation, and to a less extent, location”. 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” 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: 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 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: –It calculates its position by trilateration. –Precision: 3 meters –Physical absolute position Galileo

Indoor systems: RFID & Bluetooth 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 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 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 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 Applications –Active Bat –ParcTab

Indoor technologies: Wi-Fi & UMTS Wi-Fi networks use radio technologies called IEEE b or a 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 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!