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Mini Course

Programming Context-aware Mobile Phones

Thomas Bodin

IT University of Copenhagen

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Week agenda

09.00 - 12.00: Lectures in AUD 3

13.00 - 16.00: Exercises in room 3A52

Homepage: http://lacomoco.itu.dk/minicourse/

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Monday agenda

Context-aware computing There is more to Context than Location On location models for ubiquitous computing Positioning Technologies Mobility Lab

Introduction to week exercise The afternoon exercises will lead to a small distributed system

consisting of a client-side covering the j2ME/JSR 82 API and a server-side covering the BlipNet API.

Introduction to server-side programming Design Patterns Distributed system

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Context-aware computing

There is more to Context than Location December 1999

On location models for ubiquitous computing 25 August 2004

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There is more to Context than Location

Mobile computing vs. ultra-mobile computing Ultra-mobile devices (PDA, mobile phones, wearable computers) Related Work

Active Badge System (sensing locality of mobile users) Stick-e-notes (time and location tagging)

Observation Lack of context definition Location sensing is dominant Lack of sensor employment

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There is more to Context than Location

Context model proposal Describes the situation/environment a device/user is in Identified by a unique name that goes into two general categories

Human factors Physical environment

For each context a set of features is relevant For each relevant feature a range of values is determined by the

context Applying context in two general ways

Changes in the environment (e.g. walking tour) Improvement of the user interface (e.g. light-sensitive display and

orientation-sensitive user interface)

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There is more to Context than Location

Three application domains Adaptive user interfaces (interaction styles and display modes) Context-aware communication (filter, reroute and deliver messages

and streams in accordance with context) Proactive application scheduling (ad hoc style of interaction)

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There is more to Context than Location

Sensor technology Optical/Vision (photo-diode, color sensor, IR, UV-sensor etc.)

Main color, motion detection (low processing) Detection of objects, landmarks, people, gestures etc. (high processing)

Audio (microphone and electronics) Determination of loudness, background noise and base frequency Speaker identification

Motion (mercury switches, angular sensors and accelerometers) Detection of stationary vs. moving

Location (GPS, GSM, Wi-Fi, Bluetooth etc)

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There is more to Context than Location

Sensor technology (continued) Bio-Sensors (pulse, skin resistance, blood pressure etc.)

Emotional state can be estimated Specialized sensors (touch, temperature, air pressure etc.)

Specialized applications Security systems

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There is more to Context than Location

Sensor fusion Physical/logical sensors Cues: abstraction from physical/logical sensors

Ex 1: Artificial light, stationary or walking, room temperature, dry Ex 2: Natural light (clody or sunny), walking or running, dry or raining,

high pulse Context: description of a current situation

Ex 1: In the office Ex 2: Jogging

Scripting: including context in application

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On location models for ubiquitous computing

Crucial for location-based or context-aware applications Supporting position, nearest neighbor and range queries No location model satisfies all identified requirements (choose

location models carefully with respect to the required spatial reasoning and the involved modeling effort).

Geometric coordinates (Global Positioning System (GPS), active bat system)

Symbolic coordinates (Global System for Mobile Communications (GSM), active badge system based on infrared signals (IR) or radio frequency identification (RFID))

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On location models for ubiquitous computing

The system model consists of three kinds of components:

Applications

The location model

Positioning systems

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On location models for ubiquitous computing

Use cases for location models Position queries

Geometric position (global and local coordinate reference systems) Symbolic position (cell IDs)

Nearest Neighbor queries Searching for the n objects closest to a certain position Distance function required

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On location models for ubiquitous computing

Use cases for location models (continued) Navigation

The topological relation connected to (finding the shortest/fastest path

Range queries The topological relation contained in

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Positioning Technologies

WLAN WiFi Positioning Bluetooth Positioning

GSM GPS RFID

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WLAN

IEEE (Institute of Electrical and Electronics Engineers) is a non-profit organization that develops, defines, and reviews electronics and computer science standards.

Wireless Local Area Network (WLAN) Working Group (802.11) IEEE 802.11b – Wireless Fidelity (WiFi) providing 11 Mbps data rate

in 2.4 GHz ISM band Wireless Personal Area Network (WPAN) Working Group

(802.15) IEEE 802.15.1 – Bluetooth providing 1 Mbps data rate and 10 – 100

meter range in the 2.4 GHz ISM band

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WLAN – WiFi Positioning

A calibration model is used to calculate the device location based on the received signal strengths.

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WLAN – Bluetooth Positioning

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GSM

GSM (Global System for Mobile Communications) has become the most successful global mobile technology for mobile phones and digital cellular networks with more than one billion subscribers.

GPRS (general packet radio service) is used as a data service upgrade to the GSM network with transmission bit rates from 9.6 Kbps to more than 150 Kbps. It supplements the SMS (Short Message Service).

The new EDGE air interface has been developed specifically to meet the bandwidth needs of 3G.

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GSM

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GPS

GPS (Global Positioning System) is a satellite navigational system formed by 24 satellites making two complete orbits every 24 hours

By using three satellites, GPS can calculate the longitude and latitude of the receiver based on where the three spheres intersect (cf. triangulation).

Developed and operated by the U.S. Department of Defense. Galileo will be Europe’s own global navigation satellite system,

providing a highly accurate, guaranteed global positioning service under civilian control. It will be inter-operable with GPS and GLONASS, the two other global satellite navigation systems

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RFID

RFID (Radio Frequency Identification) A technology similar in theory to bar code identification Transmission ranges of more than 90 feet

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Mobility Lab

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Mobility Lab - Support

Webpage: http://mobilitylab.itu.dk/ Opening hours according to personal support and equipment

registration: Monday-Friday 13.00 - 14.00 Newsgroup: it-c.mobilitylab Mailinglist: mobilitylab@itu.dk

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Introduction to week exercise

The afternoon exercises will lead to a small distributed system consisting of a client-side covering the j2ME/JSR 82 API and a server-side covering the BlipNet API.

Initially, the overall functionality will be to exchange small visiting cards with name, phone number, current location etc. Also, this information exchange may include messages attached to certain locations of mobile devices. Technologically, the exchange service will rely on a certain Bluetooth profile (supported by the mobile phone), and the location of a mobile device is achieved through a Bluetooth access point (cf. cell id).

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Introduction to week exercise

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Introduction to week exercise

The SPP Server contains 4 main classes SppServer

Handles the connection to the BlipServer Spawns an SppServerSession object when a connection to a mobile

phone (cf. terminal) has been made SppServerSession

Management of input-/output stream Implementation of application protocol

SppServerDatabase Management of the JDBC in order to register terminals (bluetooth

address, name, phonenumber) SppServerException

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Introduction to week exercise

The SPP MIDlet contains 8 main classes SppMIDlet

Initializes the MIDlet SppDiscovery

Discovers the connected BlipNodes (cf. inquiry) SppBlipNodeList

Appends the BlipNodes (discovered by the SppDiscovery) to the mobile phone display

SppStream Management of input-/output stream Implementation of application protocol

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Introduction to week exercise

The SPP MIDlet contains 8 main classes (continued) SppCardForm

Handles the exchange of visiting card data (bluetooth address, name, phonenumber)

SppCardPositionForm Handles the name and area exchange (e.g. the user requests the server

with a username, and the responds with an area, if the username is registered by the server)

SppStore Handles the persistence of data (bluetooth address, name, phonenumber

and area) on the mobile phone SppException

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Introduction to week exercise

The database ’spp’ contains 3 tables The ’area’ table contains 2 columns: ’area_id’, ’type’ The ’card’ table contains 3 columns: ’card_id’, ’bluetooth_address’,

’name’, ’phonenumber’ card_position contains 3 columns: ’card_id’, ’area_id’, ’timestamp’

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Introduction to server-side programming

Design patterns Singleton pattern Observer pattern

Distributed System Application Protocol Database connectivity (JDBC)

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Design patterns

The idea behind object-oriented programming is that a computer program is composed of a collection of individual units, or objects, as opposed to a traditional view in which a program is a list of instructions to the computer. Each object is capable of receiving messages, processing data, and sending messages to other objects.

Abstraction, encapsulation, polymorphism and inheritance are key concepts in object-oriented programming

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Design patterns

Observer pattern

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Design patterns

Observer pattern UML Minimal coupling between the Subject and the Observer Support for event broadcasting

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Design patterns

Singleton pattern UML Controlled access to sole instance Permits a variable number of instances

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Design patterns

public class SppServerDatabase { private static SppServerDatabase database;

private SppServerDatabase() throws SppServerException { try { Class.forName(“org.gjt.mm.mysql.Driver”); connection = DriverManager.getConnection(“jdbc:mysql://localhost/spp”, “root”, “ml”); System.out.println(“Connection successful!”); } catch(ClassNotFoundException cnf) { throw new SppServerException(cnf.getMessage()); } catch(SQLException sqle) { throw new SppServerException(sqle.getMessage()); } }

public synchronized static SppServerDatabase getSppServerDatabase() throws SppServerException { if(database == null) database = new SppServerDatabase(); return database; }

(…)

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Distributed System

A distributed system is defined as one in which hardware or software components located at networked computers communicate and coordinate their actions only by passing messages.

This mini course focuses on the client-server model communicating over the Serial Port Profile (cf. Bluetooth).

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Distributed System

Application Protocol (server-side)

public void run() { while(true) { try { byte[] flag = new byte[1]; is.read(flag, 0, 1); int i = (int)flag[0]; switch(i) { case CARD: readCard(); break; case CARD_POSITION: break; } } catch(IOException ioe) {} }}

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Distributed System

Application Protocol (client-side)

public void sendCard(String bluetoothAddress, String name, String phonenumber) throws SppException { byte[] flag = new byte[4]; flag[0] = (byte)CARD; flag[1] = (byte)bluetoothAddress.getBytes().length; flag[2] = (byte)name.getBytes().length; flag[3] = (byte)phonenumber.getBytes().length; try { os.write(flag); os.write(bluetoothAddress.getBytes()); os.write(name.getBytes()); os.write(phonenumber.getBytes()); os.flush(); } catch(IOException ioe) { System.out.println("IO Exception!"); }}

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Distributed System

Database connectivity (JDBC)

public void setCardId(String btAddress, String name, String phonenumber) throws SppServerException {

String query = "insert into card values (null, '” + btAddress + "','" + name + "','" + phonenumber + "')";

try {

Statement statement = connection.createStatement();

statement.execute(query);

ResultSet resultSet = statement.getResultSet();

}

catch(SQLException sqle) {

throw new SppServerException(sqle.getMessage());

}

}