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Lecture 14 Pervasive Computing Applications Wireless Networks and Mobile Systems

Lecture 14 Pervasive Computing Applications Wireless Networks and Mobile Systems

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Page 1: Lecture 14 Pervasive Computing Applications Wireless Networks and Mobile Systems

Lecture 14Pervasive Computing Applications

Wireless Networks and Mobile Systems

Page 2: Lecture 14 Pervasive Computing Applications Wireless Networks and Mobile Systems

Pervasive Computing Applications 2

Lecture Objectives

● Understand characteristics and technical challenges of pervasive computing applications

● Understand system middleware and support for context-aware ubiquitous computing

● Exemplify pervasive computing applications

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Sources

● T. Kindberg and A. Fox, “System software for ubiquitous computing,” IEEE Pervasive Computing, Vol. 1, No. 1, 2002, pp. 70-81.

● A. Smailagic and D. Kogan, “Location sensing and privacy in a context-aware computing environment,” IEEE Wireless Communications, Vol. 9, No. 5, Oct. 2002, pp. 10-17.

● S.S. Yau, et al., “Reconfigurable context-sensitive middleware for pervasive computing,’’ IEEE Pervasive Computing, Vol. 1, No. 3, 2002, pp. 33-40.

● M. Roman, et al., “A middleware infrastructure for active spaces”, IEEE Pervasive Computing, Vol. 1, No. 4, 2003, pp. 74-83.

● B. Johanson, et al., “The interactive workspaces project: experiences with ubiquitous computing rooms,” IEEE Pervasive Computing, Vol. 1, No. 2, 2002, pp. 67-75.

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Agenda

● Characteristics of pervasive computing● System support to enable pervasive computing● Middleware for context-aware pervasive computing

applications● Examples of pervasive computing applications

■ Smart homes/rooms ○ UI’s Gaia-enabled Active Spaces○ Stanford’s Interactive Workspaces project

● Experimentation■ SLP-based pervasive Pocket TV application

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Pervasive Computing Characteristics (1)

● Pervasive computing is:■ An environment in which people interact with embedded

(and mostly invisible) computers and in which networked devices are aware of their surroundings and peers and are able to provide services or use services from peers effectively

■ The creation of environments saturated with computing and wireless communication, yet gracefully integrated with human users

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Pervasive Computing Characteristics (2)

● A pervasive (ubiquitous) system is characterized by:■ Physical integration: integration between computing nodes

and the physical world, e.g., a whiteboard that records what’s on

■ Instantaneous Interoperation: devices interoperate spontaneously in changing environments, e.g., a device changes its partners as it moves or as the context changes

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Non-Examples of Pervasive Applications

● Accessing email over a phone line from a laptop■ Neither physical integration nor spontaneous interoperations

○ The laptop maintains the same association with a fixed mail server

● A collection of wirelessly connected laptops based on IEEE 802.11 at a conference■ Discovery of the local network can be considered as physical

integration of laptops with a 802.11 access point○ The physical integration in pervasive computing, however,

should involve a part of the environment that has a non-electronic function (e.g., a white board, a cup, etc.)

■ No spontaneous interoperation is possible without considerable human manual intervention

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Borderline Examples of Pervasive Applications (1)

● A smart coffee cup and saucer ■ Physical integration: The cup is a regular

cup (a non-electronic function) that contains sensing, processing and networking elements that let it communicate with the saucer of its state (full or empty, held or putdown, hot or cold)

■ Instantaneous interoperation: Not satisfied if a specialized protocol is used between the cup and saucer as the owner would not be able to use the coffee cup without the saucer

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Borderline Examples of Pervasive Applications (2)

● P2P games■ Physical integration: client devices can have

sensors that allow physical integration ■ Instantaneous interoperation: not satisfied if

preconfigured components are used in the game○ A more convincing example would involve

players with generic game playing pieces that let them spontaneously join local games not encountered before

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Borderline Examples of Pervasive Applications (3)

● A Web-based object discovery system■ Devices (e.g., laptops) have small, embedded web servers that

allow objects to be accessed by physical hyperlinks■ The user is presented with a web page when it senses an

identifier of the object

● Physical integration ■ smart devices can use web functionality to allow advertised

objects to be integrated into the physical world as web pages without the need to reconfigure browsers

● Instantaneous interoperation ■ not exactly satisfied since the system requires human

intervention to keep it going. The human in the loop changes the browser’s associations to advertised web services

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Examples of Pervasive Applications (1)

● A magic mirror that shows personal data and actions of those users who face it in a meeting■ Physical integration: the mirror can sense

the presence of users in a meeting and can record their actions, in addition to its normal physical function

■ Instantaneous interoperation: the mirror would interact with the room’s other components the moment you switch it on and would make spontaneous association with all relevant local sources of information about users

….

….

….

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Examples of Pervasive Applications (2)

● A visitor brings his/her laptop into a meeting room and without manually configuring it in any way uses it to send his presentation to the room’s projector■ Physical integration: the projector can be

activated from any laptop in the room■ Instantaneous interoperation: A laptop can

spontaneously interact with the projector and control the presentation with a proper UI

■ Can be made context-sensitive, e.g., allowing only a particular visitor to do so

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Other examples: Miró display

Cornell experiment: reflections on collective experience

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Other examples: Gust of Presence

Delft Univ. of Technology: Gust of Presence project

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The Semantic Rubicon

The semantic Rubicon is the division between system and humanfor high-level decision-making or physical world semantics processing

The division should be exposed in system design and the criteria andmechanisms for crossing it should be clearly indicated

Little evidence existsto suggest that software

alone can meet ubiquitous computing challenges,

although it is desirable tohave minimum or no

interventionImage extracted fromIEEE Pervasive ComputingMagazine, Vol. 1, No. 1, 2002.

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System Support

● Discovery■ Requiring a common “syntax and vocabulary” model for

specifying services

ServiceType=“photoPrint”

ServiceType=“printing”

ServiceType=“digitalFrame”

Missedopportunity

ServiceType

Mismatched

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System Support (2)

● Interaction■ Requiring a “common” interoperation model for components

to interact○ Event systems – publish, subscribe, and handle events○ Tuple space – add, read, and remove tuples in a tuple

space

ServiceType=“Print”DataType=“JPEG”

ServiceType=“print”DataType=“JPEG”

ServiceType=“digitalFrame”DataType = “JPEG”

(Standardized)Data Oriented

Interaction Service

A common service:A tuple space or an event service

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System Support (3)

● Adaptation ■ Without human intervention for achieving “calm computing”

as well as spontaneous interaction■ Being able to display or manipulate data or UI from other

devices in a heterogeneous environment■ Possible solutions include:

○ Dynamic downloading of mobile code to handle UI and communication (as in Jini) – requiring JVM

○ Dynamic UI generation/transformation (as in Stanford’s Interactive Workspaces) – requiring a common UI description language to describe UI elements, e.g., “This control is a Boolean toggle”

Another example is to use XML for specifying UI for web services

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Human Interface Adaptation

● Use the same high-level UI description language to generate device-specific UIs to control lights and displays in a smart room for (a) a desktop HTML browser, (b) a Java-equipped device, and (c) a Palm device

Image extracted fromIEEE Pervasive ComputingMagazine, Vol. 1, No. 1, 2002.

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System Support (4)

● Physical Integration■ Context-awareness support is

required to allow an application to access different types of contexts (e.g., locations, identities, QoS conditions) while hiding how the information was sensed or collected

● Examples:■ “Show me the agenda!” - can be

made context-sensitive ■ “Show me related Web pages for

museum exhibits!” – can be based on the location and ids of exhibits sensed through barcode or Infrared beacon

Context aware

tag tag

I know who I am

photographing

I know you provide

photo printingservices

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Positioning for Location-aware Computing

● Outdoor – GPS (Global Position Sensing) normally to within 1-5 m accuracy with differential correction

● Indoor ■ Active Bat (shown below) developed by AT&T Lab

Cambridge based on ultrasonic sensors (to within 3 cm accuracy)

■ CMU-TMI (shown next) developed by CMU based on 802.11 for location tracking(to within 1-5 m accuracy)

Image extracted fromIEEE Pervasive ComputingMagazine, Vol. 1, No. 1, 2002.

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System Support – Location Tracking in Smart Spaces

● CMU has developed and deployed a Triangulation, Mapping and Interpolation (CMU-TMI) algorithm based on 802.11 for location tracking:■ Physical locations of access

points are known in advance■ A mobile device scans all access

points (at least 3) within range to determine their signal and noise strengths

■ The signal strengths are used to infer the distance between the device and the access points using an approximate relation obtained a priori

■ Triangulation technique is applied to calculate the physical location

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System Support (5)

● Programming Framework■ A programming framework for pervasive computing can be

placed at the application or middleware level:○ Application level

Providing only application-level coordination mechanisms, e.g., through a “tuple-space” API

○ Middleware level Providing more tightly integrated facilities for

achieving context awareness, QoS resource management, and adaptive control.

Determining the user’s task and intention, and facilitating associations between components to assist the user in these activities

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System Support (6)

● Robustness ■ Failure is a common case in mobile and pervasive computing■ Recovering from failures always prepared to reacquire lost

resources○ Expiration-based schemes and soft states

Periodic service advertisement and lease in the “common” data-oriented interaction service

○ Separating failure-free (logic) from failure-prone (e.g., accessing a service or file while moving) application code

More effective failure handling can be done implicitly by the middleware, e.g., retrying an idempotent operation (binding to a remote file) for a number of times

● Security – trust between devices, access control

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Middleware for Pervasive Computing

● Context-Aware middleware for pervasive computing must address two “broad” characteristics:■ Tradeoff between awareness and transparency

○ For pervasive applications, environment awareness is key to their effectiveness

■ Cooperation between development support and run time services ○ Let developers focus on application logic

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RCSM: A Reconfigurable Context Sensitive Middleware

● ASU’s RCSM addresses the following “specific” characteristics:■ Uniform development support

○ providing a uniform way to express context awareness without restricting to a specific language, OS, or environment

■ Application-specific context acquisition, analysis and detection ○ allowing developers to express the need for context data in a

platform-independent way without knowing “how” data are obtained

■ Context-triggered actions○ transparently invoking actions whenever the specified contexts

are valid■ Transparent support for ad hoc communication

○ abstracting the details of ad hoc communication from applications including proactively discovering new devices, establishing new communication links and notifying the application when a device is found

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RCSM: A Reconfigurable Context Sensitive Middleware (2)

● ASU’s RCSM provides a context-aware interface description language (CA-IDL) API for an application to ■ Define contexts used by

the application ■ Specify actions taken

based on context values

● Compilers are provided to build adaptive object containers (ADCs) based on CA-IDL

Image extracted fromIEEE Pervasive ComputingMagazine, Vol. 1, No. 3, 2002.

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Pervasive Computing Example 1: UI’s Gaia-enabled Active Spaces (1)

● Gaia is a distributed middleware infrastructure that coordinates software entities and heterogeneous network devices contained in a physical space ■ The physical space is extended into

an “active space” by adding coordination via a context-based software infrastructure

Image extracted fromIEEE Pervasive ComputingMagazine, Vol. 1, No. 4, 2002.

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Pervasive Computing Example 1: UI’s Gaia-enabled Active Spaces (2)

● Event manager service: for event channel registration/notification● Context service: for querying/registering context information such as people’s

locations● Presence service: for maintaining soft states of resources including digital

entities (applications and services using heartbeats) and physical entities (devices and people using sensors)

● Space repository: for displaying/retrieving information about all entities in the active space

● Context file system: associating data with context and format info to allow context-sensitive data retrieval presented with the right UI format, e.g., make personal data available to applications conditioned on presence

Image extracted fromIEEE Pervasive ComputingMagazine, Vol. 1, No. 4, 2002.

Example: Presentation Manager Application

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Pervasive Computing Example 1: UI’s Gaia-enabled Active Spaces (3)

● EX: Presentation Manager Application

● Speaker X with an RF active badge and a handheld walks into a Gaia-enabled room

● Presence service detects the badge and sends a “X is here” event with the user profile info of X contained■ Space repository receives the event

and displays the user info.■ Context file system obtains the

speaker’s mount point and mounts the speaker’s presentation file ready for access

● The handheld (controller) detects the directory server and then sends a heartbeat event to the heartbeat channel ■ Presence service detects and sends a

“new device” found event■ Space repository receives the event

and displays the handheld info● Both speaker X and handheld are

now entities of the active space

A prototype of Gaia-enabled active space

Context: Speaker X enters the room

Action: start the presentation manager application• Read the presentation file• Allowing X to control presentation

by control events generated from the touch screen or handheld

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Pervasive Computing Example 2: Stanford’s Interactive Workspaces (1)● Stanford’s Interactive Workspaces is based on a tuple

space data model■ Event Heap: Allowing name-type-value events (with expiration

times) to be posted and retrieved■ Data Heap: Allowing data with attributes (e.g., format) posted■ iCrafter: Providing service advertisement/invocation and a UI

generator that returns the best interface for the device

Image extracted fromIEEE Pervasive ComputingMagazine, Vol. 1, No. 2, 2002.

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Pervasive Computing Example 2: Stanford’s Interactive Workspaces (2)

● Room-based cross-platform interfaces■ The room-control system stores the geometric arrangement

of screens and lights in the room in a configuration file and will automatically provide controllers on any device supporting a UI format available through iCrafter

Java SwingPalm

html

Image extracted fromIEEE Pervasive ComputingMagazine, Vol. 1, No. 2, 2002.

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Experimentation: SLP-based Pervasive Pocket TV

● SLP (RFC 2608) is an IETF standard that provides a scalable framework for automatic resource discovery on IP networks. Three entities are defined in a SLP system: ■ User agent (UA)■ Server agent (SA)■ Directory agent (DA)

● A UA initiates service discovery on behalf of one or more applications. It can send queries to all SAs via multicast if a DA does not exist or to a DA to discover services via unicast.

● A SA works on behalf of one or more services. It responds directly to UA queries via unicast. If a DA exists, a SA can register its services with the DA to expose its services.

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Experimentation: Pervasive Pocket TV (2)

● A DA serves as a centralized information repository. It accepts SA registrations and answers UA directory service queries. The DA support is optional and is introduced for performance and scalability considerations.

Application

UA SA

DA

Service

query

reply

service registrationdirectory service query

directory service reply acknowledgment

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Experimentation: Pervasive Pocket TV (3)

● DA Discovery: Passive versus Active

UA/SA DA

Multicast SrvRqst (service:directory-agent)

Unicast DAAdvert

UA/SA DAMulticast DAAdvert

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Experimentation: Pervasive Pocket TV (4)

● Three configurations

SA UA SAMulticast SrvRqst Multicast SrvRqst

Unicast SrvRply Unicast SrvRply

UA DA

SA

SA

Unicast SrvRqst

Unicast SrvRply

Unicast SrvReg

Unicast SrvAck

Unicast SrvAck

Unicast SrvReg

Small: No DA

Medium: 1 DA

Large: Multiple DA’s

UA

UA

SA

SA SA

SA

DA

DA