wireless engineering pervasive computing sumi helal richard chapman 3 october 2002

Wireless Engineering

Pervasive Computing

Sumi Helal

Richard Chapman

3 October 2002

WIRELESS ENGINEERINGWIRELESS ENGINEERING

Pervasive Computing

1. What is Pervasive Computing2. User Interactions Context-Aware Decision Engine3. Distributed Services Jini,UPnP,Osgi,Bluetooth SDP4. Infrastructures5. MIT Oxygen Project6. HP Cooltown Project7. References


Ubiquitous Computing (1)

• Ubiquitous, Invisible Computing (Mark Weiser [1]) : Computers disappear into the background.

• Computers embedded in walls, in tabletops, and in every day objects

• A person might interact with hundreds of computers at a time, each invisibly embedded in the environment and wirelessly communicating with each other.


Ubiquitous Computing (2)

• PARCTAB System - Doors open only to the right badge wearer.

- Rooms greet people by name.

- Receptionists actually know where people are.

- Telephone calls can be automatically forwarded.

- Computer terminal retrieve the preference of whoever is

sitting at them.

• Technologies for Ubiquitous Computing :

Display, network, and ubiquitous software system


The “Personal Motor”

• Popular at turn of 20th Century

• One motor and lots of “peripherals”: washing machine, woodworking tools, sewing machine, grain milling

• System of belts and pulleys to distribute motive power

• Similar to the PC situation today

• Intel, Microsoft like it this way


The Invisible Computer

• Embed the capability where it is needed rather than centralize it

• You know you’ve succeeded when the technology becomes a fashion item

• Wristwatches: definitely

• Mobile phone: almost

• Laptop PC: nope


Pervasive Computing (1)

• A computing environment that seamlessly and ubiquitously supports users in accomplishing their tasks and that renders the actual computing devices and technology largely invisible [5].

• Environments created when computing power and network connectivity are embedded in virtually every device humans use. Anytime/anywhere, any device, any network, any data [4].

• Computation is freely available everywhere, like batteries and power sockets. Anonymous devices, either handheld or embedded in the environment, will bring computation to us, no matter where we are or in what circumstances. These devices will personalize themselves in our presence by finding whatever information and software we need [18].



• Device as portal / Application as task / Physical surroundings as computing Environment [2]

- A device is a portal into an application/data space.

- An application is a means by which a user perform a task,

not a piece of software to exploit a device’s capability.

- The computing environment is the user’s information-

enhanced physical surroundings, not a virtual space to

store and run software.



• It is all about access to your information, anytime, anywhere, from any device.

• Four major aspects [6]

- Computing is spread throughout the environment.

- Users are mobile.

- Information appliances are becoming increasingly

available.

- Communication is made easier -- between individuals,

between individuals and things, and between things.


Challenges [1-6]

• User Interactions - Different interface modalities and form factors

- Multiple user interfaces that rely upon user intent

• Distributed Services - Adaptable to users, to the environment, to change, to failure

- Dynamic service discovery, adaptation and composition

- Horizontally-layered network-based services

• Infrastructures

- Dynamically configured proximity network of sensors, actuators, and appliances.

- Limited network connectivity, intermittent & unpredictable


User Interactions (1)

• Heterogeneous devices: different user interfaces, ranging from window- and keyboard-based to pen-based to voice-based interaction.

• Data from a variety of location and motion sensors, identification tags, and on-line services.

• Maintaining task-oriented consistency across physical devices while managing the multiple interfaces in a coherent manner.

- e.g. newspaper service to home display and PDA



• New and novel interaction methods such as vocal, handwritten, video, gestural, or olfactory interface

• The application front-end should be device-neutral: no assumption about the screen size or device capabilities, even no screen.

• Allows mobile clients to discover a service interface suited to the client’s size, shape, abilities, or resource limitation.

- Berkeley IDL(Interface Definition Language) or a XML schema

- Motorola VoxML: integration of speech interfaces with web content



• From explicit commands and towards interfaces that implicitly take their direction from people’s behavior/intent.

• Make the UI fit so well into the environment that it becomes invisible (Invisible interface and intuitive user interface)

• Context aware computing attempts to coalesce knowledge of the user’s task, emotions, location, and attention with other available data such as the time and knowledge about other users.

- Georgia Tech’s CyberDesk

- Spatial location work at AT&T Laboratories Cambridge

- Xerox PARC



• Heterogeneous devices vs. Universal personal appliances

• Universal personal appliances [18]

In response to user requests, they can reconfigure themselves through software into many useful appliances such as a two-way radios, cell phones, geographical positioning systems, and PDAs.


Context-Aware Decision Engine

• University of Hong Kong, Lum and Lau [19]

• Problem: how to render content for a variety of mobile devices?

• Bad solution: store multiple representations of the content on the servers

• Better solution: proxy server, transcoding• Challenge: flexibility to handle wide variety

of evolving devices?


Context-Aware Decision Engine(2)

• WAP phones are widespread but suffer limitations

• Limited bandwidth (9600 baud 2G, 56KB 2.5G, 114Kbps Verizon east-coast CMDA1x)

• Display size (92x74 = 5 Korean characters)

• Conflicting Standards: HTML vs. WML, JPEG vs. WBMP



• What is the context?

• User preferences

• Device capabilities

• Quality of service


Context-aware Decision Engine (4)

• How to determine device capabilities

• J2ME uses configuration (e.g. CLDC) and profile (e.g. MIDP)

• Composite Capability/Preference Profile: user prefs within user agent’s set of capabilities, retrieved via http over the Internet rather than from the mobile device



• Decision engine evaluates each possible mode of presenting content

• Mode characterized by quantized user preferences, device capabilities

• Search algorithm (various ones) finds a mode that meets user preferences and device capabilities

• Mode “scores” for each user and device precalculated


Distributed Services (1)

• Building applications using composable, distributed component services, rather than static application partitioning used for multi-tier computing.

• Service should not be explicitly named, but rather specified in an abstract manner (intent-based access not through explicit location/name, but characteristics)

• Specify an abstract service description language: a means to express the expected function of a service.

• Create a task-based model for application structure:

- Tasks in a PIM calendaring application could be user authentication, browsing the appointment, and entering a new appointment.



• System must be able to dynamically discover and compose the services that are available in the local vicinity.

• The system needs to support dynamic selection of an appropriate interface, based on the device’s resources and form-factor.

• The system needs to seamlessly integrate the applications and service found in the environment (e.g. a discovered map application should be able to use a discovered GPS service.)



• At load-time, a device need to negotiate application apportioning with a server (adaptation to the device resource available).

• Support handoff of task context from one environment(e.g. newspaper service in office) to another (e.g. car): adaptation to detect changes in environment and re-apportioning.

• Service deployment, dynamic upgrade, customization, and consumer choice.



• Mobile Agent technology. And active network allowing the flexible integration of applets and servlets.

• Persistent storage: an object store to 1) preserve the structure of application data, 2) provide associative access to this data, and 3) support atomic operations.


Service Framework [7 - 13] (1)

• Dynamic discovery of functionality based on context.

• Self-managing, as devices can join and leave as necessary.

• OSGi, Jini (Sun) , UPnP (Microsoft), Bluetooth SDP, and HAVi

- Local service database vs. ARP-style request (announce-listen model)

- Query model: Java object, XML, or URI

- A resource name vs. an object written in Java or Otcl


Discovery Protocols (1)

• “Spontaneous” discovery and configuration of network devices and services

• Selection of specific types of service

• Low (preferably no) human administrative requirements

• Automatically adaptation to mobile and sporadic availability

• Interoperability across manufactures and platforms


Jini

• Bound to Java RMI

• Multicast request/Multicast announcement/Unicast discovery

• Service matching by service type and attributes

• Lease enables robust system without manual intervention.

• Remote event enables the run time composition of services.


What Jini is not

• Jini is not a name server: lookup service is similar, but does more than provide references to objects

• Jini is not Java Beans: beans communication based on direct method invocation, not remote. Also, beans do not automatically become aware of each other as do Jini objects


Strong typing is important

• In Java, an RMI defines the interface, while in CORBA, an IDL description is a wrapper around the interface

• Polymorphism works in RMI -- you can define subinterfaces; you can pass an ojbect of a subtype to remote server and the subtype methods are appropriately used (doesn’t work in CORBA).


Discovery

• Services=Devices or Software• Services collect themselves into communities• The resources available to a community are kept

track of by a lookup service• No one-to-one mapping between communities and

lookup services• Discovery=finding available lookup services


Lookup

• Downloadable proxy provided with each service item

• When any entity wants to use your service it downloads the proxy and runs it -- the proxy handles sending the remote server the necessary pieces

• Proxy can be used as a secure, network-aware device driver


Lookup cont’d

• Lookup returns a service item when queried successfully.

• Service item contains proxy object (local stub for remote object) and attributes that describe the service


Lookup, cont’d

Lookup service

Service item

Proxy

attribute

attribute Service item


Proxy scenarios

• Proxy may perform the service by itself, without any remote method invocation

• Proxy may be an RMI stub that knows how to talk to a remote service (e.g. IMAP mail server)

• Proxy uses private communication protocol to talk to legacy (non-Java) systems.


Using a Jini Service

Lookup service

Downloads proxy

Service Client

Client communicateswith service viaproxy


Universal Plug and Play (UPnP)

• Microsoft-backed

• UPnP is multistage protocol

- Discovery/Description/Control/Eventing/Presentation

• Devices, Services, and Control Points

• Based on Web technologies: IP/HTTP/XML/GENA/SOAP

• SSDP(Simple Service Discovery Protocol)

- URI style query (similar to SLP) returns URL which points to an XML file with an elaborate description of the service.

• Similar functionality to Jini plus automatic IP configuration (AutoIP)

• www.upnp.org


SSDP

• ssdp:alive (like Jini registration with lookup svc)

• ssdp:discover (like Jini discovery)

• Can work with/without control points (lookup server) in contrast to Jini


UPnP Services

• Description is stored as XML file

• Control via SOAP messages: SOAP developed for web service

• Most every language/platform has SOAP/XML libraries

• Event notification with XML in General Event Notification Architecture

• Presentation URL can be supplied by device


Open Services Gateway Initiative (OSGi)

• Open, standards based, language/OS neutral

• Consists of framework in which bundles of services that register with a registry can run

• On top of J2RE


OSGi Service Specifications

• Three version 1 services

• Logging service• Web server• Device access

• Version two services added:

• Configuration svc• Preferences svc• User admin svc• Permission admin svc• Pkg admin svc


Framework

• Allows the downloading, execution, and removal of bundles

• M anages bundle installation and updates dynamically (scalably?)

• Consistent programming model for bundle developers

• Bundles can select an available implementation at runtime through the framework registry


Bundles

• JAR files

• May include other resources (html, help files, icons, etc)

• Contains manifest

• States dependencies on other resources

• Bundle activator class


Bundles, cont’d

• Framework itself is a bundle (system bundle)

• Management bundles implement policies (e.g. from what location is a bundle to be loaded)

• Each bundle has a classloader with it, providing bundle with own namespace, permitting sharing of packages between bundles


Time for the soapbox…

• Jini has seen little market acceptance -- no one wants to be tied to Java, worried Sun will drop it

• UPnP complies with “standards++”, but almost gets it right

• Why fool with all this -- you can write your own without much fuss?

• Because XML is the only way of doing RPC that anyone can agree on

• But wait and see what happens with OSGi…


Infrastructures (1)

• Environment populated by sensors, actuators, and appliances.

• People control and monitor their environments by taking advantage of freely-available computation throughout that environment.

• Environment provides mobile devices with computational power, because they are not limited neither by size nor by power source.

- For example, in order to improve speech recognition, use video imaging of lip movement, or take into account an image-based understanding of a person’s gaze, expression, and intent.


Infrastructures (2)

• Global computing infrastructure, which spans different organizations and smaller networks

- Autonomous administration.

• Self-managing, ad-hoc, proximity network of people (mobile devices) and things (environment).

- Bluetooth, HomeRF, USB, IEEE 1394

• Location discovery

- Location beacon embedded in the walls

- GPS for outdoors


Infrastructures (3)

• Intermittent connectivity due to power, cost, bandwidth, latency and congestion limitations.

• Bluetooth and HomeRF addresses small-proximity network, intermittent connection environment, but not complex issues such as hand-off and signal strength analysis.

• Vertical handoffs to provide seamless and power efficient connectivity across a wide range of areas

• Active network infrastructure


Infrastructures (4)

• Ubiquitous persistent storage

- Coda file system designed specifically for mobile clients

- The Bayou project using a distributed database approach

• Disconnection: automatic migration and disconnected operation

• Disconnection should be distinguished from failures.

• Adapting traditional checkpoint strategies.


MIT Oxygen Project [18] (1)

• Vision: In the future, computation will be freely available everywhere, like batteries and power sockets, or oxygen in the air we breathe.

• Goals: - pervasive: it must be everywhere, with every portal reaching into the same

information base.

- embedded: it must live in our world, sensing and affecting it.

- nomadic: its users and computations must be free to move around according to their needs.

- eternal: it must never shut down or reboot; components may come and go in response to demand, errors, and upgrades, but Oxygen as a whole must be non-stop and forever.


MIT Oxygen Project (2)

• Foundation technologies



• Knowledge access technologies offer improved access to information, customized to the need of people, applications, and software systems. They allow users to access their own knowledge bases, the knowledge bases of friends and associates, and those on the web.

• Automation technologies offer natural, easy-to-use, customizable, and adaptive mechanisms for automating and tuning repetitive information and control tasks. For example, they allow users to create scripts that control devices such as doors or heating systems according to their tastes.



• Collaboration technologies enable the formation of spontaneous collaborative regions that accommodate the needs of highly mobile people and computations. They also provide support for archiving speech/video fragments from meeting, and for linking these fragments to issues, summaries, keywords, and annotations.

• Speech and Vision technologies provides the main modes of interaction in Oxygen. Multimodal integration increases the effectiveness of these perceptual technologies, for example, by using vision to augment speech understanding by recognizing facial expressions, lip movement, and gaze.



• Software environment is build to support change(adaptable). Change is occasioned by anonymous devices customizing to users, by explicit user requests, by the needs of applications, by current operating conditions, by the availability of new software and upgrades, by failures, or by other causes.

• Networks, called N21s, connect dynamically changing configurations of self-identifying mobile and stationary devices to form collaborative regions. N21s support multiple communication protocols for low-power point-to-point, building-wide, and campus-wide communication.



• Intelligent Spaces are created by stationary devices, called E21s, embedded in offices, buildings, homes, and vehicles. E21s provide large amounts of embedded computation, as well as interface to camera and microphone arrays, large area displays, and other devices.

• Mobile(Handheld) Devices, called H21s, provide mobile points of interaction for users. H21s accept speech and visual input, and they can reconfigure themselves to support multiple communication protocols or to perform a wide variety of useful functions (e.g., to serve as cellular phones, beepers, radios, televisions, GPSs, cameras or PDAs). H21s can conserve power by offloading communication and computation onto nearby E21s.


HP CoolTown

• Tim Kindberg, John Barton, HP labs (Palo Alto) [19,20]

• Link the physical presence of people/places/things in the real world to the logical presence of those people/places/things on the web

• You can “click” on things in the world


Example applications

• Aim your mobile phone at a billboard and click on it to get info about the product (actually this is done with a BREW phone by KDDI in Korea, but the spirit is similar to Cooltown), also similar to U.Florida iGrocer

• Get information on paintings with your PDA as you explore an art museum (and pay to get a high quality reproduction printed on an HP color large-format printer at the gift shop :-)

• Elders, children/education, repair/maintenance, etc


HTTP is everywhere

• Use http/web servers/post strings to handle the system -- anything can run a web server

• Users are familiar with the idea of a browser (and HP sells PDA’s with browsers)

• Developers are familiar with developing web applications, so leverage that


Infrastructure

• Somehow must add at least “tags” to things in the world

• Examples: RFID, barcode, infrared

• The web server for a thing doesn’t have to be on the “thing”, but the URL does

• No configuration for users

• Somehow must be able to infer the users context


References

[1] Mark Weiser. The computer for the 21st century. Scientific American, 265(3):94--104, September 1991.

[2] Guruduth Banavar, James Beck, Eugene Gluzberg, Jonathan Munson, Jeremy Sussman, and Deborra Zukowski, "Challenges: An Application Model for Pervasive Computing," MobiCom ‘00, August 2000, pp. 266 - 274

[3] M. Esler, J. Hightower, T. Anderson, and G. Borriello, Next century challenges:data-centric networking for invisible computing. the portolano project at the university of washington, MobiCom ‘99, August 1999.

[4] Thomas Agoston, Tatsuro Ueda, and Yukari Nisimura, Pervasive computing in a networked world, In Proc. of INET 2000.

[5] Robert Grimm, Tom Anderson, Brian Bershad, and David Wetherall, A System Architecture for Pervasive Computing, In Proceedings of the 9th ACM SIGOPS European Workshop, pages 177-182, Kolding, Denmark, September 2000.

[6] Brent A. Miller, Bluetooth Applications in Pervasive Computing, http://www.ibm.com/pvc.

[7] Robert E. McGrath, Discovery and Its Discontents: Discovery Protocols for Ubiquitous Computing, UIUC 2K project, April 2000.

[8] Steven E. Czerwinski, Ben Y. Zhao, Todd D. Hodes, Anthony D. Joseph, and Randy H. Katz, An Architecture for a Secure Service Discovery Service, MobiCom '99, August, 1999, pages 24 - 35.

WIRELESS ENGINEERINGWIRELESS ENGINEERING[ 9] Erik Guttman, Service Location Protocol: Automatic Discovery of IP Network Services, IEEE

Internet Computing, vol. 3, no. 4, July/August 1999.

[10] E. Guttman and C. Perkins, Service location protocol version 2, IETF RFC 2608, June 1999.

[11] Service Location Protocol Home Page, http://www.srvloc.org.

[12] Universal Plug and Play Device Architecture, http://www.upnp.org/resources.htm

[13] Jini specificaations v 1.1, http://www.sun.com/jini/specs

[14] Dey, A.K. et al, The Conference Assistant: Combining context-awareness with wearable computing, Proceedings of the 3rd International Symposium on Wearable Computers (ISWC '99), 1999, pp. 21-28.

[15] Dey, A.K., Salber, D., & Abowd, G.D, A Context-based infrastructure for smart environments, In Proceedings of the International Workshop on Managing Interactions in Smart Environments (MANSE `99), pp. 114-128.

[16] S. D. Gribble and et al, The ninja architecture for robust internet-scale systems and services, Special Issue of IEEE Computer Networks on Pervasive Computing, 2000.

[17] S. D. Gribble, M. Welsh, E. A. Brewer, and D. Culler, The MultiSpace: an Evolutionary Platform for Infrastructure Services, In Proceedings of the Usenix Annual Technical Conference, June 1999.

[18] MIT Project Oxygen, http://oxygen.lcs.mit.edu


[19] Lum, Wai Yip, and Francis C.M. Lau, A Context-Aware Decision Engine for Content Adaptation, Pervasive Computing, IEEE Press, Vol. 1, No. 3, pp. 41-49.

[20] People, Places, Things: Web Presence for the Real World, Tim Kindberg, John Barton, Jeff Morgan, Gene Becker, Ilja Bedner, Debbie Caswell, Phillipe Debaty, Gita Gopal, Marcos Frid, Venky Krishnan, Howard Morris, Celine Pering, John Schettino, Bill Serra and M. Spasojevic. In proceedings WMCSA2000. To appear in MONET Vol. 7, No. 5 (October 2002).

[21] A Web-Based Nomadic Computing System.Tim Kindberg & John Barton. In Computer Networks, Elsevier, vol 35, no. 4, March 2001, pp. 443-456.

wireless engineering pervasive computing sumi helal richard chapman 3 october 2002

Documents

computing environment

actual computing devices

way slide

users information

devices capability

invisible computer

piece of software

anonymous devices