Support for
Personal and Service Mobility in
Ubiquitous Computing Environments
K. El-Khatib, N.Hadibi and G. v. Bochmann
School of Information Technology and Engineering
(SITE)
University of Ottawa, Canada
Paper presented at EuroPar 2003 by Haiwei Ye
University of Montreal and UQAM, Canada
© Gregor v. Bochmann, 2003
EuroPar, Aug. 2003
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Overview
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
Introduction
Directory services
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Ubiquitous computing environments





User-device mapping (“directory service”)
The user’s home directory
Ubiquitous devices and personal access range
Personal agent
Quality of service negotiation
An example scenario
Conclusions
© Gregor v. Bochmann, 2003
EuroPar, Aug. 2003
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What is mobility ?

Device mobility: mobile, wireless
connection to the Network





Cellular phone system
Wireless Ethernet
Personal / desk-area network, e.g. Bluetooth
User mobility: user may use any device
anywhere in the world
Service (or session) mobility: an active
session may be transferred to a different
device
© Gregor v. Bochmann, 2003
EuroPar, Aug. 2003
3
Futuristic application scenario
Alice calls her grandmother
She uses her PDA-phone (device mobility) , sets
video transmission on (which is off by default)
Grandma: “Why don’t you use a better video quality” ?
Alice goes to her father’s home office and uses his
computer to continue the session (session mobility)
When Alice tells an interesting experience, Grandma polls
Grandpa’s PDA (he is working in the garden); Grandpa
joins the teleconference using his PDA
 His PDA requires lower voice and video resolution
(QoS negotiation); Alice and Grandma continue at
high quality


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User mobility: the same scenario when …


Alice is visiting a former classmate in another country
Grandma is on a tourist trip in Paris, uses hotel facilities
© Gregor v. Bochmann, 2003
EuroPar, Aug. 2003
4
Overview


Introduction
Directory services



Ubiquitous computing environments





User-device mapping (“directory service”)
The user’s home directory
Ubiquitous devices and personal access range
Personal agent
Quality of service negotiation
An example scenario
Conclusions
© Gregor v. Bochmann, 2003
EuroPar, Aug. 2003
5
User-device mapping

(“directory service”)
Question: Which device is best suited for an
incoming (or outgoing) call ?

There are several proposals, including SIP’s call
processing language (CPL), however:

User must register devices and policies for using them




therefore relatively static information
No device discovery
No session mobility
No multi-media service composition

e.g. video and voice on separate devices
© Gregor v. Bochmann, 2003
EuroPar, Aug. 2003
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The user’s home directory (HD)
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
One needs more than a “service directory”
We have proposed a “home directory”



Provides functions of “service directory”
Stores user’s QoS preferences
Possibly also stores information concerning


Authentication (e.g. public key certificate)
Authorization (e.g. subscribed information services)
© Gregor v. Bochmann, 2003
EuroPar, Aug. 2003
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User mobility and home directories:
an example
Bob’s home dir.
Alice
Alice’s home dir.
Bob’s
Home Domain
3
1
2
Internet
Alice’s
Home Domain
4
Bob
7
8
Bob’s
Visiting Domain
6
5
© Gregor v. Bochmann, 2003
EuroPar, Aug. 2003
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QoS management
We are mainly concerned with performance properties that influence
the quality of multimedia presentations:

End-user preferences and requirements: sound quality, video
quality, colour rendering, and also cost

Terminal constraints: limitations due to screen size and precision,
audio equipment, operating system’s real-time response, available
decoding software, etc.

Domain policies: e.g. restrictions on the use of video

Network constraints: available throughput, delay, jitter (mainly
access limitations)

And in case of stored documents:


Server constraints : number of users, overall throughput limitations,
access delay and jitter
Viewed document constraints: encoded information structure,
possibly scalable encodings (or several versions)
© Gregor v. Bochmann, 2003
EuroPar, Aug. 2003
9
Merging user and device profiles
User profile
User profile
Device profile
Device profile
Domain Policies
Domain Policies
Current profile
for Alice
Network constraints
© Gregor v. Bochmann, 2003
Current profile
for Bob
Current session profile
EuroPar, Aug. 2003
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Information in HD: example
QoS Preference Policies
Audio Preference:
Min Acceptable: Telephone Quality
Video Preference:
Min Acceptable FrameRate: 10
Minimum Acceptable Resolution: 320x240
Sensitivity Parameter 6
Weight factors by application:
Internet Telephony
AudioWeightFactor: 7
Video on Demand
AudioWeightFactor: 3
default:
AudioWeightFactor: 5
Price Ceiling: 0.2$/min
© Gregor v. Bochmann, 2003
Ideal: CD Quality
Ideal FrameRate: 30
Ideal Resolution: 800x600
VideoWeightFactor: 3
VideoWeightFactor: 7
VideoWeightFactor: 5
EuroPar, Aug. 2003
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Overview


Introduction
Directory services



Ubiquitous computing environments





User-device mapping (“directory service”)
The user’s home directory
Ubiquitous devices and personal access range
Personal agent
Quality of service negotiation
An example scenario
Conclusions
© Gregor v. Bochmann, 2003
EuroPar, Aug. 2003
12
“Personal” networking

Many buzzwords


PDA, wearable computers, PAN (personal area
networks, e.g. Bluetooth), personal agents
We propose a personal agent …



. . . is a kind of extension of the home directory,
possibly located in a PDA
has access to the information in the home directory
knows the devices that are close to the user


may be responsible for


This information is more up-to-date than what is in the home
directory
device selection, QoS negotiation, security aspects
may include a private key for authentication
© Gregor v. Bochmann, 2003
EuroPar, Aug. 2003
13
Device selection in the PAN
Alice
Bob’s HDA
2
1
7
Alice’s HDA
3
Internet
PA
(PDA)
6
7
© Gregor v. Bochmann, 2003
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4 4
5
4
Bob 5
4 5
5 4
5
4
EuroPar, Aug. 2003
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Functions of personal proxy



Discovers current available devices and
services in the vicinity of the user
Receives user profile from HD as soon as
activated
Merges the preferences of the user and
the capabilities of the discovered devices
to select the device(s) required for the
session (QoS negotiation)
© Gregor v. Bochmann, 2003
EuroPar, Aug. 2003
15
QoS management in a ubiquitous
computing environment
Personal Agent
Selecting
appropriate
services / devices
and QoS
for an interactive
application
User
Profile
Call Request
QoS
Selection
and
Negotiation
Agent
Selected Services
User
Activity
Monitor
Agent
Service
Discovery
Agent
Service
Registry
© Gregor v. Bochmann, 2003
EuroPar, Aug. 2003
16
Overview


Introduction
Directory services



Ubiquitous computing environments





User-device mapping (“directory service”)
The user’s home directory
Ubiquitous devices and personal access range
Personal agent
Quality of service negotiation
An example scenario
Conclusions
© Gregor v. Bochmann, 2003
EuroPar, Aug. 2003
17
An example scenario
Bob’s
Alice HD
Bob’s PDA
Bob's PA
environment
SDA
1: Profiles Req
Startup Phase
2: Profile Resp
3: SIP invite
comments
4: SIP invite
5: Service Request
6: Service Discovery Request Session Initiation
Phase
7: Service Discovery Reply
8: Update Local Service Directory
9: Service Reply
10: 200 OK
11: 200 OK
Data Exchange
Data Exchange
Phase
12: Service Discovery Request
13: Service Discovery Reply
14: Update Local Service Directory
Data Exchange
15: Service Update
16: Service Address Change
Data Exchange
© Gregor v. Bochmann, 2003
Session
Maintenace
Phase
Data Exchange
Phase
Service Hand-off
Phase
Data Exchange
Phase
EuroPar, Aug. 2003
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Issues with the Personal Proxy

Authentication
How can I be identified to the surrounding
devices (which may want to charge for their
services) ?

Authorization
Can people reach me through my supervisor’s
office phone when I am in his office ?

Geographical location and accessibility
Will the phone ring in the adjacent locked room
when I am near that room ?
© Gregor v. Bochmann, 2003
EuroPar, Aug. 2003
19
Conclusions

Main contributions:



Architecture for supporting personal mobility in
ubiquitous computing environments
The Personal Agent (PA) is a mobile agent including
the functionality of the previously proposed “home
directory”
Difficult issue: limiting the accessible range of
devices and services




Limited communication range (e.g. Bluetooth)
Pointing (e.g. through infra-red communication)
Including a floor plan to check accessibility of device
Defining policies for the authorized use of devices and
services
© Gregor v. Bochmann, 2003
EuroPar, Aug. 2003
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