Download Interactive Systems Technical Design

Interactive Systems Technical Design
Lecture #2
Wireless ad hoc networking for
mobile peer-to-peer communications
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Wireless Ad Hoc Networking
• Webster: ad hoc ~
• “formed or used for specific or immediate problems or
needs“
• ”fashioned from whatever is immediately available”
• No fixed/static network infrastructure
• Nodes provide network functionality
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Variability of the Mobile Environment
Mobility
stationary
• nomadic (pedestrian speed)
• mobile (vehicular speed)
• roaming (mobile across networks)
•
Connectivity
Mobile device capability
form factor
• GUI
• multimedia
• real-time multimedia
•
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connected
• semi-connected
(asymmetric)
• weakly connected
• disconnected
•
Source: Helal
Case Studies
Hocman – Fast Motor Bikers and Ad Hoc Networking
Mobility Studio, Interactive Institute, Sweden
Hummingbird – Inter-Personal Awareness Device
Play Studio, Interactive Institute, Sweden
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The Hocman Prototype
Fast Motor Bikers and Ad Hoc Networking
Mattias Esbjörnsson
Oskar Juhlin
Mattias Östergren
INTERACTIVE INSTITUTE
Best Paper Award
1st Int. Conf. Mobile and Ubiquitous Multimedia (MUM 2002)
Oulu, Finland, Dec 2002
http://www.mum2002.oulu.fi
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BikeTalk Project
• Ethnographic fieldwork
 Design requirements
• The Hocman prototype
• Architectural design
• Implementation
• Evaluation
• Performance evaluation
• User evaluation
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Ethnographic Fieldwork
• User-centered and contextual design
• Identification of motor biker’s activities
•
•
•
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Leisure
Social
Visual
Interaction occurs
• Opportunistic encounters
• Because it is organized
• Co-movement
• Place-centered movement
 Design requirements
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Motor Bikers’ Activities Illustrated
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Design Requirements
• Added value: augment rather than rationalize
• Social interaction: sustain encounters
• Identification: better means to get to know others
• Heterogeneous user groups: biker culture is diverse
• Invitation for joint rides: selecting participants from
previous encounters
• Simultaneous activities: user attention varies
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Architectural Design Principles
• Handheld mobile device
• Mobile context of use
• Wireless ad hoc networking
• No network infrastructure available!
• Peer-to-peer communications
• Data sharing between peers
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Network Design
• Wireless ad hoc networking
• No network infrastructure available!
 IEEE 802.11b IBSS
• ”IP over single-hop ad hoc networking”
• Requires no infrastructure
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IEEE 802.11 Topologies
Distribution System
IBSS
Independent Basic Service Set
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Infrastructure Basic Service Set
Extended Service Set
Wireless ad hoc networking with IEEE 802.11b IBSS
Each biker is a 802.11b node
IBSS
Independent Basic Service Set
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Peer-to-peer communications
• Motivation: data sharing between peers
• Requires
• Rapid mutual peer discovery
• Data transfer between peers
• Support for two modes of user attention
• Cruise: automatic download and logging while driving
• Browse: manual HTML browsing
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Rapid Mutual Peer Discovery
• Each node keeps a list of known peers
• When timer for entry expires, remove it from list
• Each node broadcasts a hello message at regular
interval
• When node A receives hello message from node B
• If present(B): reset B’s timer
• Else: append B and send reply(A,B) message
• When C receives a reply(A,B) message
• If not present(A) and (present(B) or B=C): append A
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Rapid Mutual Peer Discovery Illustrated
1. A sends hello(A)
2. B sends reply(A, B)
3. C sends reply(A, C)
B
A
1. A, B, C | A
C
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2. A, B, C | A, B
3. A, B, C | A, B, C
Data Transfer Between Peers
”Limited” HTTP 1.0
Data
• HTML pages
• Embedded resources, e.g images
Retrieval method #1: Get
1. check local cache
2. HTTP GET w/ Keep-Alive
Retrieval method #2: Reload
• HTTP GET w/ If-Modified-Since
and Keep-Alive
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Hocman architecture
Operation sequence in cruise mode
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Hocman UI (Browse Mode)
reload
cruise mode
empty log
Browser
Peers
Log
• local pages
• current peers
• event log
• remote pages
• reachable peers
• encounters
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Implementation
• Mobile devices
• Compaq iPAQ 3660 + Orinoco WLAN card
• Sympol PPT 2700 + built-in Spectrum24 WLAN
• WLAN: IEEE 802.11b IBSS
• Mobile platform
• Pocket PC
• Programming environment
• C/C++
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Hocman in Use
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Performance Evaluation
C
Peer
v
Index page size
[bytes]
A
B
Data sharing
Data sharing
C
C
# embedded
resources
A
1 310
B
921
1 (image)
8 597
C
1 241
1 (image)
7 138
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2 (image, audio)
Resource size
[bytes]
67 914
Performance Evaluation (cont.)
• Peer C drives by at three different speeds v
(50 km/h, 70 km/h and 90 km/h)
• Five repetitions for each speed
• Log and cache is cleared for each repetition
• Data sharing
• Peer C downloads data from peers A and CB
• Peers A and B download data from peer C
• Performance criteria: number of failed downloads
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Performance Evaluation (cont.)
Number of failures of the 5 repetitions
Peer
Download from
A
Data
Peer C’s speed
50
70
90
page
image
audio
.
.
.
.
.
.
.
3
4
page
image
.
2
.
.
.
2
C
B
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Performance Evaluation (cont.)
Number of failures of the 5 repetitions
Peer
Download from
Data
Peer C’s speed
50
70
90
A
C
page
image
.
.
.
.
.
1
B
C
page
image
.
.
.
.
.
.
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Performance Evaluation (cont.)
Cumulative percentage of failures of all downloads
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Data
Peer C’s speed
50 70 90
page
image
audio
.
10
.
.
.
.
.
30
80
User Evaluation
• Specific route
• Hocman in cruise mode
• Two groups of three bikers
• Monitoring of actions after the ride
• Interviews
• Results not yet available …
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Conclusion : Hocman Meets Requirements
• Added value: awareness of encounters, information sharing
• Social interaction: logs encounters, images, audio clips
• Identification: icons, downloaded pages
• Heterogeneous user groups: HTML is flexible
• Invitation for joint rides: phone numbers, URL’s, e-mail address
• Simultaneous activities: automatic background downloads, HTML
browser
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More Information
• http://www.tii.se/mobility/Biketalk/index.htm
• Publicly available
• Source code
• Binaries for ARM and MIPS
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Hummingbird
Inter-Personal Awareness Device
Lars-Erik Holmquist
Jennica Falk
Joakim Wigström
INTERACTIVE INSTITUTE
Journal of Personal Technologies, 1999
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http://www.playresearch.com/
IPAD (Inter-Personal Awareness Device)
• Contact facilitator, not mediator
• Helps to initiate a contact, but not necessarily maintain it
• Identified properties
• Inter: IPAD utilizes relationship between itself and other
IPAD’s
• Personal: IPAD is personal, carried all times
• Awareness: IPAD conveys awareness of others
• Device: IPAD is a self-sufficient device, not reliant on
any infrastructure (e.g. network) except that provided by
other IPAD’s
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Simple Principles of Functionality
• A Hummingbird does not do anything on its own
• If two or more Hummingbirds belonging to the
users in the same group are ”close” (<100 m)
they will produce a sound – they ”hum”
• Additionally, Hummingbird’s display provides the
identity of the other users in the vicinity
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Building Blocks
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•
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Microcontroller
LCD screen (2 x 8 characters)
Miniature speaker
Radio transceiver (433,92 MHz)
Rechargeable batteries (10-15 h per charge)
Two switches (hum on/off, power on/off)
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Continous Operation of A Hummingbird
• Transmitting of own identification code
• Listening for the codes of other Hummingbirds
possibly in the vicinity
• Displaying of the codes of Hummingbirds found in
the vicinity
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User Experience and Evaluation #1
Familiar setting: home, office, school, …
Key findings from a small evaluation in office setting
• Hummingbird placed in the background of user’s attention
• Awareness information provided by Hummingbird was useful but
not ”crucial”
• Possibly increased the informal interaction between users
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In familiar setting Hummingbird was mostly
in the background of the user’s attention
User Experience and Evaluation #2
Unfamiliar setting: rock festival, conference, …
Key findings from small evaluations in Roskilde rock festival
and SIGGRAPH conference
• Hummingbird promoted feeling of ”connection”
• Frustration when user could not make visual connection in addition to
Hummingbird’s connection
• Users wanted more precise information on distance and location
• Sensation of not being alone in a crowd
• Natural complement to other daily activities
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Future IPAD’s ?
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Similar Devices and Applications
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Lovegety
GroupWear
Meme Tags
Proem
Cybiko Extreme
…
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