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transcript
ISTD 2003
Interactive Systems Technical Design
Lecture #2
Wireless ad hoc networking formobile peer-to-peer communications
ISTD 2003
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
ISTD 2003
Variability of the Mobile Environment
Connectivity• connected• semi-connected (asymmetric)• weakly connected• disconnected
Mobile device capability• form factor• GUI• multimedia• real-time multimedia
Mobility• stationary• nomadic (pedestrian speed)• mobile (vehicular speed)• roaming (mobile across networks)
Source: Helal
ISTD 2003
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
ISTD 2003
The Hocman Prototype
Fast Motor Bikers and Ad Hoc Networking
Mattias EsbjörnssonOskar Juhlin
Mattias Östergren
INTERACTIVE INSTITUTE
Best Paper Award1st Int. Conf. Mobile and Ubiquitous Multimedia (MUM
2002)Oulu, Finland, Dec 2002
http://www.mum2002.oulu.fi
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BikeTalk Project
• Ethnographic fieldworkDesign requirements
• The Hocman prototype• Architectural design• Implementation
• Evaluation• Performance evaluation• User evaluation
ISTD 2003
Ethnographic Fieldwork
• User-centered and contextual design• Identification of motor biker’s activities
• Leisure• Social• Visual• Interaction occurs
• Opportunistic encounters• Because it is organized
• Co-movement• Place-centered movement
Design requirements
ISTD 2003
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
IBSSIndependent Basic Service Set Infrastructure Basic Service Set
Extended Service Set
Distribution System
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Wireless ad hoc networking with IEEE 802.11b IBSS
IBSSIndependent Basic Service Set
Each biker is a 802.11b node
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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
ISTD 2003
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
ISTD 2003
Rapid Mutual Peer Discovery Illustrated
AB
C
1. A sends hello(A)
1. A, B, C | A
2. B sends reply(A, B)
2. A, B, C | A, B
3. C sends reply(A, C)
3. A, B, C | A, B, C
ISTD 2003
Data Transfer Between Peers
”Limited” HTTP 1.0Data• HTML pages• Embedded resources, e.g images
Retrieval method #1: Get1. check local cache2. HTTP GET w/ Keep-Alive
Retrieval method #2: Reload• HTTP GET w/ If-Modified-Since and Keep-Alive
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Hocman UI (Browse Mode)
Browser
• local pages
• remote pages
Peers
• current peers
• reachable peers
Log
• event log
• encounters
empty logcruise modereload
ISTD 2003
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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Performance Evaluation
vC
Peer Index page size # embeddedResource size
[bytes] resources [bytes]
A 1 310 2 (image, audio) 67 914
B 921 1 (image) 8 597
C 1 241 1 (image) 7 138
A B
C
Data sharing
C
Data sharing
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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 Data Peer C’s speed50 70 90
page . . .A image . . 3audio . . 4
CB page . . .image 2 . 2
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Performance Evaluation (cont.)
Number of failures of the 5 repetitions
Peer Download from Data Peer C’s speed50 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
Peer C’s speedData 50 70 90page . . .
image 10 . 30audio . . 80
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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 HolmquistJennica Falk
Joakim Wigström
INTERACTIVE INSTITUTE
Journal of Personal Technologies, 1999
http://www.playresearch.com/
ISTD 2003
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
ISTD 2003
Building Blocks
• 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
In familiar setting Hummingbird was mostly in the background of the user’s attention
ISTD 2003
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