Mobile P2P - SmartLab

mashpeemoveMobile - Wireless

Nov 24, 2013 (3 years and 11 months ago)

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1

Towards Pervasive
Connectivity in Mobile
Computing

Frank Siegemund

European Microsoft Innovation Center

November 2006

2

Outline


Motivation


Related Work


System Architecture


Implementation


Application


Conclusions

3

Motivation


Most middleware assumes
basic connectivity


Web Services


Jini


Corba


Problematic in mobile scenarios


Mobile P2P systems


Mobile CSCW


Heterogeneity


Bluetooth, WLAN, IrDA, GPRS


IPv4 vs. IPv6


NATs and firewalls

4

Mobile P2P


Bootstrapping problem


Establish connectivity
between mobile users


Mobile devices as first
-
class citizens in P2P
applications


Exploit knowledge
about connectivity in the
group


More reliable/robust
group establishment


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Scenario


Content sharing
between mobile users


Conference scenario


Skiing trip


Existing group collects
connectivity parameters


Sharing by means of
visual tags/glyphs


Handheld
-
embedded
cameras for capturing
tags



6

Outline


Motivation


Related Work


System Architecture


Implementation


Application


Conclusions

7

Related Work


Capturing visual tags with handheld
devices and low
-
cost cameras


Rekimoto et al.


Visual tags in Pervasive Computing


Rohs and Zweifel


Many interesting scenarios


Visual tags to bypass Bluetooth device
discovery


Scott et al.


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Related Approaches


Out
-
of
-
band discovery for Bluetooth


IrDA


RFID


Collaborative approaches for device discovery


Siegemund and Rohs


Manual configuration


Send SMS with information about group


Complicated from user perspective


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Outline


Motivation


Related Work


System Architecture


Implementation


Application


Conclusions

10

System Architecture

11

Collecting Connectivity Data


Overlay between group members


Exploit heterogeneity


Various communication technologies in group


Different security constraints


Construct group connectivity profile


Create tags to transmit connectivity profile


Candidate group member captures tags


Simplified user interaction



12

Group Overlay


Overlay can contain both mobile and stationary
nodes


Overlay provides multicast group


Nodes in group have synchronized state


Connectivity properties of nodes shared between
group members


NATs can be dealt with via different group peers


Direct connections not always possible


Group used to circumvent connectivity
constraints

13

Visual Tags


Tags captured from
video stream


Captured by handheld
-
embedded digital
cameras


Direct user feedback
about detected tags
possible


Small video resolution
requires displaying
multiple tags


Concrete tag layout
unimportant

14

Outline


Motivation


Related Work


System Architecture


Implementation


Application


Conclusions

15

Implemenation


Heterogeneous environment


Windows Mobile 5.0 smartphones


Window XP/Vista desktops


Implementation on desktops using
Windows P2P Infrastructure


Mobile devices join/create P2P overlay


Socket interface


Lightweight database for data synchronization


Native implementation



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Visual Tags


Tag detection in
DirectShow


Analyze single video
frames


Basic algorithm


Black and white
conversion


Region detection


Identify guide bars


Decode tags


Determine tag index


Finish if all tags have
been decoded


Join group



Similar to
Rekimoto
et al.

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Improvements


Determine threshhold for black/white conversion
in feedback loop


Different lightning conditions


Mark tag in video frame to provide feedback to
users


Tag detected or not


Synchronization


Tag contains time a single tag is displayed


Capturing device can calculate schedule for reading
tags




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Evaluation


240 x 320 video frame resolution


Implementation on 195 Mhz smartphone


State of the art (no high
-
end model)


400 ms per frame


Can be improved significantly !!!


Copy filter


90 ms for thresholding


250 ms for region detection


Algorithm deals with small rotations of the tag


More sophisticated tag detection systems
available

19

Outline


Motivation


Related Work


System Architecture


Implementation


Application


Conclusions

20

Example Application


Mobile P2P chat
application


Messaging for user
groups on mobile
devices


Overlay to distribute
connectivity parameters


Tags to exchange
connectivity profiles


Deal with NATs and
connectivity constraints



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Outline


Motivation


Related Work


System Architecture


Implementation


Application


Conclusions

22

Conclusions


Basic connectivity problematic in mobile scenarios


Current middleware solutions insufficiently address
this problem


Facilitate groups to establish connectivity in mobile
scenarios


Groups create finger print of network environment


NATs and security constraints can be dealt with


Visual tags user friendly way to communicate
connection properties


Useful for mobile P2P and CSCW scenarios


Real
-
life applications

23

Contact

Frank Siegemund

European Microsoft Innovation Center

Ritterstrasse 23, 52072 Aachen

franksie@microsoft.com