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Thesis Presentation
Supervisor: Prof. Jörg Ott
Student: Junxi Yin
Espoo, 11.21.2012
Topic
Mobile Implementation of Floating Content Service
Outline
• Introduction• Delay-tolerant Networking• Floating Content Service• Application Design and Implementation• Test and Evaluation• Conclusion and Future Work• References• Appendix
Background
Scenarios where traditional Internet is not working well
Flea market
Travelling
Rural areas
Supermarket
Developing countries
…
Background
Why DTN in mobile?
• Development of DTN technology• Growing mobile market (Cheaper devices)• Growing usage of mobile devices• Growing usage of location service• Open source sw and tools
Objective
• 1. Theoretical studies
• 2. Simulations
• 3. Implementation and test
DTNDTN=Delay-Tolerant Networking [1]
• Designed for extreme conditions • Protocol Data Unit - Bundle • Convergence Layer • Custody Transfer• Store-and-Forward
D
S
Store-and-Forward
Source Node
Custodian A Destination Node
Custodian B
Persistent Storage
Forward Forward Forward
Persistent Storage
Data is stored throughout the network and forwarded when a better chance comes in hopes that it will eventually reach its destination – Opportunistic Communication
Floating Content Service
A DTN-based localized information sharing service exclusively dependent on mobile phones and other mobile devices. [2]
As long as there are enough supportive mobile devices around in the anchor zone to replicate and store a piece of content, it floats.
ar
Node with a message
Node without a message
Replication Probability
r a
1
0
p
d
Replication Probability According to Distance from Message Center
Since replication is based purely on the location of nodes, in a simple case, every node in the anchor zone should have a copy of the item.
In practice, the replication works as follows.
SimulationsONE Simulator=Opportunistic Network Environment simulator
-Written in Java-Agent-based, discrete event, network simulator-Support Mobility Models-Several built-in DTN routing algorithms [3]
More Information:
http://www.netlab.tkk.fi/tutkimus/dtn/theone/
Location Error ConsiderationRadio range: 50, Nodes: 126, ttl=3600, r=500, a=500, size=minimal, buffer=5M
Mean of all anchor pointsMean of anchor points with n>100 messages
Weighted average
Fraction of messages available <= x
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Lifetime as fraction of TTL
1
0
Radio range: 50, Nodes: 126, ttl=3600, r=500, a=500, size=minimal, buffer=5M
Mean of all anchor pointsMean of anchor points with n>100 messages
Weighted average
Fraction of messages available <= x
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Lifetime as fraction of TTL
1
0
Performance of Floating Content Service without Location Error Performance of Floating Content Service with Location Error
Please refer to ”Floating Content: Information Sharing in Urban Areas” to get more details about the performance of Floating Content service
A Closer LookRadio range: 50, Nodes: 126, ttl=3600, r=500, a=500, size=minimal, buffer=5M
Mean of all anchor pointsMean of anchor points with n>100 messages
Weighted average
Fraction of messages available <= x
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Lifetime as fraction of TTL
-0.1
0.1
Compared floating performance as a function of lifetime
Conclusion:
The location error has very limited effect to the performance of Floating Content application
System Design
User Interface
Service Engine
create
save
created data repository
received data repository
saved data repository
Output
Input
get get
get
subscribe
System Implementation
Open source tools, no costs at all.
• Java• Android• Floating Content API• SQLite Database• XML
Action Flow
Subscribed?
Message received
No
Discard
Yes
Data stores in received data
repository
Message sent out
TTL expired?
Message created
Data stores in created data
repository
No
Yes
Delete
TTL expired?No
Yes
Delete
Data stores in saved data repository
Application starts
Service engine starts
Save
Screenshots
Test Results
Transfer Time (Second)
0 1 2 3 4 5 6 7 8 9 10
Size of Attachement File (MB)
4
0
1
2
3
9
5
6
7
8
12
10
11
Transfer Speed of Floating Content Service between Two Devices
The transmission speed using Floating Content service is similar with the actual Wi-Fi speed between only two devices.
Future Work
• Deploy a systematic testbed to better evaluate the performance of Floating Content service in a real world environment
• Better user interface design
References
[1] Forrest Warthman, “Delay-Tolerant Networks (DTNs), A Tutorial”, May 2003.
[2] J. Kangasharju, J. Ott, and O. Karkilahti, “Floating Content: Information Availability in Urban Environments,” in Proc. of IEEE Percom 2010, Work in Progress session, March 2010.
[3] A. Keränen, J. Ott, and T. Kärkkäinen, “The ONE Simulator for DTN Protocol Evaluation”, in SIMUTools ’09:Proceedings of the 2nd International Conference on Simulation Tools and Techniques, NewYork, NY, USA: ICST, 2009.
