Download - Project thor
Sharing data using Distributed Hash Tables on Mobile Ad-hoc Networks
Project Thor
Prasanna Gautam ‘11
Advisor: Dr. Timothy Richards Computer Science Department
Number of Internet enabled mobile devices is increasing
(Source: ITU, Mark Lipacis, Morgan Stanley Research)
Great interest in research and defense industry
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Research Papers trend (1995-2009)
Adhoc Network MANET "Adhoc Network" and MANET
(Source: mendeley.com)
Pros Can be used in ▪ Disaster Scenarios
▪ When Infrastructure is unavailable
▪ Deploying infrastructure is too expensive
Existing implementations in major OSes (802.11 ad hoc mode) ▪ Heterogeneous setup possible
Quick setup
Cheap to deploy
Cons
Power hungry
Limited network access
Churn
▪ Nodes coming in and out of network
Difficult network management
POSIT – search and catalog application running on Android
Started in 2008
RWG Adhoc protocol implemented in collaboration with Linköping University, Sweden
Random Walk Gossip
Phones send messages randomly
until a specified number of phones have received it
POSIT is deployed in a location without network access
RWG is used After a few hours, they start draining out Some phones will never see some data
Without using network (ADP1)
Phone lasted for ~132 hours = 5.5 days
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0:00:00 24:00:00 48:00:00 72:00:00 96:00:00 120:00:00 144:00:00
Battery Level (no network usage) on HTC ADP1
Battery
Sending ~50 bytes every second
Phone lasted for 12.8 hours
▪ 14999 messages = 14999*50 bytes = 732.37 KB
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0:00:00 2:24:00 4:48:00 7:12:00 9:36:00 12:00:00 14:24:00
battery performance when sending 50 bytes per second
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Sending 1K file every 5 seconds
Phone lasted for 13.5 hours
▪ 6998 messages = 6998 KB = 6.83 MB
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battery performance when sending 1K of data every 5 seconds
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Sending 1K file every second
Phone lasted for 8 hours
▪ 14696 messages = 14696 KB = 14.35MB
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battery performance when sending 1K of data every second
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Nodes can come in an out of the network Could have multiple sub-networks Not necessarily defined structure/topology
Distributed Hash Tables (DHTs)
Distributed system provides lookup similar to hash table
Information is distributed and replicated among nodes
A Churn and Mobility Resistant Approach for DHTs (Landsiedel et. al.) r being the communication range
Data can be stored within r/2 distance to be reachable by a node n
Study algorithms based on DHT on Mobile Ad-hoc Networks
Design and implement a specialized DHT simulator program
Test various conditions
▪ Power usage
▪ Topologies
▪ Effects of churning
▪ Network Partition
RWG
constantly communicating/sending data
Random routing
Can’t handle incomplete downloads
DHT
Minimal communication
Intelligent routing
Even incomplete data is useful
DHTs have shown to
Deal with churn effectively
Reduce overall communication
Using DHTs for communication on Adhoc Networks should
Improve power usage
Handle churn better