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)

Mobile Ad-hoc Networks (MANET)

Self configuring wireless network

Great interest in research and defense industry

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1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

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

Power Usage Churn

Nodes coming in and out of the network/range

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

level

Sending 1K file every 5 seconds

Phone lasted for 13.5 hours

▪ 6998 messages = 6998 KB = 6.83 MB

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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 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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0:00:00 1:12:00 2:24:00 3:36:00 4:48:00 6:00:00 7:12:00 8:24:00 9:36:00

battery performance when sending 1K of data every second

level

Talk less When you do talk, say more

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

Used extensively by peer-to-peer applications like Bittorrent

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