A presentation given at Joint Science Presentation 2010, Trinity College.

1. Sharing data using Distributed HashTables on MobileAd-hoc Networks
ProjectThor
PrasannaGautam ‘11
Advisor: Dr.Timothy Richards
Computer Science Department

2.  Number of Internet enabled mobile devices is
increasing
(Source: ITU, Mark Lipacis, Morgan Stanley Research)

3.  Mobile Ad-hoc Networks (MANET)
 Self configuring wireless network

4.  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)

5.  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

6.  Cons
 Power hungry
 Limited network access
 Churn
▪ Nodes coming in and out of network
 Difficult network management

7.  POSIT – search and catalog application
running on Android
 Started in 2008
 RWG Adhoc protocol implemented in
collaboration with Linköping University, Sweden
 RandomWalk Gossip
 Phones send messages randomly
 until a specified number of phones have received
it

8.  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

9.  Power Usage
 Churn
 Nodes coming in and out of the network/range

10.  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

11.  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

12.  Sending 1K file every 5 seconds
 Phone lasted for 13.5 hours
▪ 6998 messages = 6998 KB = 6.83 MB
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60
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100
120
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
level

13.  Sending 1K file every second
 Phone lasted for 8 hours
▪ 14696 messages = 14696 KB = 14.35MB
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40
60
80
100
120
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

14.  Talk less
 When you do talk, say more

15.  Nodes can come in an out of the network
 Could have multiple sub-networks
 Not necessarily defined structure/topology

16.  Distributed HashTables (DHTs)
 Distributed system provides lookup similar to
hash table
 Information is distributed and replicated among
nodes

17.  Used extensively by peer-to-peer applications
like Bittorrent

18.  A Churn and Mobility ResistantApproach 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

19.  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

20.  RWG
 constantly communicating/sending data
 Random routing
 Can’t handle incomplete downloads
 DHT
 Minimal communication
 Intelligent routing
 Even incomplete data is useful

21.  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