The Case for a Multi-hop Wireless Local Area Network
(with Seungjoon Lee, Bobby Bhattacharjee)
IEEE Infocom, Hong Kong, March 2004.
My thesis work defines NICE, which is a cooperative framework for
scalably implementing distributed applications over the Internet.
Applications in NICE are cooperative: they devote a
part of their own resources to be
used by any member of a cooperative group. We have designed a
set of protocols and mechanisms
that address different aspects of implementing such cooperative
applications. The NICE protocols, in some cases achieve
orders of magnitude performance
improvements because of the cooperative nature of the protocols.
The mechanisms in NICE do not depend on any special network support.
Using the NICE framework, we have defined efficient and scalable
Secure Group Communication,
Application Layer Multicast and
The NICE application-layer multicast protocol has been implemented
and tested on the Inteernet with groups of size upto 100. We are
currently implementing a video streaming service using the Apple
media streaming server.
We are also currently implementing the other components of
As part of our ongoing work we are working on
incentive-based cooperation policies, on mechanisms to scalably
check and enforce partnerships and on protocols to ensure
privacy and integrity.
Scalable Secure Group Communication over IP Multicast
(with Bobby Bhattacharjee)
International Conference on Network Protocols (ICNP) 2001,
Riverside, California, November 2001.
Extended version appears in JSAC Special Issue on Networked Group
Communication, Volume 20, Number 8, October 2002.
Scalable Application Layer Multicast
(with Bobby Bhattacharjee, Christopher Kommareddy)
ACM Sigcomm 2002, Pittsburgh, Pennsylvania, 2002.
Extended version submitted to Transactions on Networking.
Scalable Peer Finding on the Internet
(with Bobby Bhattacharjee, Christopher Kommareddy)
To appear in Global Internet, Globecom 2002, Taipei, Taiwan, 2002.
Extended version to appear in Computer Networks Journal.
Resilient Multicast using Overlays
(with Seungjoon Lee, Bobby Bhattacharjee, Aravind Srinivasan)
ACM Sigmetrics, San Diego, June 2003.
- myns P2P simulator
Rover enables location, time and context-aware applications for
wireless devices that scale to very large user populations.
Users intereract with the Rover system through client devices
(Rover-clients) that typically are small handheld units with
a wireless communication interface.
Rover-clients can have great heterogeneity in capabilities
in terms of processing, memory and storage, graphics and
display and network interfaces.
The Rover server interacts with the clients to provide and manage
the different service requests from the Rover-clients.
To scale the Rover server operations to a very large client
set, we have defined a new Action model which allows
fine-grained, real-time scheduling of server operations.
Apart from system design, I have also been involved in project with
a team of other students in implementing different aspects
of the system.
We have implemented and demonstrated
both outdoors and indoors version of Rover. In
the outdoor case, we used a GPS unit
attached the the clients to provide location service. It had
an accuracy of less than
3 metres. For the indoor
case, we have experimented with schemes based on
signal-strength measurements from different access points. Using
even simple techniques we obtained location within an accuracy of
The accuracy can be further improved by using more
sophisticated models which we have been working on.
Battery power is a scarce resource in wireless devices,
and therefore, needs to be conserved. In this project,
we have defined energy efficient routing techniques for
multi-hop wireless networks. Existing protocols for
minimum energy routing chooses end-to-end paths depending
on the battery capacity and transmission costs of the
nodes on the path. However, they ignore the error
characteristics of the links on the path. For reliable
data delivery, data packets corrupted will be re-transmitted.
Therefore, for energy efficient routing for reliable data
transfer it is important to also consider the link
error rates in choosing end-to-end paths.
Under both, the presence or absence of link layer re-transmissions
we have defined schemes
that choose more energy efficient paths
than currently known schemes. We also showed that this technique
is optimal for the case when link layer re-transmissions are
As traffic flows through the multi-hop wireless networks,
the battery of the nodes gets drained and at some point,
the network finally gets partitioned.
The useful lifetime of a wireless network is the duration of
time till it gets partitioned.
Using our technique of choosing energy efficient paths we
have defined routing protocols that
improves the lifetime of the wireless networks over
the currently best known schemes. Implementation of our
scheme requires minimal extensions to existing routing
schemes for wireless ad-hoc networks.
We are currently working on different extensions to
our work ----
choosing energy efficient paths when it is possible to
dynamically select transmission power levels to alter
link error rates, implementing the mechanisms in a real
world multi-hop wireless network.
Power Adaptation based Optimization for Energy
Efficient Reliable Wireless Paths
(With Archan Misra)
Networking 2004, Athens, Greece, May 2004.
Energy-Efficient Broadcast and Multicast Trees for Reliable Wireless Communication
(With Archan Misra, Jihwang Yeo, Ashok Agrawala))
To appear in IEEE Wireless Communications and Networking Conference (WCNC),
New Orleans, Louisiana , March 2003.
MRPC: Maximizing Network Lifetime for Reliable Routing in Wireless Environments
(With Archan Misra)
IEEE Wireless Communications and Networking Conference (WCNC),
Orlando, Florida, March 2002.
Minimum Energy Paths for Reliable Communication
in Wireless Networks
(With Archan Misra)
ACM Mobihoc, Lausanne, Switzerland, June 2002.
Extended version to appear in Journal of Wireless Networks (WINET).
I define "Secure Space" as an enclosed area within which
wireless devices can participate in secure group communication.
A device is able to join a secure space group by the
virtue of its location within the enclosure. The devices
communicate with each other using IEEE 802.11 wireless
LAN or other similar wireless access technologies. There are
two important aspects of this problem --- (a) determining
and authenticating the location of a wireless device at
the granularity of a secure space, and (b) defining scalable
mechanisms to (re)-distribute a common group key among the
device inside the secure space, as new devices enter and
existing devices leave the space.
I solve the location determination and authentication
problem using signal strength based techniques. Results
from actual wireless experiments show the feasibility
of this scheme. I leverage scalable solutions
for secure group communication in other environments to
propose a hybrid scheme for the key redistribution
Hierarchies are useful techniques to scale applications. In this
project, we defined a clustering-based scheme to create such
hierarchies in the context of multi-hop wireless networks.
By leveraging some specific properties of the wireless medium,
the protocols guarantee a set of desirable properties in the
hierarchy. We also observed that all these properties cannot
be simultaneous met for general environments.
We have demonstrated the scalability achieved using
our hierarchy construction scheme, through
both analysis and simulations.
As part of future work, we are using this hierarchical
control structure to scale different applications in multi-hop
wireless networks. Example applications that can
be scaled using this hierarchy include
service location and discovery, location management
This work defined protocols and mechanisms to self-organize a set
of small wireless sensor devices, that are deployed for collaborative
The sensor devices are equipped with wireless devices for
UHF communication at low bandwidths and GPS interfaces to
identify their position. Additionally, a few of the devices
have very low bandwidth satellite interfaces over which
the gathered data is sent back to remote command centers.
As part of this project, we defined and implemented a suite
of protocols for end-to-end operations, which allowed
remotely located users to interact with the sensors. The
API exported by the sensor networks permitted users
to dynamically update operational parameters, set special
triggers and alerts for specific sensor attributes and
various location-dependent functionalities.
We also implemented a simulation tool
that highlights various features of the self-organizing
protocol for the sensor devices.
The goal of this project has primarily been understand the
dynamic characteristics of a network, and to look at how
current practices, as well as new techniques, are applicable
to the design and operation of computer networks.
In this project, I developed a
new technique to
estimate the available and the bottleneck
bandwidth for a network connection. We conducted experiments
on the Internet to validate the technique.
As a separate part of this project, I did some benchmarking of
NetBSD TCP/IP stack processing overheads. The processing time
measures the packet processing delays incurred by packets
as they move from application space to Ethernet level
frame processing in the kernel, and vice versa.
This work was done as an intern at HP Labs (summer 1997)
where we implemented
Intelligent I/O (I2O)
architecture on a (web) server machine.
We split the TCP/IP functionality
between the main processor and a specialized I/O card
for faster response to client file requests.
As part of this implementation on the main processor
side, I implemented a fast path with zero data copies
for the Windows NT kernel.
|Last updated on Nov 2002