Research
Current Projects
- Scalability of Blockchains
- Security of UAVs
Completed Projects
- TVWS trials -- jointly with IIT Hyderabad (funded by DeitY)
- Structured sharing of resources in a Device-to-Device (D2D) Network (funded by Intel USA)
- SPARC: Spectrum-Aware rural connectivity - Use of sub-GHz bands for rural communication in India using Cognitive Radio (funded by DeitY, GoI)
- 4G-LTE pico cell performance evaluation (funded by Cisco Pvt. Ltd.)
- Measuring performance of 2G/3G networks (funded by Ford Foundation and DST, GoI)
- Next Generation WiFi and Internet of Things (IoT) (funded by Cambridge Silicon Radio India Pvt. Ltd.)
- Middleware for Disaster Management (Indo-UK project funded by DST)
- WiMAX Mesh
- Personal Navigation System
- Robust data collection in sensor networks
- OLPC WiFi mesh networks
- Scalable Ad Hoc Networks
- Network Probing
- Traffic Modeling and Analysis
- Multiscale Sampling Theory
- Multiscale Queuing Theory
- Long-Term Document Security
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Design and Development of a Rapidly Deployable WiMAX Mesh Network (funded by Ministry of Communications and IT, GoI)
The objective of this project is to design, build, and test a wireless mesh network that provides high performance in terms of throughput and latency to enable triple-play applications. The proposed network shoould be rapidly deployable, provides increased coverage and performance, allows nomadic mobility of mesh nodes, has lower infrastructure and operational costs, and is robust to node failure. It is our belief that such a network is best deployed as a time-division multiple access (TDMA) wireless mesh based on WiMAX offering the required range and traffic prioritization. Such a network would find application in military, public safety, and in emergency situations requiring fast network deployment.
Paper:
WISARD, 2010
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Indoor Global Positioning System (funded by Marvell India Pvt. Ltd.)
The goal of this project is to build a self-contained indoor navigation system that can accurately locate the position of a user within buildings. Applications for tracking vehicular and individual movement are typically based on the Global Positioning System (GPS). GPS makes use of satellite signals for positioning and does not perform well indoors because these signals get significantly attenuated. Hence the need for a novel solution.Our navigation system will consist of several sensors that measure various physical properties such as acceleration, orientation, height etc., which together provide an estimate of the change in position of the device in three dimensions over time. This change in position when combined with the last known accurate GPS-based position of the object then gives an estimate of current position.
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Scalable Mobile Ad Hoc Networks
A Mobile Ad Hoc Network is a self-configuring network of mobile nodes
connected by wireless links. Ad Hoc networks require little
infrastructure which makes them the choice solution for communication
during disaster relief efforts, in underdeveloped parts of the world
with little infrastructure, and on battlefields. Several of the
proposed routing protocols for ad hoc networks perform well only with
small networks of a few hundred nodes. The SAFARI project at Rice University
aims to design a suite of ad hoc networking protocols that enable
large networks that consist of tens of thousands of nodes.
Paper:
WiOpt, 2006
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Optimal Sampling Strategies for Multiscale Processes
We design strategies to optimally sample multiscale stochastic
processes in order to estimate their global average optimally.
This has implications for Internet measurement, sensor
network design, environmental monitoring, etc.
A multiscale process consists of a set of univariate
random variables that are organized like the nodes of a tree. Nodes
at the bottom are called leaves and the topmost node is the
root. We associate each node with the average of a physical
process over some region with nodes at higher scales corresponding to
larger regions. The root thus represents the global average of the
process and the leaves represent local samples.
The question we address is: Among all possible sets of leaves of
size n, which set gives the best linear estimate of the root in
terms of minimum mean squared error?
Paper: Institute of Mathematical Statistics Lecture Notes - Monograph Series, 2006
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pathChirp: Efficient Available Bandwidth Estimation for Network Paths
Knowledge of the available or unused bandwidth on a
network path can be crucial for optimizing network
performance. pathChirp is a new active probing
tool for estimating the available bandwidth on a
communication network path. Based on the concept of
self-induced congestion, pathChirp features an
exponential flight pattern of probes we call a
chirp. Packet chirps offer several significant
advantages over current probing schemes based on packet
pairs or packet trains. By rapidly increasing the probing
rate within each chirp, pathChirp obtains a rich set of
information from which to dynamically estimate the
available bandwidth. Paper: Passive and Active Measurement Workshop, 2003
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STAB: Locating available bandwidth bottlenecks
The Spatio-Temporal Available Bandwidth estimator (STAB) is
a new probing tool that locates thin links - links with less available
bandwidth than those preceding them on a path. By localizing thin
links, STAB facilitates network operations and troubleshooting,
provides insight into what causes network congestion, and aids
network-aware applications such as grid computing. The tool combines
the concept of "self-induced congestion", the probing technique of
"packet tailgating", and special probing trains called "chirps" to
efficiently locate the thin links.
Paper: IEEE Internet Computing, 2004
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A Multifractal Wavelet Model with Application to TCP Network Traffic
Traffic models that capture important features of observed
Internet traffic provide synthetic data for simulation
purposes as well as give key insights into the causes of
the dynamics in traffic. We develop a new multiscale
modeling framework for characterizing positive-valued data
with long-range-dependent correlations (1/f noise) such as
network traffic. Using the Haar wavelet transform and a
special multiplicative structure on the wavelet and
scaling coefficients to ensure positive results, the model
provides a rapid O(N) cascade algorithm for synthesizing
N-point data sets. We derive a scheme for matching the
model to real data observations and, to demonstrate its
effectiveness, apply the model to network traffic
synthesis. Paper: IEEE Transactions on Information Theory, 1999
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Small-Time Scaling Behavior of
Internet Backbone Traffic
The intriguing discovery of "self-similarity" in network traffic by
Leland et al sparked considerable research to determine the causes of
this behavior. In this work we concentrate on the analysis of backbone
traffic at sub-second time scales. We observe that for a majority of
the traffic traces, the (second-order) scaling exponents at small time
scales (1ms - 100ms) are fairly close to 0.5, indicating that traffic
fluctuations at these time scales are (nearly) uncorrelated. Some
traces, however, do exhibit moderately large scaling exponents
(approximately 0.7) at small time scales. To identify the network
causes of the observed scaling behavior, we analyze the flow
composition of the traffic along two dimensions -- flow size and flow
density. Our study points to the dense flows (i.e., flows with bursts
of densely clustered packets) as the correlation-causing factor in
small time scales.
Papers: Computer Networks'05, MASCOTS'09, IFIP Networking'10
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Multiscale Queuing Analysis of Long-Range-Dependent Network Traffic
Many studies have indicated the importance of capturing
scaling properties when modeling traffic loads; however,
the influence of long-range dependence (LRD) and marginal
statistics still remains on unsure footing. We study these
two issues using a novel multiscale approach to queuing
analysis. The queuing analysis provides a simple closed
form approximation to the tail queue probability, valid
for any traffic model and any given buffer size. Our
results clearly indicate that the marginal distribution of
traffic at different time-resolutions affects queuing and
that a Gaussian assumption can lead to over-optimistic
predictions of tail queue probability even when taking LRD
into account. Paper: IEEE/ACM Transactions on Networking, 2006.
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Long-term document security (funded by Ministry of Communication and IT)
Documents such as birth certificates and professional degrees must last a lifetime. We would like be these to be stored and made available electronically. Clearly, a one time encryption with digital keys (with a short lifetime of few years) is not going to keep the documents safe. In this project we designed renewable encryption schemes to keep the documents secure. In addition, we developed a prototype professional degree server which can make such certificates available to employers.
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