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PUBLICATIONS
Conference Proceedings
Show all Abstracts
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Yogesh R Kondareddy and Prathima Agrawal, "Synchronized MAC Protocol for Multi-Hop Cognitive Radio Network",
IEEE International Conference on Communications 2008 , Beijing, China.
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Abstract-Cognitive networks enable efficient sharing of the radio spectrum.
Multi-hop cognitive network is a cooperative network in which cognitive
users take help of their neighbors to forward data to the destination.
Control signals used to enable cooperation communicate through a common control channel (CCC).
Such usage introduces conditions like channel saturation which degrades the overall
performance of the network. Thus, exchanging control information is a major challenge
in cognitive radio networks. This paper proposes an alternative MAC protocol for
multi-hop cognitive radio networks in which the use of a CCC is avoided.
The scheme is applicable in heterogeneous environments where channels have
different bandwidths and frequencies of operation. It inherently provides a solution to
issues like CCC saturation problem, Denial of Service attacks (DoS) and multi-channel hidden problem.
The proposed protocol is shown to provide better connectivity and higher throughput than a
CCC based protocol, especially when the network is congested.
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Yogesh R Kondareddy and Prathima Agrawal, "Selective Broadcasting for Multi-Hop Cognitive Radio Networks",
IEEE Sarnoff Symposium 2008 , Princeton, NJ.
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Abstract-Cognitive networks enable efficient sharing of the radio spectrum.
Control signals used to setup a communication are broadcast to the neighbors in their
respective channels of operation. But since the number of channels in a cognitive network
is potentially large, broadcasting control information over all channels will cause a
large delay in setting up the communication. Thus, exchanging control information is a
critical issue in cognitive radio networks. This paper deals with selective broadcasting
in multi-hop cognitive radio networks in which, control information is transmitted over
pre-selected set of channels. We introduce the concept of neighbor graphs and minimal
neighbor graphs to derive the essential set of channels for transmission. It is shown
through simulations that selective broadcasting reduces the delay in disseminating control
information and yet assures successful transmission of information to all its neighbors.
It is also demonstrated that selective broadcasting reduces redundancy in control information
and hence reduces network traffic.
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Yogesh R Kondareddy and Prathima Agrawal, "Cognitive Radio Network Setup without a Common Control Channel",
IEEE Military Communications Conference 2008 , San Diego, CA.
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Abstract-The concept of cognitive radio networks has introduced a new way of sharing
the open spectrum flexibly and efficiently. However, there are several issues that hinder the
deployment of such dynamic networks. The common control channel problem is one of such issue.
Cognitive radio networks are designed by assuming the availability of a dedicated control channel.
In this paper, we identify and discuss the network setup problem as a part of the common control
channel problem. Probabilistic and deterministic ways to start the initial communication and setup
a cognitive radio network without the need of having a common control channel in both centralized
and multi-hop scenarios are suggested. Extensive MATLAB simulations validate the effectiveness of
the algorithms.
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Yogesh R Kondareddy and Prathima Agrawal, "A Graph Based Routing Algorithm for Multi-hop Cognitive Radio Networks",
Wireless Internet Conference, ACM International Conference Proceeding Series 2008 , Lahaina, Hawaii.
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Abstract-Cognitive radio networks that allow dynamic spectrum access are considered
spectrally more efficient than networks using fixed spectral allocation. These networks are
characterized by dynamically changing channel sets at each node. The graph theoretic approach
used in traditional multi-hop networks fails to efficiently model multi-hop cognitive radio
networks and capture the required information for optimal routing. Hence, conventional graph-based
routing protocols such as DSR or AODV cannot be used directly, for route discovery in such networks.
In this paper, a unique multi-edge planar graph model for routing in such type of networks is proposed,
which is quite simple and could be used in conjunction with any conventional graph-based routing protocol.
The model is validated through simulations and the complexity of the model is shown to be lesser than an
earlier layered graph model.
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Yogesh R Kondareddy, Nirmal Andrews and Prathima Agrawal, "On the Capacity of Secondary Users in a Cognitive Radio Network",
IEEE Sarnoff Symposium 2009 , Princeton, NJ.
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Abstract-Cognitive radio networks deal with opportunistic
spectrum access leading to greater utilization of the spectrum.
The extent of utilization depends on the primary user's traffic
and also on the way the spectrum is accessed by the primary and
secondary users. In this paper Continuous-time Markov chains
are used to model the spectrum access. The proposed threedimensional
model represents a more accurate cognitive system
than the existing models with increased spectrum utilization and
than the random and reservation based spectrum access. A nonrandom
access method is proposed to remove the forced
termination states. In addition, call dropping and blocking
probabilities are reduced. It is further shown that channel
utilization is higher than random access and reservation based
access.
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Yogesh R Kondareddy and Prathima Agrawal, "Effect of Dynamic Spectrum access on TCP Performance",
IEEE Global Telecommunications Conference 2009 , Honolulu, Hawaii.
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Abstract-Transmission Control Protocol (TCP) is the most commonly used
transport protocol on the Internet. All indications assure that it will be an
integral part of the future internetworks. In this paper, we briefly discuss
how regular TCP which was designed for wired networks is not suitable for dynamic
spectrum access networks. We develop an analytical model to estimate
the TCP throughput of Dynamic spectrum access networks. Dynamic spectrum
access networks deal with opportunistic spectrum access leading to
greater utilization of the spectrum. The extent of utilization depends
on the primary user's traffic and also on the way the spectrum is
accessed by the primary and secondary users. The proposed model
considers primary and secondary user traffic in estimating the TCP
throughput by modeling the spectrum access using continuous-time Markov
chains, thus providing more insight on effect of dynamic spectrum access
on TCP performance than the existing models.
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Kongara H, Yogesh R Kondareddy and Prathima Agrawal, "Fairness and Gateway Classification Algorithm in
Multi-hop Wireless Mesh Networks", 41st IEEE Southeastern Symposium on System Theory 2009
, Tullahoma, Tennessee.
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Abstract-Wireless Mesh Network (WMN) appears to be a promising alternative for next generation
wireless networking. Wireless mesh networks have applications ranging from civilian wireless Internet
applications to tactical and emergency response applications. Though wireless mesh networks appear as
a viable alternative to the existing wireless infrastructure, there are still many issues which
require more investigation. In this paper, we first analyze the fairness issue in WMNs by using simulation.
We then propose Gateway Classification Algorithm (GCA) which classifies gateways into high data rate gateways
and low data rate gateways. Simulation results show that the proposed GCA can improve the performance
significantly.
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Nirmal Andrews, Yogesh R Kondareddy and Prathima Agrawal, "Prioritized Resource Sharing in WiMax and WiFi
Integrated Networks", IEEE Wireless Communications and Networking Conference 2010 , Sydney, Australia.
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Abstract-In order to ensure fair access and efficiency of bandwidth
usage in wireless integrated networks, resource allocation
algorithms should be well designed. In this paper, we briefly
discuss the complete sharing, complete partitioning and Hybrid
resource sharing approaches and their shortcomings in WiMax-
WiFi integrated networks. To overcome these shortcomings we
propose the Prioritized Resource Sharing algorithm for WiMax-
WiFi integrated networks. In this algorithm, the channels are prioritized
for different traffic classes rather than strict reservation
or open access. The prioritized resource sharing algorithm is then
extended to multiple integrated networks. Finally, we analyze
the proposed algorithm by modeling it using two dimensional
continuous time Markov chains. The simulation results indicate
that the Prioritized Sharing model achieves the best system
utilization compared to other algorithms. It is also observed that
due to heavy traffic of one class of users, other class of users are
not starved unlike in complete sharing.
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Nirmal Andrews, Yogesh R Kondareddy and Prathima Agrawal, "Channel management in collocated WiFi-WiMAX networks",
42nd IEEE Southeastern Symposium on System Theory 2010 , Tyler, Texas.
Show Abstract
pdf
Abstract-In order to ensure fair access and efficiency of bandwidth
usage in wireless integrated networks, resource allocation
algorithms should be well designed. In this paper, we briefly
discuss the complete sharing, complete partitioning and Hybrid
resource sharing approaches and their shortcomings in WiMax-
WiFi integrated networks. To overcome these shortcomings we
propose the Prioritized Resource Sharing algorithm for WiMax-
WiFi integrated networks. In this algorithm, the channels are prioritized
for different traffic classes rather than strict reservation
or open access. We analyze the proposed algorithm by modeling
it using two dimensional continuous time Markov chains. The
simulation results indicate that the Prioritized Sharing model
achieves the best system utilization compared to other algorithms.
It is also observed that due to heavy traffic of one class of users,
other class of users are not starved unlike in complete sharing.
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Giovanni D Crescenzo, Yogesh R Kondareddy and Tao Zhang, "Random Graphs in Vehicular Networks and
Security Applications", Submitted to ICALP 2010 , Bordeaux, France.
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Abstract-Random graphs have been studied extensively in literature.
Dynamic random graphs which are assumed to be a good model
of mobile ad-hoc networks such as vehicular networks have
been comparatively less explored. But it is often vague to
see that, nodes moving on a specific geographical model and
a mobility model form a random graph. In this paper, we start
by formulating well-studied geographical, mobility, and
communication model and show that these result in the spatial
distribution of nodes (vehicles) being stationary, which, in turn,
is used to prove that vehicles form a random graph G(n,p), where p
has a closed-form expression. We then extend this result to quite
general geographical, mobility, and communication models, ad still
obtain a random graph G(n,p), where p has an algorithmically computable
expression. Thus one can measure and analyze properties of mobile ad-hoc
or vehicular networks such as connectivity, broadcast time, and related
security questions, as a function of basic communication, geographic and
mobility parameters. As an application, we show how to investigate
security questions how much infrastructure is required to improve the
connectivity and malicious user detection in the vehicular network.
Simulations are used to visualize and verify the analysis.
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