P. Krishnamurthy

University of Pittsburgh, Pittsburgh, Pennsylvania, United States

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Publications (58)17.7 Total impact

  • Kunjie Xu · D. Tipper · P. Krishnamurthy · Yi Qian
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    ABSTRACT: Multihop wireless networks can be subjected to nonstationary phenomena due to a dynamic network topology and time varying traffic. However, the simulation techniques used to study multihop wireless networks focus on the steady-state performance even though transient or nonstationary periods will often occur. Moreover, the majority of the simulators suffer from poor scalability. In this paper, we develop an efficient performance modeling technique for analyzing the time varying queueing behavior of multihop wireless networks. The one-hop packet transmission (service) time is assumed to be deterministic, which could be achieved by contention-free transmission, or approximated in sparse or lightly loaded multihop wireless networks. Our model is a hybrid of time varying adjacency matrix and fluid flow based differential equations, which represent dynamic topology changes and nonstationary network queues, respectively. Numerical experiments show that the hybrid fluid based model can provide reasonably accurate results much more efficiently than standard simulators. Also an example application of the modeling technique is given showing the nonstationary network performance as a function of node mobility, traffic load and wireless link quality.
    Computing, Networking and Communications (ICNC), 2013 International Conference on; 01/2013
  • Xin Wang · P. Krishnamurthy · D. Tipper
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    ABSTRACT: Virtualization of wired networks and end computing systems has become one of the leading trends in networked ICT systems. In contrast relatively little virtualization has occurred in infrastructure based wireless networks, but the idea of virtualizing wireless access is gaining attention as it has the potential to improve spectrum utilization and perhaps create new services. In this paper we survey the state of the current research in virtualizing wireless networks. We define and describe possible architectures, the issues, hurdles and trends towards implementation of wireless network virtualization.
    Computing, Networking and Communications (ICNC), 2013 International Conference on; 01/2013
  • P. Krishnamurthy · M. Weiss · D. Tipper
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    ABSTRACT: Dynamic spectrum access (DSA), where the permission to use slices of radio spectrum is dynamically shifted (in time an in different geographical areas) across various communications services and applications, has been an area of interest from technical and public policy perspectives over the last decade. The underlying belief is that this will increase spectrum utilization, especially since many spectrum bands are relatively unused, ultimately leading to the creation of new and innovative services that exploit the increase in spectrum availability. Determining whether a slice of spectrum, allocated or licensed to a primary user, is available for use by a secondary user at a certain time and in a certain geographic area is a challenging task. This requires “context information” which is critical to the operation of DSA. Such context information can be obtained in several ways, with different costs, and different quality/usefulness of the information. In this paper, we describe the challenges in obtaining this context information, the potential for the integration of various sources of context information, and the potential for reuse of such information for related and unrelated purposes such as localization and enforcement of spectrum sharing. Since some of the infrastructure for obtaining finegrained context information is likely to be expensive, the reuse of this infrastructure/information and integration of information from less expensive sources are likely to be essential for the economical and technological viability of DSA.
    Information Reuse and Integration (IRI), 2013 IEEE 14th International Conference on; 01/2013
  • Source
    K. Pahlavan · G. Bao · Y. Ye · S. Makarov · U. Khan · P. Swar · D. Cave · A. Karellas · P. Krishnamurthy · K. Sayrafian
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    ABSTRACT: RF localization science and technology started with the global positioning systems for outdoor areas, and it then transformed into wireless indoor geolocation. The next step in the evolution of this science is the transformation into RF localization inside the human body. The first major application for this technology is the localization of the wireless video capsule endoscope (VCE) that has been in the clinical arena for 12 years. While physicians can receive clear images of abnormalities in the gastrointestinal tract with VCE devices, they have little idea of their exact location inside the GI tract. To localize intestinal abnormalities, physicians routinely use radiological, endoscopic or surgical operations. If we could use the RF signal radiated from the capsule to also locate these devices, not only can physicians discover medical problems, but they can also learn where the problems are located. However, finding a realistic RF localization solution for the endoscopy capsule is a very challenging task, because the inside of the human body is a difficult environment for experimentation and visualization. In addition, we have no-idea how the capsule moves and rotates in its 3D journey in this non-homogeneous medium for radio propagation. In this paper, we describe how we can design a cyber physical system (CPS) for experimental testing and visualization of interior of the human body that can be used for solving the RF localization problem for the endoscopy capsule. We also address the scientific challenges that face and the appropriate technical approaches for solving this problem.
    International Journal of Wireless Information Networks 12/2012; 19(4). DOI:10.1007/s10776-012-0195-z
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    K Pelechrinis · P Krishnamurthy · M Weiss · T Znati
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    ABSTRACT: A large volume of research has been conducted in the cognitive radio (CR) area the last decade. However, the deployment of a commercial CR network is yet to emerge. A large portion of the existing literature does not build on real world scenarios, hence, neglecting various important interactions of the research with commercial telecommunication networks. For instance, a lot of attention has been paid to spectrum sensing as the front line functionality that needs to be completed in an efficient and accurate manner to enable an opportunistic CR network architecture. This is necessary to detect the existence of spectrum holes without which no other procedure can be fulfilled. However, simply sensing (cooperatively or not) the energy received from a primary transmitter cannot enable correct dynamic spectrum access. For example, the low strength of a primary transmitter's signal does not assure that there will be no interference to a nearby primary receiver. In addition, the presence of a primary transmitter's signal does not mean that CR network users cannot access the spectrum since there might not be any primary receiver in the vicinity. Despite the existing elegant and clever solutions to the DSA problem no robust, implementable scheme has emerged. In this paper, we challenge the basic premises of the proposed schemes. We further argue that addressing the technical challenges we face in deploying robust CR networks can only be achieved if we radically change the way we design their basic functionalities. In support of our argument, we present a set of real-world scenarios, inspired by realistic settings in commercial telecommunications networks, focusing on spectrum sensing as a basic and critical functionality in the deployment of CRs. We use these scenarios to show why existing DSA paradigms are not amenable to realistic deployment in complex wireless environments.
    ACM SIGCOMM Computer Communication Review 01/2012; 43(2). DOI:10.1145/2479957.2479965 · 1.10 Impact Factor
  • Source
    M Weiss · P Krishnamurthy · L E Doyle · K Pelechrinis
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    ABSTRACT: Fungibility is a common assumption for market-based spectrum management. In this paper, we explore the dimensions of practical fungibility of frequency bands from the point of view of the spectrum buyer who intends to use it. The exploration shows that fungibility is a complex, multidimensional concept that cannot casually be assumed. We develop two ideas for quantifying fungibility - (i) of a fungibility space in which the “distance” between two slices of spectrum provides score of fungibility and (ii) a probabilistic score of fungibility.
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    Tae-Hoon Kim · D. Tipper · P. Krishnamurthy
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    ABSTRACT: Heterogeneous conditions can occur in multi-hop wireless networks due to a variety of factors such as variations in transmission power and signal propagation environments. Directed links can occur when the environment and/or the nodes are heterogeneous. In this paper, we examine the network connectivity for heterogeneous multi-hop wireless networks and propose an algorithm to identify the connectivity of the network. We follow this with a numerical study of the connectivity in random topologies. Lastly, we propose two schemes for constructing additional links to enhance the connectivity of the network. Our proposed schemes identify the links to be improved or created via a cluster based approach.
    Communications (ICC), 2011 IEEE International Conference on; 07/2011
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    K. Panyim · T. Hayajneh · P. Krishnamurthy · D. Tipper
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    ABSTRACT: Jamming attacks are considered one of the most devastating attacks as they are difficult to prevent and sometimes hard to detect. In this paper we consider the impact of the placement and range of limited-range jammers on ad hoc networks. Limited range jammers are more difficult to detect as they use transmission powers similar to that of regular nodes (or perhaps even smaller transmit powers). The attacker can locate his jammer(s) randomly in the network. Alternatively, jammers can be placed at strategic locations. For instance, intuitively, this can be nodes with the highest traffic inputs/outputs (discovered by sensing the traffic flow in the network). Using OPNET, we perform extensive simulations to show how significant such strategically placed attacks can be compared to random placement of limited-range jammers on both TCP and UDP traffic.
    Local Computer Networks, 2009. LCN 2009. IEEE 34th Conference on; 11/2009
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    Chih-Kuang Lin · V. Zadorozhny · P. Krishnamurthy
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    ABSTRACT: We propose a novel framework that combines probabilistic transmission with Latin squares characteristics to tune channel access, meeting various demands in network performance (Energy vs. Delay). The proposed technique is decentralized, scalable, and has low overhead. We develop an analytical model to estimate the network performance and validate the benefits of the proposed framework via simulation-based experiments.
    Sensor Technologies and Applications, 2009. SENSORCOMM '09. Third International Conference on; 07/2009
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    T. Hayajneh · P. Krishnamurthy · D. Tipper · Taehoon Kim
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    ABSTRACT: Detecting malicious packet dropping is important in ad hoc networks to combat a variety of security attacks such as blackhole, greyhole, and wormhole attacks. We consider the detection of malicious packet drops in the presence of collisions and channel errors and describe a method to distinguish between these types. We present a simple analytical model for packet loss that helps a monitoring node to detect malicious packet dropping attacks. The model is analyzed and evaluated using simulations. The results show that it is possible to detect malicious packet drops in the presence of collisions and channel errors.
    Communications, 2009. ICC '09. IEEE International Conference on; 07/2009
  • Kaveh Pahlavan · Prashant Krishnamurthy
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    Chih-Kuang Lin · V. Zadorozhny · P. Krishnamurthy
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    ABSTRACT: We introduce a distributed grid-based scheduling access scheme that mitigates high data loss in data intensive sensor networks. Our approach alleviates transmission collisions by applying virtual grids and adopting Latin Squares Characteristic to time slot assignments. We demonstrate that our technique efficiently handles sensor mobility with acceptable data loss and low overhead.
    Mobile Data Management, 2008. MDM '08. 9th International Conference on; 05/2008
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    P. Krishnamurthy · R.D. Chamberlain
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    ABSTRACT: Pipelined computing applications often have their performance modeled using queueing techniques. While networks with infinite capacity queues have well understood properties, networks with finite capacity queues and blocking between servers have resisted closed-form solutions and are typically analyzed with approximate solutions. It is this latter case that more closely represents the circumstances present for pipelined computation. In this paper, we extend an existing approximate solution technique and, more importantly, provide guidance as to when the approximate solutions work well and when they fail.
    Parallel and Distributed Processing, 2008. IPDPS 2008. IEEE International Symposium on; 05/2008
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    V. Zadorozhny · P. Krishnamurthy
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    ABSTRACT: Data Intensive Mobile Sensor Networks (DIMSNs) introduce a promising but still under-utilized technology. Meanwhile, there is a growing confidence that certain applications (Killer Apps) have a potential to create a sustained market for this technology. For example, a large team of cooperative mobile robots can be considered as a wireless sensornet composed of a number of mobile nodes most of which are powerconstrained. Such mobile robots can be deployed in conjunction with stationary sensor nodes to acquire and process data for surveillance and tracking, environmental monitoring for highly sensitive areas, or execute search and rescue operations. This example illustrates conceptual attractiveness of the DIMSN systems that generates interesting and appealing research challenges (e.g., intelligent mobile agents, semantically enriched and contextaware wireless services, smart network monitoring infrastructures). However, while providing excellent funding opportunities, those challenges often underestimate the GRAND DETERRENTS that make moves towards practical data-intensive mobile sensornets extremely difficult.
    Mobile Data Management, 2006. MDM 2006. 7th International Conference on; 06/2006
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    P. Keeratiwintakorn · P. Krishnamurthy
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    ABSTRACT: Due to broadcast nature of wireless radio transmission, security services are of paramount importance to protect information exchanged in a wireless network. However, providing security services increases the computation and hence energy consumption due to cryptographic algorithms. Energy tends to be a very limited resource for wireless devices operating on battery. Thus, energy efficient security services are necessary to operate limited wireless devices securely. In this paper, we propose Tunable Security Model (TSM) to minimize energy consumption while providing security services such that the user's security level requirement is satisfied. From our experiments in IEEE 802.11 wireless networks, it is shown that using TSM can save up to 8% energy for low-level security, and up to 43% energy for high-level security.
    Wireless Pervasive Computing, 2006 1st International Symposium on; 02/2006
  • V. Zadorozhny · D. Sharma · P. Krishnamurthy · A. Labrinidis
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    P. Krishnamurthy · J. Buhler · R. Chamberlain · M Franklin · M. Gyang · J Lancaster
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    ABSTRACT: Biosequence similarity search is an important application in modern molecular biology. Search algorithms aim to identify sets of sequences whose extensional similarity suggests a common evolutionary origin or function. The most widely used similarity search tool for biosequences is BLAST, a program designed to compare query sequences to a database. Here, we present the design of BLASTN, the version of BLAST that searches DNA sequences, on the Mercury system, an architecture that supports high-volume, high-throughput data movement off a data store and into reconfigurable hardware. An important component of application deployment on the Mercury system is the functional decomposition of the application onto both the reconfigurable hardware and the traditional processor. Both the Mercury BLASTN application design and its performance analysis are described.
    Application-Specific Systems, Architectures and Processors, 2004. Proceedings. 15th IEEE International Conference on; 10/2004
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    P. Prasithsangaree · P. Krishnamurthy
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    ABSTRACT: Energy sayings are extremely important in wireless networks where devices operate using battery power. Security in wireless networks is also becoming crucial with the deployment of wireless local area networks in hot spot areas, organizations, hospitals and so on. Security protocols depend on energy consuming operations that occur in the cryptographic primitives used in the protocols. It has been observed that different cryptographic algorithms consume different amounts of energy. Also, the amount of energy consumed can depend on the key size, the number of cryptographic operational rounds, and packet or frame size. At the same time, the strength of a security protocol also depends on the key sizes and ciphers used to build it. We apply these results to protocols in wireless local area networks and study the tradeoffs between the security strengths of these protocols and the amount of energy consumed. For the analysis, we use distributions of packet sizes based on packets collected in home and campus wireless local area networks and measurements of the number of CPU cycles taken for cryptographic computation.
    Vehicular Technology Conference, 2004. VTC2004-Fall. 2004 IEEE 60th; 10/2004
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    K. Kaemarungsi · P. Krishnamurthy
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    ABSTRACT: Indoor positioning systems that make use of received signal strength based location fingerprints and existing wireless local area network infrastructure have recently been the focus for supporting location-based services in indoor and campus areas. A knowledge and understanding of the properties of the location fingerprint can assist in improving design of algorithms and deployment of position location systems. However, most existing research work ignores the radio signal properties. This paper investigates the properties of the received signal strength reported by IEEE 802.11b wireless network interface cards. Analyses of the data are performed to understand the underlying features of location fingerprints. The performance of an indoor positioning system in terms of its precision is compared using measured data and a Gaussian model to see how closely a Gaussian model may fit the measured data.
    Mobile and Ubiquitous Systems: Networking and Services, 2004. MOBIQUITOUS 2004. The First Annual International Conference on; 09/2004
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    P. Prasithsangaree · P. Krishnamurthy
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    ABSTRACT: Recently, several authentication protocols have been proposed for wireless local area networks (WLANs) to improve security in hotspot public access and corporate networks, and some have been proposed for integrated 3G-WLAN networks. These authentication protocols are based on the extensible authentication protocol and have been directly applied to wireless networks based on their widespread use in wired networks. Depending on the 3G-WLAN architecture and how the WLAN is tied to the 3G network, these protocols could have large latency. Moreover, they do not have mechanisms for authenticating the usage time of a mobile in a WLAN. We first discuss these issues related to existing authentication protocols for a 3G-WLAN integrated network. Then, we propose a new authentication mechanism based on the dual signature concept used in secure electronic transactions that can be used in a loosely coupled architecture. Finally, we present a preliminary evaluation of the energy performance and latency of the existing and proposed protocols.
    Vehicular Technology Conference, 2004. VTC 2004-Spring. 2004 IEEE 59th; 06/2004

Publication Stats

2k Citations
17.70 Total Impact Points

Institutions

  • 2002–2013
    • University of Pittsburgh
      • • School of Information Sciences
      • • Telecommunications
      Pittsburgh, Pennsylvania, United States
  • 2009
    • Norwegian University of Science and Technology
      Nidaros, Sør-Trøndelag, Norway
  • 2003–2008
    • Washington University in St. Louis
      • Department of Computer Science and Engineering
      San Luis, Missouri, United States
  • 2006
    • King Mongkut's Institute of Technology Ladkrabang
      • Department of Electrical Engineering
      Bangkok, Bangkok, Thailand
  • 1999
    • University of Oulu
      • Centre for Wireless Communications (CWC)
      Uleoborg, Oulu, Finland
  • 1997–1999
    • Worcester Polytechnic Institute
      • Department of Electrical and Computer Engineering
      Worcester, Massachusetts, United States