T.V. Prabhakar

Delft University of Technology, Delft, South Holland, Netherlands

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Publications (25)0 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We present our ``Zero Energy Network'' (ZEN) protocol stack for energy harvesting wireless sensor networks applications. The novelty in our work is $4$ fold: (1) Energy harvesting aware fully featured MAC layer. Carrier sensing, Backoff algorithms, ARQ, RTS/CTS mechanisms, Adaptive Duty Cycling are either auto configurable or available as tunable parameters to match the available energy (b) Energy harvesting aware Routing Protocol. The multi-hop network establishes routes to the base station using a modified version of AODVjr routing protocol assisted by energy predictions. (c) Application of a time series called ``Holt-Winters'' for predicting the incoming energy. (d) A distributed smart application running over the ZEN stack which utilizes a multi parameter optimized perturbation technique to optimally use the available energy. The application is capable of programming the ZEN stack in an energy efficient manner. The energy harvested distributed smart application runs on a realistic solar energy trace with a three year seasonality database. We implement a smart application, capable of modifying itself to suit its own as well as the network's energy level. Our analytical results show a close match with the measurements conducted over EHWSN testbed.
    04/2014;
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    ABSTRACT: Emotion recognition through physiological recording is an emerging field of research with many promising results. This work is involved in the construction of a device used to identify basic human emotions indexed by Electro Dermal Activity (EDA) in real time, using a non-invasive sensor attached to a wrist band. We refer to the system as "E Lock-Holmes". The device measures changes in Skin Conductance Level (SCL) caused due to stimulating signals from brain which results from sympathetic neural activity using Ag/AgCl electrodes placed on the ventral side of the distal forearm to evaluate the emotions of the user outside the constrained laboratory environment without interrupting the normal daily routine. The device consists of an embedded system for EDA signal acquisition and a wireless communication module to send processed EDA signals to a remote system. A vibrator attached to the device is used to provide user feedback.
    Proceedings of the 2013 Texas Instruments India Educators' Conference; 04/2013
  • Conference Paper: Infinite Coffee Cup
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    ABSTRACT: Imagine you go to your favorite café house or a restaurant and the system recognizes your presence and alerts the waiter and caters to your favorite beverage you longed for the day. The main motivation to Infinite Coffee Cup is to detect the presence of a person and dynamically and non-Invasively estimate the amount of coffee in a circular cup on the table. One of the more popular devices used is Microsoft Kinect, which has cameras that capture both RGB and Depth data. Kinect is a low cost sensing device which provides two streams of images, 8 bit 3 channel RGB image and 11 bit single channel depth image. The system is fixed at the roof facing downwards and it takes a top view of the cup placed on the table. We use "libfreenect" [1] drivers which is an open source project, to stream data from kinect. We employ various image processing algorithms using Open CV (Open Source Computer Vision) which is a library of programming functions for real time computer vision. The algorithms are used to manipulate the data from kinect to, -Detect the circular coffee cups in the RGB image. -Overlay and correlate the depth values of cups in the depth image to get the height and amount of coffee in the cup.
    Proceedings of the 2013 Texas Instruments India Educators' Conference; 04/2013
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    ABSTRACT: In this work we describe our novel design of an embedded hardware communication device. The hardware is designed generically, by taking an example of a Zig Bee green radio. Our hardware completely eliminates the problem of idle listening encountered by most "mote" class hardware. Lower layers can assume node synchronization and thus transmit a minimum sized preamble. The circuit has three radios, interconnected with an antenna switch. We use simple but intelligent software to switch between the radios. Since our calculated energy savings when compared to designs without wake-up is significant, the system has the viability to be powered using harvested energy.
    Proceedings of the 2013 Texas Instruments India Educators' Conference; 04/2013
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    ABSTRACT: We describe the construction of a data mule platform running a set of services useful for small and marginal farmers. Firstly, farmers are provided information about their standing crop by instrumenting their farm lands with soil moisture sensors and measuring the associated water stress. The platform is also equipped with market prices, seed availability, latest farming practices, of pest and disease attacks, rainfall etc. Thus, the idea is to improve the livelihood of these farmers by useful information and creating an advice system so as to reap maximum benefits in terms of yield/harvest. The data mule acquires data from several sources such as: (a) soil moisture probes installed in an individual's farmland, (b) Retrieving market price and other information from official websites etc. The mule delivers the information to the farmers' mobile phones via Wi-Fi, free of cost. The data mule is powered to work by harvesting energy from bicycle dynamo and solar panel. A mobile application is developed for Android and for Symbian phones as well. The phones support local audio language for ease of use.
    Proceedings of the 2013 Texas Instruments India Educators' Conference; 04/2013
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    ABSTRACT: We propose energy harvesting technologies and cooperative relaying techniques to power the devices and improve reliability. We propose schemes to (a) maximize the packet reception ratio (PRR) by cooperation and (b) minimize the average packet delay (APD) by cooperation amongst nodes. Our key result and insight from the testbed implementation is about total data transmitted by each relay. A greedy policy that relays more data under a good harvesting condition turns out to be a sub optimal policy. This is because, energy replenishment is a slow process. The optimal scheme offers a low APD and also improves PRR.
    Consumer Communications and Networking Conference (CCNC), 2013 IEEE; 01/2013
  • T V Prabhakar, Soumya N S, Jamadagni H S
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    ABSTRACT: Physical layer security is one possible alternative for the exploding Internet of Things in the coming years. We advance the state of art in physical layer security by implementing self-jamming on ultra low power transceivers without the assistance of “friendly” nodes. The implementation supports flexible payload sizes; where the simplest implementation carries a full data payload. We consider a passive eavesdropper with varying attack potentials; constantly attempting to recover the original data from the transmitter. We show that a 3dB shift and transmit power control between transmitter and receiver is good enough to ensure data security. The key insights from this work is that large payloads have a 50% lower throughput compared to smaller payloads. Also smaller payloads have the advantage of a 25% delay performance improvement over large payloads.
    Personal Indoor and Mobile Radio Communications (PIMRC), 2013 IEEE 24th International Symposium on; 01/2013
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    ABSTRACT: Energy harvesting (EH) is a major step in solving the critical issue of availability of energy for sensor nodes. However, it throws many challenges. The applications built on the sensor networks powered by EH need to adapt their operations yet serve the purpose. We propose a distributed smart application for a multihop sensor network and in general in the future Internet of Things (IoT) where a network node executes an optimal number of policies to minimize the difference between available energy and consumed energy (called residual energy) for the execution of an application policy . We formulate this as a multi-criteria optimization problem and solve it using linear programming Parametric Analysis. We demonstrate our approach on a testbed with solar panels. We also use a realistic solar energy trace with a three year database including seasonality. The smart application is capable of adapting itself to its current energy level as well as that of the network. Our analytical results show a close match with the measurements conducted over testbed.
    Proceedings of the 11th international IFIP TC 6 conference on Networking - Volume Part II; 05/2012
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    ABSTRACT: With the growing dependence on the wireless sensor devices, it is imperative that power supply to them and their energy usage has acquired centre stage. Energy harvesting is one possible remedy. To enhance the use of devices that are using harvested energy, many novel schemes need to be devised. In this paper we propose four throughput enhancement schemes with a wide range of applicability to energy harvesting wireless sensor networks. The schemes are designed by taking into consideration available resources in the nodes as well as the energy harvesters that are used to drive the sensor nodes. All the four schemes are implemented, evaluated and compared for their performances. We present schemes from simple naive scheme which is of low complexity, to probabilistic probing scheme which incorporates advanced methods to appropriately use the harvested energy. All the schemes require minimum system resources and sufficient harvested energy before starting communication. Moreover, when the harvested energy varies due to the changes in the environment and characteristics of wireless channel varies, we found that truncated channel inversion with power control is the appropriate scheme. This article provides a thorough step by step discussion on the implementation of maximizing communication throughput in energy harvesting sensor nodes under varying environment. We also provide some insights into energy requirements for a multi-node network.
    Fourth International Conference on Communication Systems and Networks, COMSNETS 2012, Bangalore, India, January 3-7, 2012; 01/2012
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    ABSTRACT: We investigate the queue stability in Energy Harvesting Sensor (EHS) nodes under indoor conditions wherein solar energy equipped EHS nodes are deployed for intrusion detection. We implement two policies, namely Throughput Optimal and Greedy and test the conditions under which they ensure queue stability. Energy and Data are injected following a distribution. An important observation is the use of “mean harvested energy” in proposed policies. Presently it does not seem practical to use this term, but works well when nodes have apriori knowledge of its value. Our results indicate that exponential arrival of data and energy offers maximum stability under these stressful conditions.
    01/2012;
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    ABSTRACT: We implement two energy models that accurately and comprehensively estimates the system energy cost and communication energy cost for using Bluetooth and Wi-Fi interfaces. The energy models running on a system is used to smartly pick the most energy optimal network interface so that data transfer between two end points is maximized.
    Consumer Communications and Networking Conference (CCNC), 2012 IEEE; 01/2012
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    ABSTRACT: To overcome the problem of unavailability of grid power in rural India, we explore the possibility of powering WSN gateways using a bicycle dynamo. The "Data mule" bicycle generates its own power to ensure a self sustainable data transfer for information dissemination to small and marginal farmers. Our multi-interface WSN gateway is equipped with Bluetooth, Wi-Fi and GPRS technologies. To achieve our goal, we exploit the DTN stack in the energy sense and introduce necessary modifications to its configuration.
    07/2011;
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    ABSTRACT: In this work, we study the adaptability of well known cryptography algorithms to energy harvesting wireless sensor networks. We are particularly interested in algorithms that have the ability to adapt to varying power in such networks. Our investigations and implementation on hardware platforms indicate that it is optimal to precompute a few key stream bytes, store in memory and later used during the time when the system is low on harvested power level. Our demonstrable setup shows using a precomputed key stream can decrease the energy consumption by 14%. We have implemented the Trivium stream cipher for two different microcontrollers, the MSP430 and the AVR ATmega1281 and show the performance results for these implementations. We have implemented an algorithm based on universal hash functions to provide message authentication with the assistance of stream ciphers. We show that this authentication algorithm has exciting properties for energy harvesting system and more generally for resource constrained devices.
    Consumer Communications and Networking Conference (CCNC), 2011 IEEE; 02/2011
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    ABSTRACT: Powering wireless sensors with harvested energies is coming of age due to the sources providing higher power densities and the electronics performing efficient energy conversion. However, to ensure energy harvesting as a viable option, several system parameters have to be tuned. In this work, we identify these key system parameters and show that by suitably tuning them, one can drive wireless sensor networks (WSNs) with harvested energies. Some of the parameters include system's operating voltage & frequency, transceiver's Automatic Gain Control (AGC) block fine tuning, clear channel assessment and finally capacity values of energy storage buffers. Our measurements show that there are several possibilities to save energy by trading one system feature for another.
    Communication Systems and Networks (COMSNETS), 2011 Third International Conference on; 02/2011
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    ABSTRACT: A Wireless Sensor Network (WSN) powered using harvested energies is limited in its operation by instantaneous power. Since energy availability can be different across nodes in the network, network setup and collaboration is a non trivial task. At the same time, in the event of excess energy, exciting node collaboration possibilities exist; often not feasible with battery driven sensor networks. Operations such as sensing, computation, storage and communication are required to achieve the common goal for any sensor network. In this paper, we design and implement a smart application that uses a Decision Engine, and morphs itself into an energy matched application. The results are based on measurements using IRIS motes running on solar energy. We have done away with batteries; instead used low leakage super capacitors to store harvested energy. The Decision Engine utilizes two pieces of data to provide its recommendations. Firstly, a history based energy prediction model assists the engine with information about in-coming energy. The second input is the energy cost database for operations. The energy driven Decision Engine calculates the energy budgets and recommends the best possible set of operations. Under excess energy condition, the Decision Engine, promiscuously sniffs the neighborhood looking for all possible data from neighbors. This data includes neighbor's energy level and sensor data. Equipped with this data, nodes establish detailed data correlation and thus enhance collaboration such as filling up data gaps on behalf of nodes hibernating under low energy conditions. The results are encouraging. Node and network life time of the sensor nodes running the smart application is found to be significantly higher compared to the base application.
    Communication Systems and Networks (COMSNETS), 2010 Second International Conference on; 02/2010
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    ABSTRACT: We discuss the key issues in the deployment of sparse sensor networks. The network monitors several environment parameters and is deployed in a semi-arid region for the benefit of small and marginal farmers. We begin by discussing the problems of an existing unreliable 1 sq km sparse network deployed in a village. The proposed solutions are implemented in a new cluster. The new cluster is a reliable 5 sq km network. Our contributions are two fold. Firstly, we describe a novel methodology to deploy a sparse reliable data gathering sensor network and evaluate the “safe distance” or “reliable” distance between nodes using propagation models. Secondly, we address the problem of transporting data from rural aggregation servers to urban data centres. This paper tracks our steps in deploying a sensor network in a village in India, trying to provide better diagnosis for better crop management. Keywords - Rural, Agriculture, GPRS, Sparse.
    Distributed Computing and Networking, 11th International Conference, ICDCN 2010, Kolkata, India, January 3-6, 2010. Proceedings; 01/2010
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    ABSTRACT: To overcome the problem of unavailability of grid power in rural India, we explore the possibility of powering WSN Gateways using a bicycle dynamo. The “data mule” bicycle generates its own power to ensure a self sustainable data transfer scheme to benefit small and marginal farmers. In our agricultural scenario, farmers have to generate electric- ity to get access to the technology. Our power measurements show that it is indeed possible to drive GPRS technologies with this power. We propose Transfer Energy Budget - a two way metric for gateway nodes to announce the available energy for relaying data. To achieve our goal, we exploit the DTN stack and introduce necessary modifications to its configuration. The results indicate that a 50 packet buffer has the least transfer energy budget with a data latency of about 31 seconds.
    SIGMETRICS Performance Evaluation Review. 01/2010; 38:71-75.
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    ABSTRACT: This paper presents a low cost but high resolution retinal image acquisition system of the human eye. The images acquired by a CMOS image sensor are communicated through the Universal Serial Bus (USB) interface to a personal computer for viewing and further processing. The image acquisition time was estimated to be 2.5 seconds. This system can also be used in telemedicine applications.
    Consumer Electronics, 2008. ICCE 2008. Digest of Technical Papers. International Conference on; 02/2008
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    ABSTRACT: We develop several hardware and software simulation blocks for the TinyOS-2 (TOSSIM-T2) simulator. The choice of simulated hardware platform is the popular MICA2 mote. While the hardware simulation elements comprise of radio and external flash memory, the software blocks include an environment noise model, packet delivery model and an energy estimator block for the complete system. The hardware radio block uses the software environment noise model to sample the noise floor. The packet delivery model is built by establishing the SNR-PRR curve for the MICA2 system. The energy estimator block models energy consumption by Micro Controller Unit(MCU), Radio, LEDs, and external flash memory. Using the manufacturerpsilas data sheets we provide an estimate of the energy consumed by the hardware during transmission, reception and also track several of the MCUs states with the associated energy consumption. To study the effectiveness of this work, we take a case study of a paper presented in [1]. We obtain three sets of results for energy consumption through mathematical analysis, simulation using the blocks built into PowerTossim-T2 and finally laboratory measurements. Since there is a significant match between these result sets, we propose our blocks for T2 community to effectively test their application energy requirements and node life times.
    Communication Systems Software and Middleware and Workshops, 2008. COMSWARE 2008. 3rd International Conference on; 02/2008
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    ABSTRACT: In this paper we have proposed and implemented a joint medium access control (MAC) -cum- routing scheme for environment data gathering sensor networks. The design principle uses node dasiabattery lifetimepsila maximization to be traded against a network that is capable of tolerating: (a) A known percentage of combined packet losses due to packet collisions, network synchronization mismatch and channel impairments (b) Significant end-to-end delay of an order of few seconds We have achieved this with a loosely synchronized network of sensor nodes that implement slotted-aloha MAC state machine together with route information. The scheme has given encouraging results in terms of energy savings compared to other popular implementations. The overall packet loss is about 12%. The battery life time increase compared to B-MAC varies from a minimum of 30% to about 90% depending on the duty cycle.
    Proceedings of the Third International Conference on COMmunication System softWAre and MiddlewaRE (COMSWARE 2008), January 5-10, 2008, Bangalore, India; 01/2008

Publication Stats

56 Citations

Institutions

  • 2010–2012
    • Delft University of Technology
      • Faculty of Electrical Engineering, Mathematics and Computer Sciences (EEMCS)
      Delft, South Holland, Netherlands
    • Indian Institute of Management Bangalore
      Bengalūru, Karnātaka, India
  • 2007–2011
    • Indian Institute of Science
      • Centre for Electronic Design and Technology
      Bengalore, State of Karnataka, India