T.V. Prabhakar

Delft University of Technology, Delft, South Holland, Netherlands

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Publications (45)

  • Raviteja Upadrashta · Tarun Choubisa · A. Praneeth · [...] · T. V. Prabhakar
    [Show abstract] [Hide abstract] ABSTRACT: This paper presents the development of a passive infra-red sensor tower platform along with a classification algorithm to distinguish between human intrusion, animal intrusion and clutter arising from wind-blown vegetative movement in an outdoor environment. The research was aimed at exploring the potential use of wireless sensor networks as an early-warning system to help mitigate human-wildlife conflicts occurring at the edge of a forest. There are three important features to the development. Firstly, the sensor platform employs multiple sensors arranged in the form of a two-dimensional array to give it a key spatial-resolution capability that aids in classification. Secondly, given the challenges of collecting data involving animal intrusion, an Animation-based Simulation tool for Passive Infra-Red sEnsor (ASPIRE) was developed that simulates signals corresponding to human and animal intrusion and some limited models of vegetative clutter. This speeded up the process of algorithm development by allowing us to test different hypotheses in a time-efficient manner. Finally, a chirplet-based model for intruder signal was developed that significantly helped boost classification accuracy despite drawing data from a smaller number of sensors. An SVM-based classifier was used which made use of chirplet, energy and signal cross-correlation-based features. The average accuracy obtained for intruder detection and classification on real-world and simulated data sets was in excess of 97%.
    Article · Apr 2016
  • Conference Paper · Apr 2016
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    Full-text Working Paper · Mar 2016
  • Sanjeev K · Manjunath Machnoor · K.J. Vinoy · T.V. Prabhakar
    Conference Paper · Mar 2016
  • Sanjeev K. · Manjunath Machnoor · K.J. Vinoy · T.V. Prabhakar
    Conference Paper · Dec 2015
  • Sandeep Rana · TV Prabhakar · K.J. Vinoy
    Conference Paper · Dec 2015
  • [Show abstract] [Hide abstract] ABSTRACT: This work describes an ultra low power three chip system that harvests RF energy for sensing applications. The input RF power levels are typically lower than -6dBm. Our scheme uses two commercially available chips, a DC-DC boost converter and a low power microcontroller. In this paper we present the design of a third chip that compliments these to form a complete system. This chip includes an RF-DC rectifier, low power analog to digital converter (ADC) and a resistor emulation circuit (REC). While the REC helps in enhancing the efficiency of the boost converter, the ADC replaces the one present in the microcontroller and reduces the operating power requirements. The chip is designed in standard 0.18μm CMOS process technology.
    Article · Aug 2015
  • Raviteja Upadrashta · Tarun Choubisa · V.S. Aswath · [...] · T.V. Prabhakar
    [Show abstract] [Hide abstract] ABSTRACT: The development of a Passive Infra-Red (PIR) sensing based intrusion detection system is presented here having the ability to reject vegetative clutter and distinguish between human and animal intrusions. This has potential application to reducing human-animal conflicts in the vicinity of a wildlife park. The system takes on the form of a sensor-tower platform (STP) and was developed in-house. It employs a sensor array that endows the platform with a spatial-resolution capability. Given the difficulty of collecting data involving animal motion, a simulation tool was created with the aid of Blender and OpenGL software that is capable of quickly generating streams of human and animal-intrusion data. The generated data was then examined to identify a suitable collection of features that are useful in classification. The features selected corresponded to parameters that model the received signal as the super-imposition of a fixed number of chirplets, an energy signature and a cross-correlation parameter. The resultant feature vector was then passed on to a Support Vector Machine (SVM) for classification. This approach to classification was validated by making use of real-world data collected by the STP which showed both STP design as well as classification technique employed to be quite effective. The average classification accuracy with both real and simulated data was in excess of 94%.
    Article · May 2015
  • Mannam Rama Rao · Joy Kuri · T.V. Prabhakar
    [Show abstract] [Hide abstract] ABSTRACT: Demand Response is under implementation throughout the globe by many utilities to incorporate the end user as an active player in reducing supply-demand imbalances. Day-ahead pricing is provided as an option to schedule electric loads so as to take advantage of time-varying prices. However, user convenience is also a factor that must be taken into account, as users may be willing to forego some savings to reduce inconvenience. We formulate an optimal scheduling problem considering both aspects. As the search space is exponentially large, we propose two greedy algorithms to find good schedules. To assess performance, we obtain the optimal schedule via Markov Chain Monte Carlo (MCMC) based simulations. We apply the framework to two case studies; one study uses appliance energy profiles obtained by actual measurements using the Joule Jotter, a device designed and developed in-house. Results indicate that the proposed algorithms perform very well, achieving performance within 10%of the optimal.
    Article · Apr 2015
  • Ujjwal Satish · Uday Saini · T. V. Prabhakar · [...] · Bharadwaj Amrutur
    Conference Paper · Jan 2015
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    [Show abstract] [Hide abstract] ABSTRACT: We undertake a step-by-step approach in the design of two Near Field Communication (NFC) products for pervasive healthcare monitoring. Our first product is an NFC based battery charger circuit to charge a thermometer equipped with wireless communication. Our system design has a simple linear charger, with overvoltage and undervoltage protection implemented as an android App. The NFC power source provides 13 − 15 mW of continuous power and is able to charge a 45mAH battery in about 10 hours from deep discharge to full charge state. Since the weight of the charger is about 3 grams and the size is about 2 cms in diameter, this product is useful for wearable sensor devices and provides a convenient way of recharging the batteries without the need for any connectors in the device. This allows devices to be hermetically sealed, besides enabling smaller form factors. The second product is an NFC based battery-less medical grade thermometer. To obtain the temperature of a single patient, a maximum of 10 seconds is sufficient to read the sensor value starting from placement of a smartphone over the product.
    Full-text Conference Paper · Jan 2015
  • Article: PIR sensors
    Article · Jan 2015
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    [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.
    Full-text Article · Apr 2014
  • V Sesha Raghav · Varun Gowtham · H.S Jamadagni · T.V Prabhakar
    [Show abstract] [Hide abstract] ABSTRACT: In the last few years, Power Line Communication (PLC) has gained momentum due to high data rate communication over existing power lines. The Home Plug AV (HPAV) and High Definition Power Line Communication (HD-PLC) are PLC specifications designed to provide 200 Mbps of PHY channel rate between hosts connected by modems operating at 2-28 MHz frequency range for home usage. A Logical Network (LN) formed by two or more modems allows communication with each other by sharing the same network key. With most of the world's population residing in Multi Dwelling Unit (MDU), there is high chance of unintentional interference among LNs assuming each unit of MDU owns an LN. In such a case, the channel bandwidth is shared among interfering LNs; thereby reducing combined throughput of all LNs. Considering LNs are given separate power line channels and operating on different phases, they may still undergo crosstalk if the power line channels are placed closer than a certain minimum separation. This paper suggests a method to maximize the combined throughput in a MDU keeping in view the LN interference. The solution also proposes a practical case of improving throughput between application servers situation in apartment blocks.
    Conference Paper · Jan 2014
  • K. J. Vinoy · T. V. Prabhakar
    [Show abstract] [Hide abstract] ABSTRACT: Low-power wireless and sensor technologies are fast proliferating everyday life. Medical and structural implants are common examples of devices based on these technologies. A new term “Internet of Things” has been coined to encompass many such sensors and wireless nodes. One of the critical concerns for their deployment is the source of energy, especially in operational scenarios where wall power is not available. Batteries run out of energy in due course. Solar or other alternatives are not always dependable. Combining various means of energy harvesting schemes assumes significance in this context. Low energy density radiations such as ambient RF signals from various broadcast and cellular towers have been found to be a convenient and widespread source of energy. Incorporating RF harvesting circuits into such a universal energy harvesting platform also enables intentional wireless power transfer to energize the device using an RF transmitter. This chapter explains electronic circuits required for a universal energy harvesting platform to capture, store, and efficiently utilize RF energy at different power levels in combination with other sources of ambient energy such as the Solar (for high energy). For demonstration, a low power radio and the required power management circuit have been integrated with this platform.
    Chapter · Jan 2014
  • H S Jamadagni · Varun Gowtham · N S Soumya · T V Prabhakar
    [Show abstract] [Hide abstract] ABSTRACT: We describe our novel LED communication infrastructure and demonstrate its scalability across platforms. Our system achieves 50 kilo bits per second on very simple SoCs and scales to megabits bits per second rates on dual processor based mobile phone platforms.
    Conference Paper · Jan 2014
  • T V Prabhakar · Soumya N S · Jamadagni H S
    [Show abstract] [Hide abstract] 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.
    Conference Paper · Sep 2013
  • Gaurav Singh · Rahul Ponnaganti · T.V. Prabhakar · K.J. Vinoy
    [Show abstract] [Hide abstract] ABSTRACT: A circuit topology based on accumulate-and-use philosophy has been developed to harvest RF energy from ambient radiations such as those from cellular towers. Main functional units of this system are antenna, tuned rectifier, supercapacitor, a gated boost converter and the necessary power management circuits. Various RF aspects of the design philosophy for maximizing the conversion efficiency at an input power level of 15 μW are presented here. The system is characterized in an anechoic chamber and it has been established that this topology can harvest RF power densities as low as 180 μW/m2 and can adaptively operate the load depending on the incident radiation levels. The output of this system can be easily configured at a desired voltage in the range 2.2–4.5 V. A practical CMOS load – a low power wireless radio module has been demonstrated to operate intermittently by this approach. This topology can be easily modified for driving other practical loads, from harvested RF energy at different frequencies and power levels.
    Article · Jul 2013 · AEU - International Journal of Electronics and Communications
  • T. V. Prabhakar · H. S. Jamadagni · B. S. Sudhangathan
    [Show abstract] [Hide abstract] 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.
    Conference Paper · Apr 2013
  • [Show abstract] [Hide abstract] 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.
    Conference Paper · Apr 2013