scispace - formally typeset
Search or ask a question
Author

Sabarish Sridhar

Bio: Sabarish Sridhar is an academic researcher from M. S. Ramaiah Institute of Technology. The author has contributed to research in topics: Clock synchronization & Clock drift. The author has an hindex of 2, co-authored 4 publications receiving 36 citations.

Papers
More filters
Journal ArticleDOI
TL;DR: The efficacy of CheepSync is demonstrated by numerous empirical evaluations in a variety of experimental setups, and it is shown that its average (single-hop) time synchronization accuracy is in the 10 μs range.
Abstract: Clock synchronization is highly desirable in distributed systems, including many applications in the Internet of Things and Humans It improves the efficiency, modularity, and scalability of the system, and optimizes use of event triggers For IoTH, BLE - a subset of the recent Bluetooth v40 stack - provides a low-power and loosely coupled mechanism for sensor data collection with ubiquitous units (eg, smartphones and tablets) carried by humans This fundamental design paradigm of BLE is enabled by a range of broadcast advertising modes While its operational benefits are numerous, the lack of a common time reference in the broadcast mode of BLE has been a fundamental limitation This article presents and describes CheepSync, a time synchronization service for BLE advertisers, especially tailored for applications requiring high time precision on resource constrained BLE platforms Designed on top of the existing Bluetooth v40 standard, the CheepSync framework utilizes low-level timestamping and comprehensive error compensation mechanisms for overcoming uncertainties in message transmission, clock drift, and other system-specific constraints CheepSync was implemented on custom designed nRF24Cheep beacon platforms (as broadcasters) and commercial off-the-shelf Android ported smartphones (as passive listeners) We demonstrate the efficacy of CheepSync by numerous empirical evaluations in a variety of experimental setups, and show that its average (single-hop) time synchronization accuracy is in the 10 μs range

33 citations

Proceedings ArticleDOI
13 Apr 2015
TL;DR: This work presents and describes CheepSync: a time synchronization service architecture for BLE advertisers, which is implemented on custom designed nRF24Cheep beacon platforms and commercial off-the-shelf Android ported smartphones; and shows that the average time synchronization accuracy is in the 10 μs range.
Abstract: Clock synchronization is highly desirable in distributed systems, including many applications in the Internet of Things and Humans (IoTH). For IoTH, Bluetooth Low Energy (BLE) - a subset of the recent Bluetooth v4:0 stack - provides a low-power and loosely coupled mechanism for sensor data collection with ubiquitous units (e.g., smartphones and tablets) carried by humans. This fundamental design paradigm of BLE is enabled by a range of broadcast advertising modes. While its operational benefits are numerous, the lack of a common time reference in the broadcast mode of BLE has been a fundamental limitation. This work presents and describes CheepSync: a time synchronization service architecture for BLE advertisers. We implement CheepSync on custom designed nRF24Cheep beacon platforms (as broadcasters) and commercial off-the-shelf Android ported smartphones (as passive listeners); and show that the average (single hop) time synchronization accuracy is in the 10 μs range.

10 citations

Journal ArticleDOI
TL;DR: This paper aims to combine the features of watermarking, image encryption as well as image steganography to provide reliable and secure data transmission.
Abstract: Steganography, water marking and encryption are widely used in image processing and communication. A general practice is to use them independently or in combination of two - for e.g. data hiding with encryption or steganography alone. This paper aims to combine the features of watermarking, image encryption as well as image steganography to provide reliable and secure data transmission .The basics of data hiding and encryption are explained. The first step involves inserting the required watermark on the image at the optimum bit plane. The second step is to use an RSA hash to actually encrypt the image. The final step involves obtaining a cover image and hiding the encrypted image within this cover image. A set of metrics will be used for evaluation of the effectiveness of the digital water marking. The list includes Mean Squared Error, Peak Signal to Noise Ratio and Feature Similarity.

1 citations

Proceedings ArticleDOI
01 Dec 2015
TL;DR: Different methods for numerical optimization based tools which are available to automate analog design so that the design in a pseudo sense can simply be recompiled following some changes are explored.
Abstract: Design of analog CMOS circuits is time consuming and very complex. Analog circuits need to often be handcrafted as opposed to software and digital design which can simply be recompiled following a change of parameters. Further, minor changes in design parameters can have unexpected outcomes on system performance, due to which manual design space exploration can be difficult except for most non-trivial analog circuit configurations. In this paper we explore different methods for numerical optimization based tools which are available to automate analog design so that the design in a pseudo sense can simply be recompiled following some changes. We explore genetic algorithms, geometric optimization as well as finding the minimum of constrained nonlinear multivariable functions. The findings provide guidelines to Op-Amp designers looking to automate the parameter selection process.

1 citations


Cited by
More filters
Journal ArticleDOI
15 Mar 2017
TL;DR: The Internet of Things, or the IoT, is an emerging, disruptive technology that enables physical devices to communicate across disparate networks to enable seamless integration of smart grids.
Abstract: The Internet of Things, or the IoT, is an emerging, disruptive technology that enables physical devices to communicate across disparate networks. IP has been the de facto standard for seamless inte ...

88 citations

Proceedings ArticleDOI
07 Dec 2015
TL;DR: The novel features of Bluetooth LE and its applicability in 6LoWPAN networks are discussed and important research questions and pointers for potential improvement are highlighted for its greater impact.
Abstract: The past couple of years have seen a heightened interest in the Internet of Things (IoT), transcending industry, academia and government. As with new ideas that hold immense potential, the optimism of IoT has also exaggerated the underlying technologies well before they can mature into a sustainable ecosystem. While 6LoWPAN has emerged as a disruptive technology that brings IP capability to networks of resource constrained devices, a suitable radio technology for this device class is still debatable. In the recent past, Bluetooth Low Energy (LE) — a subset of the Bluetooth v4.0 stack — has surfaced as an appealing alternative that provides a low-power and loosely coupled mechanism for sensor data collection with ubiquitous units (e.g., smartphones and tablets). When Bluetooth 4.0 was first released, it was not targeted for IP-connected devices but for communication between two neighboring peers. However, the latest release of Bluetooth 4.2 offers features that makes Bluetooth LE a competitive candidate among the available low-power communication technologies in the IoT space. In this paper, we discuss the novel features of Bluetooth LE and its applicability in 6LoWPAN networks. We also highlight important research questions and pointers for potential improvement for its greater impact.

58 citations

Proceedings ArticleDOI
16 Apr 2019
TL;DR: In this article, the authors presented Heartbeats-2-Bits (H2B), which is a system for securely pairing wearable devices by generating a shared secret key from the skin vibrations caused by heartbeat.
Abstract: We present Heartbeats-2-Bits (H2B), which is a system for securely pairing wearable devices by generating a shared secret key from the skin vibrations caused by heartbeat. This work is motivated by potential power saving opportunity arising from the fact that heartbeat intervals can be detected energy-efficiently using inexpensive and power-efficient piezo sensors, which obviates the need to employ complex heartbeat monitors such as Electrocardiogram or Photoplethysmogram. Indeed, our experiments show that piezo sensors can measure heartbeat intervals on many different body locations including chest, wrist, waist, neck and ankle. Unfortunately, we also discover that the heartbeat interval signal captured by piezo vibration sensors has low Signal-to-Noise Ratio (SNR) because they are not designed as precision heartbeat monitors, which becomes the key challenge for H2B. To overcome this problem, we first apply a quantile function-based quantization method to fully extract the useful entropy from the noisy piezo measurements. We then propose a novel Compressive Sensing-based reconciliation method to correct the high bit mismatch rates between the two independently generated keys caused by low SNR. We prototype H2B using off-the-shelf piezo sensors and evaluate its performance on a dataset collected from different body positions of 23 participants. Our results show that H2B has a pairing success rate of 95.6%. We also analyze and demonstrate H2B's robustness against three types of attacks. Finally, our power measurements show that H2B is very power-efficient.

57 citations

Journal ArticleDOI
TL;DR: PISync protocols have better or comparable performance over existing protocols in the WSN literature in terms of rate of convergence and steady-state error with the additional advantages of requiring minimal CPU overhead, memory allocation, and code footprint independent of network size and topology, and of employing blind communication.
Abstract: In this paper, we present a novel control-theoretic time synchronization algorithm, named PISync for synchronizing sensor nodes in wireless sensor networks (WSNs). The PISync algorithm is based on an adaptive proportional–integral controller. It applies a proportional feedback (P) and an integral feedback (I) on the local measured synchronization errors to compensate the differences between the clock offsets and the clock speeds. We present practical flooding-based and fully distributed protocol implementations of the PISync algorithm, and we provide theoretical analysis to highlight the benefits of this approach in terms of improved steady-state error and scalability as compared with existing synchronization algorithms. We show through theoretical analysis, real-world experiments, and simulations that PISync protocols have better or comparable performance over existing protocols in the WSN literature in terms of rate of convergence and steady-state error with the additional advantages of requiring minimal CPU overhead, memory allocation, and code footprint independent of network size and topology, and of employing blind communication.

55 citations

Proceedings ArticleDOI
05 Nov 2018
TL;DR: In this article, a neural network classifier was proposed for human activity recognition using the fast Fourier and discrete wavelet transforms of a textile-based stretch sensor and accelerometer data.
Abstract: Human activity recognition (HAR) has attracted significant research interest due to its applications in health monitoring and patient rehabilitation. Recent research on HAR focuses on using smartphones due to their widespread use. However, this leads to inconvenient use, limited choice of sensors and inefficient use of resources, since smartphones are not designed for HAR. This paper presents the first HAR framework that can perform both online training and inference. The proposed framework starts with a novel technique that generates features using the fast Fourier and discrete wavelet transforms of a textile-based stretch sensor and accelerometer data. Using these features, we design a neural network classifier which is trained online using the policy gradient algorithm. Experiments on a low power IoT device (T1-CC2650 MCU) with nine users show 97.7% accuracy in identifying six activities and their transitions with less than 12.5 mW power consumption.

48 citations