Adaptive Synchronization of Robotic Sensor Networks

The main focus of recent time synchronization research is developing power-efficient synchronization methods that meet pre-defined accuracy requirements. However, an aspect that has been often overlooked is the high dynamics of the network topology due to the mobility of the nodes. Employing existing flooding-based and peer-to-peer synchronization methods, are networked robots still be able to adapt themselves and self-adjust their logical clocks under mobile network dynamics? In this paper, we present the application and the evaluation of the existing synchronization methods on robotic sensor networks. We show through simulations that Adaptive Value Tracking synchronization is robust and efficient under mobility. Hence, deducing the time synchronization problem in robotic sensor networks into a dynamic value searching problem is preferable to existing synchronization methods in the literature.Comment: First International Workshop on Robotic Sensor Networks part of Cyber-Physical Systems Week, Berlin, Germany, 14 April 201

Safe and Secure Wireless Power Transfer Networks: Challenges and Opportunities in RF-Based Systems

RF-based wireless power transfer networks (WPTNs) are deployed to transfer power to embedded devices over the air via RF waves. Up until now, a considerable amount of effort has been devoted by researchers to design WPTNs that maximize several objectives such as harvested power, energy outage and charging delay. However, inherent security and safety issues are generally overlooked and these need to be solved if WPTNs are to be become widespread. This article focuses on safety and security problems related WPTNs and highlight their cruciality in terms of efficient and dependable operation of RF-based WPTNs. We provide a overview of new research opportunities in this emerging domain.Comment: Removed some references, added new references, corrected typos, revised some sections (mostly I-B and III-C

ETAP: Energy-aware Timing Analysis of Intermittent Programs

Energy harvesting battery-free embedded devices rely only on ambient energy harvesting that enables stand-alone and sustainable IoT applications. These devices execute programs when the harvested ambient energy in their energy reservoir is sufficient to operate and stop execution abruptly (and start charging) otherwise. These intermittent programs have varying timing behavior under different energy conditions, hardware configurations, and program structures. This paper presents Energy-aware Timing Analysis of intermittent Programs (ETAP), a probabilistic symbolic execution approach that analyzes the timing and energy behavior of intermittent programs at compile time. ETAP symbolically executes the given program while taking time and energy cost models for ambient energy and dynamic energy consumption into account. We evaluated ETAP on several intermittent programs and compared the compile-time analysis results with executions on real hardware. The results show that ETAP's normalized prediction accuracy is 99.5%, and it speeds up the timing analysis by at least two orders of magnitude compared to manual testing.Comment: Corrected typos in the previous submissio

Efficient Time Synchronization in a Wireless Sensor Network by Adaptive Value Tracking

International audienceA desirable flooding-based time synchronization protocol in Wireless Sensor Networks (WSNs) should neither demand fast propagation of up-to-date time information nor keeping track of the neighboring nodes. Moreover, such a protocol is strictly required to have low computational and communication overhead as well as small memory footprint. Would there be a protocol which meets these requirements' We answer this question positively by introducing a novel time synchronization protocol whose main component is " adaptive-value tracking ". Thanks to this component , each sensor node synchronizes the rate of its clock to that of a reference clock through successive feedbacks with a considerably low computational and memory overhead. By adjusting time offset of the rate-synchronized clocks, the network-wide synchronization is established even without demanding rapid propagation of the reference clock and keeping track of the neighboring nodes. In the light of our experimental evaluation in a testbed of 20 MICAz sensor nodes, we observed that the proposed protocol provides similar synchronization under the same communication frequency with an approximately 97% less CPU overhead and 80% less memory allocation compared to the recent flooding based time synchronization protocols in WSNs. Index Terms—Distributed algorithms, flooding based time synchronization , adaptive value tracking (AVT)