Felix Sutton

GPS-Equipped wireless sensor network node for high-accuracy positioning applications

This work presents the design, implementation, and end-to-end system concept and integration of a wireless data acquisition system for high-accuracy positioning applications. A wireless network of GPS-equipped sensor nodes, built from low-cost off-the-shelf components, autonomously acquires L1 GPS data for Differential GPS (DGPS) processing of raw satellite information. The differential processing on the backend infrastructure achieves relative position and motion of individual nodes within the network with sub-centimeter accuracy. Leveraging on global GPS time synchronization, network-wide synchronized measurement scheduling, and duty-cycling coupled with power optimized operation and robustness against harsh environmental conditions make the introduced sensor node well suited for monitoring or surveying applications in remote areas. Unattended operation, high spatial and temporal coverage and low cost distinguish this approach from traditional, very costly and time consuming approaches. The prototype data acquisition system based on a low-power mote equipped with a commercially available GPS module has been successfully implemented and validated in a testbed setting.

Dynamic power management for long-term energy neutral operation of solar energy harvesting systems

In this work we consider a real-world environmental monitoring scenario that requires uninterrupted system operation over time periods on the order of multiple years. To achieve this goal, we propose a novel approach to dynamically adjust the systems performance level such that energy neutral operation, and thus long-term uninterrupted operation can be achieved. We first consider the annual dynamics of the energy source to design an appropriate power subsystem (i.e., solar panel size and energy store capacity), and then dynamically compute the long-term sustainable performance level at runtime. We show through trace-driven simulations using eleven years of real-world data that our approach outperforms existing predictive, e.g., EWMA, WCMA, and reactive, e.g., ENO-MAX, approaches in terms of average performance level by up to 177%, while reducing duty-cycle variance by up to three orders of magnitude. We further demonstrate the benefits of the dynamic power management scheme using a wireless sensor system deployed for environmental monitoring in a remote, high-alpine environment as a case study. A performance evaluation over two years reveals that the dynamic power management scheme achieves a two-fold improvement in system utility when compared to only applying appropriate capacity planning.

Zippy: On-Demand Network Flooding

In this paper, we tackle the challenge of rapidly disseminating rare events through a multi-hop network, while achieving unprecedented energy-efficiency. Contrary to state-of-the-art approaches, we circumvent the undesirable trade-offs associated with low-power duty-cycled protocols and backscatter technologies, and demonstrate a paradigm shift in low-power protocol design. We present Zippy, an on-demand flooding technique that provides robust asynchronous network wake-up, fine-grained per-hop synchronization and efficient data dissemination by leveraging low-complexity transmitter and receiver hardware. We are the first to demonstrate the on-demand flooding of rare events through a multi-hop network with end-to-end latencies of tens of milliseconds, while dissipating less than 10 microwatts during periods of inactivity. We present a prototype implementation of our proposed approach using a wireless sensor platform constructed from commercially available components. We extensively evaluate Zippys performance in a laboratory setting and in an indoor testbed.

Bolt: A Stateful Processor Interconnect

The wireless sensor network community is currently undergoing a platform paradigm shift, moving away from classical single-processor motes toward heterogeneous multi-processor architectures. These emerging platforms promise efficient concurrent processing with energy-proportional system performance. The use of shared interconnects and shared memory for inter-processor communication, however, causes interference in the time, power, and clock domains, which prevents designers from fully harnessing these benefits. We thus designed Bolt, the first ultra-low-power processor interconnect for the compositional construction of heterogeneous wireless embedded platforms. This paper presents the architectural blueprint for interconnecting two independent processors, while enabling asynchronous inter-processor communication with predictable run-time behavior. We detail a prototype implementation of Bolt, and apply formal methods to analytically derive bounds on the execution time of its message passing operations. Experiments with a custom-built dual-processor platform show that our Bolt prototype incurs a negligible power overhead relative to state-of-the-art platforms, offers predictable message passing with empirical bounds that match the analytical ones to within a few clock cycles, and achieves a high throughput of up to 3.3 Mbps.

Towards Enabling Uninterrupted Long-Term Operation of Solar Energy Harvesting Embedded Systems

In this work we describe a systematic approach to power subsystem capacity planning for solar energy harvesting embedded systems, such that uninterrupted, long-term (i.e., multiple years) operation at a predefined performance level may be achieved. We propose a power subsystem capacity planning algorithm based on a modified astronomical model to approximate the harvestable energy and compute the required battery capacity for a given load and harvesting setup. The energy availability model takes as input the deployment sites latitude, the panel orientation and inclination angles, and an indication of expected meteorological and environmental conditions.We validate the models ability to predict the harvestable energy with power measurements of a solar panel. Through simulation with 10 years of solar traces from three different geographical locations and four harvesting setups, we demonstrate that our approach achieves 100% availability at up to 53% smaller batteries when compared to the state-of-the-art.

A reliable wireless nurse call system: overview and pilot results from a summer camp for teenagers with duchenne muscular dystrophy

We present the design of a reliable nurse call system based on wireless embedded devices and multi-hop protocols. Our work is motivated by the need for such system during annual summer camps for people with muscular dystrophy and the lack of suitable alternative solutions. We describe how our prototype meets the reliability and real-time requirements of such system, and report on results from a two-week deployment during a camp with 13 affected boys in July 2013.

BLITZ: A Network Architecture for Low Latency and Energy-efficient Event-triggered Wireless Communication

We consider wireless sensing systems where an event must be rapidly communicated from its source to a remote host. Due to the non-deterministic nature of event arrivals, multi-hop dissemination using state-of-the-art radio duty-cycled protocols leads to a trade-off between latency and energy efficiency. In order to circumvent this system design constraint, we propose BLITZ, a network architecture that leverages interference-based flooding to rapidly wake-up the multi-hop network and disseminate the event on-demand. We show that by embracing network flooding in combination with simultaneous transmissions, we can realize low latency event-triggered multi-hop communication without having to sacrifice energy efficiency. We introduce an analytical model to quantify the limits of our approach, present a prototype implementation using a multi-radio wireless sensor platform, and experimentally evaluate BLITZ in a laboratory setting and in an indoor testbed.

Wake-up flooding: an asynchronous network flooding primitive

We present a new technique for overcoming the fundamental trade-off between energy-efficiency and end-to-end packet latency pervading all event-triggered wireless sensing applications. Instead of applying popular synchronous or pseudo-asynchronous protocols, we leverage state-of-the-art wake-up receivers to facilitate purely asynchronous rendezvous. We then extend the per-hop asynchrony into a multi-hop flooding primitive, termed Wake-up Flooding. We describe the underpinnings of the flooding primitive and present preliminary results of wake-up flooding implemented on a custom dual-radio wireless sensing platform deployed in an indoor testbed.

Mitigating Erroneous Wake-ups

We propose a novel method for mitigating erroneous wake-ups that are commonly associated with ultra-low power wake-up receivers. Recent research in low-power protocols has demonstrated significant improvements in energy-efficiency by employing ultra-low power wake-up receivers. However, due to the low-complexity receiver structures adopted, wake-up receivers are susceptible to external interference, which can cause the detection of non-existent wake-ups. The occurrence of these erroneous wake-ups wastes precious energy resources, thereby negating the potential energy savings in employing wake-up receivers. We address this challenging problem by extracting time-domain features from the output of the wake-up receiver, and construct a classifier to distinguish between correct and erroneous wake-ups. We describe the design of the proposed wake-up classifier and present preliminary results.

On platforms for CPS: adaptive, predictable and efficient

If visions and forecasts of industry come true then we will be soon surrounded by billions of interconnected embedded devices. We will interact with them in a cyber-human symbiosis, they will not only observe us but also our environment, and they will be part of many visible and ubiquitous objects around us. The information that is collectively gathered and analyzed is supposed to help us in our daily live, in making faithful decisions, but it will also directly be used for actuation and it will cause changes by means of local and global control loops.