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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.

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.

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.

Poster Abstract: A Heterogeneous System Architecture for Event-Triggered Wireless Sensing

We present a heterogeneous system architecture for event-triggered wireless sensing capable of supporting high spatial resolution. The key differentiator between the proposed architecture and alternative state-of-the-art approaches is the ability to simultaneously maximize operational lifetime and minimize end-to-end latency of detected events. Our novel architecture takes advantage of heterogeneity with respect to the operation of the wireless communication protocol and the construction of the sensing platform. We present a two-hop proof of concept implementation, exhibiting end-to-end latencies on the order of tenths of a second, while dissipating on the order of tens of microwatts during periods of inactivity.

Demo: Building Reliable Wireless Embedded Platforms using the Bolt Processor Interconnect

We demonstrate the capabilities of Bolt, an ultra-low-power processor interconnect for the composable construction of new multi-processor wireless embedded platforms. Bolt provides asynchronous bidirectional communication between two processors with predictable message transfer times. In this way, Bolt solves the resource interference problem inherent in todays wireless embedded platforms, enabling simpler and more robust system designs with minimal resource overhead. Using our Bolt prototype implemented on a state-of-the-art microcontroller, we demonstrate Bolts composability and decoupling in time, power, and clock domains.

Predictable wireless embedded platforms

Resource interference is a fundamental barrier to realizing predictable wireless embedded systems. We address this problem by (i) partitioning application and communication tasks onto dedicated platforms, and (ii) designing a platform interconnect to facilitate asynchronous message exchange with predictable run-time behavior. We motivate the need for this platform interconnect, termed Bolt, and describe a prototype implementation. Evaluation results indicate that the developed platform interconnect exhibits tightly bounded run-time execution with low jitter, and a negligible resource overhead with respect to state-of-the-art application and communication platforms.

Demonstration abstract: automatic speech recognition for resource-constrained embedded systems

We demonstrate the design and implementation of a prototype hardware/software architecture for automatic single word speech recognition on resource-constrained embedded de vices. Designed as a voice-activated extension of an existing wireless nurse call system, our prototype device continually listens for a pre-recorded keyword, and uses speech recognition techniques to trigger an alert upon detecting a match. Preliminary experiments show that our prototype achieves a high average detection rate of 96%, while only dissipating 28.5 mW for continuous audio sampling and duty-cycled speech recognition.