Intermittently-operating embedded computing platforms powered by energy harvesting must frequently checkpoint their computation state. Using non-volatile memory reduces checkpoint size by eliminating the need to checkpoint volatile memory but increases checkpoint frequency to cover Write After Read (WAR) dependencies. Additionally, non-volatile memory is significantly slower to access - while consuming more energy than its volatile counterpart - suggesting the use of a data cache. Unfortunately, existing data cache solutions do not fit the challenges of intermittent computing and often require additional hardware or software to detect WARs. In this paper, we extend the data cache by integrating it with WAR detection - dropping the need for an additional memory tracker. This idea forms the basis of NACHO: a data cache tailored to intermittent computing. NACHO, on average, reduces intermittent computing runtime overhead by 54% compared to state of the art cache-based systems. It also reduces the number of non-volatile memory writes by 82% compared to a data cache-less system, and 18% on average compared to multiple state of the art cache-based systems.@en

Continuous vital sign monitoring is essential for digital healthcare and self-awareness but is hindered by the limited battery life of wearable devices and barriers faced by older adults with low digital literacy. BioPulse, a battery-free patch device, addresses challenges in vital sign monitoring by using sparse sampling and NFC energy transfer to track heart rate, HRV, and blood pressure.@en

The goal of future quantum networks is to enable new internet applications that are impossible to achieve using only classical communication1, 2–3. Up to now, demonstrations of quantum network applications4, 5–6 and functionalities7, 8, 9, 10, 11–12 on quantum processors have been performed in ad hoc software that was specific to the experimental setup, programmed to perform one single task (the application experiment) directly into low-level control devices using expertise in experimental physics. Here we report on the design and implementation of an architecture capable of executing quantum network applications on quantum processors in platform-independent high-level software. We demonstrate the capability of the architecture to execute applications in high-level software by implementing it as a quantum network operating system—QNodeOS—and executing test programs, including a delegated computation from a client to a server13 on two quantum network nodes based on nitrogen-vacancy (NV) centres in diamond14,15. We show how our architecture allows us to maximize the use of quantum network hardware by multitasking different applications. Our architecture can be used to execute programs on any quantum processor platform corresponding to our system model, which we illustrate by demonstrating an extra driver for QNodeOS for a trapped-ion quantum network node based on a single 40Ca+ atom16. Our architecture lays the groundwork for computer science research in quantum network programming and paves the way for the development of software that can bring quantum network technology to society.@en

Continuous monitoring of vital signs has become increasingly important for digital healthcare and enhancing self-awareness. Wearable devices like smartwatches, earbuds, and rings are gaining widespread acceptance for health monitoring. However, two significant challenges remain: (i) the limited battery life of these devices makes them unsustainable for long-term use, and (ii) many older adults, who would benefit most from health monitoring, often face barriers due to limited digital literacy. To address these issues, we introduce BioPulse---a perpetual, patch form-factor device designed for continuous monitoring. BioPulse estimates key parameters for cardiac health such as heart rate, heart rate variability, and blood pressure. By utilising a sparse sampling algorithm alongside NFC-based energy transfer and communication, the system operates without a battery, achieving a 57.9% reduction in power consumption. The system demonstrates a mean absolute error of 5.6 mmHg for systolic blood pressure (SBP) and 4.5 mmHg for diastolic blood pressure (DBP) compared to the ground truth device. This combination ensures a more sustainable and accessible solution for vital signs monitoring.@en

The mouth offers valuable insights into the condition of the human body. Yet, deploying intraoral sensors to measure oral temperature or jaw movements poses challenges in safety and acceptability. Consequently, real-world data for intraoral research is scarce. To address this gap, we leverage the widespread use of dental retainers and enhance them with Densor: an electronic sensing platform requiring only a standard smartphone for charging and data retrieval using a Near Field Communication interface. Its low power architecture enables prolonged sensing on a single charge, making it suitable for sleep studies. It can provide practitioners with feedback on treatment compliance, and is even able to detect if the user is speaking or drinking water. Densor presents an intraoral, actively powered, battery-free platform featuring multi-modal sensors and an extended lifespan.@en

Scaling current quantum communication demonstrations to a large-scale quantum network will require not only advancements in quantum hardware capabilities, but also robust control of such devices to bridge the gap in user demand. Moreover, the abstraction of tasks and services offered by the quantum network should enable platform-independent applications to be executed without the knowledge of the underlying physical implementation. Here we experimentally demonstrate, using remote solid-state quantum network nodes, a link layer, and a physical layer protocol for entanglement-based quantum networks. The link layer abstracts the physical-layer entanglement attempts into a robust, platform-independent entanglement delivery service. The system is used to run full state tomography of the delivered entangled states, as well as preparation of a remote qubit state on a server by its client. Our results mark a clear transition from physics experiments to quantum communication systems, which will enable the development and testing of components of future quantum networks.

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We present an architecture for intermittently-powered wireless communication systems that does not require any changes to the official protocol specification. Our core idea is to save the intermediate state of the wireless protocol to non-volatile memory within each connection interval. The protocol state is then deterministically restored at a predefined (harvested energy-dependent) time, which follows the connection interval. As a case study for our architecture, we introduce FreeBie: a battery-free intermittently-powered Bluetooth Low Energy (BLE) mote. To the best of our knowledge FreeBie is the first battery-free active wireless system that sustains bi-directional communication on intermittent harvested energy. The strength of our architecture is articulated by FreeBie consuming at least 9.5 times less power during device inactivity periods than a state-of-the-art BLE device.

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Debugging and testing battery-free intermittently-powered systems is notoriously difficult. This is not only due to the additional complexity of maintaining state through power failures but also due to the lack of proper tools to test and debug these systems. As a solution, we present DIPS: a fully-featured hardware debugger for battery-free intermittently-powered systems capable of automatically verifying memory and peripheral state between power failures. Our solution seamlessly integrates an emulator allowing for emulation of any power scenario to the device under test. This allows our debugger to pause emulation and program execution when debugging or when state restoration issues are detected. Our new system is built around GNU Debugger (GDB): a widely-used debugging tool. Therefore, DIPS allows for a debugging process identical to state-of-the-art debuggers for continuously-powered devices. User studies found that our debugger is easy and intuitive to use. It allows embedded system developers to find bugs quicker in code written for battery-free devices. With our debugger we found unseen errors in state-of-the-art software frameworks for intermittently-powered systems.@en

Intermittently operating embedded computing platforms powered by energy harvesting require software frameworks to protect from errors caused by Write After Read (WAR) dependencies. A powerful method of code protection for systems with non-volatile main memory utilizes compiler analysis to insert a checkpoint inside each WAR violation in the code. However, such software frameworks are oblivious to the code structure - -and therefore, inefficient - -when many consecutive WAR violations exist. Our insight is that by transforming the input code, i.e., moving individual write operations from unique WARs close to each other, we can significantly reduce the number of checkpoints. This idea is the foundation for WARio: a set of compiler transformations for efficient code generation for intermittent computing. WARio, on average, reduces checkpoint overhead by 58%, and up to 88%, compared to the state of the art across various benchmarks.

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Any future mobile electronic device with which a user interacts (smartphone, hand-held game console) should not pollute our planet. Consequently, designers need to rethink how to build mobile devices with fewer components that negatively impact the environment (by replacing batteries with energy harvesting sources) while not compromising the user experience quality. This article addresses the challenges of battery-free mobile interaction and presents the first battery-free, personal mobile gaming device powered by energy harvested from gamer actions and sunlight. Our design implements a power failure resilient Nintendo Game Boy emulator that can run off-the-shelf classic Game Boy games like Tetris or Super Mario Land. Beyond a fun toy, our design represents the first battery-free system design for continuous user attention despite frequent power failures caused by intermittent energy harvesting.@en

Battery-powered beacon devices introduce high maintenance costs due to the finite operation time dictated by the fixed capacity of their batteries. To tackle this problem we propose FreeBLE: an indoor beacon system aimed at operating perpetually without batteries. We propose three methods to increase the utilization efficiency of harvested Radio Frequency (RF) energy in the beacon system, by which the energy consumption level becomes low enough to fit within the energy harvesting budget. We implement FreeBLE using off-the-shelf Bluetooth Low Energy (BLE) and RF energy harvesting devices, and test FreeBLE in a laboratory environment. Our results show that FreeBLE enables perpetual operation in an indoor deployment of RF-powered BLE beacon devices.

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The CHIIoT workshops bring together researchers and practitioners from industrial design, computer science, and electrical engineering working on new challenges in industry and academia. The workshop will provide a platform for participants to review and discuss challenges and opportunities in the intersection of computer-human interaction and the internet of things, focusing on human-centered applications using emerging connectivity and sensing technologies. We aim to jointly develop a design space and identify opportunities for future research.

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We present ReproducedPapers.org : an open online repository for teaching and structuring machine learning reproducibility. We evaluate doing a reproduction project among students and the added value of an online reproduction repository among AI researchers. We use anonymous self-assessment surveys and obtained 144 responses. Results suggest that students who do a reproduction project place more value on scientific reproductions and become more critical thinkers. Students and AI researchers agree that our online reproduction repository is valuable.

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Age of Information (AoI) is a key metric to understand data freshness in Internet of Things (IoT) devices. In this paper we analyse an intermittently—powered IoT sensor-with mixed-memory (volatile and non-volatile) architecture—that uses a Time-Dependent Checkpointing (TDC) scheme. We derive the average Peak Age of Information (PAoI) and average AoI of the system, and use these metrics to understand which device parameters most significantly influence performance. We go on to consider how the average PAoI of a mixed-memory system compares with entirely volatile or entirely non-volatile architecture, and also introduce an alternative TDC strategy to improve system resilience in unpredictable environmental conditions.@en

The CHIIoT workshop series brings together researchers and practitioners from human-computer interaction (HCI) design, computer science, and electrical engineering working on new challenges in industry and academia. In EICS 2021, This workshop will provide a platform for participants to review and discuss challenges and opportunities in the intersection of computer-human interaction and the internet of things, focusing on human-centered applications using emerging connectivity and sensing technologies. We aim to jointly develop a design space and identify opportunities for future research.

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Energy-harvesting devices have enabled Internet of Things applications that were impossible before. One core challenge of batteryless sensors that operate intermittently is reliable timekeeping. State-of-the-art low-power real-time clocks suffer from long start-up times (order of seconds) and have low timekeeping granularity (tens of milliseconds at best), often not matching timing requirements of devices that experience numerous power outages per second. Our key insight is that time can be inferred by measuring alternative physical phenomena, like the discharge of a simple RC circuit, and that timekeeping energy cost and accuracy can be modulated depending on the run-time requirements. We achieve these goals with a multi-tier timekeeping architecture, named Cascaded Hierarchical Remanence Timekeeper (CHRT), featuring an array of different RC circuits to be used for dynamic timekeeping requirements. The CHRT and its accompanying software interface are embedded into a fresh batteryless wireless sensing platform, called Botoks, capable of tracking time across power failures. Low start-up time (max 5 ms), high resolution (up to 1 ms) and run-time reconfigurability are the key features of our timekeeping platform. We developed two time-sensitive batteryless applications to demonstrate the approach: a bicycle analytics tool-where the CHRT is used to track time between revolutions of a bicycle wheel, and wireless communication-where the CHRT enables radio synchronization between two intermittently-powered sensors.

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Tiny energy harvesting sensors that operate intermittently, without batteries, have become an increasingly appealing way to gather data in hard to reach places at low cost. Frequent power failures make forward progress, data preservation and consistency, and timely operation challenging. Unfortunately, state-of-the-art systems ask the programmer to solve these challenges, and have high memory overhead, lack critical programming features like pointers and recursion, and are only dimly aware of the passing of time and its effect on application quality. We present Time-sensitive Intermittent Computing System (TICS), a new platform for intermittent computing, which provides simple programming abstractions for handling the passing of time through intermittent failures, and uses this to make decisions about when data can be used or thrown away. Moreover, TICS provides predictable checkpoint sizes by keeping checkpoint and restore times small and reduces the cognitive burden of rewriting embedded code for intermittency without limiting expressibility or language functionality, enabling numerous existing embedded applications to run intermittently.

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Intermittent computing could be combined with low-powered visible light communication systems to facilitate novel sensor networks. This position paper provides a framework for future research by highlighting synergies between the technologies, and explores how techniques developed in intermittently-powered systems can be used to provide enhanced stability to ultra-low power visible light communication.

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We present ENGAGE, the first battery-free, personal mobile gaming device powered by energy harvested from the gamer actions and sunlight. Our design implements a power failure resilient Nintendo Game Boy emulator that can run off-the-shelf classic Game Boy games like Tetris or Super Mario Land. This emulator is capable of intermittent operation by tracking memory usage, avoiding the need for always checkpointing all volatile memory, and decouples the game loop from user interface mechanics allowing for restoration after power failure. We build custom hardware that harvests energy from gamer button presses and sunlight, and leverages a mixed volatility memory architecture for efficient intermittent emulation of game binaries. Beyond a fun toy, our design represents the first battery-free system design for continuous user attention despite frequent power failures caused by intermittent energy harvesting. We tackle key challenges in intermittent computing for interaction including seamless displays and dynamic incentive-based gameplay for energy harvesting. This work provides a reference implementation and framework for a future of battery-free mobile gaming in a more sustainable Internet of Things.

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