Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies
Recent advancements in object-tracking technologies can turn mundane constructive assemblies into... more Recent advancements in object-tracking technologies can turn mundane constructive assemblies into Tangible User Interfaces (TUI) media. Users rely on instructions or their own creativity to build both permanent and temporary structures out of such objects. However, most existing object-tracking technologies focus on tracking structures as monoliths, making it impossible to infer and track the user's assembly process and the resulting structures. Technologies that can track the assembly process often rely on specially fabricated assemblies, limiting the types of objects and structures they can track. Here, we present StructureSense, a tracking system based on passive UHF-RFID sensing that infers constructive assembly structures from object motion. We illustrated StructureSense in two use cases (as guided instructions and authoring tool) on two different constructive sets (wooden lamp and Jumbo Blocks), and evaluated system performance and usability. Our results showed the feasibi...
A common problem for healthcare providers is accurately tracking patients’ adherence to medicatio... more A common problem for healthcare providers is accurately tracking patients’ adherence to medication and providing real-time feedback on the management of their medication regimen. This is a particular problem for eye drop medications, as the current commercially available monitors focus on measuring adherence to pills, and not to eye drops. This work presents an intelligent bottle sleeve that slides onto a prescription eye drop medication bottle. The intelligent sleeve is capable of detecting eye drop use, measuring fluid level, and sending use information to a healthcare team to facilitate intervention. The electronics embedded into the sleeve measure fluid level, dropper orientation, the state of the dropper top (on/off), and rates of angular motion during an application. The sleeve was tested with ten patients (age ≥65) and successfully identified and timestamped 94% of use events. On-board processing enabled event detection and the measurement of fluid levels at a 0.4 mL resoluti...
Proceedings of the Twenty-First International Conference on Architectural Support for Programming Languages and Operating Systems, 2016
Energy-autonomous computing devices have the potential to extend the reach of computing to a scal... more Energy-autonomous computing devices have the potential to extend the reach of computing to a scale beyond either wired or battery-powered systems. However, these devices pose a unique set of challenges to application developers who lack both hardware and software support tools. Energy harvesting devices experience power intermittence which causes the system to reset and power-cycle unpredictably, tens to hundreds of times per second. This can result in code execution errors that are not possible in continuouslypowered systems and cannot be diagnosed with conventional debugging tools such as JTAG and/or oscilloscopes. We propose the Energy-interference-free Debugger, a hardware and software platform for monitoring and debugging intermittent systems without adversely effecting their energy state. The Energy-interference-free Debugger recreates a familiar debugging environment for intermittent software and augments it with debugging primitives for effective diagnosis of intermittence bugs. Our evaluation of the Energy-interference-free Debugger quantifies its energy-interference-freedom and shows its value in a set of debugging tasks in complex test programs and several real applications, including RFID code and a machine-learningbased activity recognition system.
We argue that sensing and computation platforms that leverage RFID technology can realize "smart-... more We argue that sensing and computation platforms that leverage RFID technology can realize "smart-dust" applications that have eluded the sensor network community. RFID sensor networks (RSNs), which consist of RFID readers and RFID sensor nodes (WISPs), extend RFID to include sensing and bring the advantages of small, inexpensive and long-lived RFID tags to wireless sensor networks. We describe sample applications suited to the space between existing sensor networks and RFID. We highlight the research challenges in realizing RSNs such as the use of intermittent power and RFID protocols suited to sensor queries.
Proceedings of the ACM on Human-Computer Interaction
Augmented Reality (AR) has the potential to leverage environmental information to better facilita... more Augmented Reality (AR) has the potential to leverage environmental information to better facilitate distributed collaboration, however, such applications are difficult to develop. We present XSpace, a toolkit for creating spatially-aware AR applications for distributed collaboration. Based on a review of existing applications and developer tools, we design XSpace to support three methods for creating shared virtual spaces, each emphasizing a different aspect: shared objects, user perspectives, and environmental meshes. XSpace implements these methods in a developer toolkit, and also provides a set of complimentary visual authoring tools to allow developers to preview a variety of configurations for a shared virtual space. We present five example applications to illustrate that XSpace can support the development of a rich set of collaborative AR experiences that are difficult to produce with current solutions. Through XSpace, we discuss implications for future application design, inc...
Proceedings of the ACM on Human-Computer Interaction
Pervasive and interactive displays promise to present our digital content seamlessly throughout o... more Pervasive and interactive displays promise to present our digital content seamlessly throughout our environment. However, traditional display technologies do not scale to room-wide applications due to high per-unit-area costs and the need for constant wired power and data infrastructure. This research proposes the use of photochromic paint as a display medium. Applying the paint to any surface or object creates ultra-low-cost displays, which can change color when exposed to specific wavelengths of light. We develop new paint formulations that enable wide area application of photochromic material. Along with a specially modified wide-area laser projector and depth camera that can draw custom images and create on-demand, room-wide user interfaces on photochromic enabled surfaces. System parameters such as light intensity, material activation time, and user readability are examined to optimize the display. Results show that images and user interfaces can last up to 16 minutes and can b...
Proceedings of the 28th Annual International Conference on Mobile Computing And Networking
Magnetic sensing is emerging as an enabling technology for various engaging applications. Represe... more Magnetic sensing is emerging as an enabling technology for various engaging applications. Representative use cases include highaccuracy posture tracking, human-machine interaction, and haptic sensing. This technology uses multiple MEMS magnetometers to capture the changing magnetic field at a close distance. However, magnetometers are susceptible to real-world disturbances, such as hard-and soft-iron effects. As a result, users need to perform a cumbersome and lengthy calibration process frequently, severely limiting the usability of magnetic tracking. To remove/mitigate this limitation, we propose MAGIC (MAGnetometer automatIc Calibration), a systematic framework to automatically calibrate both soft-and hard-iron disturbances for a MEMS magnetometer array. To minimize the need for user intervention, we introduce a novel auto-triggering module. Unlike the legacy manual calibration method, MAGIC achieves superior calibration performance (e.g., for tracking applications) with minimal user attention. Via empirical studies, we show MAGIC also incurs marginal overhead and cost, such as a total energy cost of 0.108 J.
IEEE Transactions on Dependable and Secure Computing
Emerging ultra-low-power tiny scale computing devices run on harvested energy, are intermittently... more Emerging ultra-low-power tiny scale computing devices run on harvested energy, are intermittently powered, have limited computational capability, and perform sensing and actuation functions under the control of a dedicated firmware operating without the supervisory control of an operating system. Wirelessly updating or patching firmware of such devices is inevitable. We consider the challenging problem of simultaneous and secure firmware updates or patching for a typical class of such devices-Computational Radio Frequency Identification (CRFID) devices. We propose Wisecr , the first secure and simultaneous wireless code dissemination mechanism to multiple devices that prevents malicious code injection attacks and intellectual property (IP) theft, whilst enabling remote attestation of code installation. Importantly, Wisecr is engineered to comply with existing ISO compliant communication protocol standards employed by CRFID devices and systems. We comprehensively evaluate Wisecr 's overhead, demonstrate its implementation over standards compliant protocols, analyze its security, implement an end-to-end realization with popular CRFID devices and open-source the complete software package on GitHub.
2019 IEEE International Conference on Pervasive Computing and Communications (PerCom, 2019
Falls have serious consequences and are prevalent in acute hospitals and nursing homes caring for... more Falls have serious consequences and are prevalent in acute hospitals and nursing homes caring for older people. Most falls occur in bedrooms and near the bed. Technological interventions to mitigate the risk of falling aim to automatically monitor bed-exit events and subsequently alert healthcare personnel to provide timely supervisions. We observe that frequency-domain information related to patient activities exist predominantly in very low frequencies. Therefore, we recognise the potential to employ a low resolution acceleration sensing modality in contrast to powering and sensing with a conventional MEMS (Micro Electro Mechanical System) accelerometer. Consequently, we investigate a batteryless sensing modality with low cost wirelessly powered Radio Frequency Identification (RFID) technology with the potential for convenient integration into clothing, such as hospital gowns. We design and build a passive accelerometerbased RFID sensor embodiment-ID-Sensor-for our study. The sensor design allows deriving ultra low resolution acceleration data from the rate of change of unique RFID tag identifiers in accordance with the movement of a patient's upper body. We investigate two convolutional neural network architectures for learning from raw RFID-only data streams and compare performance with a traditional shallow classifier with engineered features. We evaluate performance with 23 hospitalized older patients. We demonstrate, for the first time and to the best of knowledge, that: i) the low resolution acceleration data embedded in the RF powered ID-Sensor data stream can provide a practicable method for activity recognition; and ii) highly discriminative features can be efficiently learned from the raw RFID-only data stream using a fully convolutional network architecture.
Proceedings of the 2018 ACM International Joint Conference and 2018 International Symposium on Pervasive and Ubiquitous Computing and Wearable Computers, 2018
Most existing wireless power transfer (WPT) solutions are limited to 2-D configurations, which li... more Most existing wireless power transfer (WPT) solutions are limited to 2-D configurations, which limits mobility when charging electronics. What is needed are 3-D WPT, which can deliver power anywhere in large volumes (e.g., factories, rooms, toolbox, etc). WPT using quasistatic cavity resonators (QSCR) proposed a route towards truly ubiquitous WPT, which safely charges devices as they enter a WPT enabled space. However, several drawbacks exist to this approach such as the need for a central pole and the spatially non-uniform power availability. To address these issues, we demonstrate a WPT system based on "multimode" QSCR [4]; this structure possess two resonant modes: pole dependent (PD) mode, which resembles the previous QSCR work and pole independent (PI) mode, which works whether or not the pole exist. This structure enables two operations: (i) pole-less operation, which works to the same degree as the previous QSCR without the central pole and (ii) dual-mode operation, which although requires the central pole, enables high-efficiency WPT all over the volume.
2019 IEEE International Conference on RFID (RFID), 2019
Augmented reality (AR) promises to revolutionize the way people interact with their surroundings ... more Augmented reality (AR) promises to revolutionize the way people interact with their surroundings by seamlessly overlaying virtual information onto the physical world. To improve the quality of such information, AR systems need to identify the object with which the user is interacting. AR systems today heavily rely on computer vision for object identification; however, state-of-the-art computer vision systems can only identify the general object categories, rather than their precise identity. In this work, we propose IDCam, a system that fuses RFID and computer vision for precise item identification in AR objectoriented interactions. IDCam simultaneously tracks users' hands using a depth camera and generates motion traces for RFIDtagged objects. The system then correlates traces from vision and RFID to match item identities with user interactions. We tested our system through a simulated retail scenario where 5 participants interacted with a clothing rack simultaneously. In our evaluation study deployed in a lab environment, IDCam identified item interactions with an accuracy of 82.0% within 2 seconds.
2019 IEEE International Conference on RFID (RFID), 2019
The Internet of Things (IoT) promises to revolutionize the way people interact with their surroun... more The Internet of Things (IoT) promises to revolutionize the way people interact with their surrounding environment and the objects within it by creating a ubiquitous network of physical devices. However, recent advancements have been focused on creating battery-powered electronics. There remains a huge gap between the collection of smart devices and the massive number of everyday physical objects. In this work, we bridge this gap by enhancing the sensing capabilities of everyday objects using commercial long-range RFID. We apply signal processing and machine learning techniques towards its communication channel parameters to detect the presence of users and to understand their daily activities. Different from prior work, our system can adapt to different environments and objects types. In a naturalistic user study deployed in a home environment, IDAct detected user presence with an F1 score of 96.7% and recognizes 24 different daily activities with an F1 score of 82.8%.
Proceedings of the 27th Annual International Conference on Mobile Computing and Networking, 2021
Figure 1: MagX provides a wearable and untethered sensing module, with customizable array sizes a... more Figure 1: MagX provides a wearable and untethered sensing module, with customizable array sizes and versatile form factors by using passive magnets. (A) MagX with three different sensor array sizes; (B) three form factors with different magnet configurations. Both images are on the same scale.
Proceedings of the 2018 CHI Conference on Human Factors in Computing Systems, 2018
Human environments are typified by walls-homes, offices, schools, museums, hospitals and pretty m... more Human environments are typified by walls-homes, offices, schools, museums, hospitals and pretty much every indoor context one can imagine has walls. In many cases, they make up a majority of readily accessible indoor surface area, and yet they are static-their primary function is to be a wall, separating spaces and hiding infrastructure. We present Wall++, a low-cost sensing approach that allows walls to become a smart infrastructure. Instead of merely separating spaces, walls can now enhance rooms with sensing and interactivity. Our wall treatment and sensing hardware can track users' touch and gestures, as well as estimate body pose if they are close. By capturing airborne electromagnetic noise, we can also detect what appliances are active and where they are located. Through a series of evaluations, we demonstrate Wall++ can enable robust room-scale interactive and context-aware applications.
IEEE Transactions on Dependable and Secure Computing, 2019
The simplicity of deployment and perpetual operation of energy harvesting devices provides a comp... more The simplicity of deployment and perpetual operation of energy harvesting devices provides a compelling proposition for a new class of edge devices for the Internet of Things. In particular, Computational Radio Frequency Identification (CRFID) devices are an emerging class of battery free, computational, sensing enhanced devices that harvest all of their energy for operation. Despite wireless connectivity and powering, secure wireless firmware updates remains an open challenge for CRFID devices due to: intermittent powering, limited computational capabilities, and the absence of a supervisory operating system. We present, for the first time, a secure wireless code dissemination (SecuCode) mechanism for CRFIDs by entangling a device intrinsic hardware security primitive-Static Random Access Memory Physical Unclonable Function (SRAM PUF)-to a firmware update protocol. The design of SecuCode: i) overcomes the resource-constrained and intermittently powered nature of the CRFID devices; ii) is fully compatible with existing communication protocols employed by CRFID devices-in particular, ISO-18000-6C protocol; and ii) is built upon a standard and industry compliant firmware compilation and update method realized by extending a recent framework for firmware updates provided by Texas Instruments. We build an end-to-end SecuCode implementation and conduct extensive experiments to demonstrate standards compliance, evaluate performance and security.
Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies, 2018
The rise of the Internet of Things (IoT) has led to a significant increase in the number of conne... more The rise of the Internet of Things (IoT) has led to a significant increase in the number of connected devices that stream data in our homes, offices and industrial spaces. However, as the number of these devices increases, the costs of actively maintaining and replacing batteries becomes prohibitive at scale. Recent work on Quasistatic Cavity Resonance (QSCR), offers the possibility of seamless wireless power transfer (WPT) to receivers placed anywhere inside large indoor spaces. This work aims to solve two unexplored and critical missing pieces needed to realize this vision of ubiquitous WPT. First, we demonstrate a full end-to-end QSCR-based WPT system that is capable of simultaneously charging multiple custom designed nodes nearly anywhere in the 4.9 m x 4.9 m x 2.3 m test room. Second, this work utilizes the WPT mechanism as a communication channel, where nodes communicate with a centralized reader and to each other via load modulation. Through analysis and experiments, the prop...
The Journal of heart and lung transplantation : the official publication of the International Society for Heart Transplantation, Jan 11, 2018
Models of power delivery within an intact organism have been limited to ionizing radiation and, t... more Models of power delivery within an intact organism have been limited to ionizing radiation and, to some extent, sound and magnetic waves for diagnostic purposes. Traditional electrical power delivery within the intact human body relies on implanted batteries that limit the amount and duration of delivered power. The efficiency of current battery technology limits the substantial demands required, such as continuous operation of an implantable artificial heart pump within a human body. The fully implantable, miniaturized, Free-range Resonant Electrical Energy Delivery (FREE-D) system, compatible with any type of ventricular assist device (VAD), has been tested in a swine model (HVAD) for up to 3hours. Key features of the system, the use of high-quality factor (Q) resonators together with an automatic tuning scheme, were tested over an extended operating range. Temperature changes of implanted components were measured to address safety and regulatory concerns of the FREE-D system in t...
Wireless power delivery has the potential to seamlessly power our electrical devices as easily as... more Wireless power delivery has the potential to seamlessly power our electrical devices as easily as data is transmitted through the air. However, existing solutions are limited to near contact distances and do not provide the geometric freedom to enable automatic and unaided charging. We introduce quasistatic cavity resonance (QSCR), which can enable purposebuilt structures, such as cabinets, rooms, and warehouses, to generate quasistatic magnetic fields that safely deliver kilowatts of power to mobile receivers contained nearly anywhere within. A theoretical model of a quasistatic cavity resonator is derived, and field distributions along with power transfer efficiency are validated against measured results. An experimental demonstration shows that a 54 m 3 QSCR room can deliver power to small coil receivers in nearly any position with 40% to 95% efficiency. Finally, a detailed safety analysis shows that up to 1900 watts can be transmitted to a coil receiver enabling safe and ubiquitous wireless power.
Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies
Recent advancements in object-tracking technologies can turn mundane constructive assemblies into... more Recent advancements in object-tracking technologies can turn mundane constructive assemblies into Tangible User Interfaces (TUI) media. Users rely on instructions or their own creativity to build both permanent and temporary structures out of such objects. However, most existing object-tracking technologies focus on tracking structures as monoliths, making it impossible to infer and track the user's assembly process and the resulting structures. Technologies that can track the assembly process often rely on specially fabricated assemblies, limiting the types of objects and structures they can track. Here, we present StructureSense, a tracking system based on passive UHF-RFID sensing that infers constructive assembly structures from object motion. We illustrated StructureSense in two use cases (as guided instructions and authoring tool) on two different constructive sets (wooden lamp and Jumbo Blocks), and evaluated system performance and usability. Our results showed the feasibi...
A common problem for healthcare providers is accurately tracking patients’ adherence to medicatio... more A common problem for healthcare providers is accurately tracking patients’ adherence to medication and providing real-time feedback on the management of their medication regimen. This is a particular problem for eye drop medications, as the current commercially available monitors focus on measuring adherence to pills, and not to eye drops. This work presents an intelligent bottle sleeve that slides onto a prescription eye drop medication bottle. The intelligent sleeve is capable of detecting eye drop use, measuring fluid level, and sending use information to a healthcare team to facilitate intervention. The electronics embedded into the sleeve measure fluid level, dropper orientation, the state of the dropper top (on/off), and rates of angular motion during an application. The sleeve was tested with ten patients (age ≥65) and successfully identified and timestamped 94% of use events. On-board processing enabled event detection and the measurement of fluid levels at a 0.4 mL resoluti...
Proceedings of the Twenty-First International Conference on Architectural Support for Programming Languages and Operating Systems, 2016
Energy-autonomous computing devices have the potential to extend the reach of computing to a scal... more Energy-autonomous computing devices have the potential to extend the reach of computing to a scale beyond either wired or battery-powered systems. However, these devices pose a unique set of challenges to application developers who lack both hardware and software support tools. Energy harvesting devices experience power intermittence which causes the system to reset and power-cycle unpredictably, tens to hundreds of times per second. This can result in code execution errors that are not possible in continuouslypowered systems and cannot be diagnosed with conventional debugging tools such as JTAG and/or oscilloscopes. We propose the Energy-interference-free Debugger, a hardware and software platform for monitoring and debugging intermittent systems without adversely effecting their energy state. The Energy-interference-free Debugger recreates a familiar debugging environment for intermittent software and augments it with debugging primitives for effective diagnosis of intermittence bugs. Our evaluation of the Energy-interference-free Debugger quantifies its energy-interference-freedom and shows its value in a set of debugging tasks in complex test programs and several real applications, including RFID code and a machine-learningbased activity recognition system.
We argue that sensing and computation platforms that leverage RFID technology can realize "smart-... more We argue that sensing and computation platforms that leverage RFID technology can realize "smart-dust" applications that have eluded the sensor network community. RFID sensor networks (RSNs), which consist of RFID readers and RFID sensor nodes (WISPs), extend RFID to include sensing and bring the advantages of small, inexpensive and long-lived RFID tags to wireless sensor networks. We describe sample applications suited to the space between existing sensor networks and RFID. We highlight the research challenges in realizing RSNs such as the use of intermittent power and RFID protocols suited to sensor queries.
Proceedings of the ACM on Human-Computer Interaction
Augmented Reality (AR) has the potential to leverage environmental information to better facilita... more Augmented Reality (AR) has the potential to leverage environmental information to better facilitate distributed collaboration, however, such applications are difficult to develop. We present XSpace, a toolkit for creating spatially-aware AR applications for distributed collaboration. Based on a review of existing applications and developer tools, we design XSpace to support three methods for creating shared virtual spaces, each emphasizing a different aspect: shared objects, user perspectives, and environmental meshes. XSpace implements these methods in a developer toolkit, and also provides a set of complimentary visual authoring tools to allow developers to preview a variety of configurations for a shared virtual space. We present five example applications to illustrate that XSpace can support the development of a rich set of collaborative AR experiences that are difficult to produce with current solutions. Through XSpace, we discuss implications for future application design, inc...
Proceedings of the ACM on Human-Computer Interaction
Pervasive and interactive displays promise to present our digital content seamlessly throughout o... more Pervasive and interactive displays promise to present our digital content seamlessly throughout our environment. However, traditional display technologies do not scale to room-wide applications due to high per-unit-area costs and the need for constant wired power and data infrastructure. This research proposes the use of photochromic paint as a display medium. Applying the paint to any surface or object creates ultra-low-cost displays, which can change color when exposed to specific wavelengths of light. We develop new paint formulations that enable wide area application of photochromic material. Along with a specially modified wide-area laser projector and depth camera that can draw custom images and create on-demand, room-wide user interfaces on photochromic enabled surfaces. System parameters such as light intensity, material activation time, and user readability are examined to optimize the display. Results show that images and user interfaces can last up to 16 minutes and can b...
Proceedings of the 28th Annual International Conference on Mobile Computing And Networking
Magnetic sensing is emerging as an enabling technology for various engaging applications. Represe... more Magnetic sensing is emerging as an enabling technology for various engaging applications. Representative use cases include highaccuracy posture tracking, human-machine interaction, and haptic sensing. This technology uses multiple MEMS magnetometers to capture the changing magnetic field at a close distance. However, magnetometers are susceptible to real-world disturbances, such as hard-and soft-iron effects. As a result, users need to perform a cumbersome and lengthy calibration process frequently, severely limiting the usability of magnetic tracking. To remove/mitigate this limitation, we propose MAGIC (MAGnetometer automatIc Calibration), a systematic framework to automatically calibrate both soft-and hard-iron disturbances for a MEMS magnetometer array. To minimize the need for user intervention, we introduce a novel auto-triggering module. Unlike the legacy manual calibration method, MAGIC achieves superior calibration performance (e.g., for tracking applications) with minimal user attention. Via empirical studies, we show MAGIC also incurs marginal overhead and cost, such as a total energy cost of 0.108 J.
IEEE Transactions on Dependable and Secure Computing
Emerging ultra-low-power tiny scale computing devices run on harvested energy, are intermittently... more Emerging ultra-low-power tiny scale computing devices run on harvested energy, are intermittently powered, have limited computational capability, and perform sensing and actuation functions under the control of a dedicated firmware operating without the supervisory control of an operating system. Wirelessly updating or patching firmware of such devices is inevitable. We consider the challenging problem of simultaneous and secure firmware updates or patching for a typical class of such devices-Computational Radio Frequency Identification (CRFID) devices. We propose Wisecr , the first secure and simultaneous wireless code dissemination mechanism to multiple devices that prevents malicious code injection attacks and intellectual property (IP) theft, whilst enabling remote attestation of code installation. Importantly, Wisecr is engineered to comply with existing ISO compliant communication protocol standards employed by CRFID devices and systems. We comprehensively evaluate Wisecr 's overhead, demonstrate its implementation over standards compliant protocols, analyze its security, implement an end-to-end realization with popular CRFID devices and open-source the complete software package on GitHub.
2019 IEEE International Conference on Pervasive Computing and Communications (PerCom, 2019
Falls have serious consequences and are prevalent in acute hospitals and nursing homes caring for... more Falls have serious consequences and are prevalent in acute hospitals and nursing homes caring for older people. Most falls occur in bedrooms and near the bed. Technological interventions to mitigate the risk of falling aim to automatically monitor bed-exit events and subsequently alert healthcare personnel to provide timely supervisions. We observe that frequency-domain information related to patient activities exist predominantly in very low frequencies. Therefore, we recognise the potential to employ a low resolution acceleration sensing modality in contrast to powering and sensing with a conventional MEMS (Micro Electro Mechanical System) accelerometer. Consequently, we investigate a batteryless sensing modality with low cost wirelessly powered Radio Frequency Identification (RFID) technology with the potential for convenient integration into clothing, such as hospital gowns. We design and build a passive accelerometerbased RFID sensor embodiment-ID-Sensor-for our study. The sensor design allows deriving ultra low resolution acceleration data from the rate of change of unique RFID tag identifiers in accordance with the movement of a patient's upper body. We investigate two convolutional neural network architectures for learning from raw RFID-only data streams and compare performance with a traditional shallow classifier with engineered features. We evaluate performance with 23 hospitalized older patients. We demonstrate, for the first time and to the best of knowledge, that: i) the low resolution acceleration data embedded in the RF powered ID-Sensor data stream can provide a practicable method for activity recognition; and ii) highly discriminative features can be efficiently learned from the raw RFID-only data stream using a fully convolutional network architecture.
Proceedings of the 2018 ACM International Joint Conference and 2018 International Symposium on Pervasive and Ubiquitous Computing and Wearable Computers, 2018
Most existing wireless power transfer (WPT) solutions are limited to 2-D configurations, which li... more Most existing wireless power transfer (WPT) solutions are limited to 2-D configurations, which limits mobility when charging electronics. What is needed are 3-D WPT, which can deliver power anywhere in large volumes (e.g., factories, rooms, toolbox, etc). WPT using quasistatic cavity resonators (QSCR) proposed a route towards truly ubiquitous WPT, which safely charges devices as they enter a WPT enabled space. However, several drawbacks exist to this approach such as the need for a central pole and the spatially non-uniform power availability. To address these issues, we demonstrate a WPT system based on "multimode" QSCR [4]; this structure possess two resonant modes: pole dependent (PD) mode, which resembles the previous QSCR work and pole independent (PI) mode, which works whether or not the pole exist. This structure enables two operations: (i) pole-less operation, which works to the same degree as the previous QSCR without the central pole and (ii) dual-mode operation, which although requires the central pole, enables high-efficiency WPT all over the volume.
2019 IEEE International Conference on RFID (RFID), 2019
Augmented reality (AR) promises to revolutionize the way people interact with their surroundings ... more Augmented reality (AR) promises to revolutionize the way people interact with their surroundings by seamlessly overlaying virtual information onto the physical world. To improve the quality of such information, AR systems need to identify the object with which the user is interacting. AR systems today heavily rely on computer vision for object identification; however, state-of-the-art computer vision systems can only identify the general object categories, rather than their precise identity. In this work, we propose IDCam, a system that fuses RFID and computer vision for precise item identification in AR objectoriented interactions. IDCam simultaneously tracks users' hands using a depth camera and generates motion traces for RFIDtagged objects. The system then correlates traces from vision and RFID to match item identities with user interactions. We tested our system through a simulated retail scenario where 5 participants interacted with a clothing rack simultaneously. In our evaluation study deployed in a lab environment, IDCam identified item interactions with an accuracy of 82.0% within 2 seconds.
2019 IEEE International Conference on RFID (RFID), 2019
The Internet of Things (IoT) promises to revolutionize the way people interact with their surroun... more The Internet of Things (IoT) promises to revolutionize the way people interact with their surrounding environment and the objects within it by creating a ubiquitous network of physical devices. However, recent advancements have been focused on creating battery-powered electronics. There remains a huge gap between the collection of smart devices and the massive number of everyday physical objects. In this work, we bridge this gap by enhancing the sensing capabilities of everyday objects using commercial long-range RFID. We apply signal processing and machine learning techniques towards its communication channel parameters to detect the presence of users and to understand their daily activities. Different from prior work, our system can adapt to different environments and objects types. In a naturalistic user study deployed in a home environment, IDAct detected user presence with an F1 score of 96.7% and recognizes 24 different daily activities with an F1 score of 82.8%.
Proceedings of the 27th Annual International Conference on Mobile Computing and Networking, 2021
Figure 1: MagX provides a wearable and untethered sensing module, with customizable array sizes a... more Figure 1: MagX provides a wearable and untethered sensing module, with customizable array sizes and versatile form factors by using passive magnets. (A) MagX with three different sensor array sizes; (B) three form factors with different magnet configurations. Both images are on the same scale.
Proceedings of the 2018 CHI Conference on Human Factors in Computing Systems, 2018
Human environments are typified by walls-homes, offices, schools, museums, hospitals and pretty m... more Human environments are typified by walls-homes, offices, schools, museums, hospitals and pretty much every indoor context one can imagine has walls. In many cases, they make up a majority of readily accessible indoor surface area, and yet they are static-their primary function is to be a wall, separating spaces and hiding infrastructure. We present Wall++, a low-cost sensing approach that allows walls to become a smart infrastructure. Instead of merely separating spaces, walls can now enhance rooms with sensing and interactivity. Our wall treatment and sensing hardware can track users' touch and gestures, as well as estimate body pose if they are close. By capturing airborne electromagnetic noise, we can also detect what appliances are active and where they are located. Through a series of evaluations, we demonstrate Wall++ can enable robust room-scale interactive and context-aware applications.
IEEE Transactions on Dependable and Secure Computing, 2019
The simplicity of deployment and perpetual operation of energy harvesting devices provides a comp... more The simplicity of deployment and perpetual operation of energy harvesting devices provides a compelling proposition for a new class of edge devices for the Internet of Things. In particular, Computational Radio Frequency Identification (CRFID) devices are an emerging class of battery free, computational, sensing enhanced devices that harvest all of their energy for operation. Despite wireless connectivity and powering, secure wireless firmware updates remains an open challenge for CRFID devices due to: intermittent powering, limited computational capabilities, and the absence of a supervisory operating system. We present, for the first time, a secure wireless code dissemination (SecuCode) mechanism for CRFIDs by entangling a device intrinsic hardware security primitive-Static Random Access Memory Physical Unclonable Function (SRAM PUF)-to a firmware update protocol. The design of SecuCode: i) overcomes the resource-constrained and intermittently powered nature of the CRFID devices; ii) is fully compatible with existing communication protocols employed by CRFID devices-in particular, ISO-18000-6C protocol; and ii) is built upon a standard and industry compliant firmware compilation and update method realized by extending a recent framework for firmware updates provided by Texas Instruments. We build an end-to-end SecuCode implementation and conduct extensive experiments to demonstrate standards compliance, evaluate performance and security.
Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies, 2018
The rise of the Internet of Things (IoT) has led to a significant increase in the number of conne... more The rise of the Internet of Things (IoT) has led to a significant increase in the number of connected devices that stream data in our homes, offices and industrial spaces. However, as the number of these devices increases, the costs of actively maintaining and replacing batteries becomes prohibitive at scale. Recent work on Quasistatic Cavity Resonance (QSCR), offers the possibility of seamless wireless power transfer (WPT) to receivers placed anywhere inside large indoor spaces. This work aims to solve two unexplored and critical missing pieces needed to realize this vision of ubiquitous WPT. First, we demonstrate a full end-to-end QSCR-based WPT system that is capable of simultaneously charging multiple custom designed nodes nearly anywhere in the 4.9 m x 4.9 m x 2.3 m test room. Second, this work utilizes the WPT mechanism as a communication channel, where nodes communicate with a centralized reader and to each other via load modulation. Through analysis and experiments, the prop...
The Journal of heart and lung transplantation : the official publication of the International Society for Heart Transplantation, Jan 11, 2018
Models of power delivery within an intact organism have been limited to ionizing radiation and, t... more Models of power delivery within an intact organism have been limited to ionizing radiation and, to some extent, sound and magnetic waves for diagnostic purposes. Traditional electrical power delivery within the intact human body relies on implanted batteries that limit the amount and duration of delivered power. The efficiency of current battery technology limits the substantial demands required, such as continuous operation of an implantable artificial heart pump within a human body. The fully implantable, miniaturized, Free-range Resonant Electrical Energy Delivery (FREE-D) system, compatible with any type of ventricular assist device (VAD), has been tested in a swine model (HVAD) for up to 3hours. Key features of the system, the use of high-quality factor (Q) resonators together with an automatic tuning scheme, were tested over an extended operating range. Temperature changes of implanted components were measured to address safety and regulatory concerns of the FREE-D system in t...
Wireless power delivery has the potential to seamlessly power our electrical devices as easily as... more Wireless power delivery has the potential to seamlessly power our electrical devices as easily as data is transmitted through the air. However, existing solutions are limited to near contact distances and do not provide the geometric freedom to enable automatic and unaided charging. We introduce quasistatic cavity resonance (QSCR), which can enable purposebuilt structures, such as cabinets, rooms, and warehouses, to generate quasistatic magnetic fields that safely deliver kilowatts of power to mobile receivers contained nearly anywhere within. A theoretical model of a quasistatic cavity resonator is derived, and field distributions along with power transfer efficiency are validated against measured results. An experimental demonstration shows that a 54 m 3 QSCR room can deliver power to small coil receivers in nearly any position with 40% to 95% efficiency. Finally, a detailed safety analysis shows that up to 1900 watts can be transmitted to a coil receiver enabling safe and ubiquitous wireless power.
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Papers by Alanson Sample