Wearable internet of things (IoT) are transforming diverse healthcare applications including rehabilitation, vital symptom monitoring, and activity recognition. However, the small form-factor of wearable devices constrains the battery capacity and the operating lifetime, thus requiring frequent recharging or battery replacements. Frequent recharging and battery replacement leads to lower quality of service and user satisfaction. Harvesting energy from ambient sources to augment the battery has emerged as an effective solution to improving its operating lifetime. However, ambient energy sources are highly stochastic, making energy management challenging. Prior approaches typically use point predictions for estimating future energy and do not explicitly account for the uncertainty. In strong contrast to prior approaches, this paper presents a conformal predictionbased method for future energy harvest that provides small uncertainty regions with provable coverage guarantees (true output is within the uncertainty region). The uncertainty regions over energy harvest are then leveraged in an energy management algorithm that employs Monte Carlo sampling to evaluate the quality of multiple decisions with varying energy harvests. The decisions are then combined using a lightweight machine learning model to make an energy management decision that is close to the optimal. Experiments on two diverse real-world datasets with about 10 users show that conformal prediction achieves more than 90% coverage with tight prediction intervals; and the energy management algorithm produces decisions that are on average within 2 J of an optimal Oracle, thus showing its effectiveness in improving the quality of service.

Achieving good health and well-being through lower mortality rates of non-communicable diseases and early warning of health risks are key goals of United Nations (UN). Wearable internet of things (IoT) are one of the most promising technology to achieve these goals through their ubiquitous monitoring of key health indicators and in-situ data processing. However, small form-factor of wearable devices constrains the battery capacity, thus requiring frequent recharging or battery replacements, which lowers their adoption rate and benefits. Augmentation of battery energy by scavenging ambient sources, such as light, is a promising solution to improve operating lifetime of IoT devices. However, ambient energy sources are highly uncertain, making energy management (EM) challenging. To handle these challenges, this paper presents a novel uncertainty-aware EM approach. First, we develop a conformal prediction-based method for future energy harvest (EH) that provides small uncertainty regions with provable coverage guarantees (true output vector is within the region). The EH uncertainty regions are then leveraged in an EM algorithm that uses overhead-aware sampling to evaluate the quality of multiple decisions with varying EH before making a decision using a lightweight machine learning model. Experiments on two diverse real-world datasets with 10 users show that conformal prediction achieves more than 90% coverage with tight prediction intervals; and the EM algorithm produces decisions that are, on average, within 2 Joules of an optimal Oracle.

Wearable devices that have low-power sensors, processors, and communication capabilities are gaining wide adoption in several health applications. The machine learning algorithms on these devices assume that data from all sensors are available during runtime. However, data from one or more sensors may be unavailable due to energy or communication challenges. This loss of sensor data can result in accuracy degradation of the application. Prior approaches to handle missing data, such as generative models or training multiple classifiers for each combination of missing sensors are not suitable for low-energy wearable devices due to their high overhead at runtime. In contrast to prior approaches, we present an energy-efficient approach, referred to as Sensor-Aware iMputation (SAM), to accurately impute missing data at runtime and recover application accuracy. SAM first uses unsupervised clustering to obtain clusters of similar sensor data patterns. Next, it learns inter-relationship between clusters to obtain imputation patterns for each combination of clusters using a principled sensor-aware search algorithm. Using sensor data for clustering before choosing imputation patterns ensures that the imputation is aware of sensor data observations. Experiments on seven diverse wearable sensor-based time-series datasets demonstrate that SAM is able to maintain accuracy within 5% of the baseline with no missing data when one sensor is missing. We also compare SAM against generative adversarial imputation networks (GAIN), transformers, and k-nearest neighbor methods. Results show that SAM outperforms all three approaches on average by more than 25% when two sensors are missing with negligible overhead compared to the baseline.

Wearable and Internet of Things (IoT) devices are becoming popular in several applications, such as health monitoring, wide area sensing, and digital agriculture. These devices are energy-constrained due to limited battery capacities. As such, IoT devices harvest energy from the environment and manage it to prolong operation of the system. Stochastic nature of ambient energy, coupled with small battery sizes may lead to insufficient energy for obtaining data from all sensors. As a result, sensors either have to be duty cycled or subsampled to meet the energy budget. However, machine learning (ML) models for these applications are typically trained with the assumption that data from all sensors are available, leading to loss in accuracy. To overcome this, we propose a novel approach that combines data imputation with energy management (EM). Data imputation aims to substitute missing data with appropriate values so that complete sensor data are available for application processing, while EM makes energy budget decisions on the devices. We use the energy budget to obtain complete data from as many sensors as possible and turn off other sensors instead of duty cycling all sensors. Then, we use a low-overhead imputation technique for unavailable sensors and use them in ML models. Evaluations with six diverse datasets show that the proposed EM with imputation approach achieves 25%–55% higher accuracy when compared to duty cycling or subsampling without using additional energy.

Human activity recognition (HAR) and, more broadly, activities of daily life recognition using wearable devices have the potential to transform a number of applications, including mobile healthcare, smart homes, and fitness monitoring. Recent approaches for HAR use multiple sensors on various locations on the body to achieve higher accuracy for complex activities. While multiple sensors increase the accuracy, they are also susceptible to reliability issues when one or more sensors are unable to provide data to the application due to sensor malfunction, user error, or energy limitations. Training multiple activity classifiers that use a subset of sensors is not desirable, since it may lead to reduced accuracy for applications. To handle these limitations, we propose a novel generative approach that recovers the missing data of sensors using data available from other sensors. The recovered data are then used to seamlessly classify activities. Experiments using three publicly available activity datasets show that with data missing from one sensor, the proposed approach achieves accuracy that is within 10% of the accuracy with no missing data. Moreover, implementation on a wearable device prototype shows that the proposed approach takes about 1.5 ms for recovering data in the w-HAR dataset, which results in an energy consumption of 606 μJ. The low-energy consumption ensures that SensorGAN is suitable for effectively recovering data in tinyML applications on energy-constrained devices.

Wearable and internet of things (IoT) devices are transforming a number of high-impact applications. Machine learning (ML) algorithms on wearable devices assume that data from all sensors is available at runtime. However, one or more sensors may be unavailable at runtime due to malfunction, energy constraints or communication challenges. Loss of sensor data can potentially lead to severe degradation in application accuracy and quality of service. Commonly employed generative ML methods to recover missing data are not suitable for resource-constrained wearables because they incur significant memory, execution time, and energy overhead at runtime. In contrast to prior methods, this paper presents a novel search-based accuracy-preserving imputation (AIM) algorithm that obtains most likely imputation patterns of sensor data for each missing data scenario via offline analytics. Specifically, for each missing data condition, we store the most likely recovery patterns which preserve ML classifier-based application accuracy in a look up table and use it appropriately at runtime. The key insight behind AIM is that we do not need exact recovery of the missing data as long as the ML classifier-based application accuracy (e.g., health assessment) is preserved. To further improve the overall effectiveness of AIM, we train the ML classifiers to be robust to small errors in data recovery. Experiments on four diverse wearable sensor based time-series benchmarks demonstrate that AIM is able to maintain accuracy within 5% of the baseline with no missing data when one sensor is missing, and improves the overall accuracy by 15% compared to a state-of-the-art baseline. AIM achieves this improvement with negligible energy consumption overhead.

Human activity recognition (HAR) is an important component in a number of health applications, including rehabilitation, Parkinson’s disease, daily activity monitoring, and fitness monitoring. State-of-the-art HAR approaches use multiple sensors on the body to accurately identify activities at runtime. These approaches typically assume that data from all sensors are available for runtime activity recognition. However, data from one or more sensors may be unavailable due to malfunction, energy constraints, or communication challenges between the sensors. Missing data can lead to significant degradation in the accuracy, thus affecting quality of service to users. A common approach for handling missing data is to train classifiers or sensor data recovery algorithms for each combination of missing sensors. However, this results in significant memory and energy overhead on resource-constrained wearable devices. In strong contrast to prior approaches, this paper presents a clustering-based approach (CIM) to impute missing data at runtime. We first define a set of possible clusters and representative data patterns for each sensor in HAR. Then, we create and store a mapping between clusters across sensors. At runtime, when data from a sensor are missing, we utilize the stored mapping table to obtain most likely cluster for the missing sensor. The representative window for the identified cluster is then used as imputation to perform activity classification. We also provide a method to obtain imputation-aware activity prediction sets to handle uncertainty in data when using imputation. Experiments on three HAR datasets show that CIM achieves accuracy within 10% of a baseline without missing data for one missing sensor when providing single activity labels. The accuracy gap drops to less than 1% with imputation-aware classification. Measurements on a low-power processor show that CIM achieves close to 100% energy savings compared to state-of-the-art generative approaches.

Wearable devices that integrate multiple sensors, processors, and communication technologies have the potential to transform mobile health for remote monitoring of health parameters. However, the small form factor of the wearable devices limits the battery size and operating lifetime. As a result, the devices require frequent recharging, which has limited their widespread adoption. Energy harvesting has emerged as an effective method towards sustainable operation of wearable devices. Unfortunately, energy harvesting alone is not sufficient to fulfill the energy requirements of wearable devices. This paper studies the novel problem of adaptive energy management towards the goal of self-sustainable wearables by using harvested energy to supplement the battery energy and to reduce manual recharging by users. To solve this problem, we propose a principled algorithm referred as AdaEM. There are two key ideas behind AdaEM. First, it uses machine learning (ML) methods to learn predictive models of user activity and energy usage patterns. These models allow us to estimate the potential of energy harvesting in a day as a function of the user activities. Second, it reasons about the uncertainty in predictions and estimations from the ML models to optimize the energy management decisions using a dynamic robust optimization (DyRO) formulation. We propose a light-weight solution for DyRO to meet the practical needs of deployment. We validate the AdaEM approach on a wearable device prototype consisting of solar and motion energy harvesting using real-world data of user activities. Experiments show that AdaEM achieves solutions that are within 5% of the optimal with less than 0.005% execution time and energy overhead.

Human activity recognition (HAR) is widely used in applications ranging from activity tracking to rehabilitation of patients. HAR classifiers are typically trained with data collected from a known set of users while assuming that all the sensors needed for activity recognition are working perfectly and there are no missing samples. However, real-world usage of the HAR classifier may encounter missing data samples due to user error, device error, or battery limitations. The missing samples, in turn, lead to a significant reduction in accuracy. To address this limitation, we propose an adaptive method that either uses low-power mean imputation or generative adversarial imputation networks (GAIN) to recover the missing data samples before classifying the activities. Experiments on a public HAR dataset with 22 users show that the proposed robust HAR classifier achieves 94% classification accuracy with as much as 20% missing samples from the sensors with 390 μJ energy consumption per imputation.

Wearable devices are becoming popular for health and activity monitoring. The machine learning (ML) models for these applications are trained by collecting data in a laboratory with precise control of experimental settings. However, during real-world deployment/usage, the experimental settings (e.g., sensor position or sampling rate) may deviate from those used during training. This discrepancy can degrade the accuracy and effectiveness of the health monitoring applications. Therefore, there is a great need to develop reliable ML approaches that provide high accuracy for real-world deployment. In this paper, we propose a novel statistical optimization approach referred as StatOpt that automatically accounts for the real-world disturbances in sensing data to improve the reliability of ML models for wearable devices. We theoretically derive the upper bounds on sensor data disturbance for StatOpt to produce a ML model with reliability certificates. We validate StatOpt on two publicly available datasets for human activity recognition. Our results show that compared to standard ML algorithms, the reliable ML classifiers enabled by the StatOpt approach improve the accuracy up to 50% in real-world settings with zero overhead, while baseline approaches incur significant overhead and fail to achieve comparable accuracy.

The cluster between Internet of Things (IoT) and social networks (SNs) enables the connection of people to the ubiquitous computing universe. In this framework, the information coming from the environment is provided by the IoT, and the SN brings the glue to allow human-to-device interactions. This paper explores the novel paradigm for ubiquitous computing beyond IoT, denoted by Social Internet of Things (SIoT). Although there have been early-stage studies in social-driven IoT, they merely use one or some properties of SIoT to improve a number of specific performance variables. Therefore, this paper first addresses a complete view on SIoT and key perspectives to envision the real ubiquitous computing. Thereafter, a literature review is presented along with the evolutionary history of IoT research from Intranet of Things to SIoT. Finally, this paper proposes a generic SIoT architecture and presents a discussion about enabling technologies, research challenges, and open issues.

The concept of connectedness, as inspired by Social Networking Service, is a key factor which participates in changing the way people interact with each other over the Internet. On the other hand, connected world as envisioned by the Internet of Things aims to expand the idea of connectivity to include everything in the physical world to a big network called the Internet. In order to realize the integration between the world of connected people and the world of connected devices, intelligence including semantics and recommendation acts as a key factor to expand the basic communication functionalities to include search, discovery, mashup of new services and filtering. We propose a framework to facilitate the next generation of communication between people and devices, and a preliminary prototype including three modules DPWSim, ThingsGate, ThingsChat along with a use case discussion.

Adopting Web 2.0 technologies and techniques in modern e-learning systems guarantees a more interactive e-learning experience. It leverages collaboration among learners and enhances accessibility to various learning resources. Providing such functionalities as web services within an integrated e-learning system achieves interoperability and reduces redundancy. Our aim in this paper is to identify recurrent Web 2.0 and Service-oriented architecture (SOA) design and architectural patterns that would provide reusable building blocks for any Web 2.0 based service-oriented e-learning system. The paper builds on induction theory techniques to validate taxonomy related to Web 2.0 and SOA behavioural and technological patterns. We identified 3 elementary design patterns, inter-connectivity, file sharing and content re-mixing, a well as 4 secondary design patterns, streaming, content authoring, content aggregation and tagging. The proposed design patterns share three elementary architecture types, client-server, peer-peer and SOA. The paper also builds on UML4SOA techniques in modelling requirements prior application of proposed patterns in the case study.