Energy conservation techniques for sensor networks typically rely on the assumption that data sensing and processing consume considerable less energy than communication. This assumption does not hold in some practical application scenarios, where ad hoc developed sensor units require power consumption comparable with, or even larger than, that of the radio. In this paper we focus on an embedded sensor for monitoring snow composition in mountain slopes for avalanche forecasting. To lower the sensor energy consumption we propose an adaptive sampling algorithm able to dynamically estimate the optimal sampling frequency of the signal to be monitored. In turn, this minimizes the activity of both the sensor and the radio (hence saving energy) while maintaining an acceptable accuracy on the acquired data. Simulation experiments show that the suggested solution can save up to 97% of the energy consumed for sensing when the sensor is always on, while maintaining the error at acceptable levels.

Severe constraints on memory and computation characterizing the Internet-of-Things (IoT) units may prevent the execution of Deep Learning (DL)-based solutions, which typically demand large memory and high processing load. In order to support a real-time execution of the considered DL model at the IoT unit level, DL solutions must be designed having in mind constraints on memory and processing capability exposed by the chosen IoT technology. In this paper, we introduce a design methodology aiming at allocating the execution of Convolutional Neural Networks (CNNs) on a distributed IoT application. Such a methodology is formalized as an optimization problem where the latency between the data-gathering phase and the subsequent decision-making one is minimized, within the given constraints on memory and processing load at the units level. The methodology supports multiple sources of data as well as multiple CNNs in execution on the same IoT system allowing the design of CNN-based applications demanding autonomy, low decision-latency, and high Quality-of-Service.

Tiny machine learning (TML) is a new research area whose goal is to design machine and deep learning (DL) techniques able to operate in embedded systems and the Internet-of-Things (IoT) units, hence satisfying the severe technological constraints on memory, computation, and energy characterizing these pervasive devices. Interestingly, the related literature mainly focused on reducing the computational and memory demand of the inference phase of machine and deep learning models. At the same time, the training is typically assumed to be carried out in cloud or edge computing systems (due to the larger memory and computational requirements). This assumption results in TML solutions that might become obsolete when the process generating the data is affected by concept drift (e.g., due to periodicity or seasonality effect, faults or malfunctioning affecting sensors or actuators, or changes in the users’ behavior), a common situation in real-world application scenarios. For the first time in the literature, this article introduces a TML for concept drift (TML-CD) solution based on deep learning feature extractors and a $k$ -nearest neighbors ( $k$ -NNs) classifier integrating a hybrid adaptation module able to deal with concept drift affecting the data-generating process. This adaptation module continuously updates (in a passive way) the knowledge base of TML-CD and, at the same time, employs a change detection test (CDT) to inspect for changes (in an active way) to quickly adapt to concept drift by removing obsolete knowledge. Experimental results on both image and audio benchmarks show the effectiveness of the proposed solution, whilst the porting of TML-CD on three off-the-shelf micro-controller units (MCUs) shows the feasibility of what is proposed in real-world pervasive systems.

Incremental on-device learning is one of the most relevant and interesting challenges in the field of Tiny Machine Learning (TinyML). Indeed, differently from traditional TinyML solutions where the training is typically carried out on the Cloud and inference only occurs on the tiny devices (e.g., embedded systems or Internet-of-Things units), incremental on-device TinyML allows both the inference and the training of TinyML models directly on tiny devices. This ability paves the way for TinyML-enabled intelligent devices that can learn directly on the field and adapt to evolving environments, different working conditions, or specific users. The literature in this field is quite limited with very few solutions focusing only on the incremental fine-tuning of machine learning models, whereas a general solution encompassing algorithms and code generation for incremental on-device TinyML is still perceived as missing. The aim of this article is to introduce, to the best of our knowledge for the first time in the literature, a toolbox called TyBox for the automatic design and code generation of incremental on-device TinyML classification models. In more detail, starting from a “static” TinyML model, TyBox is able to (i) automatically design the “incremental” on-device version of the TinyML model that has been suitably designed to take into account the technological constraint on the RAM memory of the target tiny device, and (ii) autonomously provide the C++ codes and libraries to support the inference and learning of the incremental on-device TinyML model directly on the tiny devices. TyBox has been extensively compared with a state-of-the-art incremental learning solution for TinyML and tested on an off-the-shelf tiny device (i.e., the Arduino Nano 33 BLE) in three relevant TinyML application tasks and scenarios: binary image classification, multi-class image classification, and ultra-wide-band human activity recognition. In addition, TyBox is released to the scientific community as a public repository.

The widespread proliferation of Internet of Things (IoT) devices has pushed for the development of novel transformer-based Anomaly Detection (AD) tools for an accurate monitoring of functionalities in industrial systems. Despite their outstanding performances, transformer models often rely on large Neural Networks (NNs) that are difficult to be executed by IoT devices due to their energy/computing constraints. This paper focuses on introducing tiny transformer-based AD tools to make them viable solutions for on-device AD. Starting from the state-of-the-art Anomaly Transformer (AT) model, which has been shown to provide accurate AD functionalities but it is characterized by high computational and memory demand, we propose a tiny AD framework that finds an optimized configuration of the AT model and uses it for devising a compressed version compatible with resource-constrained IoT systems. A knowledge distillation tool is developed to obtain a highly compressed AT model without degrading the AD performance. The proposed framework is firstly analyzed on four widely-adopted AD datasets and then assessed using data extracted from a real-world monitoring facility. The results show that the tiny AD tool provides a compressed AT model with a staggering 99.93% reduction in the number of trainable parameters compared to the original implementation (from 4.8 million to 3300 or 1400 according to the input dataset), without significantly compromising the accuracy in AD. Moreover, the compressed model substantially outperforms a popular Recurrent Neural Network (RNN)-based AD tool having a similar number of trainable weights as well as a conventional One-Class Support Vector Machine (OCSVM) algorithm.