Embedding-based real-time change point detection with application to activity segmentation in smart home time series data

[EN]Human activity recognition systems are essential to enable many assistive applications. Those systems can be sensor-based or vision-based. When sensor-based systems are deployed in real environments, they must segment sensor data streams on the fly in order to extract features and recognize the ongoing activities. This segmentation can be done with different approaches. One effective approach is to employ change point detection (CPD) algorithms to detect activity transitions (i.e. determine when activities start and end). In this paper, we present a novel real-time CPD method to perform activity segmentation, where neural embeddings (vectors of continuous numbers) are used to represent sensor events. Through empirical evaluation with 3 publicly available benchmark datasets, we conclude that our method is useful for segmenting sensor data, offering significant better performance than state of the art algorithms in two of them. Besides, we propose the use of retrofitting, a graph-based technique, to adjust the embeddings and introduce expert knowledge in the activity segmentation task, showing empirically that it can improve the performance of our method using three graphs generated from two sources of information. Finally, we discuss the advantages of our approach regarding computational cost, manual effort reduction (no need of hand-crafted features) and cross-environment possibilities (transfer learning) in comparison to others.This work was carried out with the financial support of FuturAALEgo (RTI2018-101045-A-C22) granted by Spanish Ministry of Science, Innovation and Universities

A Comparative Analysis of Human Behavior Prediction Approaches in Intelligent Environments

Behavior modeling has multiple applications in the intelligent environment domain. It has been used in different tasks, such as the stratification of different pathologies, prediction of the user actions and activities, or modeling the energy usage. Specifically, behavior prediction can be used to forecast the future evolution of the users and to identify those behaviors that deviate from the expected conduct. In this paper, we propose the use of embeddings to represent the user actions, and study and compare several behavior prediction approaches. We test multiple model (LSTM, CNNs, GCNs, and transformers) architectures to ascertain the best approach to using embeddings for behavior modeling and also evaluate multiple embedding retrofitting approaches. To do so, we use the Kasteren dataset for intelligent environments, which is one of the most widely used datasets in the areas of activity recognition and behavior modeling.This work was carried out with the financial support of FuturAAL-Ego (RTI2018-101045-A-C22) and FuturAAL-Context (RTI2018-101045-B-C21) granted by Spanish Ministry of Science, Innovation and Universities

Behavior Modeling for a Beacon-Based Indoor Location System

In this work we performed a comparison between two different approaches to track a person in indoor environments using a locating system based on BLE technology with a smartphone and a smartwatch as monitoring devices. To do so, we provide the system architecture we designed and describe how the different elements of the proposed system interact with each other. Moreover, we have evaluated the system’s performance by computing the mean percentage error in the detection of the indoor position. Finally, we present a novel location prediction system based on neural embeddings, and a soft-attention mechanism, which is able to predict user’s next location with 67% accuracy

Performance Evaluation of Indoor Positioning Systems based on Smartphone and Wearable Device

Recently, most solutions designed for Ambient Assisting Living systems are based on indoor positioning systems. There are several technologies and approaches to develop indoor tracking and positioning with different advantages and shortcomings. Taking into account as a starting point some limits and issues analyzed in related scientific works focused on smart AAL systems able to improve the life quality of elderly people, this work aims to carry out a performance comparison between two different approaches to track a person in indoor environments. Both a smartphone and a wearable device have been used in our tests, analyzing the differences of each approach

A lightweight semantic-location system for indoor and outdoor behavior modelling

In intelligent environments, one of the most common available input data is location. It can be easily captured with little additional infrastructure thanks to the ever-present smartphones or smartwatches that enable new opportunities and services in the field of pervasive computing and sensing. However, in some cases, such as in an elderly care context, it is useful to infer additional information, such as identifying unusual activities or abnormal behaviors of monitored users. In this paper, a system that uses location data to infer additional semantic information about a user's behavior is presented. The semantic location data can then be transformed into behavioral indicators that can be used to analyze the user's activities. In order to infer user activities, the proposed system requires a minimal infrastructure

Location Based Indoor and Outdoor Lightweight Activity Recognition System

In intelligent environments one of the most relevant information that can be gathered about users is their location. Their position can be easily captured without the need for a large infrastructure through devices such as smartphones or smartwatches that we easily carry around in our daily life, providing new opportunities and services in the field of pervasive computing and sensing. Location data can be very useful to infer additional information in some cases such as elderly or sick care, where inferring additional information such as the activities or types of activities they perform can provide daily indicators about their behavior and habits. To do so, we present a system able to infer user activities in indoor and outdoor environments using Global Positioning System (GPS) data together with open data sources such as OpenStreetMaps (OSM) to analyse the user’s daily activities, requiring a minimal infrastructure