# An Overview of Indoor Localization System for Human Activity Recognition (HAR) in Healthcare
## 1 Introduction  
Human activity recognition (HAR) is the scientific field that studies the identification of movements or actions performed by a person through the detection of signals sent by wearable sensors or smartphones or through video frames or images. The activities are carried outdoors, such as walking, sitting, stairs, and standing. It is also essential to know where the practical activities are carried out. In interpreting human movement, computer technology and artificial vision are used [1]. HAR has multiple applications such as surveillance, anti-terrorist security, lifelogging, and assistance. These systems have proven very useful in providing efficient home care for the elderly and indoor tracking systems. The percentage of older adults currently continues to grow, consequently determining a need for assistance for those subjects who, losing autonomy and wanting to continue living in their own home, require continuous support in real time. Therefore, it becomes essential to note what the older adult does regarding daily activities. The basic principle is to monitor older people at home or in a nursing home. The system must be able to detect anomalies or deviations in daily activities that are indicative of a decline in people's capabilities. It should also be able to detect emergencies [2]. A positioning system is necessary to ensure these systems' effectiveness. The developments in artificial intelligence, wireless communication systems, and nanotechnologies have allowed the creation of intelligent home care systems, avoiding hospitalization, with an evident reduction in healthcare costs. The HAR system has three main components:* The sensing module continuously collects information through sensors on the activities carried out. * The processing and selection module extracts features that help discriminate between activities. * The classification module uses the features to identify the individual's activity. The exact position of the subject can be associated with improving the system's accuracy. Internal positioning systems are used to acquire this information. The indoor positioning system (IPS) provides continuous real-time localization of objects or people within an enclosed space in different environments, using a network of transmitters and receivers. The value of these systems is identified in the following performances:  
* Know in real-time how people move within a structure. * Identify where a particular subject is. * Activate alarms when particular situations are identified. * Support security and emergency services to direct them where their intervention is needed. * Track personnel at risk when they reach designated collection points in the event of an evacuation. The technologies available today are different and allow a wide range of positioning accuracy from meters to millimeters. These techniques cover a wide range of applications: to ensure assistance to patients in need of assistance, for real-time home tracking of physical assets within industrial facilities or identification of assets in supermarkets, museums, or galleries, for the identification of a specific work of art, or, in the field of transportation and logistics, identification of the position of the objects to be shipped [3]. With the proliferation of the Internet of things (IoT) devices in the home, various IoT service scenarios have been proposed, including IPS [4]. In addition, IoT is a heterogeneous set of technologies and communication that makes it possible to connect any intelligent device, favoring human subjects' connection for exchanging information. Current positioning techniques are divided into systems for external and internal positioning. Regarding external positioning, with current techniques, good results in the accuracy of the position obtained have been achieved.