# Improvements of the xAAL Home Automation System
## 1 Introduction  
Ambient Assisted Living (AAL) technologies aim to use digital products and services to ensure that dependents and seniors at home stay safe, healthy, active and independent. It includes smart devices, communication networks and software applications. Home automation solutions provide comfort and wellbeing at home, and medical sensors allow personal health care and telehealth. In [1], the authors provide a full review of the AAL field. They carried out a literature survey of the state-of-the-art of AAL frameworks, systems and platforms. In conclusion, they found that most AAL systems are confined to a limited set of features, that standards and technologies are used in a limited and isolated manner. Among other points, they noticed a lack of interoperability between solutions. More recently, the authors of [2] have proposed an overview of the state-of-the-art in the field and have investigated AAL system requirements and implementation. They organized the analysis by considering the Reference Models (RM) and Reference Architectures (RA). They noticed that interoperability is now considered in some of the reviewed systems. They also conclude that most of the available platforms lack standardization. This is likely due to the fact that the systems described in AAL papers are generally research oriented and mainly established with one specific concern. According to the authors, there is still a need for improvement and consolidation for future designs of the AAL models and architectures. This article focuses on the ambient aspects of AAL systems, and the interoperability issues involved. Smart home systems, home automation, the Internet of Things bring the promise of improving the quality of life at home, with comfort, wellbeing, energy optimization, ambient assisted living. A set of connected devices, sensors and actuators would allow new services to emerge, in theory. In practice, one has to face the issue of interoperability between devices. Each manufacturer (or, sometimes consortium of manufacturers) comes with its own technology, which is, without surprise, not compatible with the competitors. The counterpart is that such a strategy refrains consumers taking the free step towards these products. The high diversity of low-level proprietary communication mechanisms developed by manufacturers push nowadays the interoperability question at an upper layer, that is to say at the service level. The xAAL system was designed with this idea in mind [3; 4]. The architecture organizes services into functional components along a communication bus. A protocol is designed, as well as components interfaces. As a result, xAAL is a solution for home automation interoperability. Simply speaking, it allows a device from vendor A (e.g., a switch) to talk to a device from vendor B (e.g., a lamp). Advanced usages include wellbeing [5; 6] or assistive robotic [7; 8]. A simple home automation setup can be improved with little effort to get an advanced one. For the wellbeing scenarios, missing environmental sensors have been added (dust, brightness, noise levels, CO\({}^{2}\)) to supplement the existing ones (temperature, humidity, PIR). Also, a dedicated gateway has been added to the home automation bus to forward selected data to logging and coaching services in clouds. For assistive robotic scenarios, code has been added on the robot to advertise itself as a device on the home automation bus and play its scenarios: react to alerts from fall sensors, come and talk to the user, secure the apartment (switch off the oven), call the family or the emergency services. The improvement is carried out by an additive process, simply by adding new devices to the network, without any revision of the existing home setup. The xAAL specification defines: (i) a functional distributed architecture; (ii) a means to describe and to discover the interface and the expected behavior of participating nodes by the means of so-called schemas; and (iii) a secure communications layer via an IP (multicast) bus.