# A Review of Systems and Technologies for Smart Homes and Smart Grids
## 2 State of the Art
### The Advent of Smart Homes  
The interaction between humans and their surroundings can take place in different ways. People usually do everyday activities at home and numerous advantages would be gained if the environmentcould react to humans' behavior and gestures. The smart home is an intelligent space that is able to respond accordingly to the behavior of residents [7]. The concept of smart homes has been developed since the 1990s. According to one of the most recent definitions provided by [PERSON], _\"a home which is smart enough to assist the inhabitants to live independently and comfortably with the help of technology is termed as smart home. In a smart home, all the mechanical and digital devices are interconnected to form a network, which can communicate with each other and with the user to create an interactive space\"_ [8]. [PERSON] and [PERSON] [5] define the smart home as an application that is able to automatize or assist the users through different forms such as ambient intelligence, remote home control or home automation systems. These descriptions confirm that, the primary objective of a smart home is to increase occupants' comfort and make daily life easier [9]. This goal might be achieved, in two ways: (i) by identifying the relevant human activities and increasing their automation in home environments, or (ii) by using remote home control in order to provide high comfort levels, improve security, facilitate energy management, reduce environmental emissions and save energy [10; 11]. Smart homes aim to establish a better quality of living by deploying fully-automated control of appliances and providing assistive support [5]. They allow energy efficiency to be enhanced by adapting the operation of devices to occupancy. In a smart home, users and appliances are (inter)connected by an enhanced communication network comprising twisted-pair power lines or fiber optics, which transfer digital signals according to a given communication protocol. Most smart homes have a central communication device, which enables occupants to control home appliances remotely [12]. According to [PERSON] _et al._[13], smart homes have the following five fundamental characteristics:  
* Automation: the ability to accommodate automatic devices or perform automatic functions;
* Multi-functionality: the ability to perform various duties or generate different outcomes;
* Adaptability: the ability to learn, predict and meet the needs of users;
* Interactivity: the ability to allow the interaction among users;
* Efficiency: the ability to perform functions in a convenient manner that saves time and costs. However, despite their features, smart homes do not automatically become components of the smart grid [14; 15; 16]. The Advent of the Smart Grid: A Communication Method for Smart Homes to Overcome Traditional Power Grids  
Given the rapidly rising electricity usage in private households and the increasing of environmental and regulatory restraints, the need to improve the overall efficiency of electrical grids has never been greater. Energy efficiency is hence one of the central issues that smart homes and smart grids have to face. Smart technologies monitor household energy usage, and users can control home electricity usage through a direct and bidirectional communication with home appliances. It is also expected a lower fluctuation in the load and a subsequent reduction of network dynamics, higher stability, fewer line losses, and lower operational costs in terms of matching the energy demand with the offer [17]. This is one of the strategies that appears promising to cover the performance gap created by the predicted energy performance of a building and its actual energy usage. Considering that primary energy used in buildings worldwide accounts for approximately 40% of global primary energy usage [18], the improvement of energy efficiency in buildings constitutes a critical issue concerning primary energy saving and a corresponding carbon footprint reduction [19].