# Bluetooth Low Power Modes Applied to the Data Transportation Network in Home Automation Systems
## 1 Introduction  
Home automation [1] is an emerging vision that offers efficient home management system with convenience, comfort, energy efficiency and security. Generally speaking, it is defined as the introduction of technology inside the home to enhance the quality of life of its occupants, by providing them with different services such as smart health [2], tele-health [3], multimedia entertainment or energy conservation [4]. Home automation solutions can be conservative or wireless. The conservative home automation solutions are usually based on power line or wired communication technologies. They are complex, expensive, inflexible, and involve time-consuming installations. On the other hand, wireless home automation architectures have gained popularity in home automation for numerous advantages such as plug and play nature, flexibility, interoperability and cost effectiveness. Usually, wireless approaches comprise smart devices, mainly wireless embedded sensors and actuators, which communicate with each other directly or via a centralized server to achieve defined automation functionalities [5], usually monitoring and control applications for home user comfort and efficient home management [6]. Devices with sensing and recognition capabilities as well as collection and processing are typically a part of home automation systems. Such systems are a multidisciplinary approach [7], as they require the convergence of many areas of Computer Science in order to fulfill the purpose of improving the quality of life of the residents. Then, electronic systems to interconnect nodes and communicate the measured data can be found in many home automation deployments [8]. Here, every device must be capable to transmit and receive the context information that is collected by the sensors. However, since in many homes the context information usually changes at low pace, the continuous sensing of the information is not mandatory. Thus, the nodes can sleep at regular intervals. In fact, home automation deployments composed of wireless multi-hop networks frequently require long-life sensor nodes to be interconnected through a communication network. Therefore, working with devices in low power mode is almost mandatory in home automation deployments [9]. The nodes can be connected to the electricity supply so that there is no need to worry about the power consumption of the nodes. In addition, if a battery is added to the node, the node will be fully operational in the case of blackouts. In the case there is no chance to connect the nodes to the electricity supply, the nodes must include a battery power supply. Moreover, they must work in low power mode so that the lifecycle of the node is as long as possible. The inactivity intervals of the gateway and sensor nodes that work in low power mode can be scheduled to reduce their power consumption and, hence, the consumption of the whole network. However, the inactivity intervals degrade significantly the time performance of the network. Thus, whether the nodes included in the network are connected to the electricity supply or not, it is important to reduce the power bill of the home automation deployment without degrading significantly its performance in terms of response time or latency. Actually, the analysis of the time performance of wireless networks is a key point in the design and management of such networks [10]. It is a fact that the transmission medium in wireless communications is usually unreliable. However, the use of wireless networks for limited response time applications is increasing. As a result, latency is a key metric when defining the Quality of Service (QoS) of a communication system [11]. Any application that shares the measured data for their collaborative use is considered here. There is a wide range of applications that satisfy this feature. However, this paper focuses on home automation deployments [12]. There are many wireless communication standards to implement home automation networks [5].