## 2 Related Work
### Academic Solutions  
#### 2.2.1 Home Automation Systems for Heterogeneous Networks  
In the last few years, several academic researchers have presented a number of relevant home automation systems based on the use of multi-technology devices. For example, some authors [19] studied the problem of integrating varied wireless technologies (ZigBee, Wi-Fi, GSM/GPRS) in home automation environments. Specifically, the researchers used a LabVIEW-based PC that acted as a ZigBee coordinator for collecting data from different ambient sensors (temperature, humidity, light) and that is able to control certain actuators (e.g., lighting or irrigation). Similarly, other authors made use of a PC as ZigBee coordinator in order to create an HAS based on intelligent power outlets [41]. An example of a multi-transceiver (X10, Serial, EIB, ZigBee, Bluetooth, DTMF, CAN and GSM/GPRS/UMTS) HAS is presented in [20]. In such a paper, the authors detail an indoor ambient intelligence platform and an IP-based messaging protocol to communicate the home automation controller with the rest of the equipment. [PERSON] et al. [21] presented a low-cost HAS based on the use of a gateway consisting of an Arduino MEGA with Ethernet and ZigBee shields, and an Android tablet that acted as home controller. The system uses ZigBee for connecting wireless sensor nodes and X10 for wired communications. An Arduino MEGA, an Ethernet shield and an Android phone are also used in [42], but, in this case, the sensors and actuators were connected directly to pins of the Arduino. CONDE [43] is another HAS whose objective is to improve energy efficiency in smart buildings. CONDE is decentralized and thus allows for reducing response time and power consumption with respect to traditional centralized systems. CONDE was tested by using MICAz motes, which were able to lower decision delay times and increase energy savings when evaluating lighting and Heating, Ventilation and Air-Conditioning (HVAC) systems. Other researchers have also proposed home controllers and gateways for HAS that support only WiFi [44; 45; 46], only ZigBee [22] or both technologies [23; 24; 25]. Most of them [22; 23; 24; 25] do not use open messaging systems but proprietary ad hoc protocols, while some of the latest use MQTT [45; 46] or Extensible Messaging and Presence Protocol (XMPP) [44]. For instance, in [45], it is proposed the use of low-cost WiFi modules to transform a traditional house into a smart home. For such a purpose, the authors make use of ESP8266 WiFi modules for the nodes, a Raspberry Pi 2 for the gateway, MQTT \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Technology** & **Medium** & **Openness** & **Data Rate** \\ \hline KNN & EG, RF, TP & Open & 9.6 Kpps \\ \hline LonWorks & EG, RF, OF, Coxial, TP & Open & 1.25 Mbps \\ X10 & EG & Open & 60 bps \\ \hline Insteon & EG, RF & Proprietary & 38.4 Kpps \\ \hline ModBus & TP & Open & RTU: 19 2 Kpps-TCP: 10/100/1000 Mbps \\ \hline BacNet & TP & Open & \(10/100/1000\)Mbps \\ \hline Z-Wave & RF & Partially open (open-source layer for integration) & 9.6 Kpps \\ \hline EnOcean & RF & Partially open (open OSI layers 1-3) & 25 Kpps \\ \hline ZigBee & RF & Open & 256 kpps \\ \hline WiFi & RF & Open & 60/54 Mbps \\ \hline Bluetooth & RF & Open & 1 Mbps \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Characteristics of the most common home automation technologies. RF: Radio Frequency, EG: Electric Grid, OF: Optical Fiber, TP: Twisted Pair. for data exchanges and OpenHAB as home automation server. Similarly, in [46], a simple HAS based on MQTT is presented, but the home controller is implemented on a PC. Regarding ZigBee-based home automation systems, they are not very popular when having to interact directly with mobile devices, but some researchers have demonstrated that it is possible to connect Android phones/tablets to a ZigBee dongle [47]. With respect to hybrid systems, it is worth mentioning the work of [PERSON] et al. [25], who presented a WiFi-ZigBee gateway aimed at enabling IoT services in an HAS.