## 4 Communication Technologies for WSANs Applied to the SG
### From Home Area Network to Wide Area Network
#### 4.2.1 Home Area Networks and Neighborhood Area Networks  
As defined previously, HANs and NANs constitute the two lowest levels of the SG network. Considering Figure 6, these levels cover the MG area and play a key role in DSM applications and home automation [71]. Moreover, they are particularly adapted to the deployment of low cost wireless communication solutions and WSANs. Consequently, the communication protocols employed at HAN and NAN levels must fulfill the MG and DSM application needs, mainly low coverage range, small amount of information to be transmitted, limited number of nodes, and maximal battery lifetime of the wireless sensors and actuators. The main candidate wireless communication technologies for HAN and NAN levels include the following.  
* Bluetooth: This low power consumption wireless communication protocol, whose physical layer is defined by the IEEE 802.15.1 standard, was designed to be applied in personal area networks (PANs). Bluetooth has a short-range coverage of 10 m that can be enlarged to 100 m by means of repeaters, offering a data rate of about 720 kbps. In HANs, Bluetooth and their low-energy version (Bluetooth LE [72; 73]) are interesting solutions to interface smart meters and customer devices.
* ZigBee: Based on the IEEE 802.15.4 standard and adapted to mesh networking and low duty-cycle applications, ZigBee proposes a data rate of 250 kbps for a coverage range of 100 m without repeaters. It is able to transmit data employing different ISM frequency bands such as 868 MHz, 915 MHz and 2.4 GHz. Nowadays, ZigBee is considered one of the most suitable technologies for networking devices in HANs. Consequently, it is frequently used as communication protocol for WSANs applications, such as consumer appliances control, distribution system monitoring or smart power monitoring.
* Wireless Fidelity (WiFi): Nowadays, WiFi is the wireless technology most commonly deployed in homes and buildings, and their characteristics make WiFi an attractive communication protocol for NANs. Based on the IEEE 802.11 standard, this low cost solution offers a high data rate, up to few Gbps, along with a coverage range of about 200 m. However, the high power consumption is the main drawback for WiFi to be used as communication protocol in WSANs.
* Other solutions that can be applied at HAN and NAN levels are the ultra-low-power emerging wireless communication technologies adapted to M2M applications and particularly, to WSANs [74]. These wireless technologies, proposed for instance by Wavenis, LoRa or SIGFOX, present a long-range coverage, from 200 m to few tens of kilometers, with low data rates (up to 100 kbps) [75].  
Finally, it is always possible to adapt the existent protocols to a particular WSAN that operates in a well-defined scenario, in order to optimize the communication performances, maximizing at the same time the battery life of the sensor and actuator nodes. In this way, Medium Access Control (MAC) protocols have evolved in order to match the needs of WSANs [76], and new specific routing algorithms have also been proposed to reduce the energy consumption [77].