# Experimental Study of 6 LoPLC for Home Energy Management Systems
## 2 Motivation and Related Work  
The role of the HEMS controller is to monitor and optimise energy consumption in the home. While home users justifiably continue to acquire more devices, insufficient attention is paid to energy consumption arising from the use of those appliances. Interestingly, homes account for a significant percentage of energy consumption; hence, efficiency in the home could result in far-reaching benefits on the main grid. To underscore this, in the U.S. for instance, buildings consume 40% of available energy [12], and a similar trend exists in the U.K., where residential dwellings alone are responsible for 26.7% of consumption [4]. Clearly, the home must be included in the overarching energy management strategy to achieve the much-needed security and sustainability objectives of the smart grid [13; 14]. At the heart of such an intelligent system is a pervasive, low-cost, low-rate communication system. Like other control networks, the design philosophy behind HEMS is that in-home smart appliances add more value when they are integrated and function as a network, than autonomous deployment of individual entities. The resulting network is as resilient as the underlying communication technology enabling it. In terms of communications for HEMS, the forerunners are mostly wireless technologies, for instance Wi-Fi [15; 16; 17], ZigBee [18; 19] and Bluetooth [20]. However, similar to other communication systems, these wireless technologies have limitations. For example, signal propagation issues, such as limited range and physical barriers constraints, including Line of Sight (LOS) requirements, are known to inhibit channel performance. Although research in home networking is growing, the main enabling standards for interconnecting devices in the HAN are IEEE 1905.1 and International Telecommunication Union's Telecommunication standardization sector specification for Gigabit home networking (ITU-T G.hn). These standards can deliver data rates from several Mbps up to 1 Gbps [21]. Hence, they are more suitable for broadband applications. In the quest to find a suitable communication system for HEMS applications, PLC has been considered in some studies [19; 22; 23]. However, the focus of those studies was to facilitate the exchange of control and monitoring information between the electrical loads and the management system over power lines. Exploitation of low-rate, low-power PLC for monitoring and control was not considered. Furthermore, the HomePlug Green PHY standard was developed for smart home and home automation generally over power lines. To reduce cost and power consumption, it was developed to support only the Quadrature Phase Shift Keying (QPSK) modulation scheme [24]. All communication technologies have their strengths and weaknesses; however, this work is not a direct comparison between PLC-based systems and other techniques. Therefore, rather than debate the merits or otherwise of LoWPAN for HEMS applications, this paper accepts the substantial work already done in that area and extends some of its capabilities into PLC networks. This should inspire a new wave of complimentary or alternate low-rate communication systems for HEMS applications. For example, wireless communication in buildings with metallic walls, cellars and underground structures can be severely challenging and often results in blind spots (locations where the wireless signal is weak or absent). PLC is specifically suitable for such situations and generally appealing for HEMS, because not only is it pervasive in most homes, but also it provides the scalability and availability needed by HEMS applications. In HEMS, ZigBee is one of the widely-deployed low-power communication technologies, with solutions such as SEP 1.x and SEP 2.0 available on the market.