# A Cyber-Physical Approach for Residential Energy Management: Current State and Future Directions
## 3 Architecture for Home Energy Management Systems  
A significant number of researchers has discussed IoT-based architectures for HEMS and other smart grid applications, such as activity recognition [16]. Commonly, three to five layers are needed including appliances, metering devices, communication technologies, middleware technologies, and user interaction. The authors of [74] described traditional three-layered architectures with a perception layer (including all meters and actuators), a communication network, and an application layer. Four-layered architectures usually define the communication system in two parts, one in the field (inside the house), and the remote network (referring to the external network that allows data exchange with the server in which data are processed) [74; 75]. On the other hand, the authors of [16; 76] proposed a five-layered structure that separates home appliances in a physical things layer from metering devices in the perception layer. These implementations are also known as cloud-based architectures since they benefit from middleware technologies for processing the data [74]. Table 2 summarizes the main characteristics of proposed architectures in the revised literature. The \"Validation\" column refers to the practical implementation of the architecture, either a testbed or at a major scale. Figure 1 highlights the main composition of the previous IoT architectures for HEMS. The major goal of existing studies is layered architectures to control and manage home appliances remotely. Four-layered architectures are an extension of three-layered architectures by dividing the communication network layer in home area network and remote communication network, which are also defined inside the middle \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Reference** & **Type** & **Year** & **Layers** & **Validation** \\ \hline
[77] & Survey & 2017 & DA, M, A & X \\
[78] & Technical & 2017 & DA, CN, M, A & X \\
[79] & Survey & 2019 & DA, CN, MS, MA, A & X \\
[80] & Technical & 2019 & DAM, CN, M, A & ✓ \\
[75] & Survey & 2019 & DAM, CN, M, A & X \\
[81] & Technical & 2019 & DA, CN, M & ✓ \\
[82] & Technical & 2020 & DA, CN, A & ✓ \\
[83] & Survey & 2020 & DA, CN, M, A, B & X \\
[84] & Survey & 2021 & DA, DAM, CN, M, A & X \\
[66] & Technical & 2021 & DA, CN, M, A & X \\
[85] & Technical & 2021 & DA, CN, M & X \\
[47] & Technical & 2021 & DA, CN, M, A & X \\
[16] & Survey & 2021 & DA, DAM, CN, M, A & X \\
[86] & Survey & 2021 & DA, M, A & X \\
[13] & Survey & 2021 & DA, CN, DAn, A & X \\ This work & Survey & 2022 & DA, CN, DAn & ✓ \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Main characteristics of previous IoT architectures for HEMS. Layers are represented as follows: Data Acquisition [Appliances and Meters] Layer (DA), Data Acquisition [Appliances] Layer (DAA), Data Acquisition [Meters] Layer (DAM), Communication Network Layer (CN), Middleware Layer [Storage and Analytics] (M), Middleware Layer [Storage] (MS), Middleware Layer [Analytics] (MA), Data Analytics (DAn), and Application Layer (A). fore, both representations are very generic. The authors of [74] argued on the benefits of implementing three or four layers to the detriment of having five or more layers. Based on the analysis given above, we can identify a HEMS by three main stages: Data Acquisition, Communication Network, and Data Analytics, as shown in Figure 2. This is also highlighted in the last row of Table 2. The first stage includes both appliances and metering devices. A level up, the Communication Network Layer allows data exchange between the sensing devices and a server. Data is transmitted inside the home area network using WiFi, ZigBee, or other short-distance communication technologies. Then, the information is forwarded to the upper Data Analytics Layer through long-distance communication technologies such as 5G, allowing data transmission between physical devices and middleware technologies in which Data Analytics processing is hosted (i.e., provide connectivity through the WAN).