# Internet of Things for Modern Energy Systems: State-of-the-Art, Challenges, and Open Issues
## 3 IoT Challenges in Energy Systems
### Global Architecture for Energy Internet  
Architecture design is another challenge in IoT-enabled energy systems. System architectures are designed based on its applications and use. A basic architecture for an IoT system includes three layers: application layer, network layer, and perception layer [116]. The application layer is the top layer in which transferred data from network layer are proceed and used to provide services. Network layer is the middle layer, which is responsible to receive information from perception layer and transmit it application layer. Most IoT components such as communication systems' components and protocols are categorized in this layer. The lowest layer in three-layer IoT architecture is the perception layer. Collecting information from sensors and processing of data are considered in this layer. The three-layer architecture is introduced by standards, like IEEE P2413 [114]. This architecture is also recommended for health care systems and smart grids [117; 118]. The three-layer architecture is well known because of its simplicity, and it is easy to apply. However, some details may be missed by defining the IoT system through three layer. In this regard, some other architectures are introduced in the literature, including more layers with more details in each layer, or targeting a goal and introducing it as an additional layer. In this regard, security as one of the most important features in every IoT systems is considered as another perspective of the architecture [119]. In [120], a generic architecture is introduced to deal with an interoperability challenge in IoT where a distributed architecture is designed to deal with heterogeneity, scalability, \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Technology Name** & **Standard Name** & **Frequency Band** & **Coverage Range** & **Data Rate** \\ \hline ZigBee & ZigBee & 2.4 GHz & 100 m & 250 Kbps \\ WiFi & IEEE 802.11 & 2.4 GHz, 5 GHz & 150 m & 1 Gbps \\ WiMAX & IEEE 802.16 & 10-6 GHz & 50 km & 75 Mbps \\ Thread & IEEE 802.15.4 & 2.4 GHz & 30 m & 250 Kbps \\ Z-Wave & Z-Wave & 900 MHz & 30 m & 100 Kbps \\ Bluetooth & IEEE 801.15.1 & 2.4 GHz & 10 m & 1 Mbps \\ Cellular & 4G & 1.4–20 MHz & 50 km & 100 Mbps \\ LoRa & LoRa & 863, 915 MHz & +10 km & 100 Kbps \\ Sigfox & Sigfox & 863, 915 MHz & +10 km & 10, 100 Kbps \\ PLC & IEEE 1901 & 500 kHz & 3 km & 10–500 kbps \\ Ethernet & IEEE 802.3 & 100 MHz & 100 m & 100 Mbps–10 Gbps \\ Fiber optic & IEEE 802.3 & 500 MHz & 100 km & 40 Gbps \\ Satellite & IEEE 521 & 30–300 GHz & 6000 km & 1 Mbps \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Communication technologies and standards. interoperability, security and privacy, etc. In this attempt, a three-layer architecture is presented, and an extra distributed module, called security management, is presented. This module is distributed among the main three layers, and by doing so, modeling and enforcement of security, policies are supported. In [121], a five-layer architecture is introduced including objects layer, object abstraction layer, service management layer, application layer, and business layer. In the business layer, BD analysis and end-user privacy is mentioned. In the application layer, services are presented to consumers. The service management layer plays the role of the middleware layer. Hence, in this layer, processing of data received from the object abstraction layer will be done. In the object abstraction layer, transferring the information between sensors and the service layer is handled. This layer acts as communication layer, so different communication technologies like WiFi, ZigBee, etc. are categorized in this layer. The very basic layer is objects layer in which things are presented as physical sensors. In this layer, information are collected from objects. IoT-based energy system's architecture is illustrated in Figure 3.  
What is evident by reviewing IoT architectures introduced in literature is that every team tries to follow its goal by defining an architecture for an IoT-based system.