# IoT Middleware Platforms for Smart Energy Systems: An Empirical Expert Survey
## 2 Background
### IoT Platform Definition and Architecture
On the other hand, in comparison with ZigBee, Z-Wave allows connecting a limited number of nodes, with lower data rates. * Bluetooth [64]: A wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances using Ultra High Frequency (UHF) radio waves and building personal area networks (PANs) instead of wire connections. In the most widely used mode, transmission power is limited to 2.5 milliwatts, giving it a very short range of up to 10 m (30 feet). * WiFi [65]: It (also called 802.11) was released in 1997. It is a wireless technology that transmits data using high frequencies over short ranges (100 m/300 feet outdoors and 50 m/150 feet indoors). WiFi has different types based on the chosen frequency and transmission rate, such as 802.11a, 802.11b, 802.11g and 802.11n. The main limitations of WiFi include its susceptibility to interference from devices that use the same frequency band such as Bluetooth devices, in addition to the impact of obstructions on its signal path, which may lock the signal in some cases. * 4G/Long Term Evolution (LTE) [66]: Telecommunication networks are classified into generations based on speed, connectivity and reliability standards set by the International Telecommunications Union-Radio communications sector (ITU-R). 4G is the 4 th generation of communication services. It was developed in 2009 after the two older generations 2G and 3G. It has slowly replaced 3G, since it is about 10 times faster than 3G. It also provides more capacity than older generations, and thus larger bandwidth. LTE is the technology behind 4G, and it was designed at the same time as some other standards, such as the UMB (Ultra Mobile Broadband) and the Worldwide Interoperability for Microwave Access (WiMax). LTE is the global standard technology for cellular communications. It is an open, interoperable standard used by virtually all carriers. It provides mobile and broadband data, telephone service with high speed and supports public safety functions as well. * 5G [67]: The 5 th generation mobile network is a wireless standard which was designed after 4G networks. 5G networks connects virtually everyone and everything, including machines, objects and devices. The main advantage of the 5G wireless technology is meant to deliver higher multi-Gbps peak data speeds, ultra low latency, more reliability, higher network capacity and more availability than any previous mobile network technologies. * LoRAWN: One of the low-power wide area networking (LPWAN) technologies. It is a wireless networking protocol which uses the LoRa radio modulation technique layer. It features low-power operation (around 10 years of battery lifetime), a low data rate and a long communication range. It was developed by Cycleo, a French company acquired by Semtech [68]. * Low-Power Personal Wireless Area Networks (6 LoWPAN): A developing standard from the Internet Engineering Task Force (IETF) 6 LoWPAN Working Group. It was designed from the start to be used in small/pico sensor networks [69]. This type of wireless sensor network sends data as packets using IPv6--and here is where the name comes from--over Low-Power Personal Wireless Area Networks. * Long-term evolution machine (LTE-M) [70]: An LPWAN technology (also called LTE-MTC or LTE Cat M) which allows the reuse of an LTE installed base with extended coverage. LTE M, which stands for LTE-Machine Type Communication (MTC), is also a LPWAN technology developed by 3 GPP to enable devices and services specifically for IoT applications. * Narrow Band Iot (NB-IoT) [70]: An LPWAN radio technology deployed over mobile networks which is especially suited for indoor coverage, low cost, long battery life and a large number of devices. Perception layer: Physical/device layer, which includes all the passive, semi-passive and active hardware needed for gathering information from the environment, or taking actions in the physical system, such as sensors, actuators and other physical devices.