*4.2. Wireless Technologies*

Trends to use wireless technologies in MG have been rising to reduce the complexity and cost of the system. Table 5 represents wireless technologies specification, namely data rates, coverage, application in MGMS, and merits and demerits of each technology. There are several wireless technologies, including Wireless Personal Area Network (WPAN), Wireless LAN (WLAN), cellular networks, Low Power Wide-Area Network (LPWAN), and Satellite Network within different standards applied in MG, of which noticeable ones will be discussed, following [21,26,45–49].

#### 4.2.1. ZigBee

ZigBee is one of the widely used wireless technologies in HAN, especially in cases of the smart home because of low cost, energy consumption, and complexity working in the unlicensed band of 2.4 GHz. It is also one of the integrated communication technologies of metering equipment. ZigBee can provide tree, star, and mesh network topologies by Direct Sequence Spread Spectrum (DSSS) modulation. However, it suffers from common weak points of Industrial, Scientific, and Medical (ISM) license-free spectrum, which is at the risk of interference, although there are some approaches, such as the channel discovery algorithm based on Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) interference, that have been deployed to deal with this issue. It has been noted that in monitoring operation use cases, Zigbee is a prominent one.
