# Experimental Performance Analysis of Wi-SUN Channel Modelling Applied to Smart Grid Applications
## 2 AMI Architecture and Last-Mile Communication  
The AMI system architecture is fairly flexible depending on the requirement of AMI functionality, communication technologies and smart meter interoperability. AMI basically consists of a smart meter (SM), communication networks, a head-end system (HES) and a meter data management system (MDMS), as shown in Figure 1. Furthermore, a data concentrator unit (DCU), which is used to collect data from a group of smart meters and send the collected data to the HES, is employed in some AMI system architectures, such as the RF-mesh-based and power line communication (PLC) AMI systems. MDMS is used to collect, manage and store the smart meter data; capture and filter the events and alarms; validate, estimate and edit (VEE) the 15-min load profile data; and conduct data analytics and advanced data processing, such as a virtual metering, load research and DMS. MDMS also provides the application programming interface (API) for the integration of multiple HESs or single HES connection. In some commercial solutions, HES and MDMS are bundled in the same system architecture. Last but not least, a smart meter is developed from the electronic meter with an enhancement by the essential AMI's functions. ; for example, dynamic tariff, clock synchronization, connect/disconnect load control, power quality monitoring, limiter, prepayment metering, push notifications, and remote firmware upgrade. The smart meter measures and collects customer's data, grids' statuses and the power quality data, and sends them to the DCU via wired or wireless communication networks, known as a field-area network (FAN). The cellular network and the optical fiber network are often used as the backhaul communication network between the DCU and HES. There are several choices of FAN in both wired and wireless communication technologies. The typical wired communication in FAN is power line communication (PLC), which provides a connectivity over an AC power line, as a communication medium. G3 PLC and power line intelligent metering evolution (PRIME) are narrowband PLC technologies, which are mainly used in Europe [10; 11]. High-speed PLC (HS PLC) or broadband PLC is a broadband PLC technology, which is mainly used in Korea [5]. On the other hand, the choice of wireless communications for FAN is comprised of a wireless local area net work (Wi-Fi), a cellular network (3G, 4G and LTE), and a low-power wide-area network (LP-WAN). Although Wi-Fi, and the cellular network provide a high throughput, they also require high energy consumption and high bandwidth. Hence, the LP-WAN technology is mainly used in FAN due to the advantages of low power consumption, large coverage areas, and low bandwidth [12]. They also communicate with low data rate for small packets and provide a long battery life operation in the field. LP-WAN devices are constrained to use low bandwidth with limited frequency bands and duty-cycles. LP-WAN can support massive IoT devices by sharing network resources. The example of LP-WAN is LTE-M (Cat-M1), Narrowband IoT (NB-IoT), SIGFOX, LoRaWAN and RF-mesh networks, such as Zigbee and wireless smart utility network (Wi-SUN). In fact, each LP-WAN technology has strong and weak points in different aspects, such as a network topology, coverage, throughput, bandwidth, latency and scalability. The LP-WAN network topology consists of (1) a star topology (Cat-M1, NB-IoT, SIGFOX, LoRaWAN, etc.) and (2) an RF-mesh topology (Zigbee, Wi-SUN, etc.). The star topology has a direct connection between the gateway and end-devices in the network. On the other hand, the gateway in the mesh topology can communicate with neighboring devices on their network, which serve as conduits. The mesh topology provides more redundant connections, and reduces the obstruction effects, especially in urban areas where constructions and temporary obstacles are normally presented.