RFWi-SUN FAN: Architecture, Features, and Benefits
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This document describes the Wi-SUN Network Architecture and outlines the benefits and advantages of Wi-SUN FAN (Field Area Network) as an IoT technology.
What is Wi-SUN?
Wi-SUN stands for Wireless Smart Ubiquitous Network Field Area Network. The physical layer specifications are defined in IEEE 802.15.4g, and the MAC layer specifications are defined in IEEE 802.15.4e. The Wi-SUN Alliance manages the promotion, certification, and interoperability of Wi-SUN devices.
Unlike star-based networks like WiFi or LTE, Wi-SUN uses a mesh topology. Devices communicate with their neighbors, allowing messages to travel longer distances by hopping between nodes. Wi-SUN FAN supports a greater number of end nodes and covers larger distances compared to Zigbee and Thread.
Applications of Wi-SUN
Wi-SUN has numerous applications, including:
- AMI Metering
- EV charging infrastructure
- Distribution automation
- Direct load control
- SCADA
- Distributed generation
- Outdoor street lighting
- Pollution monitoring
- Noise detection
- Public safety
- Traffic management
- Parking
- Smart city sensors (waste management, vending machines)
- Distributed energy resources in the grid
Wi-SUN Network Architecture
Figure-1: Wi-SUN Network Architecture
Wi-SUN FAN can operate in star or mesh topology. In star mode, communication occurs between devices and a PAN (Personal Area Network) coordinator. In mesh mode, any two devices can communicate if they are within range of other mesh nodes, enabling multi-hop forwarding.
- FFD (Full Function Device): Can act as a border router, router node, or leaf node.
- Leaf Node: Offers minimal capabilities, such as discovery/joining PANs and sending/receiving IPv6 packets.
- RFD (Reduced Function Device): Cannot allow other devices to associate and can only function as a leaf node.
- Border Router: Provides WAN connectivity to the FAN, maintains source routing tables, offers node authentication and key management, and disseminates PAN-wide information.
The architecture consists of multiple Wi-SUN nodes (routers) forming a FAN or PAN. These nodes, such as smart water meters, communicate directly with each other.
Network Communication
All nodes in a FAN communicate with a “Border Router” within range. The border router interfaces with a WAN backhaul (public or private cloud network) via cellular, fiber optic, or Ethernet. WAN networks are monitored and controlled from a NOC (Network Operations Center), often located at a local authority office. A typical Wi-SUN FAN mesh network includes LED street lights and traffic signals, connected to one or multiple border routers.
Because Wi-SUN nodes route messages themselves, they are often referred to as “routers.”
Key Features of Wi-SUN Technology
- Operating Frequency: 470-510MHz, 779-787MHz, and 920.5-924.5MHz (China), 863-870MHz and 870-876MHz (Europe), 920-928MHz (USA, Canada, Japan), 2.45 GHz ISM band (worldwide IoT)
- Data Rate: Up to 300 Kbps
- Latency: 0.02 to 1 seconds
- Security: PKI authentication, AES (packet encryption), IETF EAP-TLS (network authentication), IEEE 802.11i (key management), IPv6 protocol (address resources, device authentication, encrypted communication)
- Coverage Distance: 4 km point-to-point using 1W output from non-directional antenna
- Maximum Network Size: Approximately 300 nodes per border router (recommended by TI for 144KB RAM device as defined in Wi-SUN FAN 1.0)
- Maximum Network Hops: Up to 24 hops (Wi-SUN FAN 1.0)
- Power Consumption: 2µA (at rest), ~8mA (listening), <14mA at +10dBm (transmission)
Benefits and Advantages of Wi-SUN Technology
- Wi-SUN FAN is a robust, low-power IoT wireless mesh network.
- It is self-forming, allowing easy addition of new devices.
- It is self-healing; if a pathway fails, the network automatically re-routes to the gateway.
- It is scalable, with approximately 95 million devices already installed worldwide.
- Wi-SUN uses a hybrid deployment approach: mesh topology for dense networks (e.g., smart meters) and star topology for linking assets in the field.
- It uses unlicensed spectrum, unlike cellular technologies.
- It is preferred for smart city development due to scalability, interoperability, security, and broad application support.
- Wi-SUN offers higher data rates and lower latency compared to LoRaWAN and LTE NB-IoT networks.
- Battery-powered Wi-SUN network devices can last for about 15 years.
