Wi-SUN FAN architecture | Benefits or Advantages of Wi-SUN network

This page describes Wi-SUN Network Architecture. It mentions benefits or advantages of Wi-SUN FAN (Field Area Network) as IoT technology.

What is Wi-SUN ?

Wi-SUN is the short form of Wireless Smart Ubiquitous Network Field Area Network. Physical layer specifications of Wi-SUN are defined in IEEE 802.15.4g and MAC layer specifications are defined in IEEE 802.15.4e standard. Wi-SUN alliance manages promotion of Wi-SUN devices, certifications and interoperability among them. Wi-SUN is a mesh topology based networking protocol unlike star based WiFi or LTE.

As it follows mesh topology, devices talk to its neighbours and hence messages can travel to longer distances by hopping between nodes in the network. Wi-SUN FAN (Field Area Network) supports greater number of end nodes to cover greater distances unlike Zigbee and Thread technologies.

There are numerous applications of Wi-SUN which include 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 etc. It handles smart city sensors used in waste management, vending machines and distributed energy resources used in the grid.

Wi-SUN network architecture

The Wi-SUN FAN can operate in star topology or mesh topology. In star mode, communication is established between devices and PAN coordinator. In mesh mode, any two devices can communicate with another if they are in range of other mesh nodes. In mesh mode, multi-hop forwarding is enabled. Here FFD refers to Full Function Device which can act as border router, router node or leaf node. Leaf node is a node which offers minimum capabilities e.g. discovery/Join PAN, send/receive IPv6 packets etc. RFD is a reduced function device. RFD does not allow other devices to associate and can only function as leaf node. Border router is a node which provides WAN connectivity to FAN. Border router maintains source routing tables. It provides node authentication and key maangement services and disseminates PAN wide information.

The figure depicts Wi-SUN network architecture with its elements. As shown multiple Wi-SUN nodes i.e. routers form FAN (Field Area Network) or PAN (Personal Area Network). These nodes are Wi-SUN compliant smart water meters installed in consumer premises. All the nodes communicate with each other directly. All the nodes of a FAN communicate with "Border Router" in their vicinity. The border router interfaces with WAN backhaul which can be public cloud or private cloud network. The connectivity between border router and WAN can be cellular, fiber optic or ethernet. These WAN networks are monitored and controlled from NOC (Network Operations Center) located at local authority office. Typically Wi-SUN FAN mesh network consists of LED street lights, traffic signals and so on. All these nodes are connected with one or multiple border routers as per their range. As individual Wi-SUN themselves route the messages, they are also referred as "router" due to their functionality.

The typical features of Wi-SUN technology are as follows.
• Operating frequency : 470-510MHz, 779-787MHz and 920.5-924.5MHz in China, 863-870MHz and 870-876MHz in Europe, or 920-928MHz in USA, Canada and Japan, 2.45 GHz ISM band (unlicensed) for worldwide IoT applications
• Data rate : Up to 300 Kbps
• Latency : 0.02 to 1 seconds
• Security : PKI (Public Key Infrastructure) authentication , AES (for packet encryption) , IETF EAP-TLS (for network authentication), IEEE 802.11i (as key management), IPv6 protocol (for sufficient address resources, device authentication and encrypted communication)
• Coverage distance or range : 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 standard
• Maximum network hops : Up to 24 hops as defined in Wi-SUN FAN 1.0 standard
• Power consumption : 2µA (while at rest), approx. 8mA (during listening), <14mA at +10dBm (during transmission)

Benefits or advantages of Wi-SUN technology

Following are the benefits or advantages of Wi-SUN technology.
➨Wi-SUN FAN is highly robust and low power IoT wireless mesh network.
➨Wi-SUN FAN is self forming. Hence new devices can easily be added to the network.
➨Wi-SUN FAN is self healing. Hence if pathway fails, network will re-route to the gateway automatically.
➨Wi-SUN FAN is scalable and hence about 95 million Wi-SUN devices have already been installed worldwide.
➨Wi-SUN uses hybrid approach for deployment. It uses mesh topology for dense networks such as smart meters in neighbourhood where as star topology for linking assets in the field.
➨Wi-SUN uses unlicensed spectrum unlike cellular mobile technologies.
➨Wi-SUN is preferred for smart city development due to its scalability, interoperability, security and wide support for existing and upcoming applications.
➨Wi-SUN offers high data rates and low latency compare to LoRaWAN and LTE NB-IoT networks.
➨Wi-SUN based network devices with battery last for about 15 years.

References:
• Wi-SUN FAN Overview from tools.ietf.org
• wi-sun.org

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