Terminology » Other Wireless » Wi-SUN Border Router: Function and Working Explained

Wi-SUN Border Router: Function and Working Explained

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This page describes the functions and working principles of a Wi-SUN Border Router.

Introduction:

Wi-SUN is a wireless technology designed for a variety of applications including utilities, smart homes, smart cities, and the broader Internet of Things (IoT). It adheres to several IEEE, IETF, and ANSI/TIA standards for the development of its devices, nodes, and routers.

A Wi-SUN Field Area Network (FAN) is built upon various protocol layers:

  • PHY (Physical Layer): IEEE 802.15.4g
  • MAC (Medium Access Control Layer): IEEE 802.15.4e
  • Network Layer: IPv6 over 6LoWPAN
  • Transport Layer: UDP
  • Application Layer
  • Security Layers

Wi-SUN operates on different frequency bands below 1 GHz in various countries. Globally, it utilizes the 2.45 GHz band for IoT applications.

Functions of a Wi-SUN Border Router

Wi-SUN FANs can be deployed in either a star or a full mesh topology. The border router is a crucial node that provides Wide Area Network (WAN) connectivity to the FAN. Its primary functions include:

  • Maintaining source routing tables.
  • Providing node authentication and key management services.
  • Disseminating network-wide information.

Wi-SUN Border Router

Figure-1: Border Router in a Wi-SUN network

The term FAN refers to a network comprised of one or more Personal Area Networks (PANs). As illustrated in Figure 1, a Wi-SUN network consists of router nodes, lead nodes, and a border router. The border router interfaces with the WAN using technologies such as cellular, Ethernet, or fiber optic links.

PAN networks include two types of devices:

  • RFD (Reduced Function Device): These devices are limited and cannot allow other devices to associate with them. An RFD can only function as a leaf node.
  • FFD (Full Function Device): These devices are more capable and can act as a border router, a router node, or a leaf node.
  • Router Node: These nodes forward packets both upwards and downwards within the network. They also add security to the packets being transported and manage address management protocols.
  • Leaf Node: These nodes offer a minimum set of capabilities, such as discovering a PAN, joining a PAN, sending IPv6 packets, and receiving IPv6 packets.

How Wi-SUN Border Routers Work

Wi-SUN FAN utilizes a non-storing mode of the Routing Protocol for Low-Power and Lossy Networks (RPL), which necessitates the establishment of Destination-Oriented Directed Acyclic Graphs (DODAGs).

To establish a DODAG, the border router multicasts a Destination Information Object (DIO) message to its neighboring nodes. Short addresses (16 bits) are used, with different types for unicast (one-to-one), multicast (one-to-many within a group), and broadcast (one-to-all) communications.

In Wi-SUN’s non-storing mode for peer-to-peer communication, a packet originating from a source node first travels up to the border router. From there, it is delivered to the destination node via source routing, as defined in RFC6997.

References:

Wi-SUN Resources:

  • Wi-SUN Benefits
  • Wi-SUN PHY Modes
  • Wi-SUN Protocol Stack
  • Wi-SUN vs WiFi
  • Wi-SUN vs LoRaWAN vs NB-IoT