ZigBee nodes

There are three general types of node that can exist in a ZigBee network:

  • Coordinator

  • Router

  • End Device

Note: These roles exist at the network level - a ZigBee node may also be performing tasks at the Application level, independent of the role it plays in the network.

For example, a network of ZigBee devices measuring temperature may have a temperature sensor application in each node, irrespective of whether the node is an End Device, Router, or the Coordinator.

The roles of these node types are described in the sub-sections below.

Coordinator

All ZigBee networks must have one (and only one) Coordinator.

At the network level, the Coordinator is mainly needed at system initialization - it is the first node to be started and performs the following initialization tasks:

  • Selects the frequency channel to be used by the network (usually the one with the least detected activity)

  • Starts the network

  • Allows child nodes to join the network through it

The Coordinator can additionally provide other services such as message routing and security management. It may also provide services at the Application level. If any of these additional services are used, the Coordinator must be able to provide them at all times. However, if none of these additional services are used, the network will be able to operate normally even if the Coordinator fails or is switched off.

Parent topic:ZigBee nodes

Router

A ZigBee PRO network usually has at least one Router. The main tasks of a Router are:

  • Relays messages from one node to another.

  • Allows child nodes to join the network through it.

Note: An important feature of the Router is that it cannot sleep, as it must always be available for routing.

Parent topic:ZigBee nodes

End Device

The main task of an End Device at the network level is sending and receiving messages. An End Device can only communicate directly with its parent, so all messages to/from an End Device pass via its parent.

An End Device can be battery-powered and, when not transmitting or receiving, can sleep in order to conserve power. The parent device buffers messages destined for a sleep-enabled End Device. The End Device collects these messages once it is awake (also see Section 3.2.2 Network topology below).

Note: End Devices cannot relay messages and cannot allow other nodes to connect to the network through them. In other words, it implies that they cannot have children.

Parent topic:ZigBee nodes

Parent topic:Network level concepts