Zigbee Coordinator Operation; Form A Network; Security Policy; Channel Selection - Digi XBee 3 ZigBee User Manual

Zigbee networks

Zigbee coordinator operation

Form a network

The coordinator is responsible for selecting the channel, PAN ID, security policy, and stack profile for a
network. Since a coordinator is the only device type that can start a network, each Zigbee network
must have one coordinator. After the coordinator has started a network, it can allow new devices to
join the network. It can also route data packets and communicate with other devices on the network.
To ensure the coordinator starts on a good channel and unused PAN ID, the coordinator performs a
series of scans to discover any RF activity on different channels (energy scan) and to discover any
nearby operating PANs (PAN scan). The process for selecting the channel and PAN ID are described in
the following topics.

Security policy

The security policy determines which devices are allowed to join the network, and which device(s) can
authenticate joining devices. See

Channel selection

When starting a network, the coordinator must select a "good" channel for the network to operate
on. To do this, it performs an energy scan on multiple channels (that is, frequencies) to detect energy
levels on each channel. The coordinator removes channels with excessive energy levels from its list of
potential channels to start on.

PAN ID selection

After completing the energy scan, the coordinator scans its list of potential channels (remaining
channels after the energy scan) to obtain a list of neighboring PANs. To do this, the coordinator sends
a beacon request (broadcast) transmission on each potential channel. All nearby coordinators and
routers that have already joined a Zigbee network respond to the beacon request by sending a
beacon back to the coordinator. The beacon contains information about which PAN the device is on,
including the PAN identifiers (16-bit and 64-bit). This scan (collecting beacons on the potential
channels) is typically called an active scan or PAN scan.
After the coordinator completes the channel and PAN scan, it selects a random channel and unused
16-bit PAN ID to start on.

Persistent data

Once a coordinator starts a network, it retains the following information through power cycle or reset
events:
PAN ID
n
Operating channel
n
Security policy and frame counter value
n
Child table (end device children that are joined to the coordinator)
n
Binding table
n
Group table
n
Digi XBee® 3 Zigbee® RF Module
Zigbee security for a detailed discussion of various security policies.
Zigbee coordinator operation
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