Zigbee Network Join and Rejoin Time: Understanding Connectivity Metrics

In Zigbee networks, Network Join Time and Rejoin Time are critical performance metrics that refer to the time it takes for devices to join or rejoin a network. This is essential for ensuring efficient network operation, especially in dynamic and large-scale deployments.

Network Join Time in Zigbee Network

Network Join Time refers to the amount of time it takes for a device to join the Zigbee network for the first time after being powered on or reset. This process involves several steps, including discovering the network, authenticating, and establishing communication with a Zigbee Coordinator (the central device that manages the network).

Key Steps in the Network Join Process:

• Scan: The device scans for available Zigbee networks in its vicinity. It listens for Beacon frames from Zigbee Coordinators to identify networks.
• Authentication and Security: The joining device must pass any security checks, such as providing the correct network key or being authorized to join the network.
• Association: The device requests to join the network by sending an association request to the Zigbee Coordinator.
• Network Parameters Setup: After successful association, the device receives the network parameters (such as PAN ID, channel, security settings, etc.) and configures itself to operate within the network.
• Routing Information: The device may need to learn or receive routing information to participate in network communication.

• Network Join Time is typically around 30 to 60 seconds but can vary depending on the network setup and environmental conditions.

Rejoin Time in Zigbee

Rejoin Time refers to the time it takes for a Zigbee device to rejoin the network after being temporarily disconnected. This can occur due to various reasons, such as device power down, network interference, or device mobility. Rejoining a network is faster than the initial network join because the device usually retains some of the network parameters (like network key and PAN ID), and it does not need to perform all of the initial setup steps.

Key Steps in the Rejoin Process:

• Reconnection Attempt: The device attempts to reconnect to the network by sending a rejoin request to the Zigbee Coordinator or an existing Zigbee Router.
• Reauthentication: The device may need to reauthenticate, especially if its session was terminated or if it was previously removed from the network.
• Network Parameters Retrieval: The device may not need to request all network parameters but will retrieve any necessary updates to network settings or routing information.
• Route Discovery: If the device is unable to find a direct path to the Coordinator or Router, it will use a route discovery process to find the best available route.

• Rejoin Time is typically faster than Network Join Time, often around 1 to 10 seconds, depending on the circumstances. This is because the device already has some network parameters cached from the previous session.

Key Differences Between Network Join Time and Rejoin Time

Conclusion

Both join and rejoin times are important for ensuring efficient operation of Zigbee networks, particularly in applications where devices frequently join and leave the network, such as in smart homes, industrial IoT, and utility networks. Optimizing these times helps improve the overall responsiveness and performance of the Zigbee network.