What is PAN?

A Personal Area Network (PAN) is a network used for communication between electronic devices around an individual, typically for mobile and wearable applications, and this is reflected in the design.
On the other hand, it is distinguished from home networks, which are based on fixed use of the home and peripheral devices, and local area networks, in which multiple users interconnect numerous devices.
There are two main types of PAN.

Wired PAN: USB, FireWire, IEEE1394, Lightning, Dock CONNECTORS, Thunderbolt, etc.
Wireless PAN: IrDA, Bluetooth, UWB, Z-Wave, ZigBee, etc.

In a ZigBee network, each network is distinguished by a 16-bit identifier called a PAN ID. This means that there is a 16-bit address space, which is sufficient to configure a large PAN, and theoretically, a maximum of 64,000 or more devices can be accommodated in a single network.

When a device attempts to join an existing ZigBee network, the following process is initiated:

Device Discovery

To generate a PAN, the coordinator first checks the usage status of each channel to find a channel with minimal interference power, then performs an active scan to check if there are any similar coordinators in the vicinity, and then selects the channel and PAN ID to be used by the PAN.

Association Request

The 64-bit address of the device that responded to the beacon signal is stored in the Node Descriptor obtained by active scanning. Based on this information, the device selects a ZigBee network and then sends an association request to the coordinator.

Association Response

The coordinator processes the association request and determines whether the device should join the network. A 16-bit address is assigned to the joining device. This address is used for addressing within the network. The coordinator then sends an association response back to the device.

Network Integration

Upon receiving the association response, the joining device initializes itself to become part of the ZigBee network, and then broadcasts its 64-bit address, 16-bit address pair, and device attribute information to the entire network.

Routing Table Updates

When a router joins the network, the coordinator and existing routers update their routing tables, ensuring that data is routed efficiently through the network, establishing the mesh network commonly found in ZigBee networks.

Security Establishment

Security is a major concern in ZigBee networks. After joining the network, devices establish a secure communication channel using encryption keys. The encryption keys for the PAN are distributed and managed by a trust center, usually a coordinator, located within the PAN.