The Beacon-Enabled Mode is synchronized as the coordinator sends out beacons periodically. These beacons use the IEEE802.15.4 superframe structure. This network mode is recommended for applications where the data flow is mainly downstream (coordinator transmits to sensor nodes). The superframe consists of an inactive and an active period. This allows the PAN-Coordinator to go to sleeping mode in between beacons. Thus it is used whenever the PAN-Coordinator is running in an energy critical application. Since beacons can be used to specify which device has pending packets, not all nodes have to keep polling the Coordinator for data.

The Beacon-Enabled mode causes every sensor to wake up within the active period even if it does not have to transmit data. This increases the energy consumption of sensor devices. The active period duration has to be set as a trade off between power consumption and data-rate. The setup of the beacon mode causes a delay in packet transmission it is not possible to transit messages at any time..

If the device losses connection, it tries to resynchronize with the coordinator until it is able to track the beacon again. This is done by "listening" to its intended frequency.

Advantages:

• Super frame allows PAN-Coordinator to be inactive (sleep). This is not possible in Frequency hopping or Non-Beacon mode
• Synchronization and tracking provided
• Good if you can estimate your data transmission rate and know your system well

Disadvantages:

• Beacon causes every device to wake up and thus wastes power on devices which would not have to send data during a particular superframe
• Beacon leads to delay in transmission
• Devices might not be able to transmit or receive their required data within the active period
• If you do not know your network, there might be to many or to less active time