Transmission, addressing, and routing RF packet routing
XBee/XBee-PRO ZigBee RF Modules User Guide 62
Sample route request (broadcast) transmission where R3 is trying to discover a route to R6.
When the destination node receives a route request, it compares the ‘path cost’ field against previously received
route request commands. If the path cost stored in the route request is better than any previously received, the
destination node will transmit a route reply packet to the node that originated the route request. Intermediate
nodes receive and forward the route reply packet to the source node (the node that originated route request).
Sample route reply (unicast) where R6 sends a route reply to R3.
Note R6 could send multiple replies if it identifies a better route.
Retries and acknowledgments
ZigBee includes acknowledgment packets at both the Mac and Application Support (APS) layers. When data is
transmitted to a remote device, it may traverse multiple hops to reach the destination. As data is transmitted
from one node to its neighbor, an acknowledgment packet (Ack) is transmitted in the opposite direction to
indicate that the transmission was successfully received. If the Ack is not received, the transmitting device will
retransmit the data, up to four times. This Ack is called the Mac layer acknowledgment.
In addition, the device that originated the transmission expects to receive an Ack from the destination device.
This Ack will traverse the same path that the data traversed, but in the opposite direction. If the originator fails to
receive this Ack, it will retransmit the data, up to two times until an Ack is received. This Ack is called the ZigBee
APS layer acknowledgment.
Note Refer to the ZigBee specification for more details.
To Next Page
Loading...
Need help?
General
