What happen, inside the XBee S2 module, after a Network ACK Failure (ACK timeout)?

Question

Consider sending a ZigBee Transmit Request frame with a frame ID greater than zero (so, I will receive a ZigBee Transmit Status frame). Suppose I set my timeout response to 200 ms, then, when timeout response is triggered I will receive a ZigBee Transmit Status frame with a status of Network ACK Failure.

I would like to know what exactly happen inside the XBee S2 module: the response can still be received? Or the module block any response that would be received?

Answer 1

The network ack failure indicates that the packet failed to be received by the recipient within the specified time frame. This could be the result of several reasons including but not limited to:

- module out of range
- module no longer in the network
- Broken link resulting in a node discovery to be required but do to time constraints, it was not able to occur
- Timeout set to short to allow enough time for the packet to reach the recipient due to the number of hops required.

As far as the radio is concerned, once the failure occurs, the status frame is generated and issued out the UART (API mode only). At that point, nothing more will occur on the originator even if the packet is received later.

Comments

I was concerned about sending other packet to any device and this "later received packet" mess it up the transmission. Can this happen?