Morse_cli set ack_timeout_adjust?

Software
1

I am hoping someone can explain exactly what “morse_cli set ack_timeout_adjust X” does? I had assumed it was just an additional usecs of time added to the expected ack timeout to allow for tuning of link distances. For example, 4 miles in the air - 2 there and 2 back - would be about 20us. If I set the ack_timeout_adjust to that the performance plummets compared to the 300us default. So … I guess it’s not that. Any help in understanding how to calculate the ideal?

Thanks
Tim

2

It’s used to tune the timeout for receiver responses at the MAC layer. The total time required for this knob would include the processing time by both chips both of their respective packets, the TX and RX time, handoffs between the layers, etc.

Performance degradation would be due to the timeout being too low and aggressive resulting in excessive dropped packets and subsequent retries.

3

Thanks for this. I understand that in a very general sense. What I’m trying to understand is exactly how to tune it - the formula I need to use to feed it things like bandwidth, modulation, distance, etc (or none of these?) and get a value I can use to set it more optimally than the default. If this was a wifi coverage class I’d know what I’m doing, but here I dont.

4

Alright after of a bit of spelunking into IEEE 802.11 2024, it looks to have been derived by applying the S1G ACK related values (aSIFSTime, aSlotTime, aRxPHYStartDelay) from the S1G PHY characteristics table[1] into the PHY/MAC acknowledgement procedure[2]. So the preset value would be more of an adjustment for compliance with the spec.

The user facing setting in morse_ctrl would be more for allowing increasing the timeout threshold to adjust performance for extreme range experiments/applications. Reducing that window would just lead to missing the ACK timing requirements and end with a reduction in network performance due to the resultant retries from packets being reported as dropped or lost.

[1] IEEE-802.11-2024 Section 23.4.4 Table 23-41 – S1G PHY characteristics pg 3855
[2] IEEE-802.11-2024 Section 10.3.2.11 Acknowledgment procedure pg 1905