Limit TX/RX speeds

[aanon4]

Limit the speed of the wifi. It might be useful to stop a device continually trying to bump the speed up if that's not ever practical for a given link. Might produce more consistent performance (maybe).

[ae6xe]

This was my understanding in researching this issue in the past - I assume the available documentation still represents today's implementation. In ath9k, the rate selection logic tests the throughput with up to 10% of the traffic continually trying adjacent rates to measure. For a higher rate to be selected, these probing/testing tries would have to be a higher max throughput over a period of time before bumping up/down the rate selection. This hysteresis delay would avoid the jitter of up/down/up/down concerns. In inspection of the rate selection table, adjacent rates are tested, not all rates. If a weak signal, the higher rates would have negligible to no attempts. The rates tested are like a bell curve around the highest throughput rate -- only testing a few rates higher/lower than the max_tp.