Rate Control with ath(4)

The Atheros 11abgn PCI/PCIe devices rely on the host CPU to do packet scheduling and this includes choosing a suitable TX rate to use for any given node.

Historically the net80211 wifi stack would rely on the driver to choose the transmission rates and related information - this would be typically done in the firmware running on the NIC. For ath(4) cards however this was done in the driver. This was traditionally known as ath_rate(4).

There are three rate control modules in ath(4):

• ath_rate_onoe
• ath_rate_amrr
• ath_rate_sample - John Bickett's sample rate control module