[ath9k-devel] Fixing the rate and rate relationship to OFDM

[Felix Fietkau <nbd@openwrt.org>]

On 2013-03-27 7:49 PM, John Clark wrote:
> Many people seem to desire the bit rate to be the 'highest possible',
> and have that automagically set.
What's wrong with the current behavior of picking the rate that causes
the least wasted airtime?

> For some applications, I like to be able to set a specific bit rate,
> and have that bit rate used no matter the resulting errors.
That can be quite problematic with 802.11n aggregation. Any frame
transmission that has failed after too many retries causes a BlockAck
Request to be sent, which can cause other (potentially unrelated) frames
to be dropped on the receiver side.
Why do you want to do this at all?

> I have looked a the code briefly, and it seems that there is the
> possibility for setting up several retries, with changes in bit
> rate.
> 
> So, the questions are:
> 
> 1) how to 'fix' a rate, disable adjustments on retries, etc?
To do this per application, you'd have to put some ugly hacks into
various layers.

> 2) What is the relationship between the bit rate selected at this OS level,
> and the subcarrier modulation of the RF signal?
The standard describes what modulations are used for specific bitrates.

- Felix