wifi rate control

Pavel Roskin proski
Thu Nov 10 11:28:17 PST 2011

On Thu, 10 Nov 2011 07:58:51 -0800 (PST)
hong zhang <henryzhang62 at yahoo.com> wrote:

> List,
> I am thinking why wifi driver needs rate control and ethernet does
> not have it.
> For example, if Tx fifo is full, then stop_queue is called so that
> upper lay will stop sending packet. When Tx fifo is empty then kernel
> starts sending packet again.
> Does wifi chip have some special registers to control rate?

Yes.  In wifi, it's possible to send each packet at a separate
rate.  Ethernet devices negotiate the rate once and use it for all

It's much more likely to lose a packet in a wireless network than on a
wire. That's why important packets are sent at lower rates.  If the
losses are too high, most packets are sent at a lower rates.  Some
smart rate control algorithms would still send some packets at a higher
rate to see if the connection has improved.

I'm not sure if such approach would be useful on a wire.  Perhaps it
could be done, but it won't be ethernet as we know it.

Pavel Roskin

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