Re: [ath9k-devel] Delayed Block Ack support ?

[Olivier Marce]

Hi,
many thanks for these hints.





In slide 2 I assume that :
- Retry=0 at transmitted side
- No Ack set at received side


Best regards


On 01/03/2014 02:59, Adrian Chadd wrote:

When looking at the details needed to implement Delayed BA, I have concerns with the HW behavior. In the best of my understanding, HW manages the sent/received ACK as well as the frame retransmission. Then I wonder how the transmitter HW will behave when it will get a Delayed BA. Attached are some flow charts that depict my understanding of normal behavior (slide 1) and how a SW Delayed BA could behave (slide 2) - Delayed BA is not handled by HW at transmitted side, but I don't know how to make it possible.

hi,

Well, the point is that the receiver will know what was successfully
transmitted as it's tracking the sequence number space of the received
packets.

So, you need

* some way on the receiver to construct a bitmap from that to
determine what the current block-ack response should look like;
* add in the code to handle a block-ack request and respond with the
current block-ack window (in a manual BA, right? I forget.)
* announce you can do delayed-blockack;

Then on the transmitter:

* add in logic to transmit frames with no-ACK set;
* then add some way to know when to send the BA request - eg, once the
hardware has reported it's finished sending the frame (it won't have
an ACK, but it'll at least tell you that it's actually DMAed it out
and sent it out the air)
* .. then send the BA request
* And then add code to handle the BA response and update the transmit
side BA tracking (that's done right now by looking inside the TX
completion descriptor.)



-a


On 28 February 2014 02:26, Olivier Marce
<olivier.ma...@alcatel-lucent.com> wrote:

Hi,
I'm looking for Delayed Block Ack support in ath9k.

Is the situation different than on Nov 2012 ?
https://lists.ath9k.org/pipermail/ath9k-devel/2012-November/009867.html

I wonder how what have been suggested could work:

* send aggregate frames, up to whatever your window size is;
* wait a  little bit;

waiting from when ? Once the frames passed to the HW to be transmitted ?
But will not the HW transmit Immediate BA ? If disabled, how to get a
status of received/not received frames ?

  > * send a BA;
BAR I guess

  > * respond with a manually constructed BA frame with the current

state of the BA window.

See before : how to get the state of the BA window if the HW did not
complete the transmission.

Thanks

--
Olivier Marcé
Alcatel-Lucent Bell Labs France
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--
Olivier Marcé
Alcatel-Lucent Bell Labs France

DelayedBAFlowChart.pdf
Description: Adobe PDF document

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