[Make-wifi-fast] [Cerowrt-devel] closing up my make-wifi-fast lab

[Bob McMahon]

Hi Jonathan,
I think in 802.11ax the AP can schedule STAs to some extent so it looks
like that technique is coming soon.  It is a bw tradeoff per the RUs per
user.

Multi-User Uplink Operation

To coordinate uplink MU-MIMO or uplink OFDMA transmissions the AP sends a
trigger frame to all users. This frame indicates the number of spatial
streams and/or the OFDMA allocations (frequency and RU sizes) of each user.
It also contains power control information, such that individual users can
increase or reduce their transmitted power, in an effort to equalize the
power that the AP receives from all uplink users and improve reception of
frames from nodes farther away. The AP also instructs all users when to
start and stop transmitting. As Figure 10depicts, the AP sends a multi-user
uplink trigger frame that indicates to all users the exact moment at which
they all start transmitting, and the exact duration of their frame, to
ensure that they all finish transmitting simultaneously as well. Once the
AP receives the frames from all users, it sends them back a block ACK to
finish the operation.



*Figure 10. Coordinating uplink multi-user operation*




On Mon, Aug 27, 2018 at 12:52 AM Jonathan Morton <chromatix99 at gmail.com>
wrote:

> > On 27 Aug, 2018, at 10:06 am, Bob McMahon <bob.mcmahon at broadcom.com>
> wrote:
> >
> > How can a centralized device predict the many "end stations'" network
> demand in its time scheduling?
>
> DOCSIS does it by initially giving stations a tiny window into which to
> send requests for time, which are granted by the head-end.  This introduces
> some latency.  Further requests for time can be appended to a real
> transmission, which helps efficiency slightly.
>
> Developing from that model, an AP might initially divide time evenly
> between stations, allowing them to send single large packets or several
> small packets without an explicit request for time - this is good for
> latency.  Along with that packet, the station could indicate to the AP that
> it has a queue of packets waiting, and the AP would take that into account
> when producing its next schedule.  It would also take into account its own
> queue.
>
> It may be possible to combine TDM with orthogonal coding.  Here the AP
> monitors the received signal strength of its stations, and instructs them
> to change power so as to minimise the difference between them.  This
> maximises the SNR for each, should two transmit simultaneously.  The
> tradeoff, of course, is that orthogonal coding permits a reduction in
> waiting to transmit, but requires a reduction in data rate during the
> transmission.  I'm sure other people have better data on that than I do.
>
>  - Jonathan Morton
>
>
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