[Bloat] [Cerowrt-devel] uplink bufferbloat and scheduling problems

[Jan Ceuleers]

On 01/12/2021 21:26, David P. Reed wrote:
> In any CSMA link (WiFi), there is no "up" or "down". There is only
> sender and receiver, and each station and the AP are always doing both.

Generally though the silicon used in WiFi APs is much more capable than
that used in STAs. The capabilities of (particularly STA-side) silicon
are different as they relate to uplink and downlink.

Of course for a given AP-STA link a common subset of capabilities needs
to be used, but that subset might be different in either direction.

The antennas (number and gain), receiver sensitivity and transmit power
are also different.

A simple example of a reason why uplink and downlink might be different:
the achievable bitrate on the AP-to-STA downlink might be higher than
the uplink because the AP's transmit power is higher. In order to be
able to achieve the same bitrate if the STA's transmit power is lower
the AP's receiver sensitivity would have to be that much better.

Generalising to other shared-media technologies: whenever the UL/DL link
budgets are different the link is going to by asymmetric.

Jan