wifi: Operational rate set is assumed to hold all mandatory rates
In a note in wifi-phy.h, it is mentioned that the Operational rate set of some devices may not contain all the mandatory rates mentioned in the standard, whereas in the ns-3 implementation assumes that the two sets are identical.
* A quick note is appropriate here (well, here is as good a place
* as any I can find)...
*
* In the standard there is no text that explicitly precludes
* production of a device that does not support some rates that are
* mandatory (according to the standard) for PHYs that the device
* happens to fully or partially support.
*
* This approach is taken by some devices which choose to only support,
* for example, 6 and 9 Mbps ERP-OFDM rates for cost and power
* consumption reasons (i.e., these devices don't need to be designed
* for and waste current on the increased linearity requirement of
* higher-order constellations when 6 and 9 Mbps more than meet their
* data requirements). The wording of the standard allows such devices
* to have an OperationalRateSet which includes 6 and 9 Mbps ERP-OFDM
* rates, despite 12 and 24 Mbps being "mandatory" rates for the
* ERP-OFDM PHY.
*
* Now this doesn't actually have any impact on code, yet. It is,
* however, something that we need to keep in mind for the
* future. Basically, the key point is that we can't be making
* assumptions like "the Operational Rate Set will contain all the
* mandatory rates".
This note has been written by Dean in yans-wifi-phy.h back in 2010 (cd6ccc18) and moved to wifi-phy.h by Sébastien in 1e6e44b3