What is the meaning of "20in80" and "40in80" of 802.11ac 80MHz in WIFI regulatory power setting?

[ZHMI_4627546]

When check WIFI regulatory power limit setting by "wl curpower",  I observed that 20in80, 40in80 and 80MHz regulatory limit of 802.11ac 80MHz at low and middle 5GHz band are not the same,  20in80 and 40in80 are using the regulatory limit for 20MHz and 40MHz bandwidth respectively.    On the contrary, 20in40 and 40MHz regulatory limit of 802.11ac 40MHz and 802.11n 40MHz are the same.

I want to know what is the limit setting of "20in80, 40in80" for?  Regulatory power limit of 80MHz is not the limit of each 20MHz "sub-channel"?

Thanks!

[GauravS_31 · Accepted solution]

The power limit on a subchannel is governed on the basis of subchannel rules. For instance, if STA is allowed to transmit on 80MHz channel but wants to transmit on its 20MHz subchannel, it would use the 20in80 subchannel rule. For 20in80, depending on the channel, the power limit could be 20MHz or the lower of 20MHz and 80MHz. Similarly, for 40in80, the power limit could be 40MHz or the lower of 40MHz or 80MHz. The subchannel rules are set in the CLM table internally.

[ZHMI_4627546]

Thanks a lot for your helpful and quick reply. 

A further question is,  any selection guide for power limit of subchannels?  As you said, " the power limit could be 20MHz or the lower of 20MHz and 80MHz."   How can I know which one is more reasonable?

Thanks in advance.

[GauravS_31]

Sorry but the channel mapping table for the subchannels based on the subchannel rules is applied internally by Cypress during CLM blob creation process and cannot be shared externally.

[ZHMI_4627546]

Understood. But why not set the power limit of 20MHz subchannel in 80MHz/40MHz to an available higher value (for instance limit for 20MHz, which is higher than 80MHz in most cases) for a better TRP?  What are the considerations of setting  power limit of 20MHz subchannel to a lower value (some as 80MHz in most cases)?

[GauravS_31]

For subchannels with band edge restrictions, the subchannel rules would limit the power numbers. This is especially true for countries with FCC and IC regulations. Otherwise the 20in80 would be assigned 20MHz.