Question: Should FCC-region 6 GHz entries use the India PSD methodology?

[Louis Kotze]

Hi Chen-Yu,

Following the patch series I just submitted, I have a question about
the FCC-region 6 GHz entries.

Currently 12 countries (US, CA, BR, AR, CO, PE, SV, MX, CL, KY, HN,
PY) use 12 dBm for 6 GHz LPI. I understand this was chosen as the
absolute minimum across all device types and channel widths.

However, the India (IN) entry (commit 5db6ce73) uses a different
methodology — PSD at 20 MHz minimum channel width:

  India: 11 dBm/MHz × 20 MHz = 24 dBm

Applying the same approach to FCC (5 dBm/MHz PSD):

  FCC: 5 dBm/MHz × 20 MHz = 18 dBm

18 dBm is compliant at every standard WiFi channel width (>=20 MHz)
for both AP and client devices:

  Width   PSD limit   FCC client max   18 dBm   Legal?
  20 MHz    18 dBm       24 dBm        18 dBm   Yes
  40 MHz    21 dBm       24 dBm        18 dBm   Yes
  80 MHz    24 dBm       24 dBm        18 dBm   Yes
  160 MHz   27 dBm       24 dBm        18 dBm   Yes
  320 MHz   30 dBm       24 dBm        18 dBm   Yes

The reason I ask: during my work on the South Africa (ZA) fix, the
9 dBm gap between the regdb (14 dBm) and the AP's advertised power
(23 dBm) caused repeated "regulatory prevented using AP config,
downgraded" errors and complete 6 GHz association failure. The FCC
gap is 18 dBm (12 vs 30), which would cause the same or worse
symptoms for any Linux user connecting to a standard FCC LPI access
point on 6 GHz.

Would the India PSD-at-20-MHz methodology be appropriate for FCC
countries as well?

Thanks,
Louis