Offline CSI phase processing HT mode in generic ESP32 device #261

Checklist

• Checked the issue tracker for similar issues to ensure this is not a duplicate.
• Provided a clear description of your suggestion.
• Included any relevant context or examples.

Issue or Suggestion Description

According to IEEE standard "In 40 MHz HT transmission, two adjacent 20 MHz channels form a 128‑subcarrier grid with pilots at −53, −25, −11, +11, +25, and +53, while data occupy −58 to −2 and +2 to +58; whereas in legacy duplicate mode, the same data stream is repeated across both 20 MHz channels, using −58 to −6 and +6 to +58 for data, leaving the central ±5 subcarriers unused.'

On collecting CSI data in ESP32 with Flags: sig_mode = 1, bandwidth = 1, channel = 1, secondary = 1, stbc = 0
, CSI phase across packets varies likely due to random switching of context between HT transmission and legacy duplicate mode in 40 MHz channel.

Could you please help to provide a mathematical approach /pseudocode so that CSI phase in both scenarios would be same and align? @NingYuxiang @NingYuxiang

Provide additional description on the above observation too.