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[STDS-802-11-TGBE] Follow up on the discussions of EHT PPDU scrambler (DCN: 11-20-0563)

Dear all,

Thanks for the discussions on the call yesterday. To make the discussions on this topic more efficient in future calls, this is a follow up to address the feedback I got.

If I captured correctly, there are mainly two issues raised on the call: 1) the motivation: if it’s very often to see contiguous “0”s or “1”s over WiFi transmission. 2) any other solutions? E.g. per tone phase rotation.

 

Response to the 1st question: I did simple experiments and include the results in page 14 and 15 of 11-20-0563r1 on the server.

  • Took a photo of all black (ISO set to lowest value to avoid color noise from the camera) and save in “RAW” format. As shown in page 14 left, a large number of contiguous “0” show up.
  • Took a photo of colorful and save in “RAW” format. As shown in page 14 right, better than all black but still see a large number of contiguous “1” or “0”.
  • Took a photo of all black or color and save in “JPEG” format. As shown in page 15, The pattern is very random due to compression.

Compression helps to randomize the data but there are a large number of photos are saved in “RAW” format because there will be huge benefit if you want to do post processing in future (I save 80% of photos in RAW). Photo file is just an example that I can easily repeat from my end, video and audio file are the same as long as they are saved in uncompressed for post processing. Although encryption can help randomize the data, but it is not mandatory in fields.

Bottom line: As a standard group we cannot control the behavior of end user (how people save files and whether encryption is conducted or not), but what we can do is to optimize the standard and technology to accommodate the WiFi usage scenario in the field.

 

Response to the 2nd question: As I mentioned on the call, very likely we can find other options to approach the performance of the one proposed in my contribution. However, the question is if it worth to find another one? The scrambler has been used since 11a and was proved to work well so far. Simply extend the polynomial with a higher order (to accommodate 11be high QAM, large BW) has the benefit of reusing existing implementation structure.

 

Please kindly let me know if I missed any comments or any further question you have. Thanks.

 

BRs,

Xiaogang.

 

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