802.11 error frame reception

humptydumpty
Posts: 27
Joined: Thu Sep 07, 2017 10:26 am

802.11 error frame reception

Postby humptydumpty » Sun Feb 03, 2019 3:24 pm

For a commercial application we need 802.11 error frame reception in promiscuous mode. Purpose is to implement Reed-Solomon-Code for error correction of broadcast packets. Is it possible?

ESP_Angus
Posts: 2344
Joined: Sun May 08, 2016 4:11 am

Re: 802.11 error frame reception

Postby ESP_Angus » Mon Feb 04, 2019 6:45 am

Do I understand correctly that you want to be able to receive invalid 802.11 data frames?

I don't think this is possible on ESP32, the lower MAC layer discards them at an early stage (it more or less has to, in order to maintain good throughput of valid frames.)

Maybe I don't understand your full purpose, but as you probably know 802.11 already makes use of forward error correction algorithms.

humptydumpty
Posts: 27
Joined: Thu Sep 07, 2017 10:26 am

Re: 802.11 error frame reception

Postby humptydumpty » Thu Feb 07, 2019 12:30 am

I understand that 802.11 already has forward error correction. However, when the error correction fails for one or more blocks within a packet, the entire packet is discarded.

Due to the highly repetitive nature of the data we are sending, it would be useful to receive the discarded packets. The remaining blocks could be used. This would considerably extend the usable range of the device.

We could also just send a lot of short packets of course. But the overhead would be quite large. And the ESP32 seems to be limited to about 1.2 milliseconds per packet. So we couldn't get such a big improvement this way without sacrificing necessary throughput.

ESP_Angus
Posts: 2344
Joined: Sun May 08, 2016 4:11 am

Re: 802.11 error frame reception

Postby ESP_Angus » Thu Feb 07, 2019 4:21 am

I see, thanks for explaining. I've asked the Wi-Fi team if it's possible to forward frames with bad FEC to the sniffer (promiscuous) interface.

We won't get an answer until next week, due to the Spring Festival holiday.

ESP_Angus
Posts: 2344
Joined: Sun May 08, 2016 4:11 am

Re: 802.11 error frame reception

Postby ESP_Angus » Mon Feb 25, 2019 3:08 am

It seems like this may be possible in a future release, but I'm afraid I don't have any ETA.

humptydumpty
Posts: 27
Joined: Thu Sep 07, 2017 10:26 am

Re: 802.11 error frame reception

Postby humptydumpty » Mon Feb 25, 2019 10:03 am

Thanks for asking. Would also be useful to be able to sniff for Bluetooth.

While I understand there are certification issues as far as radio transmission is concerned, I don't see why the radio functions have to be so undocumented on the reception side.

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