CYW43455 5G WiFi : DFS, Channel Availability Test (CAC)

[bhushanpawar]

Dear Cypress/Infineon Team,

We are currently using  CYW43455 Single-Chip 5G WiFi IEEE 802.11n/ac MAC/Baseband/ Radio with Integrated Bluetooth 4.2 module for one of our products.

For the DFS, we are using sequence of commands mentioned in Section 4.2.6. from the Regulatory Manual, Here is the sequence,

wl down
wl ap 1
wl mpc 0
wl country DE
wl band a
wl dfs_preism 1

wl spect 1
wl chanspec 100/20
wl up
wl radar 1
wl ssid DFS_AP
wl status
wl dfs_ism_monitor 0
wl chan_info

However, we observed that when we execute all commands one after the other, "DFS_AP" transmission starts before 60 seconds scan is completed.

As the regulatory manual explains, transmission should not start before 60 seconds irrespective of presence of radar signal on the channel.

Channel Availability Check (CAC) :
This test applies to devices that are capable of detecting radar signals. The Channel Availability Check (CAC) test is
where the radio scans a target DFS channel (that it would like to utilize) for radar signals for a period of 60 seconds.
After the 60 second scan, if no radar signals are detected, the radio can transmit on the target DFS channel.

Is there any specific way, CAC test should be performed? Why the transmission starts before 60 seconds?

Thanks and Regards,

Bhushan Pawar

[YashM]

Hi

Could you please let me know the firmware version being used here (wl clmver output)?

Thanks

[bhushanpawar]

Hi,

Thank you for your message.

I checked the firmware version as suggested. Below are details for the same,

wl clmver
API: 12.2
Data: 9.10.136
Compiler: 1.29.4
ClmImport: 1.36.3
Creation: 2019-05-02 02:31:30

Thanks ! @YashM 

[YashM]

Hi

Could you please use the latest firmware Cypress-Linux-WiFi-Driver-Release-FMAC-2021-01-14/td-p/268899 and test your setup?

Please let me know what you observe.

Regards

[BeKr_3338931]

Hi,

Is the new firmware compatible with older FMAC drivers (we are still on kernel 4.14.78) or do we need to consume the driver patches as well?
Also, do we need to update the clm_blob as well form the latest release?

Thanks

[YashM]

Hi

So, just for DFS testing purposes, you can just replace the firmware and clm_blob file. If you need more features (which are not available in older versions) then you might require to do those back-porting given in README.

Thanks

[BeKr_3338931]

Thanks,

Unfortunately if I replace both I get a wl: error -20 for the wl chanspec 100/20 command, also wl chan_info does not list any DFS channels.
If I keep the old clm_blob with the new driver chanspec works but I see no difference in behavior.
I also noticed that on an otherwise silent channel 100, when wl up is executed from the command sequence from chapter 4.2.6 of the Regulatory Manual I see a Clear-to-send frame sent from an unknown Broadcom MAC and then there is a 3-4 kbytes long frame of seemingly bogus data. These seem to come from or device. Right after these the AP starts to send the beacons normally, however we are still well within the CAC period. Wireshark capture attached.

Regards

[YashM]

Hi

We are trying to reproduce this issue at our end and will get back to you but in the mean-time could you please test your setup with country code US/0 or BE/4 and can you let me know your observations?

Thanks

[bhushanpawar]

Hi,

Thank you for your message.

We tried both the country codes suggested by you. Please find attached log files for the same.

As you can see in the log file, we create a batch file (DFS_CH100_CACon_ISMon.sh) for command execution (Example batch file attached).

Regardless of the change in Country Code US/0 or BE/4,

Status of channel 100 changes from Passive to Radar Sensitive (Active) immediately after AP was enabled.

Channel 100 A Band, RADAR Sensitive

and

'DFS_AP' is visible before 60secs scanning time is completed.

Thank you @YashM Please look into the issue.

Regards,

Bhushan

[BeKr_3338931]

Yes, and with packet capture I still see the strange Clear-to-send frame for both US/0 and BE/4 country codes right after 'wl up'. And then the AP starts transmitting beacons immediately. I have tried different firmware and clm_blob versions but see no difference.

[YashM]

Hi,

So, we did the test and we found that "wl dfs_preism 1" is changing the timer values. This particular command is used to speed up the lab certification testing. Hence, by setting "wl dfs_preism 1" you force the CAC timer to ~1sec instead of 60 secs.

The default value of "wl dfs_preism" is "-1" which is 60 secs. Hence, if you want to test and wait for 60 secs, I would recommend you to not add that command in your script. 

Note: Please unload the insmod (firmware) after removing the "wl dfs_preism" command and then load the insmod again or else it would take the previously set value.

After passing "wl chan_info" you can pass "wl dfs_status" to check the CAC timer.

Please follow the above steps and let me know your observations.

Thanks and Regards

[bhushanpawar · Accepted solution]

Hi @YashM ,

Thank you for your help.

Using wl dfs_preism -1 command resolves the issue. This command sets the CAC scan time to default (60sec/10mins) based on the channel selection.

Thanks and Regards,

Bhushan