Periodic Scan Issue

Hi Sanjay,

I'm now able to configure "Periodic Scan" successfully. Thanks.

However, I tried the following "Periodic Scan" test scenario (with the same configuration - as mentioned earlier):

Scenario 1:  a) Configured the OMAP3530 EVM to do Periodic Scan. b) Turned 2 APs (Access Point) on. c) Used CLI and print the scan list ("Connection" and "Bssid_list"). Result: The 2 APs were showed in the scan list.

Scenario 2: a) Stopped and configure the OMAP3530 EVM to do "Periodic Scan" again. b) Used CLI and print the scan list ("Connection" and "Bssid_list"). Both APs were showed in the scan list. c) Switched one of the APs off. d) Used CLI and print the scan list ("Connection" and "Bssid_list"). Result: 2 APs were showed in the scan list - even though one of them is switched off.

I tried Scenario 2, point d) for a period of 40 seconds (considering the used configuration: 10 scan cycles w/ intervals of 5000ms = 5 secs, the periodic scan shall last 45-50 seconds): Still, 2 APs were showed in the scan list - even though one of the AP has all the time (40 secs) been switched off.

So, here are my questions:

1) Why does CLI only add APs (alive) to the scan list – but does not remove them, even when the APs are switched off? Is this the expected behavior? Why?

2) Given the following: Num. of scan cycle = 10; Probe Request Number = 3 and Interval (in milliseconds) = 5000. I would expect 30 "Probe Requests" after 10 scan cycles (3 probe requests from the OMAP3530 EVM to the AP - every 5 secs). However, I got sometimes 40, 39, 35, 45, 34 - but not 30. E.g.: Here's how the 10 scan cycles "Probe Requests" were distributed (every 5 secs) to yield 45: 4, 4, 4, 6, 3, 4, 3, 6, 6, 5. Only 2 times out of 10 is as configured.  Is this OK? Why?

3) I now tried to increase the "Num. of scan cycles" from 10 to 20. I therefore, expected the scan cycles to last a double of 45-50 secs (90-100 secs). But it lasted 5min and 45 secs. So, no linearity. Is this OK? Why?

Note: Wireshark were used all the time (in scenario 1 & 2 and in question 3) to collect the info presented above. Please, see the attachment - for details.

2705.Periodic_Scan_Issue_Data.xls.xls

Hi,

Can you please tell me the driver version?

The scan mechanism is changed during the versions.

In most versions we have an aging mechanism which keeps the AP in the list for a specific period (default is usualy 60 sec) even if it was not found during a scan in this period.

In older version the mechnism only add/update new APs and doesn't delete any of them ( as you mentioned in Q.1)

Nisim , 

Hi Nisim,

Hi Tony,

Sorry if I missed the driver info at the first message.

The driver version you are using is quite old and there were many improvements and bug fixes since then.

If it is possible for you I can recommend to download the latest driver version from the following link:

http://software-dl.ti.com/dsps/dsps_public_sw/sdo_sb/ecs/WL1271_Linux_SDK/3_00_01_06/index_FDS.html

You can use our wiki page for instructions on how to do it:

http://processors.wiki.ti.com/index.php/OMAP35x_%26_AM/DM37x_Wireless_Connectivity_Platform

Thanks Nisim

Hi Nisim,

I have now upgraded to the latest release (OMAP3530 Beta2 Release) - as you recommended:

\> Driver/, Connection/, Management/, Show/, Privacy/, scAn/, roaminG/, qOs/, poWer/, eVents/, Bt coexsistance/, Report/, dEbug/, biT/, aboUt, Quit
u
Driver version: WiLink_Driver_6.1.0.0.144_NOCCX
Firmware version: Rev 6.1.0.0.335

Unfortunately, all three points (1, 2 & 3) reported above (on the old version) are still present on the new one as well.

For Point 1: Are APIs to achieve "the desired behavior" (once in Periodic Scan, remove AP when the station is not avaialble or turned off) available in the current driver release? If, yes, can you please provide a code sample on how to use the APIs to achieve "the desired behavior"? Otherwise, what is required to achieve "this desired behavior"? Is there any particular reason (e.g.: performance issues) why you choose not  to implement "this desired behavior"?

Can you please provide the answers for point 2 & 3?

Thanks,

Tony.

Hi Tony

I just made a test with my ZOOM setup and the following version.

Driver version: WiLink_Driver_6.1.0.0.144_NOCCX

Firmware version: Rev 6.1.0.0.335

The results are just as desired:

1.       Running scan (/a s) command from wlan_cu CLI.

2.       Show the AP list ( / c b ). Shows my AP ( nisim_ap).

3.       Turn off AP.

4.       Running scan again (/ a s ).

5.       Show the AP list ( / c b ). Does not show my AP ( nisim_ap) if aging period was over ( in my .ini file it was set to 20 sec) .  

If I’m turning on the periodic scan (/ a e t) the results are the same except of the fact I do not need the manual scan as I did in steps 1, 4 above.

As for the periodic scan timings I will need to check.   

Thanks,

Nisim.

Hi Nisim,

Your test scenario1 (the application scan) has never been a problem - it worked from day one.

However, scenario2 (Periodic Scan) is still not working. I tried "ScanResultAging" 60 (default); 20; 5; 0; (from my .ini file) - but none of them seems to help. The result is still the same: AP are added to scan list, but not removed - even when the AP is switched off. In miss to see where did you configure your Periodic Scan parameters?

Can you please show me your "Periodic Scan parameters" (issue "/ a e d", just before "/ a e t") and both ".ini files" (tiwlan.ini & tiwlan_dual.ini)?

Attached is my "Periodic Scan parameters" and both ".ini files" - for comparison.

Thanks,

Tony.6837.PeriodicScanParameters.zip

Hi Tony

When starting periodic scan from CLI the driver clears its Bssid_list list and send periodic scan command to firmware.

For each relevant Probe-Rsp the firmware is updating the driver with the Bssid name.

For that reason the driver is not deleting the previous Bssids, just adding new ones.

So actually your only way to see your AP is missing, when you turn it off, is to run ( / a e t ) again.

As for the probe timings - According to my tests I saw the probe–req is being sent correctly so I will publish the parameters description in our wiki pages in the next future.

I will be able to help you more if you can share with me what are you trying to achieve with this periodic scan. Main purpose of periodic scan is to let the FW scan for your known APs without waking up the device.

Thanks,

Nisim  

Hi Nisim,

Our long discussion is probably drifting away from its main point - sorry for that & your patience is appreciated.

Lets summarize:

Periodic Scan:

a) What I want to achieve with Periodic Scan is as you described in your third "Replay": "If I’m turning on the periodic scan (/ a e t) the results are the same except of the fact I do not need the manual scan as I did in steps 1, 4 above.". I was able to verify this beahvior only - for new discovered AP. But NOT for already in STA's scan list and switched off AP - even with low "ScanResultAging" of zero (0) or 5 secs.

Based on your last "Replay" (above), if I understand correctly, STA only adds - but will not delete switched off AP from the scan list. But again, I understood from your 1st "Reply " that older driver versions work this way - as new drivers implement the "aging process" (which keeps a switched off AP in STA's list - only for a configurable period = ScanResultAging).
b) How is Active Periodic Scan expected to work (see my third post - question 1 for details) for Driver version: WiLink_Driver_6.1.0.0.144_NOCCX & Firmware version: Rev 6.1.0.0.335?

c) If possible, how can I achieve point "a)" also for already in STA's scan list and switched off AP - without manual scan?

Regards,

Tony.

Tony,

I’m basing my checks on the version: WiLink_Driver_6.1.0.0.144_NOCCX & Firmware version: Rev 6.1.0.0.335. There were many changes during the version tree and it is irrelevant to deal with them as relate to your current problem.

As I wrote before my tests shows that periodic scan only adds new APs as you mentioned. I will check if there is any way to achieve your goal, but I won’t have answers before next week.

As for the Periodic scan mechanism – I will publish explanation in our wiki pages. Hope to have it by next week.

Thanks,

Nisim

Hi Nisim,

What could be the reason for sending more than 3 probe requests by the wl1271? I also have logs that shows more probe requests from the station (08:00:28:77:34:56)  than  configured (3 probe requests).

Best Regards,

Sinoj

Hi,

The number of configured Prob-req is per channel. If you configured the device to scan all channels the sniffer might see Prob-req from a neighbor channel also.

To avoid such case while testing you can set the scanned channels to be 1,6,11 for example.

Thanks;

Nisim

Hi Nisim,

Thank you for your help. I will set the channels to 1, 6 and 11 and do testing.

Best Regards,

Sinoj

Hi

You can use the following WIKI page to get instructions for periodic scan / background scan:

http://processors.wiki.ti.com/index.php/ARM_Processor_Wireless_Connectivity_FAQ#How_to_set_periodic_scan.3F

Nisim