Roaming between 2 APs with WDS

Víctor Andrés victor
Tue Oct 14 00:44:43 PDT 2014

Hi Dan,

If I set the search in one channel, it's out of transmitting for 110 ms 
(more or less). But if I set in the configuration for search only for 
the channel in use, it will scan in 2 channels, and the time searching 
(not transmitting) will be for 200 ms (more or less).

I need to transmit data at 1000 Hz, so with this time searching, I have 
small breaks in the flow data. The data aren't lost, but in the flow 
data you can see that small stops.
Any other alternative? I think less than 100 ms of searching and 
transmitting is not possible, isn't it?

Wpa_supplicant log, for scanning only in channel 2412 MHz (cannel 1):
1413272106.062501: nl80211: Scan frequency 2412 MHz
1413272106.064362: Scan requested (ret=0) - scan timeout 30 seconds
1413272106.065553: nl80211: Event message available
1413272106.066987: nl80211: Drv Event 33 (NL80211_CMD_TRIGGER_SCAN) 
received for mlan0
1413272106.067902: mlan0: nl80211: Scan trigger
1413272106.068665: mlan0: Event SCAN_STARTED (49) received
1413272106.069001: mlan0: Own scan request started a scan in 0.003479 
1413272106.069733: mlan0: CTRL-EVENT-SCAN-STARTED
1413272106.180420: nl80211: Event message available
1413272106.180694: nl80211: Drv Event 34 (NL80211_CMD_NEW_SCAN_RESULTS) 
received for mlan0
1413272106.180847: mlan0: nl80211: New scan results available
1413272106.180908: nl80211: Scan probed for SSID 'WIRELES1'
1413272106.181000: nl80211: Scan included frequencies: 2412
1413272106.181091: mlan0: Event SCAN_RESULTS (3) received
1413272106.181183: mlan0: Scan completed in 0.112213 seconds


El 10/10/2014 19:29, Dan Williams escribi?:
> On Fri, 2014-10-10 at 11:56 +0200, V?ctor Andr?s wrote:
>> Hi Avinash,
>> I'm using the firmware version 14.66.9.p192
>> (;a=commit;h=633d06edab7a2b82efaa134ec5591cd20f9ac0a3)
>> and testing the recent commit p52 version
>> (;a=commit;h=3f45b8c4cc1eb1d102bc3486b19677332dd215ab),
>> but I'm not sure of this last commit, becauseeven if it was posted more
>> recent, it's a previous versionof the FW.
>> Yes, the roaming is working now. I'm trying to reduce the scanning
>> timein order toscan only the channel in use or only for the known bssid.
>> When the interface is scanning it isn't transmitting data, and what I
>> need is a continuous flow of data.
> Scanning only the channel-in-use doesn't work very well for roaming,
> because close-by APs are quite likely to be on a different channel to
> ensure they don't interfere with each other.  Scanning for a known BSSID
> doesn't work very well because you still have to scan a bunch of
> channels to find the BSSID you're looking for.  The driver/mac80211
> should be capable of partial scans (send PS, scan 2 or 3 channels, jump
> back to operating channel for a while), is that not happening?  How long
> is the card off the operating channel for, and what are your latency
> requirements?  Is 100ms too long to pause data transmission?
> Dan

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