2012-09-07 22:25:31

by Cedric DEBARGE

[permalink] [raw]
Subject: Unexpected periodical Wi-Fi speed drop

Hi all,

I am encountering a periodic (each 1 second) Wi-Fi transmission speed drop
(from 54Mbps to 6Mbps) during an iperf between two mesh portals.
The speed stays stuck to 6Mbps during about 300ms and then recovers its 54Mbps
rate. About 1 second later this happen again.

The Wi-Fi speed drops from 54Mbps to 6Mbps without any intermediate speed nor
frame loss.

My channel is clear from any other Wi-Fi devices disturbances.

My system is as follow :
__ _ __ _
192.168.2.41 [__]|=| Wireless devices [__]|=| 192.168.2.38
1c:75:08:0b:76:52 /::/|_| are close to each /::/|_| 08:00:27:6e:54:11
| other (about 15cm) ^
Ethernet| | Ethernet
| |_|_| |_|_| |
'---->[____?] [____?]-----'
Mesh Portal Mesh Portal
90:A4:DE:21:4F:11 00:1B:B1:58:F6:DD

Kernel : 2.6.33.7
Compat Wireless : 2012-06-14
Radio chipset : AR9160 (ath9k)

Please find attached a wireshark wireless trace of the drop itself
(between packets 6 and 7).

Can you give me some clue how to work it out ?
Thanks in advance,

Best regards,

C?dric DEBARGE | ACKSYS Support Team
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T : +33 1 30 56 46 46 | F?: +33 1 30 56 12 95?
[email protected] |?http://www.acksys.fr
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Attachments:
drop_capture.pcap (14.64 kB)
drop_capture.pcap