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My Atheros-based wifi router has a really good SNR (usually above +20, also because I am just a few meters away from it) but very poor performance. Most of the time ping is awful (see end of post), TCP is obviously not much better, and often it cannot even complete WPA key exchange or get its IP address.

The antenna gain is 3 dB and the router is at a heights of approx. 1.3 m. It is very close to a DECT base station (less than 10 cm). There is a wall behind it. There is a wooden cupboard about 1 meter away from the router, but it's not in the path between the access point and the laptop. In the neighborhood I can see up to 4 active access points including mine. The access point is only broadcasting one SSID even though it could theoretically do two with different MAC addresses.

Other probably irrelevant information: the router is in bridged mode and the uplink is to a wired network, which is relatively complex because it also hosts my home office but has good performance (ping time < 2 ms).

Here is a ping example collected with no other traffic on the wifi. No lost packets, but it appears to me like the network is being shut for noticeable periods, ranging from 0.2 to 2 seconds (but I've even seen five pings arriving at the same time after 5 seconds of blackout):

64 bytes from icmp_seq=0 ttl=64 time=17.549 ms
64 bytes from icmp_seq=1 ttl=64 time=844.128 ms
64 bytes from icmp_seq=2 ttl=64 time=19.354 ms
64 bytes from icmp_seq=3 ttl=64 time=268.005 ms
64 bytes from icmp_seq=4 ttl=64 time=292.110 ms
64 bytes from icmp_seq=5 ttl=64 time=823.084 ms
64 bytes from icmp_seq=6 ttl=64 time=1.353 ms
64 bytes from icmp_seq=7 ttl=64 time=676.620 ms
64 bytes from icmp_seq=8 ttl=64 time=176.904 ms
64 bytes from icmp_seq=9 ttl=64 time=11.536 ms
64 bytes from icmp_seq=10 ttl=64 time=1.413 ms
64 bytes from icmp_seq=11 ttl=64 time=862.640 ms
64 bytes from icmp_seq=12 ttl=64 time=1.436 ms
64 bytes from icmp_seq=13 ttl=64 time=822.594 ms
64 bytes from icmp_seq=14 ttl=64 time=1.419 ms
64 bytes from icmp_seq=15 ttl=64 time=870.897 ms
64 bytes from icmp_seq=16 ttl=64 time=1.417 ms
64 bytes from icmp_seq=17 ttl=64 time=918.914 ms
64 bytes from icmp_seq=18 ttl=64 time=6.308 ms
64 bytes from icmp_seq=19 ttl=64 time=848.949 ms
64 bytes from icmp_seq=20 ttl=64 time=8.535 ms

Additional info, the behavior where "every other second something goes bad" is true even when wifi works. It just doesn't go as bad...

64 bytes from icmp_seq=42 ttl=64 time=8.209 ms
64 bytes from icmp_seq=43 ttl=64 time=2.727 ms
64 bytes from icmp_seq=44 ttl=64 time=11.154 ms
64 bytes from icmp_seq=45 ttl=64 time=1.931 ms
64 bytes from icmp_seq=46 ttl=64 time=12.076 ms
64 bytes from icmp_seq=47 ttl=64 time=2.908 ms
64 bytes from icmp_seq=48 ttl=64 time=15.090 ms
64 bytes from icmp_seq=49 ttl=64 time=1.805 ms
64 bytes from icmp_seq=50 ttl=64 time=15.800 ms
64 bytes from icmp_seq=51 ttl=64 time=2.382 ms
64 bytes from icmp_seq=52 ttl=64 time=17.613 ms
64 bytes from icmp_seq=53 ttl=64 time=1.841 ms
64 bytes from icmp_seq=54 ttl=64 time=19.485 ms
64 bytes from icmp_seq=55 ttl=64 time=1.876 ms
64 bytes from icmp_seq=56 ttl=64 time=21.485 ms
64 bytes from icmp_seq=57 ttl=64 time=1.888 ms
64 bytes from icmp_seq=58 ttl=64 time=23.365 ms
64 bytes from icmp_seq=59 ttl=64 time=1.876 ms

Also, turning off the DECT station changes nothing.

share|improve this question
Did you try the obvious: Powering down the base station temporarily and then moving the router around to see if it makes an impact on the performance? – AndrejaKo Sep 11 '11 at 18:00
No, and I will. :) But if that could help, shouldn't the interference cause a higher noise value? – Paolo Bonzini Sep 11 '11 at 18:19
Well, I have no idea. Some DECT devices operate in the 2.4 GHz band and may cause interference in non-obvious way. There are interoperability sections in relevant standards and in some cases it could happen that for example the router will wait for other devices in the band to finish and only then transmit (just like in your case). You could get high SNR, but that's no guarantee that the signal will be continuous. It just literally means that the reception of the signal is good. – AndrejaKo Sep 11 '11 at 18:31
Note European DECT is 1.9 GHz. – Paolo Bonzini Sep 12 '11 at 7:52
DECT 6 is 1.9 GHz everywhere. – Joshua Sep 12 '11 at 17:39

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