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duby2291
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PostPosted: Sat Dec 29, 2012 10:57 pm    Post subject: very high packet loss over wifi. Reply with quote

Hey guys. This is not a gentoo specific problem, however there are too many guru's here to ignore.

The problem comes down to my neighbors new router... Ever since I saw that dang ssid pop up I've been getting very high packet loss on my router. I've tried using a dozen different channels with no success. The wifi adapter is USB, so I got a couple USB extenstions and moved the adapter as close to the router as the extensions would allow. I have a great signal, always have. It stays in the 90% range... I'm just at a loss as to what I can do now...

I think I may need to get a new wifi adapter that is less sensitive to interference. What do you guys think I should do?

EDIT: I didnt let it run very long, but this is just an example of what I'm experiencing. This is with an 88% signal.

Code:
--- 192.168.1.1 ping statistics ---
74 packets transmitted, 29 received, 60% packet loss, time 73028ms
rtt min/avg/max/mdev = 2.020/38.609/1007.334/183.077 ms, pipe 2

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cach0rr0
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PostPosted: Sat Dec 29, 2012 11:12 pm    Post subject: Reply with quote

how flexible are you in what you can buy and what you'd see as an "acceptable" solution?

Because moving to the 5GHz spectrum should clear things up nicely

I'm in a major metro area, and every idiot around me has a wifi router. So, where I have devices that support it, moving to 5GHz has done quite nicely
For the handful of devices that aren't capable (including the laptop I'm on currently), setting my wireless AP to run in "N-only" mode has helped. Before, it was in B/G/N mode. If that makes sense. And I can only guess that caused my crappy connectivity and interference. Moved to N-only and life has been much better.

...of course, I'm also affected by the fact that intel wireless cards on linux suck. Firmware breaks, something in the kernel breaks, it's just an ongoing fight. BUT, in your case, if you're still on the same kernel, same firmware, as when things were good, and the only variable is that you now have tons of neighbors abusing the wireless interwebs, lean towards N-only, or, go 5GHz.
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duby2291
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PostPosted: Sat Dec 29, 2012 11:29 pm    Post subject: Reply with quote

Does it make sense that certain times of the day are better than others? Evenings are by far the worst. I can' only just barely browse between 4:00 and 7:00.. Other times of the day it is bearable....

But yeah, I can get a new router and adapter. That shouldnt be a problem. Are there any brands that are preferred? Is any one chip better than the rest of them?
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fpemud
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PostPosted: Sun Dec 30, 2012 2:00 am    Post subject: Reply with quote

I'm having the similar problem, not very serious though.
besides packet loss, I also encounters long round-trip time, RTT is 1~2ms when normal, but can be 3~10s when problem happens.
signal strength is irrelavant to my problem either.
i can see >=10 AP on my network-manager.

i can imagine not only I have this problem.
So I suspect there must be some people already changed to 11N or 5G device.
What to do when 11N or 5G is full of people? Can this new tech contain more channels than 2.4G a/b/g?

Before buying new 11N or 5G hardware, i want to make sure the problem is not cause by my own configuration or driver(ath9k, NetGear WNA1100 [Atheros AR9271]).
Can you give me some idea or doc on how to do this test?
and can I know which AP i'm conlicting with by some command?


Last edited by fpemud on Sun Dec 30, 2012 1:44 pm; edited 1 time in total
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cach0rr0
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PostPosted: Sun Dec 30, 2012 5:07 am    Post subject: Reply with quote

duby2291 wrote:

But yeah, I can get a new router and adapter. That shouldnt be a problem. Are there any brands that are preferred? Is any one chip better than the rest of them?


I'd go the "free" route first, and see if you can set your router to N-only

new hardware is the lazy, "i dont feel like troubleshooting" route. Which, is a route I quite like generally when it's my own money, not so keen on it when it's someone else's money.

As for wireless routers, a generic answer: whatever seems to be well supported by dd-wrt.
As for wireless adapters, I don't know what's the best chipset nowadays. It used to be atheros, may still be atheros.


fpemud wrote:
I'm having the similar problem, not very serious though.
besides packet loss, I also encounters long round-trip time, RTT is 1~2ms when normal, but can be 3~10s when problem happens.
signal strength is irrelavant to my problem either.
i can see >=10 AP on my network-manager.

i can imagine not only I have this problem.
So I suspect there must be some people already changed to 11N or 5G device.
What to do when 11N or 5G is full of people? Can this new tech contain more channels than 2.4G a/b/g?

Before buying new 11N or 5G hardware, i want to make sure the problem is not cause by my own configuration or driver(ath9k).
Can you give me some idea or doc on how to do this test?
and can I know which AP i'm conlicting with by some command?


this is why im hesitant to tell people "buy new hardware!". Namely
a)it's not my money
b)there's no guarantee that that's the root of the problem, so the money spent may be a waste.

I too, have run into a situation where occasionally my wireless card shits itself, and I'm getting 3-10 *seconds* latency pinging the gateway.
But in my case, I'm using iwlagn, with iwl-1000-ucode. There are known bugs with both the iwl1000 kernel driver and microcode that are causing it for me.

This is part of the hell with linux wireless. As I mentioned above, I *did* resolve one issue by changing one wireless AP from BGN mode to N-only mode. But then along comes a kernel bug, and a microcode bug, that spawn entirely new problems. I can say somewhat definitively, for anyone with the same wireless hardware as me, where to look for a problem. But for anyone else? Just generic "this MIGHT work" stuff.

Don't know how helpful that is. Far as 5GHz becoming saturated - by the time that happens, your current wireless router and/or adapter will likely have already fried.
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eccerr0r
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PostPosted: Sun Dec 30, 2012 6:32 am    Post subject: Reply with quote

I wish people would understand that wireless is a limited resource... and use it when it's absolutely necessary, not because it's convenient...

Running HD video and Bittorrent over wireless (wifi or cellular, same difference) has to be the most abominable usage of the limited resource. Also poor channel selection also wastes bandwidth. Some of this you can't control - it's other people using their wifi at the same time that makes it hard. Also the confusion of overlapping channels isn't clear when you also have to deal with DSSS vs OFDM vs channel width (depends on mode too) vs MIMO..and more...

You should at least try changing channels to see if it helps. However if your neighbor is using 802.11n on channel 6, they are being really inconsiderate and should be shot.
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duby2291
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PostPosted: Sun Dec 30, 2012 6:53 am    Post subject: Reply with quote

The reason that I'm not wired is because it would require drilling a hole thorough the outside wall (twice, adapter side and router side) and running the line along the outside of the house... It's a perfectly good option that I may resort to if it comes to that. But this is exactly the point of wifi. I suppose I could fish the line through the wall into the attic and back down through the other wall... But I really suck at it. I dont have the patience for it.

I'vr tried just about all of the channels and it doesnt seem to make a difference. The router does support n-only mode, but the adapter is g-only. so at minimum I would have to buy a new adapter to support n-only. Thanks for the tips guys. I'll see what can be done and post back here when I have more info.

I would like to have some more info on good linux supported n adapters though. If anybody has a good one that they think is awesome, let me know.
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PostPosted: Sun Dec 30, 2012 10:06 am    Post subject: Reply with quote

What eccerr0r said. ... use it when it's absolutely necessary, not because it's convenient ...
Everything is wired in my house, in rare cases when I take my laptop outside I turn on my AP, otherwise I keep it off.
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wcg
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PostPosted: Sun Dec 30, 2012 1:39 pm    Post subject: Reply with quote

I have a wifi router on a different floor than the wifi clients.
Wiring them up is inconvenient. On one, where signal strength
was low using a usb wifi adapter, I hooked up an external
usb hub and plugged the wifi adapter into it, then put an
aluminum pie plate from a pot pie under the wifi adapter.
The aluminum plate has a nice dish shape, not really
parabolic but close enough, and signal strenth improved
right away.

Maybe you can do something similar with a foot (or more)
of aluminum roof flashing. It should want to roll up when
it comes off of the roll. Put a clothespin or similar in between
the ends that want to roll together to hold them apart.
Set it around your router or router antenna(s), then rotate
it until it reflects signals from the neighbors away from
the router while not interfering with the direct path from
the router to your own workstations. (One might be
able to do something similar in a more compact area
with a hacked tennis ball can, partially surrounding only
the antenna itself. Aluminum foil would be another alternative.)

I would not expect this to entirely block signals from
the neighbors' adapters and routers, simply to reduce
their signal strength at your router antenna(s), while
perhaps increasing the signal strength between your own
stations and the router.

minstrel (CONFIG_MAC80211_RC_MINSTREL) will record some
statistics in debugfs if you have debugfs enabled in the kernel and
mounted:
http://wireless.kernel.org/en/developers/Documentation/mac80211/RateControl/minstrel
(I don't see that they report access point SSIDs or MAC addresses, though.)

"ET phone home."
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duby2291
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PostPosted: Sun Dec 30, 2012 3:38 pm    Post subject: Reply with quote

Jaglover wrote:
What eccerr0r said. ... use it when it's absolutely necessary, not because it's convenient ...
Everything is wired in my house, in rare cases when I take my laptop outside I turn on my AP, otherwise I keep it off.


That doesnt answer my question at all tho. I do understand your concerns about wifi, but the question was if you did need to use it what wifi adapter would you choose?
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eccerr0r
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PostPosted: Sun Dec 30, 2012 6:30 pm    Post subject: Reply with quote

(BTW, if your neighbor is using channel 6 for 802.11n in the 2.4GHz range, your best channel is... channel 6 802.11n... Theoretically this should be the least wasteful channel. Unfortunately this just adds to the problem...)
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Jaglover
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PostPosted: Sun Dec 30, 2012 10:55 pm    Post subject: Reply with quote

duby2291 wrote:
Jaglover wrote:
What eccerr0r said. ... use it when it's absolutely necessary, not because it's convenient ...
Everything is wired in my house, in rare cases when I take my laptop outside I turn on my AP, otherwise I keep it off.


That doesnt answer my question at all tho. I do understand your concerns about wifi, but the question was if you did need to use it what wifi adapter would you choose?


I know, sorry for that. I used to work with radio equipment and I happen to know how unreliable radio waves are when we need to transfer digital code losslessly.
Anyhow, you have three choices, they can be combined.
A. Go wired - can't beat that.
B. Shield. Use some high-frequency shield to protect your property from interfering AP-s. Expensive, pointless in your situation, but has to be mentioned for completeness.
C. Directional antenna (for AP) to strengthen the signal in area where your mobile wireless device is used. This is your best option if you refuse to go wired.

You cannot improve the situation by choosing different adapters unless you switch to another frequency range which may be less contaminated (for now).
Adding random elements (tennis ball can or whatever) to your AP will not fix it. Although it is not rocket science it is science, chances to improve your wireless that way are same as have a monkey to paint Mona Lisa. Antenna elements preciseness in GHz range are in range of fraction of millimeter.
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duby2291
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PostPosted: Mon Dec 31, 2012 2:22 am    Post subject: Reply with quote

I've pretty much already decided to upgrade to wireless N. I just dont know which chip or brand to choose. I think I've got the hint that Intel's drivers suck, so nothing with an Intel chipset. But is there anything specific I should look at as a good N compatible adapter?

About shielding... I have tried putting thick layers of aluminum foil behind the router in the direction of the neighbors house. Also behind the adapter in the direction of the neighbors house. Didnt make much of a difference really. Both the router and the adapter have dipole antennas and neither of them are upgradeable. The routers antenna is internal, and the adapters antenna is a little swivel thingy.

I don't know much about EM, but does the aluminum foil need to be grounded to function as a shielding?
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PostPosted: Mon Dec 31, 2012 2:29 am    Post subject: Reply with quote

This is not the router you need to shield. To make it work you need to shield the wireless clients - effectively the whole property.
In short. Setting up wireless in convenient. Using it is not.
Setting up wired network is not convenient. Using it is.
Invest in some drill bits to drill the bricks and enjoy gigabit network, let your neighbors struggle, why should you?
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PostPosted: Mon Dec 31, 2012 4:04 am    Post subject: Reply with quote

duby2291 wrote:
I think I've got the hint that Intel's drivers suck, so nothing with an Intel chipset. But is there anything specific I should look at as a good N compatible adapter?


i should clarify on that a bit
probably 99% of the time my connection is perfectly happy and fine
but
occasionally, it will just crap itself, the firmware will go titsup, and I have to rmmod and re-modprobe the damn driver (or reboot, but screw that)

some intel cards are better than others. Likely, because some intel firmware seems to be better off than others.

Broadcom chipset used to be an absolute no-go. But nowadays if your adapter supports the newer broadcom open source driver (brcmscmac i think it's called - something like that), things are just fine.

Atheros used to be bulletproof, but then, we have one poster in this thread stating their ath9k rig is misbehaving.

The Arch Wiki has a fair bit of good information
I used to use the aircrack docs, but those seem to have not been updated for a couple of years.
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PostPosted: Mon Dec 31, 2012 7:33 am    Post subject: Reply with quote

An anecdote: when I was setting up a wifi adapter, I had both a Zydas 1211B
USB wifi adapter and a realtek 8185 pci wifi adapter. I assumed that I would
get better throughput with the realtek because of the external antenna
(not removeable, but it sticks out beyond the end of the case farther than
the USB adapter, and you can adjust the angle, rotate it, etc). Both kernel
drivers (zd1211rw with external firmware and rtl818x with no firmware
load needed) worked without problems on the kernel I was using.

So I am pinging the router and looking at ping times. Abysmal compared
to wiring the same workstation up with cat5, but I expected that. (Still faster
than the broadband ISP connection by at least an order of magnitude,
so using the wifi in place of ethernet networking only affects host to host
communications on the lan.) I was getting a little faster, more consistent
ping times with the USB adapter, which seemed odd. (Its signal strength
had never been that impressive hooked up to a windows box on another
floor.) I switched back to the pci wifi adapter to play with the antenna on it.

I changed the angle, rotated it, etc, etc, with no visible, consistent change
in ping times, until I happened to tilt it up against an edge of the aluminum
case that the system was installed in. Ping times dropped. Not a lot,
maybe 10-15%, but it was an obvious, visible improvement in antenna
performance.

(Still slower than the USB adapter with the Zydas chipset, though,
so I ended up using that.)

I have not experimented with any of these wireless N devices, so I have
no useful advice on newer hardware.
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