WLAN channel interferences

English Network/Internet
#1

I’d like to get optimal performance from my WLAN connection. WLAN is very popular so I see multiple APs when I execute a scan on my system.

According List of WLAN channels - Wikipedia, the free encyclopedia I should use Channel 1, 6 or 11. Right now I use Channel 6, there is anoth AP on Chan 1 and 11. But unfortunately somebody uses Chan 10 which interferes with with my chan 6. Now my question: Should I switch to chan 1 or 11 and share the chan with others and will get better throughput or should I stick with chan 6 - even I have interferences with another AP on chan 10?

#2

On 05/01/2010 01:56 PM, framp wrote:
>
> I’d like to get optimal performance from my WLAN connection. WLAN is
> very popular so I see multiple APs when I execute a scan on my system.
>
> According ‘List of WLAN channels - Wikipedia, the free encyclopedia’
> (http://en.wikipedia.org/wiki/List_of_WLAN_channels) I should use
> Channel 1, 6 or 11. Right now I use Channel 6, there is anoth AP on Chan
> 1 and 11. But unfortunately somebody uses Chan 10 which interferes with
> with my chan 6. Now my question: Should I switch to chan 1 or 11 and
> share the chan with others and will get better throughput or should I
> stick with chan 6 - even I have interferences with another AP on chan
> 10?

Making this decision is not easy. Of course, 11 is also interfered with
by 10. On 6, you only get partial interference from channel 10, whereas
using 1 with another AP there gets interference across the entire width
of the channel.

The best solution would be to locate the owner of the AP on channel 10
and convince them that these channels are not like TV. If not possible,
then pick the clear channel whose interference is the weakest.

#3

Thank you very much for your answer. The main question I have whether it’s better to use the same channel as somebody else or to use a channel not used by anybody but which has interferences to other channels.

You are right - I should talk to the guy using chan 10 - but frankly I don’t know who’s using this chan. I may hack his AP because he’s using WEP and let him know about this issue - but that’s not legal and don’t do this.

#4

Because I can’t locate the owner of WLAN channel 19 which interferes with my WLAN channel 6 I now have to possibilities:

  1. Stay with WLAN chan 6 and accept WLAN interferences with chan 10
  2. Switch to chan 1 which is alreday used by another AP but doesn’t have any interferences

Which way will give me better theoretical WLAN performance?

#5

Hi
The other options are to move the AP’s location and/or change the angle
of the antenna(s) to reduce interference. There is another option,
purchase a directional antenna that will cover your location?

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Cheers Malcolm °¿° (Linux Counter #276890)
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#6

Oops - just detected my typo: Channel 19 doesn’t exist at all - I meant channel 10 :shame:

That’s a great idea - but I frankly don’t want to spend any additional money on this.

Maybe I should use my labtop and walk around on the street and locate the AP by watching the signal strength …

#7

On 05/03/2010 02:36 PM, framp wrote:
> Maybe I should use my labtop and walk around on the street and locate
> the AP by watching the signal strength …

That is what I would do.

#8

I will. But I’m still interested to know from a WLAN technical point of view which scenario is worse :wink:

#9

On 05/04/2010 12:26 PM, framp wrote:
>
> lwfinger;2160769 Wrote:
>> That is what I would do.
> I will. But I’m still interested to know from a WLAN technical point of
> view which scenario is worse :wink:

I don’t think it makes any difference whether another AP interferes with
the whole width of a given channel’s spread, or just a part of it;
however, I posted your question on the wireless mailing list. The answer
there is that it depends on how busy those other APs are. The
recommendation is to pick 1, 6, or 11 and measure throughput using iperf
or tcpperf with the server in your LAN. If you don’t have a suitable
server, then it probably doesn’t matter. Any configuration is likely to
be faster than your broadband connection.

#10

Thx you forwarded my question to the mailing list. Given this I’m optimal if I have <= 2 WLAN peers. I fortunately don’t detect that much WLAN APs from my neighbors - but I’ve seen iwlist outputs with > 10 APs and interfering channels. So I’m wondering why they decided to define 13/14 WLAN chans only. WLAN is used more and more - and the WLAN AP density grows more and more.

#11

On 05/04/2010 03:36 PM, framp wrote:
> Thx you forwarded my question to the mailing list. Given this I’m
> optimal if I have <= 2 WLAN peers. I fortunately don’t detect that much
> WLAN APs from my neighbors - but I’ve seen iwlist outputs with > 10 APs
> and interfering channels. So I’m wondering why they decided to define
> 13/14 WLAN chans only. WLAN is used more and more - and the WLAN AP
> density grows more and more.

The 2.4 GHz region is pretty crowded, which limits the total bandwidth
for everything. It is even more crowded in the US - that explains why
channels only up to 11.

I do not know why the channels are spaced at 5 MHz, but the channel
width is 20 MHz.

My suspicion is that 802.11b/g/n is a whole lot more popular that anyone
expected 10 years ago when all this stuff was standardized. If you want
clear channels, go to 802.11a. The 5 GHz bands are practically empty. In
addition, you get better range. The APs used to be quite expensive
(~$200), but Amazon has a dual-band D-Link DI-784 router for $70.