Re: Wifi Signal Quality

Geoff Lane wrote:
> I am a wee bit puzzled as to the relationship between signal quality,
> signal level and noise level.
>
> A sudo iwlist scan gives the following results.
>
> wlan0 Scan completed :
> Cell 01 - Address: 00:1CF:81:05:71
> ESSID:"Belkin_N_ADSL_810571"
> Mode:Master
> Channel:6
> Frequency:2.437 GHz (Channel 6)
> Quality=7/100 Signal level:-73 dBm Noise level=-78 dBm
> Encryption keyff
>
> Cell 02 - Address: 00:09:5B:43:1A:38
> ESSID:"ds%kQDb!LR"
> Mode:Master
> Channel:11
> Frequency:2.462 GHz (Channel 11)
> Quality=17/100 Signal level:-95 dBm Noise level=-106 dBm
> Encryption keyn
>
> Cell 03 - Address: 00:14:6C:EE:B5:22
> ESSID:"SKY84737"
> Mode:Master
> Channel:11
> Frequency:2.462 GHz (Channel 11)
> Quality=0/100 Signal level:-91 dBm Noise level=-91 dBm
> Encryption keyn
>
> My connection is cell 02, Network-Manager shows the signal strength as
> pretty good, no percentage shown but looks around 80% but the iwscan
> list shows quality that appears to look like 17%.
>
> Any advice appreciated.
>
> Geoff Lane

Cells 2 and 3 are occupying the same channel, which
means that the signal of cell 2 is noise for cell 3
and vice versa. The signal report of iwconfig shows
no useable signal for cell 3.

The useful signal measure (signal dBm - noise dBm) is
best on cell 2, anyway.

Get rid of cell 3 base station or change channel for
the desired cell 2.

--

Tauno Voipio
tauno voipio at iki fi

Geoff Lane wrote:

> Cell 03 is an unknown neighbour's so I have no control.
>
> A relative's Vista laptop loses wifi connection completely for some
> reason if I change my AP to channel 3 to avoid a clash.

Maybe because of regulatory domain restrictions. In some countries not the
whole frequency range of 802.11 may be used. Depending on the OS and driver
used, those channels must be enables explicitly. But do so only then, if
the use of those channels is permitted wher eyou live.

You should also check if you may use 802.11a in the 5GHz band. There are far
fewer users in that band. I use it myself for that reason.


Wolfgang

Tauno Voipio wrote:
> Geoff Lane wrote:
>>
>> [snip]
>>
>> Channel:6
>>
>> [snip]
>>
>> Channel:11
>>
>> [snip]
>>
>> Channel:11
>>
>> [snip]
>>
>> Any advice appreciated.
>
> Cells 2 and 3 are occupying the same channel, which
> means that the signal of cell 2 is noise for cell 3
> and vice versa. The signal report of iwconfig shows
> no useable signal for cell 3.
>
> The useful signal measure (signal dBm - noise dBm) is
> best on cell 2, anyway.
>
> Get rid of cell 3 base station or change channel for
> the desired cell 2.

Or just switch to Channel 1, since that looks wide open. Be glad you
live in such a low population density that the choice is so obvious.

Geoff Lane wrote:
> Allen Kistler wrote:
>> Or just switch to Channel 1, since that looks wide open. Be glad you
>> live in such a low population density that the choice is so obvious.
>
> I may be getting this completely wrong but was under the impression it
> was best to avoid channels on the edge of the band such as 1 and 13.

Nope. The thing you want to avoid (and have your neighbors avoid) is
anything other than 1, 6, and 11, because of the overlap. The channel
number refers to the center frequency, but each channel is actually
about 5 "center frequencies" wide. There's room below 1 and above 13 in
the band (1-13 for you, 1-11 for folks in NA).

So the band starts at 2.4 GHz, but the center frequency of channel 1 is
2.412 GHz. Each channel is 22 MHz wide. Channel 5 at 2.432 has just a
bit of overlap with 1, since it's not quite 22 MHz away, but Channel 6
at 2.437 GHz has no overlap.

Theoretically in Europe, where channels 12 and 13 are legal, you could
use 1, 5, 9, and 13, to have 4 usable channels with just a bit of
overlap. But unless you can get everybody in your neighborhood to
follow that convention, it makes more sense to just use 1, 6, and 11
like North Americans. Picking other numbers just means you're getting
stepped on by (and stepping on) more people.

Otherwise you just have to put up with ham radio operators, garage door
openers, and wireless (not mobile) phones, because they use the same
frequencies as 802.11bg.