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Old 02-16-2011, 11:56 PM
Tim
 
Default WiFi: why not a diagram showing access points?

On Wed, 2011-02-16 at 15:54 +0100, Timothy Murphy wrote:
> But I'm not in a built-up area.
> I do see one other (hidden) network, but it is quite weak.

As Patrick said, cordless phones can interfere. Plus leaky microwave
ovens, wireless home security equipment, gigaHertz video senders,
lighting dimmers and switchmode power supplies. Whilst the latter two
don't, directly, work in the frequency range of WiFi, they can radiate
an awful lot of hash that disrupts many things.

--
[tim@localhost ~]$ uname -r
2.6.27.25-78.2.56.fc9.i686

Don't send private replies to my address, the mailbox is ignored. I
read messages from the public lists.



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Old 02-17-2011, 02:54 AM
Robert Moskowitz
 
Default WiFi: why not a diagram showing access points?

On 02/16/2011 07:56 PM, Tim wrote:
> On Wed, 2011-02-16 at 15:54 +0100, Timothy Murphy wrote:
>> But I'm not in a built-up area.
>> I do see one other (hidden) network, but it is quite weak.
> As Patrick said, cordless phones can interfere. Plus leaky microwave
> ovens, wireless home security equipment, gigaHertz video senders,
> lighting dimmers and switchmode power supplies. Whilst the latter two
> don't, directly, work in the frequency range of WiFi, they can radiate
> an awful lot of hash that disrupts many things.

We often mention at the 802 wireless sessions (both 802.11 and 802.15)
how amazing it is that this stuff works at all!


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Old 02-17-2011, 03:42 AM
Robert Nichols
 
Default WiFi: why not a diagram showing access points?

On 02/16/2011 09:54 PM, Robert Moskowitz wrote:
> On 02/16/2011 07:56 PM, Tim wrote:
>> On Wed, 2011-02-16 at 15:54 +0100, Timothy Murphy wrote:
>>> But I'm not in a built-up area.
>>> I do see one other (hidden) network, but it is quite weak.
>> As Patrick said, cordless phones can interfere. Plus leaky microwave
>> ovens, wireless home security equipment, gigaHertz video senders,
>> lighting dimmers and switchmode power supplies. Whilst the latter two
>> don't, directly, work in the frequency range of WiFi, they can radiate
>> an awful lot of hash that disrupts many things.
>
> We often mention at the 802 wireless sessions (both 802.11 and 802.15)
> how amazing it is that this stuff works at all!

For quite a while I could see, from my home, 3 wireless networks, all
on channel 6, all with SSID "Linksys", and all with decent signal strength.
How that managed to work for those people I have no idea.

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Old 02-17-2011, 04:09 AM
Robert Moskowitz
 
Default WiFi: why not a diagram showing access points?

On 02/16/2011 11:42 PM, Robert Nichols wrote:
> On 02/16/2011 09:54 PM, Robert Moskowitz wrote:
>> On 02/16/2011 07:56 PM, Tim wrote:
>>> On Wed, 2011-02-16 at 15:54 +0100, Timothy Murphy wrote:
>>>> But I'm not in a built-up area.
>>>> I do see one other (hidden) network, but it is quite weak.
>>> As Patrick said, cordless phones can interfere. Plus leaky microwave
>>> ovens, wireless home security equipment, gigaHertz video senders,
>>> lighting dimmers and switchmode power supplies. Whilst the latter two
>>> don't, directly, work in the frequency range of WiFi, they can radiate
>>> an awful lot of hash that disrupts many things.
>> We often mention at the 802 wireless sessions (both 802.11 and 802.15)
>> how amazing it is that this stuff works at all!
> For quite a while I could see, from my home, 3 wireless networks, all
> on channel 6, all with SSID "Linksys", and all with decent signal strength.
> How that managed to work for those people I have no idea.

You could have been in the middle, seeing them, and they not seeing each
other. The hidden node problem.

Or they just lived with things going blewy. Or they were all open so it
did not matter which AP any of the used!


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Old 02-17-2011, 07:01 AM
Tim
 
Default WiFi: why not a diagram showing access points?

On Wed, 2011-02-16 at 22:54 -0500, Robert Moskowitz wrote:
> We often mention at the 802 wireless sessions (both 802.11 and 802.15)
> how amazing it is that this stuff works at all!

I feel much the same. It's all well and good when you're not sharing
airspace with anybody, but in a crowded location, I'm surprised if it
works well.

Years of having to deal with hassles of multi-transmitter interference
while using wireless microphones and walkie-talkies has made me
reluctant to use anything wireless when I could plug a cable in.

What defines a crowded location is variable. You could be in the middle
of a few access points, and few clients, spread fairly widely, where
it's merely a case of which one too choose, and you can use any of them
without *too* much trouble. You could be in a block of flats, with
access points and multiple clients behind every wall, floor, and
ceiling, with several on the same channel, blocking each other.

--
[tim@localhost ~]$ uname -r
2.6.27.25-78.2.56.fc9.i686

Don't send private replies to my address, the mailbox is ignored. I
read messages from the public lists.



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Old 02-17-2011, 11:43 AM
Timothy Murphy
 
Default WiFi: why not a diagram showing access points?

Timothy Murphy wrote:

> I'm having terrible problems with my modem/router at the moment.
> The WiFi connection on my Thinkpad laptop drops every 10 minutes or so.
> I have to restart the network service to get the connection back.

Just to keep the story up-to-date,
a third modem/router from TI (Telecom Italia)
seems to have solved the problem completely;
the connection has held up for a day so far.

The history is a little puzzling to me.
The connection worked perfectly for a couple of years,
until last December when it suddenly stopped completely.
A technician came round (a very rare event)
and tested the line.
He said the line was fine and told me to change the modem
at a TI agent in a neighbouring town.

I did this, and the new modem could at least make a connection,
but it kept dropping the line, on both WiFi and ethernet.
I rang TI innumerable times (a painful business on each occasion),
and they replied each time that the line was fine,
and "the problem lies between modem and computer"
(a phrase they seem to like).

I didn't really believe them about the line,
as it goes along a rather odd route,
down a pipe (like a drain-pipe) for about 5 metres,
and then under a road.
It seemed to me very likely that there was water in the pipe,
and this was the cause of the problem.
However, I have been proved completely wrong;
the line _is_ good, as TI repeatedly told me.

My present conjecture is that TI changed their feed in some way,
perhaps from ADSL to ADSL2, and the first modem was unable to cope.
All 3 modems look the same; they have no marking except TI,
but research leads me to think that the model is Pirelli AH4021.

I was amused to find a site devoted entirely to rants about TI
<http://www.beginningwithi.com/comments/2006/08/30/share-your-experiences-
with-telecom-italia/>
which leads me to think that I have been relatively lucky.
Though I have had similar problems communicating with ISPs about modems
in Ireland and England (Telecom Eireann and Onetel).
I'm not sure which of them was the worst.
One would think that companies involved in communication
would be good at communicating, but the opposite seems to be the case.

Sadly, I've come to the conclusion that the ADSL modem
is just another neuron in the brain,
and its failure is tantamount to a minor stroke ...

--
Timothy Murphy
e-mail: gayleard /at/ eircom.net
tel: +353-86-2336090, +353-1-2842366
s-mail: School of Mathematics, Trinity College, Dublin 2, Ireland

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Old 02-17-2011, 11:45 AM
Robert Moskowitz
 
Default WiFi: why not a diagram showing access points?

On 02/17/2011 03:01 AM, Tim wrote:
> On Wed, 2011-02-16 at 22:54 -0500, Robert Moskowitz wrote:
>> We often mention at the 802 wireless sessions (both 802.11 and 802.15)
>> how amazing it is that this stuff works at all!
> I feel much the same. It's all well and good when you're not sharing
> airspace with anybody, but in a crowded location, I'm surprised if it
> works well.
>
> Years of having to deal with hassles of multi-transmitter interference
> while using wireless microphones and walkie-talkies has made me
> reluctant to use anything wireless when I could plug a cable in.

Oh, the you should be following TV-white space! 802.11af

Check out the 802.11 document server
https://mentor.ieee.org/802.11/documents?is_group=00af for all the fun
and games that are going on there to 'intelligently' share the spectrum...

Also 802.22

> What defines a crowded location is variable. You could be in the middle
> of a few access points, and few clients, spread fairly widely, where
> it's merely a case of which one too choose, and you can use any of them
> without *too* much trouble. You could be in a block of flats, with
> access points and multiple clients behind every wall, floor, and
> ceiling, with several on the same channel, blocking each other.
>
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Old 02-17-2011, 12:07 PM
Craig White
 
Default WiFi: why not a diagram showing access points?

On Thu, 2011-02-17 at 13:43 +0100, Timothy Murphy wrote:
> Sadly, I've come to the conclusion that the ADSL modem
> is just another neuron in the brain,
> and its failure is tantamount to a minor stroke ...
----
just an FYI - ADSL is the most common used technology in the US by the
telephone companies and it works rather well considering that some of
the copper cables have been tolerant of poor design and systemic neglect
which POTS seems to mostly ignore but can make a high frequency digital
signal fade in/out. You would probably be better off not drawing large
conclusions based upon a single anecdotal reference/incident.

Craig


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Old 02-17-2011, 01:30 PM
Robert Nichols
 
Default WiFi: why not a diagram showing access points?

On 02/16/2011 11:09 PM, Robert Moskowitz wrote:
> On 02/16/2011 11:42 PM, Robert Nichols wrote:
>> On 02/16/2011 09:54 PM, Robert Moskowitz wrote:
>>> On 02/16/2011 07:56 PM, Tim wrote:
>>>> On Wed, 2011-02-16 at 15:54 +0100, Timothy Murphy wrote:
>>>>> But I'm not in a built-up area.
>>>>> I do see one other (hidden) network, but it is quite weak.
>>>> As Patrick said, cordless phones can interfere. Plus leaky microwave
>>>> ovens, wireless home security equipment, gigaHertz video senders,
>>>> lighting dimmers and switchmode power supplies. Whilst the latter two
>>>> don't, directly, work in the frequency range of WiFi, they can radiate
>>>> an awful lot of hash that disrupts many things.
>>> We often mention at the 802 wireless sessions (both 802.11 and 802.15)
>>> how amazing it is that this stuff works at all!
>> For quite a while I could see, from my home, 3 wireless networks, all
>> on channel 6, all with SSID "Linksys", and all with decent signal strength.
>> How that managed to work for those people I have no idea.
>
> You could have been in the middle, seeing them, and they not seeing each
> other. The hidden node problem.
>
> Or they just lived with things going blewy. Or they were all open so it
> did not matter which AP any of the used!

I neglected to mention that they were, indeed, all unencrypted. I'm
pretty sure at least two of them were in roughly the same direction.
Whatever. That was a couple of years ago, and I don't see any of those
networks now.

--
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Do NOT delete it.

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Old 02-17-2011, 04:01 PM
Tim
 
Default WiFi: why not a diagram showing access points?

On Thu, 2011-02-17 at 13:43 +0100, Timothy Murphy wrote:
> Just to keep the story up-to-date,
> a third modem/router from TI (Telecom Italia)
> seems to have solved the problem completely;
> the connection has held up for a day so far.
>
> The history is a little puzzling to me.
> The connection worked perfectly for a couple of years,
> until last December when it suddenly stopped completely.
> A technician came round (a very rare event)
> and tested the line.
> He said the line was fine and told me to change the modem
> at a TI agent in a neighbouring town.

And had anything else changed in your system at that time?

A friend of mine would consistently lose connection every time he
started burning a DVD.

I would lose connection whenever I had a USB hard drive plugged in. It
had one of those crappy power boxes in the middle of a cord, and it just
radiated crud. I could cause the fault to happen with 100% reliability,
just by having the drive plugged into a computer.

e.g. Take a computer system off the network, just plug the PC into the
mains, a monitor into the PC (and the mains), and the USB drive into the
PC (and it's power brick into the mains). The OS didn't even have to be
booted. The moment the connection was made, or the power turned on, the
modem would disconnect. And continuously fail while trying to
reconnect. This test computer wasn't connected to anything else, and
the fault would occur no matter where I plugged into into power in the
house. Yes, all the gear was earthed (PC, monitor, and USB drive all
had equipment ground going to mains earth), and the mains earth line is
working.

I could even do it by plugging the USB drive into a laptop running off
batteries, so the USB drive was the only thing connected to the mains,
in any way.

I'm rather loathsome of switchmode power supplies being put into
everything, these days, especially where they're not really needed.

--
[tim@localhost ~]$ uname -r
2.6.27.25-78.2.56.fc9.i686

Don't send private replies to my address, the mailbox is ignored. I
read messages from the public lists.



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