Well the broadband dongle worked..but..

[The Natural Philosopher]

Just thought I would report back on the use of the three network USB dongle when I finally got the Linux laptop to an area where there was internet broadband mobile coverage.

Basically it did work. But for some reason the DNS did not. Three offered the right DNS servers, but despite use of the 'usepeerdens' in what I think were the right places, it refused to use them. Fortunately I discovered it was running BIND anyway, and do just told it to use localhost, whatever.

(Linux/debian lenny ppp etc etc)

The other odd thing was when I arrived on site to set it up, late afternoon, we got good throughput..I didn't check, but it seemed about a couple of hundred kbps.

Later on, at dusk, we seemed to be on 'crap dialup speeds' - looked like a 9600 modem!

Finally, after dusk,we got no connection at all. A friend with a 3G phone saw exactly the same degradation..

Can anyone explain why this is?

[tony sayer]

In article , The Natural Philosopher scribeth thus

Kids home from school;?...

[Brian Morrison]

3G W-CDMA suffers from a phenomenon called "cell breathing". This occurs because unlike GSM where each logical link has its own timeslot, in 3G all the signals overlay each other on a single frequency but the different spreading codes allocated to each separate them in a similar way. The link power is accurately controlled so that all the signals arriving at the base station are at the same level (within 0.2dB I think) to ensure that no one signal can overload the analogue to digital converters in the receiver.

If there are many signals, the effective sensitivity of the receiver reduces a little; think of it as the wanted-to-interferer power ratio decreasing, the bit error rate goes up a bit. So, if you are at a fair distance from the node, you get better performance when there are few other users but as the user numbers increase things get worse. Taken to its logical conclusion, it may well cause you to be unable to connect at all if you are at just beyond the minimum cell radius for the path loss between you and the node.

Take the above with a small pinch of salt, you may be seeing a different effect, but the one I have described definitely exists.

[The Natural Philosopher]

Ah..so as people start turning up, with phones, that's likely to bugger the connection.The reduced S/N in the presence of many spread spectrums devices makes PERFECT sense, thanks.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember The Natural Philosopher saying something like:

Also, if you are right at the edge of the cell coverage, foliage and atmospherics play a part in killing (or helping) the signal.

[The Natural Philosopher]

Not much foliage in an airfield..

[tony sayer]

In article , Grimly Curmudgeon scribeth thus

Yes we're some 900 metres from a 3 and Vodafone main site. 3 is almost useless indoors and not to good outdoors and Voodo fone is marginal inside and OK outside but rarely more then a bar of level on the meter.

And all that gets worse in summer;(...

[Geo]

You've not been to Ed's then - 80 foot hedge an 120 foot trees...

[tony sayer]

In article , Brian Morrison scribeth thus

Thats interesting how they see to it that it does that!..

So why would this get worse as the day goes on when the cell traffic reduces , well mobile voice does a bit tho the net is possibly likely to go up...

And thats all with a pinch of snuff;)..

[bod43]

Might be worth coinsidering getting a USB extension cable and hanging your important bits out the window - or otherwise positioning them advantageously.

USB cables are limited in length.

I read recently of wireless routers that would also take 3G USB. Could then stick that well away from the computer and use 802.11 or ethernet or combination thereof for the link to it.

work too I would imagine.

[George Weston]

Can't you get arrested for that? ;-)

George

[Rodney Pont]

3 do one for the usb 3G dongles.

friend had a problem with the signal at times and he bought a usb wi-fi dongle for his PC and put the router+3G dongle upstairs on the top of his wardrobe and is very happy with it.

[The Natural Philosopher]

Well its to run a sales terminal in a tent in the middle of an airfield, so getting altitude is not easy, except for the model planes. Nor is mains power..running off a genny.

But all is OK, they are running off the copy database and not using the 'link back home' Too unreliable.

Especially with a load of 2.4Ghz R/C gear around splattering the wifi bands

[PCPaul]

Use 802.11a if you can get the kit - it works at 5GHz. Only band B is strictly allowed for outdoor use.

[tony sayer]

Just the one airfield?..

Go 5.8 then;))..

[tony sayer]

In article , PCPaul scribeth thus

Yes .. "outdoor nomadic" use they rather quaintly term it...

[Hactar]

If you can't get a single cable long enough, you can interpose a router or three.

[Dave Liquorice]

But you have a damp tent...

By tent do you mean a domestic camping tent or gazeebo or a marque?

Just poking the dongle through the hole in canvas of a marque at the support pole will make quite a difference. Getting up there might not be so easy but even in free air on the pole has high as possible may well make a difference compared to stuck into the back of a laptop on a table surrounded by bags of water (people).

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember [e-mail] (Hactar) saying something like:

Or an active 5m cable and daisy-chain them up to 25m. You can also get USB->Ethernet converters and go mad, but it's not particularly cheap.

[The Natural Philosopher]

Why not go the whole hog and unreel a glass fibre cable extension cable all the way back to Telehouse? Sheesh. some people.