Anyone know how mobile broadband dongles work?

Cos I am getting this thing to work under Linux. Its a qualcomm chipset
MF622 from ZTE provided by Three..

I have been messing with it and it seems to work OK, looks a bit like a
modem that is always connected..

So teh dial up logs are full of ATZ and so on, it says 'CONNECTED' ppp
starts and packets flow..it even says CHAP succeeded..i.e. the name and
password supplied (which everyone says are irrelevant anyway) work.

BUT I don't get any IP, or DHCP stuff and after a couple of minutes the
thing 'hangs up'

This got me puzzled for a long time, till I looked at the coverage map
of Three, and discovered it was only 2G or 3G, not mobile broadband, here.

Now I naively had thought that when it said 'carrier present' it meant
it had an end to end connection to whatever it talks to. But I am
wondering if in fact it just fakes all that locally, and the
password/CHAP stuff, says its connected, goes looking for a mobile
broadband signal, doesn't find it and eventually times out and issues a
'lost carrier' signal back to the pppd daemon.

I will be getting a cheap secondhand laptop to go with it shortly, but I
thought I would ask anyway, to see if anyone else has invented this
particular wheel..i.e. knows what happens when you fire up pppd against
a working dongle that has no proper signal.

"The Natural Philosopher" <(E-Mail Removed)> wrote in message
news:gs6uqr$aji$(E-Mail Removed)...
>
> So teh dial up logs are full of ATZ and so on, it says 'CONNECTED' ppp
> starts and packets flow..it even says CHAP succeeded..i.e. the name and
> password supplied (which everyone says are irrelevant anyway) work.

Sounds like there is a connection then. Although the username/password are
irrelevant for most (or even all) mobile data services (they identify you by
IMSI) the phone doesn't know that, and IME of GPRS connections (which I've
worked with and debugged at every level) there has to be some successful
signalling before anything can seriously believe that the CHAP has
succeeded.

There isn't a real end to end PPP negotiation, by the way, it's done with
some signalling messages still in the GSM/UMTS layer three stuff, although
it's quite likely to fake up normal PPP negotiation towards the client
computer. Only after all this has completed does the phone switch to
whatever packet transport it has for the IP. So, if you're getting PPP
negotiation complete but no IP packets it sounds like you've got a perfectly
good signalling connection but can't get any packet data transported.

I don't know anything about 3G, but in an area with no 3G coverage I'd
expect the dongle to step down to EDGE, and if it can't find that to boring
old GPRS.

--
Tim Ward - posting as an individual unless otherwise clear
Brett Ward Limited - www.brettward.co.uk
Cambridge Accommodation Notice Board - www.brettward.co.uk/canb
Cambridge City Councillor

I had similar issues when using Ubuntu 8.04 (hardy heron) - linux
reported connected but not getting any application level connectivity
(I was using a cable-linked 3G phone). In the end it wasn't important
enough to me to sort it out. However once I moved to Ubuntu 8.10
(intrepid), this included 3G modem support - and the desktop set-up
widget got it right with very little fiddling (mostly issues
configuring the phone handset rather than linux).

"Tim Ward" <(E-Mail Removed)> gurgled happily, sounding much like they
were saying:

> I don't know anything about 3G, but in an area with no 3G coverage I'd
> expect the dongle to step down to EDGE

There's very little EDGE coverage in the UK. I think O2 are the only ones
with an EDGE network - and even that'll probably go sooner or later,
since the iPhone 3G removes their only real need for it.

Three piggy-back off T-mobile, so there'd be no EDGE access for a Three
card.

The Natural Philosopher <(E-Mail Removed)> gurgled happily, sounding
much like they were saying:

> This got me puzzled for a long time, till I looked at the coverage map
> of Three, and discovered it was only 2G or 3G, not mobile broadband,
> here.

Umm, what - other than 3G - are you expecting for "mobile broadband"?

In article <(E-Mail Removed)>, Tim Ward
<(E-Mail Removed)> scribeth thus
>"The Natural Philosopher" <(E-Mail Removed)> wrote in message
>news:gs6uqr$aji$(E-Mail Removed)...
>>
>> So teh dial up logs are full of ATZ and so on, it says 'CONNECTED' ppp
>> starts and packets flow..it even says CHAP succeeded..i.e. the name and
>> password supplied (which everyone says are irrelevant anyway) work.
>
>Sounds like there is a connection then. Although the username/password are
>irrelevant for most (or even all) mobile data services (they identify you by
>IMSI) the phone doesn't know that, and IME of GPRS connections (which I've
>worked with and debugged at every level) there has to be some successful
>signalling before anything can seriously believe that the CHAP has
>succeeded.
>
>There isn't a real end to end PPP negotiation, by the way, it's done with
>some signalling messages still in the GSM/UMTS layer three stuff, although
>it's quite likely to fake up normal PPP negotiation towards the client
>computer. Only after all this has completed does the phone switch to
>whatever packet transport it has for the IP. So, if you're getting PPP
>negotiation complete but no IP packets it sounds like you've got a perfectly
>good signalling connection but can't get any packet data transported.
>
>I don't know anything about 3G, but in an area with no 3G coverage I'd
>expect the dongle to step down to EDGE, and if it can't find that to boring
>old GPRS.
>

More then likely the 3G coverage seems to have only been rolled out in
city areas..

Even 2G voice is lacking in quite a bit of rural Cambs even, let alone
further afield;!..
--
Tony Sayer

On Thu, 16 Apr 2009 10:47:05 +0100, The Natural Philosopher
<(E-Mail Removed)> wrote:

> Cos I am getting this thing to work under Linux. Its a qualcomm chipset
> MF622 from ZTE provided by Three..
>
> I have been messing with it and it seems to work OK, looks a bit like a
> modem that is always connected..
>
> So teh dial up logs are full of ATZ and so on, it says 'CONNECTED' ppp
> starts and packets flow..it even says CHAP succeeded..i.e. the name and
> password supplied (which everyone says are irrelevant anyway) work.
>
> BUT I don't get any IP, or DHCP stuff and after a couple of minutes the
> thing 'hangs up'
>
> This got me puzzled for a long time, till I looked at the coverage map
> of Three, and discovered it was only 2G or 3G, not mobile broadband,
> here.
>
> Now I naively had thought that when it said 'carrier present' it meant
> it had an end to end connection to whatever it talks to. But I am
> wondering if in fact it just fakes all that locally, and the
> password/CHAP stuff, says its connected, goes looking for a mobile
> broadband signal, doesn't find it and eventually times out and issues a
> 'lost carrier' signal back to the pppd daemon.
>
> I will be getting a cheap secondhand laptop to go with it shortly, but I
> thought I would ask anyway, to see if anyone else has invented this
> particular wheel..i.e. knows what happens when you fire up pppd against
> a working dongle that has no proper signal.


If it's only making a 2G connection & it's configured for 3G only then
nothing happens. Ringing your networks the only way you can get a real
clue though, if your cell's not got any spare bandwidth you;re at the
bottom of the tree & don't get any packets.

On Thu, 16 Apr 2009 11:27:24 +0100, Adrian <(E-Mail Removed)> wrote:

> The Natural Philosopher <(E-Mail Removed)> gurgled happily, sounding
> much like they were saying:
>
>> This got me puzzled for a long time, till I looked at the coverage map
>> of Three, and discovered it was only 2G or 3G, not mobile broadband,
>> here.
>
> Umm, what - other than 3G - are you expecting for "mobile broadband"?


Dependent on configuration upto 7.2M instead of 384K.

Adrian <(E-Mail Removed)> wrote:
> "Tim Ward" <(E-Mail Removed)> gurgled happily, sounding much like they
> were saying:
>
> > I don't know anything about 3G, but in an area with no 3G coverage I'd
> > expect the dongle to step down to EDGE [or GPRS]

It will, unless it's set to 3G or HSPA only. I don't know the ZTE dongle,
but some can be set this way.

'Mobile broadband' is probably code for HSPA. If you don't get an HSPA
signal you'll use 3G/UMTS or 2G/GPRS.

> Three piggy-back off T-mobile, so there'd be no EDGE access for a Three
> card.

Three have their own 3G network. They also share 3G network with T-Mobile.
When there's no Three or T-mob 3G, they use Orange 2G.

However fallback on Orange GPRS is pants. See my stats:
http://groups.google.co.uk/group/uk....5?dmode=source

Theo

"The Natural Philosopher" <(E-Mail Removed)> wrote in message
news:gs6uqr$aji$(E-Mail Removed)...
> Cos I am getting this thing to work under Linux. Its a qualcomm chipset
> MF622 from ZTE provided by Three..
>
> I have been messing with it and it seems to work OK, looks a bit like a
> modem that is always connected..
>
> So teh dial up logs are full of ATZ and so on, it says 'CONNECTED' ppp
> starts and packets flow..it even says CHAP succeeded..i.e. the name and
> password supplied (which everyone says are irrelevant anyway) work.
>
> BUT I don't get any IP, or DHCP stuff and after a couple of minutes the
> thing 'hangs up'
>
> This got me puzzled for a long time, till I looked at the coverage map of
> Three, and discovered it was only 2G or 3G, not mobile broadband, here.
>
> Now I naively had thought that when it said 'carrier present' it meant it
> had an end to end connection to whatever it talks to. But I am wondering
> if in fact it just fakes all that locally, and the password/CHAP stuff,
> says its connected, goes looking for a mobile broadband signal, doesn't
> find it and eventually times out and issues a 'lost carrier' signal back
> to the pppd daemon.
>
> I will be getting a cheap secondhand laptop to go with it shortly, but I
> thought I would ask anyway, to see if anyone else has invented this
> particular wheel..i.e. knows what happens when you fire up pppd against a
> working dongle that has no proper signal.

I installed a Three 3g dongle for someone six weeks ago.
The first dongle was duff and didn't work.
I could get a 2G connection and send SMS messages but no IP connection.
The second dongle worked first time.

When I took it back there was a second person swapping an identical dongle
so either they are unreliable or there was a network fault that cleared by
the time I got the second dongle.

Can't help you with linux though, this was windows.