Anyone know how mobile broadband dongles work?

[The Natural Philosopher]

Well their website seems to say otherwise.

Which make of dongle?

Anyway, is internet possible over just 2G?

[Tim Ward]

So, "internet on your mobile" is listed as needing 3G as minimum, and you can only get 2G, and you can't get internet.. Sounds as if they're failing to deliver exactly as promised then?

[Tim Ward]

It's physically possible, yes, using at least the following choice of transports, and I have seen all of these working:

(1) dial-up data call (2) GPRS (or EDGE) (3) SMS (believe it or not).

Which of these any particular operator chooses to offer, and which a particular combination of phone and operating system and driver software can be bothered to implement, are different matters.

[The Natural Philosopher]

Yes, however my issue was, that how come I appear to get a valid chap negotiation, hence the question..

Its not for use here..I am just testing a setup..

Plus basic curiosity as to whether it will all work in a 3G only area..

[Paul Rudin]

internet is *possible* over carrier pigeon... whether you can find an isp that'll play ball is another question ;)

[Theo Markettos]

Marketing, schmarketing. They don't advertise data on 2G because it's so much slower than their advertised HSPA speeds that the ASA et al would jump on them for false advertising. But MMS uses GPRS to supply picture messages to a phone, so that will definitely work.

(FSVO 'work', given the tests I linked to in my other post)

That's an incorrect assumption. What the USB dongle does isn't determined from what their network does. Anyway, an HSPA dongle that wouldn't drop back to UMTS or 2G is in something of chocolate teapot territory.

Anyway, this:

it does UMTS/EDGE/GPRS/GSM too. And if you're able to translate the Chinglish it has 'Manual mode removal', 'GSM-only and GSM-preferred modes removal' and 'Splitting 2G and 3G in manual mode selection' in the Windows software... which can no doubt be selected by an AT command if you could find out which one.

However this suggests that 'mobile broadband' SIMs don't work in 2G areas, but normal phone SIMs do:

[e-mail]/msg1210444.html ...which is nothing to do with the dongle.

I only have a phone SIM to test, and no HSPA hardware, so I can't verify this.

Theo

[Tim Ward]

That's curious as to why they would set it up that way, yes, but as I said the CHAP negotiation only uses signalling paths which are available with a

2G cell.

[Tim Ward]

Not necessarily. The MMS service could be using an APN which points at some sort of walled garden with no access to the public internet. An attempt using the same phone and the same SIM to connect over 2G GPRS to an APN which allows public internet access could be administratively blocked. (But why anyone would do that is hard to imagine, unless perhaps they charge lots more for MMS than for IP and don't want the limited GPRS bandwidth saturated by people paying the lower price.)

[David Hansen]

On 16 Apr 2009 20:20:39 +0100 (BST) someone who may be Theo Markettos wrote this:-

USB dongles have a SIM in them and I have seen a few work where only

2G is available. It isn't exactly fast, but is acceptable for low bandwidth tasks.

They tend to come setup to automatically switch between 2G and 3G, forcing them into either mode can be useful at times.

[The Natural Philosopher]

Ah. That sounds fairly conclusive then. @I talkl PPP and chap, but I don't do IP'

Sounds hopeful that it will work when I get it to a suitable area.

[The Natural Philosopher]

says it does UMTS/EDGE/GPRS/GSM too. And if you're able to translate the

Hmm. Qualcomm might know

Aha. Now that does make sense.

[Steve Firth]

HSDPA dongles that I have used work perfectly will in 2G areas, but they fall back to GPRS, so they work but work slowly. Depending on the provider/dongle you may need to run the configuration software to select GPRS but there's usually a setting to prefer 3G and fall back to GPRS when 3G isn't available.

Works fine for me with a Vodafone dongle. Colleagues use Orange/3/T-Mobile and O2. We travel around the country and the dongles work with varying degrees of success over much of the country. However 3G is only available along motorways and in major conurbations. It's useless to me out on the Downs. In fact I can only get 2G to work by climbing to the third floor, and hanging the dongle out of a window on a long USB extension.

Ah yes, get a long USB extension, you'll need it even in London.

[Tim Ward]

In fact it's not quite talking PPP As We Know It, in that there isn't a sequence of PPP subprotocol messages backwards and forwards as you'd see in something like a dial-up landline connection, it's somewhat faked up.

It's done by the Protocol Configuration Options IE in the Activate PDP Context Request and Activate PDP Context Accept messages (see whatever version of GSM 04.08 you prefer). Unlike a "real" PPP negotiation, where messages for each subprotocol go backwards and forwards as often as is needed until the negotiation succeeds, and each subprotocol is negotiated in turn, the phone gets one chance to send a single bunch of options in the Request message for all subprotocols at once, and the network gets one chance to reply to them all in one go in the Accept message.

And quite which PPP subprotocols and messages and options etc are and aren't allowed in Protocol Configuration Options, and what the semantics of the truncated negotiation are, isn't written down anywhere so far as I can see - it does rather look like one of those areas of GSM that only works because people on both ends of the protocol happen to have picked up the same folklore.

[The Natural Philosopher]

So, can you confirm that 3 will do some sort of IP over 2G?

If I could but find the right magic spell?

[Roland Perry]

In message , at 20:08:29 on Thu, 16 Apr 2009, Tim Ward remarked:

That worked on 1G phones too (assuming 1G = analogue). For some reason I think 4.8K was the optimal speed.

And Orange had a proprietary "High Speed Data" option.

[Isn't GPRS 2.5G??]

[Roland Perry]

In message , at 19:58:28 on Thu, 16 Apr

2009, The Natural Philosopher remarked:

My "3" dongle does.

[Roland Perry]

In message , at 20:02:34 on Thu, 16 Apr 2009, Tim Ward remarked:

Maybe they think that "Internet on your mobile" is only viable at HDPSA speeds, synonymous as it is with Flash-infested video content.

If you are picking up email/usenet with a dongle and laptop, the slower fallback speeds are adequate.

[John Rumm]

On ETACS the speed would presumably have been adaptive - as on an ordinary phone line.

Straight GSM dial up data was/is 9.6 kbps - ok for text email but not much else these days...

[Roland Perry]

In message , at 20:57:29 on Thu, 16 Apr 2009, Steve Firth remarked:

My "3" one does.

Indeed.

My "out of the box" Windows software for the "3" dongle has an option to force 2G/2.5G, but it's greyed out. As a result it always tries to use

3G, even when sticking with 2G/2.5G might be a better solution (eg when on a train). I've always assumed this was because they have to pay a fallback carrier, and so want to use their own network as much as possible. The problem is that switching trashes the session (and any tunnels).

[Roland Perry]

In message , at

22:11:50 on Thu, 16 Apr 2009, John Rumm remarked:

And 4.8k was the best bet. Faster than 2.4k and also faster overall than a retrying 9.6K.

I spent a week last New Year using it for email and usenet... Couldn't get GPRS working at all. Never worked out if it was a configuration or subscription issue.