Forums

Anyone work with GSM &3G?

Started by Bob Sutton January 18, 2012
I am seeking specific information regarding the signal structure of
GSM and 3G.

Does anyone here work for a Telco, or is familliar with the make up
and comparative capabilities of these?

In particular, I am interested in the types of modulation inherent to
these standards which are technically available (utilized or not) for
transmission of _analog_ signals, ie FM, PWM, etc.

Bob Sutton
On Jan 18, 2:10=A0am, bobsut...@protolux.com (Bob Sutton) wrote:
> I am seeking specific information regarding the signal structure of > GSM and 3G. > > Does anyone here work for a Telco, or is familliar with the make up > and comparative capabilities of these? > > In particular, I am interested in the types of modulation inherent to > these standards which are technically available (utilized or not) for > transmission of _analog_ signals, ie FM, PWM, etc. > > Bob Sutton
Yes, I do work for a Telco, but with more mundane DOCSIS etc., Please check http://www.3gpp.org which has a huge collection of protocol specification/standards documentation for GSM, UMTS and related protocols, as well as links to other relevant sites.
On Tue, 17 Jan 2012 23:51:19 -0800 (PST), Daku <dakupoto@gmail.com>
wrote:

>Please check http://www.3gpp.org which has a huge collection >of protocol specification/standards documentation for GSM, UMTS >and related protocols, as well as links to other relevant sites. >
Thanks for the link. But it appears to be a bit of a labyrinth. I suspect even a specialist would be hard pressed to navigate this. Where are the signal specs?? Occupied frequencies, modulations, etc. I found this: http://www.techmind.org/gsm/ If one wanted to FM the pulse train with an analog signal, which component of the signal would be most suitable, without substantial modifications to the transmitter? Also the page cited does not give a comparison of the GSM signal structure with that of 3G. Bob Sutton
On Jan 18, 3:43=A0am, bobsut...@protolux.com (Bob Sutton) wrote:
> On Tue, 17 Jan 2012 23:51:19 -0800 (PST), Daku <dakup...@gmail.com> > wrote: > > >Please checkhttp://www.3gpp.orgwhich has a huge collection > >of protocol specification/standards documentation for GSM, UMTS > >and related protocols, as well as links to other relevant sites. > > Thanks for the link. But it appears to be a bit of a labyrinth. I > suspect even a specialist would be hard pressed to navigate this. > > Where are the signal specs?? Occupied frequencies, modulations, etc. > > I found this:http://www.techmind.org/gsm/ > > If one wanted to FM the pulse train with an analog signal, which > component of the signal would be most suitable, without substantial > modifications to the transmitter? > > Also the page cited does not give a comparison of the GSM signal > structure with that of 3G. > > Bob Sutton
My initial thought is that your questions are too simplistic to give any sort of meaningful answer. GSM and 3G (such as UMTS) are two very different things. I agree 3gpp is too complex a signalling system for any one person to digest. Don't bother. As to occupied frequencies, etc..., that will depend on where the devices are deployed as each country sets if frequency use regulations, in concert with international treaties, etc... You're unlikely to find a single document anywhere with this information already compiled for you. (And even if you did, how helpful would that really be?) Furthermore, the technical parameters (occupied bandwidth, modulations, etc..) also vary according to an almost bewildering set of circumstances and conditions, not the least of which are those same various regulatory environments in which the systems and designs are intended to operate. So, to the extent you won't find the basics all nicely summarized, don't expect to discover the drill-down either. Also, (if I understand your question correctly), you appear to have a fundamental misconception of how modern-day systems and networks are built. Essentially, they are all software-defined radios. So if you want to "FM the pulse train" of anything with an analog signal (whatever that means?), your question might really be about how to modify the software. Because frankly, if it can't be coded in software, these days it can't be done. As to GSM - though that is still a very widely deployed platform, it's days are definitely numbered (in my humble opinion). Capacity demands and the relentless march towards "progress" will eventually push it out the back door in favor of 4G, LTE and future network designs. I assume you're either tinkering with some used wireless base station gear, or are "inventing" some new hopeful intellectual property. Either way, it certainly seems you are on the outside looking in - meaning you don't come across as being tightly affiliated with a carrier, or device manufacturer, supplier, etc.... Now I could be wrong, but my intent was simply to stress that whatever you're attempting to do is very likely not a trivial undertaking in any sense. For the questions you've asked, I would expect a team of engineers to have to work on a problem like that non-stop for a really large chunk of time with an amazing budget and resource behind them. If this is a home-brew project.... well, you can pretty much gather where I see that's headed. Best of luck to you though. -mpm
On Wed, 18 Jan 2012 11:12:13 -0800 (PST), mpm <mpmillard@aol.com>
wrote:

>My initial thought is that your questions are too simplistic to give >any sort of meaningful answer. >
With due respect, I was hoping for an answer from someone who had done some study in this area. As I understand the basic GSM and 3G signal standards are relatively fixed. For example, the carrier, modulation and keying frequencies. Accordinly, I would like to find a description of these, and their characteristics. I am not concerned with local variants, only the generic capabilities of the transmitter. Furthermore, without direct experience, I do not see how anyone can claim the controlling software canot be modified. Thanks for your time, but someone please re-read my OP and provide a bit of further information? Bob Sutton
On 19 Jan., 00:08, bobsut...@protolux.com (Bob Sutton) wrote:
> On Wed, 18 Jan 2012 11:12:13 -0800 (PST), mpm <mpmill...@aol.com> > wrote: > > >My initial thought is that your questions are too simplistic to give > >any sort of meaningful answer. > > With due respect, I was hoping for an answer from someone who had done > some study in this area. As I understand the basic GSM and 3G signal > standards are relatively fixed. For example, the carrier, =A0modulation > and keying frequencies. >
google? http://www.radio-electronics.com/info/cellulartelecomms/gsm_technic= al/gsm-radio-air-interface-slot-burst.php
> Accordinly, I would like to find a description of these, and their > characteristics. I am not concerned with local variants, only the > generic capabilities of the transmitter. > > Furthermore, without direct experience, I do not see how anyone can > claim the controlling software canot be modified. >
it is partly so of course it can be modified, anything is possible in theory those who makes gsm chipset don't want competion to find out how they do it, and those who control the phone frequencies don't want people hacking the gsm baseband in their phones, potentially screwing up the network, so good luck -Lasse
On Wed, 18 Jan 2012 15:51:27 -0800 (PST), "langwadt@fonz.dk"
<langwadt@fonz.dk> wrote:


>http://www.radio-electronics.com/info/cellulartelecomms >
Thanks. The info there is alot more accessible. But I would still like to see a commented spectrum analysis plot of 2G and 3G transmissions. Bob
On Jan 19, 3:10=A0am, bobsut...@protolux.com (Bob Sutton) wrote:
> On Wed, 18 Jan 2012 15:51:27 -0800 (PST), "langw...@fonz.dk" > > <langw...@fonz.dk> wrote: > >http://www.radio-electronics.com/info/cellulartelecomms > > Thanks. The info there is alot more accessible. > > But I would still like to see a commented spectrum analysis plot of 2G > and 3G transmissions. > > Bob
What do you mean by "spectrum analysis plot"? Do you just want to see what these look like off-air with a spectrum analyzer or receiver? If so, I can send you that. I don't see how such a plot would even remotely address what it is I thought I understood your original post to be about. Is it that you want to frequency modulate some portion of the underlying "whatever" that constitutes the actual waveform that is broadcast by a cellular or PCS 3G base station? And whatever that FM'd portion is, it would constitute some additional "information" that would be superimposed on the signal. Is that correct? (I'm using the terms "whatever" and "information" here as a placeholders so we don't get into a pissing contest.) Because if so, I'm certain that is not possible (at least for CDMA, W- CDMA, UMTS and LTE) without totally destroying the usability of the signaling format. For one thing, you would lose UE synchronization with the network. Otherwise, I have no idea what you're talking about. My familarity is with the Ericsson UMTS, and Nokia GSM equip. Again, best of luck. -mpm