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.
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?
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
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