We seem to be on the same frequency, if you'll pardon the expression.
Just a minor 'correction'. The NMR data IS actually available to SIM toolkit, and I am using precisely that to get the info. However the SIM toolkit application (if you can call it that) just sends the info to the network, and it is equipment at the network that does the clever work of 'guessing' the position. (I know that SIM toolkit can do it not becasue I am some expert or genius, but simply because I am actually making use of it)
The data available actually has all the information you could possibly extract that is of any use for obtaining a location, namely:
- CellId of the serving cell
- Signal level of the serving cell (in decibels above -111dBm)
- Timing advance
- BCCH frequency, signal level and BSIC of the six strongest - neighbouring cell
To make use of these you of course need detailed information of the network, even for the simplest of algorithms. One reason is that the SIM toolkit will only give you frequency and BSIC of the neighbouring cells. To make use of that you need to have a table which maps the frequency/BSIC to the Cellid and of course the actual locations and antenna directions of those CELLIds. I am in quite a priviledged position in this regard because I am actually responsible for running a GSM network. My guess is that if you are not actually employed with a GSM network operator, the chance of obtaining such data is quite slim, as such information is normally considered to be highly sensitive information for a whole array of reasons, therefore any such effort would necessarily be done either by the network operator itself or by a trusted partner of the network operator.
There is however a simple but laborious way around it. Whether it is feasible or not will depend on how much time you have available and what area you want to cover.
You could actually drive around the places you want to have recognised by the system and just record data as it is. From this you build up a database of what you can expect to receive from where. When the system is eventually being used, the mobile will report the info from its location, and you would compare that to the accumulated data and obtain a best fit.
Of course that is the very simplest way of doing it and there are endless ways of improving it.
Back to the original subject, given that the SIM toolkit can provide the data required, one wonders if the Symbian OS can somehow ask the SIM toolkit to give it the information. I found some clues in an include file called RSAT something or other (in one of the forums actually), it does mention NMR in some places, but the way I seem to understand it is that you can aske the STK the question:
"Can you provide NMR data to the network?"
but you cannot ask it the question:
"Please give me the NMR data?"
To sum it all up, I am stuck and don't seem to be getting anywhere. It seems that the problem can be solved by either a Nokia expert or by some hacker type who manages to get at the registers and things.