hi,

I was wondering how to transmit and receive using layer1.  I have 

been reading some of the gsm specs. I have been looking around in

the

source code a lot, and there many functions that are used for transmit

and receive. Which are the right few to use?

there are only two types of data between L1 and L2: data frames and channel request burst. all the other functions control the radio and the channel in which to communicate. the layer 1 is controlled by the radio ressource protocol (gsm48_rr.c). in order to understand the channel multiplexing, you should read GSM TS 05.02.

Is there any way to send a text message to a different phone by simulating a base station?

osmocom is not (yet) able to control baseband hardware to act as a BTS.

Do I need two phones or one phone to transmit and receive as a base

station?

in order to have more than a BCCH, you need two phones. one phone is not able to send and receive at a time. continuouly transmission is required for other phones to find a cell.

Is there any way to make a half duplex base station on a BCCH channel with only one subscriber phone at a time, and what would that entail code-wise?

you can limit the number of active calls by limiting the number of channels on the BTS, but you cannot limit the number of phones camping on the BTS.

Would it be legal to run a very low power base station in

the USA on a different unused cellular band/frequency?

you need to check the FCC for laws and test licenses.

I have a lot of free time since I do school at home and I could probably help develop some new parts of the osmocom-bb project if you want me to. I know C,

some x86 assembly, and a few other languages. I have also had

practice

fixing compile-time errors, and bugs in code. I apologize if this is too many questions. You don't have to answer them all if you don't

want to.

if you are really interested. you should start reading with TS 04.08. this is what i did. it describes all the three "layer 3" protocols.

Thank you for helping, Calvin E. Balke