below is an email I had written to Josh Blum, but I just saw his webpage, and realized he might not get time to reply at the earliest, so I am forwarding at this list as well, so I can get all the help that I can.
Dear Sir
I am a BSc electrical engineering student, in my final year. As part of my senior year project, I am working on co-operative communication using USRP boards. I have downloaded GnuRadio+Drivers, and read many tutorials, seen your webpages, and other related information.
My supervisor insists that I use discrete blocks, instead of already combined blocks (for certain modulation schemes, like qpsk etc). I am working on that, however I have particularly no idea as to what a block needs (like input), what it does to the output, and what each parameter does. I have tired visiting the C code (its all too messy for me to understand). I have visited examples as well, but no luck.
Here is what I am planning. I am thinking of writing my own Fortran blocks (we are a team of 4 so yes that is possible) and integrating that with python; NumPy and then use that to connect with other basic blocks. Please tell me if that will work (as in how much efficient would that be), and whether there is a way round understanding the blocks.
Let me give you an example:
Our supervisor says, that given a data source of bits 1,1,1,1,1,0,1,0,1,0,0,1,0,1,0 for QPSK we first get the data to 2bits each symbol and then calculate its phase (map encoder) and then for differential decoding we get differential decoder (which is basically just adding the previous phase to the current phase) and then have it in I and Q form, followed by pulseshaping.
Now I have read the API doxygen, the Simple GNU Radio User Manual, and I cannot relate clearly as to what for example gr.map_bb() block does, or why is the differential encoder using y[k]=y[k-1]+x[k]%M (like why is there a mod in it ? ). Moreover, for a me a discrete pulseshaping filter would want kronecker delta pulses at its inputs and then have the pulse made around the delta pulses as its output, but even that i donot understand. Furthermore, how will use the demodulation block to determine the signal using 'nearest distance metri
We are okay in making our own Fortran blocks and working, but we need to be sure. And would really like if we can find some book/manual to understand on what convention was the blocks already existing made, etc, so we use most of the existing work done.
I know you are busy person, and I am not sure, if you will even get time to read or reply to our email at the earliest (as we need to get to our supervisor, at the earliest with our weekly progress) but please do help us, or refere to someone else.
Thank you for your time,
Regards,
U B