Default How to distinguish between GSM and GPRS?

I made a program to obtain band strength values mixing tstril and some instructions posted in this forum. Now I pretend to distinguish between GSM and GPRS, because if GPRS is not connected it returns a GSM value.

Any ideas?

P.D.: if possible, does anybody knows how to measure GSM when GPRS is active. All of this was made using the functions shown in ril.h

Thanks.