Software defined radio can be used for multi-standard compatibly. Ideal software radio can convert the RF signal directly into digital signal and all the following operation can be done in software. Thus when the user has to change the protocal, he need only to change the software in the ROM instead of changing the hardware. Because of the limit of the technology, ideal SDR is not pratical. But now some receivers ultilize the digital IF instead of the digital RF to realize the SDR.
I have searched a book about the SDR in this forum, this book maybe helpful for you.
The SDR should have the capability to modulate/demodulate GMSK, QPSK, 16 QAM and 64 QAM and support CDMA/GSM/WCDMA, police and military communication standards. The major parts of the modulation/demodulation were done in the DSP software instead of the hardware.