Qualcomm Modem Field Test Engineer interview questions

This was a contract position and I was applied through a staffing agency. I was interviewed by 3-4 people through the phone. The interview was quite short, less than 20 min. I guess I didn't match well.

One phone interview: what is qpsk/ offset qpsk? what are channel coding and source coding? Two signals transmitting form same antenna at same power, which will have better range.. 1800 or 1900? What is rf wave propogation, free question, explain whatever you know! what is OFDMA? how it is different from CDMA? Communication circuit block diagram, source to antenna..