Qualcomm Research Intern interview questions

I put my resume on qualcomm website, the position I applied is system test intern, but 2 weeks later, I received an email from qualcomm, asked me to schedule a interview, the group is phy/mac layer design. There is an about 45 minutes phone intervew, mainly talked about my resume and some basic wireless communication problems, like the influence of the carrier offset on OFDM system

Basically they asked me what I did for my phd. I basically explained my current research and also some course projects. They also asked me some brain teaser questions. The problem is not that hard. Since the positions I was looking for is about doing computer vision, they also asked me some really basic stuffs about it.