Qualcomm interview questions

HR contacted me via email to set up a phone interview. The interviewer asked mostly about my research, followed by a couple of simple technical questions. A few days later, HR contacted me again for a second phone interview. This time, the interviewer briefly asked about my research, then followed by a more in-depth technical questions. I got a rejection email two days later. I think I should have answered the questions better, and also, based on my impression after talking to both interviewers, my research background probably doesn't sound like a perfect fit for them.

The initial process of the interviews were very planned and organized. There were total of 6 interviews.. with 1 telephonic screening interview and 5 onsite face to face interviews and i was interviewing for entry-level position. They directly went into technical stuff. And the interviews were are scenario based. like i am facing this issue what is the problem and how can it be resolved. Qualcomm is well known for its tough interviews.