Get a call from recruiter then follow by 2 phone technical interview asking a lot of questions on data structure and algorithm. Questions are not hard but some are tricky like operator priority but I didn't expect those question. I was thought they gonna asking questions on LTE design. Didn't get on site.

I applied through their career sites and got the phone interview scheduled. After few weeks, I was invited for onsite interview. There are 6 rounds throughout the day. The interview difficulty is average. I still don't understand why didn't I get the offer.