You have to be good in programming and problem solving. Knowledge of the telecommunication is preferred. Please brush your fundea before interview it would help you to crack it. There might be some puzzles and aptitude questions as well. Rest it depends on the interviewer.

Mostly interview will be based on 2 things 1. What all you did in past 2. What is required for current position There will be minimum 2 rounds followed by HR round. All questions will start with basics and then goes in depth. If you don't know answer, say it loud n clear. Don't fake it.