wicom viva

I had studied a lot of WiCom in the last few days. Except for the cordless telephony part. So i was confident.
The viva was good. Following were the questions asked:
1. Tell me whatever u know about CDMA.
A. So i explained the basics. Then also the external was quiet. So i started with its features.
I said it has soft capacity ie. after all channels are used, then also a call request will be served but a lower GoS.

2. Then he asked my partner Amit “How does this happen?”
A. He said BW / user reduces. But Srija mam said BW is 1.25MHz for all, how’ll it reduce.
Then he said something on PN sequence length(which is right i feel).

3. What are different channels in CDMA spectrum?
A. I said 1.25 MHz is divided into channels which are coded with different Walsh codes.

4. No no, that pilot channel etc.
A. Pilot, synch, paging & traffic.

5. There is 1 more information in it. What’s that?
A. No idea.(It was power control info).

6. What are Walsh codes? Explain in terms of matrix.
A. I showed him Hadamard matrix.

7. Walsh codes are orthogonal to each other. Explain(in the matrix).
A. I showed him that the Hadamard matrix A*A transpose= scalar matrix. He wasn’t convinced.
Then i had to tell from basics that 1 row multiplied with itself gives nonzero, & with other rows gives zero result.

Then we left. So overall it was quite good for me. But Amit was in trouble. He answered only 1 out of 3 questions. Hope he gets good marks(& me too). I expect 21/25.


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