Question

In soft decision approach what does -127 mean?

(a) Certainly one

(b) Certainly zero

(c) Very likely zero

(d) Very likely one

This question was addressed to me by my college professor while I was bunking the class.

This key question is from Shannon Hartley Theorem and Turbo Codes topic in portion Channel Coding of Digital Communications

Answer 1

The correct choice is (b) Certainly zero

To explain: The decoder front end produces an integer for each bit in the data stream. This integer is the measure of how likely it is that the bit 0 or 1 and is called as soft bit. It ranges from -127 to 127. Here -127 represents certainly zero.