Question

In a communication system, noise due to quantization error is
1. Linear and signal-dependent
2. Nonlinear and signal-dependent
3. Linear and signal independent at low frequencies only
4. Non-linear and signal-dependent at low frequencies only

Answer 1

Correct Answer - Option 2 : Nonlinear and signal-dependent

In a communication system, noise due to quantization error is known as a signal to quantization noise ratio and it is defined as:

\(SQNR = \frac{{Normalized~Signal~Power}}{{Normalized~noise~power}}\)

\(SQNR = \frac{{3P}}{{{{\left( {{A_m}} \right)}^2}}}{.2^{{2^n}}}\)

Where:

P = message signal power

A_m = Amplitude of message signal

N = number of bits used during the quantization process.

So, by seeing the expression of SQNR, we get SQNR is nonlinear and signal-dependent.

Hence, option (2) is correct.

Important Point:

1) Quantization error is the difference between the input and output of a Quantizer.

2) In dB, SQNR isSQNR (in dB) = 1.8 + 6n