Quantisation-Digital Communication Systems-Lecture Slides, Slides of Digital Communication Systems

Download Quantisation-Digital Communication Systems-Lecture Slides and more Slides Digital Communication Systems in PDF only on Docsity!

Sources of Corruption in the sampled and quantised pulses

• Sampling and Quantization Effects

– Quantization (Granularity) Noise: Results when quantization

levels are not finely spaced apart enough to accurately

approximate input signal resulting in truncation or rounding

error.

– Quantizer Saturation or Overload Noise: Results when input

signal is larger in magnitude than highest quantization level

resulting in clipping of the signal.

– Timing Jitter: Error caused by a shift in the sampler position.

Can be isolated with stable clock reference.

Nonuniform Quantization

• Nonuniform quantizers have unequally spaced levels
  • The spacing can be chosen to optimize the Signal-to-Noise Ratio for a particular type of signal
• It is characterized by:
  • Variable step size
  • Quantizer size depend on signal size
• Sometimes non-uniform spacing is preferred to uniform spacing
• Many signals such as speech have a nonuniform distribution
• Basic principle is to use fine quantization (small step size) for weak signals and coarse quantization (large step size) for strong signals