Question

Consider binary data transmission at a rate of 56 kbps using baseband binary pulse amplitude modulation (PAM) that is designed to have a raised-cosine spectrum. The transmission bandwidth (in kHz) required for a roll-off factor of 0.25 is ________∙

Answer 1

Concept: 

The bit rate of base baseband binary pulse amplitude modulation (PAM) with a raised-cosine spectrum is given as:

\({\rm{Bit\ rate}} = \frac{{2\left( {{\rm{BW}}} \right)}}{{\left( {1 + {\rm{α }}} \right)}}\)

Where,

BW= Transmission Bandwidth of PAM signal.

α = Roll-off factor. (α < 1)

Calculation: 

Given: Bit rate = 56 kbps, α =.25

we know that,

\({\rm{Bit\ rate}} = \frac{{2\left( {{\rm{BW}}} \right)}}{{\left( {1 + {\rm{α }}} \right)}}\)

So,

\(56 = \frac{{2\left( {{\rm{BW}}} \right)}}{{1 + 0.25}} \)

B.W. = 28 × 1.25

B.W. = 35 kHz