Question :

(a) "Pulse Code Modulation (PCM), as used in telephony, samples a signal at 8 kHz using 256 quantization levels". Outline how this scheme works with the help of sketches and, by reference to the Nyquist's Theorem, explain how the sampling rate was chosen.

(b) Provide advantages that digital transmission has over analogue transmission.

(c) Describe types of communication impairments that you are familiar with and, with reference to a standard communication model, state where the above-mentioned impairments usually occur.

(d)

I. Data is to be transmitted using a modem at 9600 bits per second. Calculate the minimum bandwidth of a transmission system that uses 8- level signalling.

II. For the above data rate to be achieved at the above bandwidth, use Shannon's Theorem to calculate the allowable signal to noise ratio in decibels.