Question

Briefly Give one to two line logical answer to the following Question

(a)IN PCM How the parameters fieldlity bandwidth and time delay can be traded off?

(b)If the number of bits in signal to noise ration is increased what will be its effect?How to reduce signal to noise ratio?If number of bits are incraesed signal to noise ratio is decrease?

(c)non unform quantization is better than uniform quantization?

(d)Why is it often preffered to use units of normalized bandwidth,WT,comapred with bandwidth alone?

(e)What is the dfference between PCM andPAM?Which one is better?

(f)  For a known signal space how you can determine the number of correlators used at the receiver ?

(g) Which type of binary signaling you prefer to use in digital communication among unipolar , antipodal and orthogonal ?

Answer 1

ANSWER (A)

In PCM the process of quantization adds quantization noise to orignal signal. So to improve signal quality and reduce noise we need to increase number of quantization levels.More number of levels will increase data transfer rate this higher data rate will increase bandwidth with permissible delay.

Hence to have better fieldlity of signal you must use higher bit levels and increase badwidth.

Answer (b)

More number of bits means quantization is done at fineest level means we are increasing signal quality. Hence better will be SNR(signal to noise ratio).

By decresing number of bits or reducing data transfer rate or reducing bandwidth in PCM we can reduce SNR.

ANswer(c)

IN PCM quantization noise is directly proposnal to step size . So if step size uniform during quatanization process it is called as uniform quantanization.

In uniform quantanization Low level signal quality is bad because Noise effects badly .

Hence uniform quantanization is used for high level signals.

In non uniform quantanization step size is not uniform hence they can be used for weak level signal like human voice etc and avoided to use for high level signal .

Answer(d)

WT(time bandwidth product) OR W/R (Where R is Pulse rate of signal) tells us important information about signal and with how much efficiency the transmission bandwidth is getting utilized .It is just Relative measure of bandwidth which helps to campare two waveforms easily in terms of bandwidth utilization .Thats why it is preffered over bandwidth alone .