Advantages of PCM | disadvantages of PCM

This page covers advantages and disadvantages of PCM. It mentions PCM advantages or benefits and PCM disadvantages or drawbacks. PCM stands for Pulse Code Modulation.

What is PCM?

The short form of the Pulse Code Modulation is PCM. In PCM, the analog speech waveform is sampled and converted directly into a multibit digital code by an Analog to Digital converter. The digital code is stored in the memory and which is later re-called for the playback.

In this type of modulation, analog data is sampled and quantized before being represented to digital binary form. Hence using PCM, continuous amplitude and continuous time signal waveform is converted into discrete amplitude and discrete time waveform.

If there is a n bit quantizer and sampling rate is Fs then bit rate will be
➨Rb(bits/sec) = n * Fs

PCM-Pulse Code Modulation

In PCM, we represent each quantized level by a code number and later transmit the code number rather than sample value itself. Code number is in the form of binary representation. The digits of binary representation of the code number are transmitted as pulses.

In general, if M numbers 0,1,....,M-1 are to be represented then N binary digit sequence KN-1,...K0 is required where M =2. In PCM we are compressing not the signal m(t) as shown but its samples.

DS0 carry basic digital signaling rate which is 64 kbps. To carry a typical phone call, audio sound is digitized at 8 KHz sampling rate using 8 bit PCM.

Benefits or advantages of PCM

Following are the benefits or advantages of PCM:
➨It is robust against noise and interference.
➨Uniform transmission quality.
➨Efficient SNR and bandwidth trade off.
➨It provides secure data transmission.
➨It offers efficient regenenation.
➨It is easy to add or drop channels.

Drawbacks or disadvantages of PCM

Following are the drawbacks or disadvantages of PCM:
➨Overload appears when modulating signal changes between samplings, by an amount greater than the size of the step.
➨Large bandwidth is required for transmission.
➨Noise and crosstalk leaves low but rises attenuation.
➨An IDN (Integrated Digital Network) can only be realized by gradual extension of noise.
➨The difference between original analog signal and translated digital signal is called quantizing error.

Also refer advantages and disadvantages of DPCM >> and ADPCM >> techniques.

Modulation types

BPSK -This page describes BPSK modulation technique with equation and constellation diagram.
QPSK -This page describes QPSK modulation technique with equation and constellation diagram.
QAM-This page describes QAM modulation technique with equation and constellation diagram.
MSK-GMSK MSK modulation,GMSK modulation and GMSK demodulation.
8PSK 8-PSK modulation or multilevel PSK or phase shift keying modulation technique.
BPSK vs QPSK -Difference Between BPSK and QPSK modulation techniques.
QPSK vs OQPSK vs pi/4QPSK-Difference between QPSK,OQPSK and pi/4QPSK modulation techniques
Differential Encoder and Decoder

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