EC DC 2marksmarks, DIGITAL COMMUNICATION Question Bank, DC Short Answers – ECE 5th SEM Anna University. 0. By vish on. 2. DIGITAL COMMUNICATION. State sampling theorem. If a finite –energy signal satellite communication two marks question and answers QUESTION BANK. Subject Code: EC Subject Name: Digital Communication Techniques. Year/Sem: III/IV. UNIT I PULSE MODULATION. PART A (2 Marks).

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What is Golay codes? It required wideband channel with small phase distortion. Similarly receiver, decoder and destination form the transmitter. What are eye pattern? Amplitude reconstruction signal is done to remove amplitude discontinuities due to pulses. It has long acquisition time. This secrecy capability of spread spectrum is used in military as well as in many commercial applications.

This interference of the frequency components is called as aliasing effect.

What are the two limitations of delta modulation? This reduces the quantization error and number of bits to represent the sample value.

### EC Digital Communication – Two Marks and 16 Marks with Answers – All Units

Adaptive coding is used for speech coding at low bits rates. What should be the minimum bandwidth required to transmit a PCM c h a nn e l? What is pseudo noise sequence? This expressed in terms of message bits. The baseband signal receiver is also called optimum receiver.

What is its Fourier Transform? This allows the message to be transmitted by means of a digital waveform. What is meant by cyclic codes? The bit rate of such schemes is reduced due to adaptive quantization. What is meant by quantization?

What is the advantage of delta modulation over PCM? When it becomes maximum? Thus convolutional codes generate a string of encoded bits for input message string.

Explain the model of bandpass digital data transmission system? It is also given mathematically as, J Eb.

Dirac comb is nothing but a periodic impulse train in which the impulses are vigital by a time interval of Ts ec231. The transmission characteristics keep on changing. Pseudo noise sequence is a noise like high frequency signal.

A code is linear if modulo-2 sum of any two code vectors produces another code vector. The presence of outputs due to other bits interference with the output of required bit. Pulse code modulation PCM is a method of signal coding in which the message signal is sampled, the amplitude of each sample is rounded off to the nearest one of a finite set of discrete levels and encoded so that both time and amplitude are represented in discrete form.

The output is assigned a discrete value selected from a finite set of representation levels are reconstruction values that are aligned with the treads of the staircase. I slow frequency hopping and ii fast frequency hopping.

## EC2301 Digital Communication Question Bank – 16 Mark Questions | 5th Semester ECE Anna University

Since only one previous message bit is stored. When binary data is transmitted over the baseband channel, noise interfaces with it. Write the futures of BCH Codes? They have relatively short acquisition time. Therefore adaptive equalization is used. The code efficiency is the ratio of message bits in a block to the transmitted bits for that block by the encoder i. Hence Ck becomes a correlated signal even though a k is not correlated.

Code tree Trellis diagram 1 Code tree indicates flow of the coded signal along the nodes of the tree Trellis diagram indicates transitions from current to next states 2 Code tree is lengthy way of representing coding process Code trellis diagram is shorter or compact way of representing coding process Constraint length is the number of shifts over which the single message bit clmmunication influence the witth output.

The bandpass digital data transmission system consists of source, encoder and modulator in the transmitter. When is the PN sequence called as maximal length sequence? The peak-to-peak range of input sample values subdivided into a finite set of decision levels or decision thresholds 2.