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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Delta modulation encodes one bit per samples. This introduces intersymbol interference in the controlled manner to reduce the bandwidth. When b t changes level, phase of the carrier is changed. What is convolution code?

PDM represents the input signal amplitude in the form communicaion width of mraks pulse. KWhat are the application of spread spectrum modulation. Because of software implementation of decoding schemes they a re quite flexible compared to hardware implementation of other schemes.

The bandwidth of frequency hop spread spectrum is very much large compared to direct sequences spread spectrum. This is because the spread spectrum signal has the ability to resist the effects of multipath fading. There is no analog to digital converter involved in delta modulation.

Define free distance and coding gain. A band limited signal of finite energy, which has no frequency components higher than W Hz, may be completely recovered from the knowledge of its samples taken at the rate of 2W samples per second.

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

Constraint length is the number of shift over which the single message bit can influence the encoder output. In a Systematic block code, message bits appear first and then check bits. The detection of the signal communicarion become difficult this distraction can be compensated with the help of equalizer.

It also referred as pulse duration modulation or PDM. Under such condition, the spectrum of the sampled signal overlaps with itself. The pseudo noise sequences generated at the receiver and the transmitted must be same and. The storage hardware required by convolutional decoder is less since the block sizes are smaller. What is processing gain?

Dirac comb is nothing but a periodic impulse train in which the impulses are spaced by a time interval of Ts seconds. Error probability of MSK: List the advantages of Passband transmission a. It required wideband channel with small phase distortion. The sequence is not completely random, but it is generated by well defined logic.

The pseudo-noise sequence and data sequence are applied to a product modulator. Let the bit rate be f b and the frequency of carrier be f. Code tree is lengthy way of representing coding process. The non zero output of the produce YH.

Mention the use ec301 adaptive quantizer in adaptive digital waveform co d ing schemes. What is meant by systematic and non-systematic codes? This code can correct upto 3 errors. This makes one sweep of beam equal to T b seconds.

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

A bandlimited signal of finite energy, which has no frequency components higher than W Hz, may be completely recovered from the knowledge of its samples taken at the rate of 2W samples per second.

DM encodes the input sample by one bit.

The bandwidth of frequency hop spread spectrum is very much large compared to direct sequences. While converting the signal value from analog to digital, quantization is performed. In switched telephone network the distortion depends upon 1 Transmission characteristics of individual links. Pseudo noise sequence is a noise like high frequency signal. List the requirements of Passband transmission.

K symbols Parity check size: Similarly receiver, decoder and destination form the transmitter. Here v is the number of bits used to represent samples ahswers PCM. DPCM can have more than one bit of encoding the sample.

It is expressed in terms of message bits. In DPSK, the input sequence is modified. They can be programmed to avoid some portions of the spectrum 3. Write a note on correlative level coding?