dcs

                                            DATA COMMUNICATION SYSTEMS

UNIT -1

1.      (a) What is the difference between the communication of data and communication of  information?

(b) What is the difference between electrical noise and thermal noise? For an electronic device operating at 17°C with a bandwidth of 10 KHz, determine the thermal noise power in watts and dBm.

2.      (a) What is a topology? Explain the topologies in Data Communications?

             (b) Give the block diagram of DM and explain clearly the procedure for generation and

             demodulation of delta modulated signals.

3.      (a) Compare peer-to-peer client/server network and dedicated client/server network.

(b) What is a signal-to-noise power ratio? For a circuit with a signal power of 100W and a noise power of 0.002mW, determine the signal-to-noise power ratio in absolute and dB values.

      4.   (a) What is an open system? Explain in detail about open systems interconnection.

            (b) Explain in detail about amplitude modulation and quadrature amplitude modulation.

      5.   (a) What is meant by a layered protocol? Why are protocol layered? Explain.

            (b) What is meant by M-ary encoding? Explain higher-than-binary encoding with an        

            example.

UNIT -2

1.      (a) What is a transverse electromagnetic wave? Explain with a neat diagram.

(b) What is an optical fiber mode? Explain the three practical types of optical fiber modes.

     2.   (a) What is a metallic transmission line? Explain the five types of metallic transmission  

            line losses.

            (b) State Snell’s law for refraction and outline its significance for optical fiber cables.

     3.    (a) What is a transmission line? Compare balanced and unbalanced transmission lines.

           (b) What is an optical communication system? Explain an optical fiber communication

            system with a neat block diagram.

4.      (a) Explain the losses in a metallic transmission line.          

(b) Discuss the modes of propagation of light through an optical fiber cable.

       5.    (a) Explain the advantages and disadvantages of optical fiber cables.

               (b) Explain about STP and UTP metallic cables.

UNIT -3

1.       (a) Determine the Transmission Bandwidth in PCM.

 (b) Briefly explain the T1-Digital carrier system.

       2.     (a) What do you understand by signal voltage-to-quantization noise voltage ratio? Give

                its relationship to resolution, dynamic range, and the maximum number of bits in a

              pulse code modulation (PCM).

              (b) Compare wavelength division multiplexing (WDM) and dense wave division

              multiplexing (D-WDM); and also list the advantages and disadvantages of WDM.

3          (a) What do you understand by companding? Compare analog companding and digital

  companding.

  (b) A PCM-TDM system multiplexes 24 voice-band channels. Each sample is encoded   

   into 7-bits., and a framing bit is added to each frame. The sampling rate is 9000

   samples per second. Determine the line speed in bps.

4        (a) What is the relationship between dynamic range and the number of bits in a pulse

code modulation (PCM) code? For a PCM system with the minimum dynamic range: 46dB, determine minimum number of bits used in the PCM code.

(b) What is super frame and extended super frame time division multiplexing (TDM) format? Explain each with an example.

      5.     (a) What is pulse code modulation (PCM) line speed? For single-channel PCM system

              with a sample rate, f_s=6000 samples per second and a 7-bit compressed PCM code,

              determine the line speed.

              (b) What is a T-carrier system? What is a fractional T carrier? Describe, in detail, the

                various T-carrier systems.

 UNIT -4

1.      (a) What is a radio wave? What are the optical properties of radio waves? Explain all the details of how they relate to radio wave propagation?

(b) What is meant by a free space path loss of an electromagnetic wave? Give the mathematical equation in decibel form. Determine, in dB, the free space path loss for a frequency of 6 GHz travelling a distance of 50Km.

       2.   (a) Explain the terrestrial propagation of EM waves.

            (b) Explain clearly the classification of microwave sources.

       3.    (a) What are the three modes of terrestrial propagation of electromagnetic waves?

             Explian.

              (b) What is a satellite multiple accessing arrangement? List and describe, in detail with

            neat diagrams, the three forms of satellite multiple accessing arrangements.

4        (a) Explain about ray, wavefront, and inverse square law.

(b) Explain about electromagnetic polarization, wave attenuation and wave absorption?

       5     (a) Explain about microwave radio link.

              (b) Explain about different satellite communications systems. 

 download