please help Name EECE32218S s01 4/26/2018 1. How do guided media differ from ung

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Name EECE32218S s01 4/26/2018 1. How do guided media differ from unguided media? 2. List three main multiplexing techniques 3. Distinguish between synchronous and statistical time division. 4. Why is statistical time division more efficient than synchronous time division? The least expensive and most widely used guided transmission medium for both analog and digital signals is 5. Define FHSS and explain how it achieves bandwidth spreading 6. Assume that a voice channel occupies a bandwidth of 4 kHz. We need to multiplex 10 voice channels with guard bands of 500 Hz using FDM. Calculate the required bandwidth 7. What two functions do antennas serve?

Explanation / Answer

1. Difference between Guided media and unguided media is:-
- The signal required for guided media is through physical path while unguided media broadcast the signal through air.
- Guided media is wired communication while unguided is wireless.
- Guided media provides direction to signal while unguided does not provide any direction.
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2. Three main multiplexing techniques are:-
i) Frequency division multiplexing.
ii) Wavelength division multiplexing.
iii) Time division multiplexing.
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3. The difference between synchronous and statistical time division is:-
- In Synchronous data flow of each connection input is divided into units and each input occupy one output time slot while in statistical TDM slots are allotted dynamically.
- In Synchronous TDM no. of slots in each frame are equal to no. of input lines and in statistical TDM, No. of slots in each frame are less than the no. of input lines.
- In Synchronous TDM bits are used at the beginning of each frame and in statistical no synchronization bits are used.
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4. A statistical TDM is more efficient than a synchronous TDM because it allocates time slots dynamically on demand and does not dedicate channel capacity to inactive low speed lines.
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The least expensive and most widely used guided transmission medium for both analog and digital signal is twisted pair cable. It has two types :-
i)Unshielded Twisted Pair (UTP)
ii)Shielded Twisted Pair (STP)
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5. The frequency hopping spread spectrum (FHSS) technique uses M different carrier frequencies that are modulated by the source signal.
- It achievs bandwidth spreading as:- The signal modulates one carrier frequency; at the next moment, the signal modulates another carrier frequency.

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7. The two functions of antennas are:-
i)For transmission of a signal:- electrical energy from the transmitter is converted into electromagnetic energy by the antenna and radiated into the surrounding environmen.
ii) For reception of a signal:- electromagnetic energy impinging on the antenna is converted into radio-frequency electrical energy and fed into the receiver.

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