Assignment_chapter-1 Advances in information communication Networks

 

_Information Communication Networks

3351601
 Assignment #chap-1

1: Explain amplitude shift keying in detail with diagram.

Answer:-

-It is a form of modulation that represent digital data as variation in the amplitude of carrier wave.

-Amplitude of an analog carrier signal changes accordingly with modulation signal. But frequency and phase remains constant.

-The level of amplitude can be defined by binary 1 and 0, like ON-OFF key .

-In final modulation signal, bit 0 is represented by absence of carrier and bit 1 is represented by presence of carrier.

-Peak amplitude of signal during each bit is constant, depends on 1 and 0 bit of modulating signal.

2: Explain FSK in detail with diagram.

Answer:-

-Frequency of carrier signal varied according to amplitude of message signal.

-It is a modulation technique in which digital data is transmitted through different frequency changes of carrier signal.

-Frequency is constant during each bit duration.

-Amplitude and phase is constant during whole signal.

Basic FSK is called as Binary FSK where Bit 1 and 0 are called as Mark frequency and space frequency respectively.

  

3: Explain phase shift keying in detail with diagram.

Answer:-

-In PSK phase of carrier signal changes according to bit stream of digital modulating signal.

-Phase of signal is changed for representing bit 1 and 0.

-During one bit duration phase remains constant. As bit changes phase is also changes.

-Frequency of carrier signal and peak amplitude both remains constant.

-When Signal starts with phase of 0°, it is represented as binary 0. and when it changes the phase value by 180° it is represented as binary 1.

-Hence phase are seperated by shifts of 180°.

  

4: Draw ASK, FSK, and PSK waveform for digital stream '11011001'.

Answer:-

-

5: What is linear digital modulation? Explain QPSK and OQPSK with comparison.

Answer:-

-In Linear digital modulation amplitude of carrier signal varies linearly with modulating digital signal.

-Due to bandwidth efficient of linear technique it is very useful in wireless communication.

-Most Popular linear modulation techniques are :- QPSK, OQPSK and π/4 QPSK .

-QPSK:-maximum phase shift is limited to about 90°.

-OQPSK:-maximum phase shift is about +/- 90°.

-The only difference between QPSK and OQPSK is that, I and Q are shifted such that the alignment of these two baseband waveform is offset by T.

6: Explain QAM with neat diagram.

Answer:-

-QAM is combination of PSK and ASK.

-PSK has limitation to make a small phase difference. This limits its potential bit rate.

-So instead of one characteristics, we shuffling two characteristics but not frequency.

-Although, no of amplitude changes are fewer than no of phase changes because ASK is more noise susceptible.

7: Explain coding methods for digital transmission.

Answer:-

-It is the method to represent digital data into digital signal. for example you send dat from computer to printer. 

-There are three method for represent digital data into digital signal:-

1)Unipolar #   2)Polar#   3)Bipolar#

Unipolar:-It is very simple encoding method uses only one voltage.

1 is represented by high voltage.

0 is represented by zero voltage.

Polar:-This method uses two voltage levels.

Positive voltage for high (1)

Negative voltage for low (0)

Bipolar:- This method uses three voltage levels.

1)positive  2)negative   3)Zero

-Bit 0 is represented by zero level, bit 1 is represented by alternate positive or negative level.

8: what do you meant by digital transmission code? Draw NRZ, RZ, and Bipolar waveforms for data stream '1100001111001'.

Answer:-

-It is the method to represent digital data into digital signal.

9: Short Note:- Advantages, Disadvantages and application of wireless communication.

Answer:-

-Advantage:-

Main feature is mobility and flexibility.

-Neat and easily installation no cable running here and there.

-Because of its wireless nature, there is no cost of cabling infrastructure.

-We can add or remove devices from our system without any disruption to the rest of the system.

-Disadvantage:-

-major problem is limited radio spectrum available for communication.

-More security is needed to secure data and bandwidth.

-Relatively lower bandwidth speed as user increases.

-Application:-

-It is used in security systems, television remote control, represented by zero wi-fi, cell phone, wireless power transfer and various wireless communication based systems.

10: Define:- (1)Spectrum efficiency (2)wireless communication (3)shift keying .

Answer:-

-Spectrum efficiency:-The data transmitted with a minimum transmission error over a given spectrum or bandwidth

-Wireless communication:-The communication in which we don't require physical media and any cable infrastructure is said to be wireless communication.

-Shift keying:-During modulation, modification occurs in amplitude, frequency, and phase, this modification is called as shift keying.

11: Define (1)bit interval  (2)bit rate  (3) baud rate (4) symbol rate. 

Answer:-

-Bit interval:-The time required to send one single bit is called as Bit interval.

-Bit rate:-The number of bits transmitted during one second (bps) is called as bit rate. 

-Baud rate:- The no of signals to represent those bits transmitted during one second is called as Baud rate.

-Symbol rate:-The bit rate divided by the number of bits that can be transmitted with each symbol is called as symbol rate.