_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:-
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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.
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