After you read and made yourself familiar with the following topics, please answer /discuss the following 15 questions. Your answers should have detailed explanations. Topics: Digital communication, Pulse code modulation, line code, Frequency shift keying, phase shift keying, Quadrature amplitude modulation, constellation.Questions:1) What do these terms stand for? CW, ICW, ASK, OOK, FSK, PSK.2) What do these terms stand for? VCO, BPSK, DPSK, QPSK, MSK, GMSK.3) Is ASK (Amplitude Shift Keying) usually used alone in digital communications?4) An analog signal is sampled at 2KHz by a 3-bit A/D. If a full-scale voltage of A/D is 6V what is the binary sequence for 2.25V?5) A unipolar signal is passed through an 8-bit A/D with 25 V, full scale voltage range. Find the step size of this quantizer.6) 16 band-limited baseband channels with 4 kHz bandwidth are samples at their minimum periodic sampling rate and TDM multiplexed. After TDM multiplexing, a 16-bit A/D is used to generate the PCM signal. The minimum required bandwidth for transmission of PCM is 2.048 MHz. Is this a correct answer?7) In a PPM (Pulse Position/Phase Modulation), the information is modulated on _______ of the pulse.8) Where is the anti-aliasing filter used?9) What happens to the distortion of a spectrum, if a bandlimited signal with 8 kHz bandwidth is sampled periodically using a 40 kHz pulse and its duty cycle of the sampling pulse is reduced from 30% to 5%.?10) What is the main disadvantage of digital communications?11) What is the resolution (quantization error) of an 8-bit A/D with 8V max voltage?12) What are the main advantages of digital communications?13) Does 4-bit A/D with 7 V, full scale voltage have a smaller or larger step size than an 8-bit A/D with the same full-scale voltage?14) What is the disadvantage of PSK over DPSK?15) A band-limited signal that has been sampled at a sampling rate more than twice of the BW of the signal is not reproducible from its samples, Is this a correct statement?