QUESTION 2 2.1 Sketch the labeled graphs to illustrate the properties of a DAC. (10) 2.2 Sketch a labeled block diagram to illustrate Fundamental building blocks of digital communication systems. (12) 2.3 Consider a noiseless channel with a bandwidth of 6000 Hz transmitting a signal with two signal levels to calculate the maximum bit rate. (4) 2.4 The signal-to-noise ratio is often given in decibels. Assume that SNRdB = 36 and the channel bandwidth is 2 MHz to calculate the theoretical channel capacity. (6)
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3: Calculate the maximum bit rate for a noiseless channel. Given: Bandwidth (B) = 6000 Hz, Number of signal levels (M) = 2 According to Nyquist's theorem, the maximum bit rate (C) for a noiseless channel is given by: $C = 2B \log_2(M)$ Show more…
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QUESTION 2 a) Describe briefly some advantages of digital over analog transmission. (2 marks) b) With the aid of diagrams describe the process of creating a PCM signal out of an analog waveform. (3 marks) c) Describe factors that can degrade the performance of a communication system. (2 marks) An analog signal is sampled at Nyquist rate and 5-bit PCM encoded using a bit interval of Tb=100ÎĽs. The PCM signal is received with a Peak S/N of 30 dB. d) Find the null bandwidth necessary for transmitting the PCM signal using Unipolar NRZ pulses. (2 marks) e) Find the null bandwidth necessary for transmitting the PCM signal using Manchester NRZ pulses. (2 marks) f) Compare Unipolar NRZ and Manchester NRZ line coding regarding bandwidth requirement, DC value and synchronization signal generation. (3 marks) g) Calculate the average noise power of the received PCM signal if the Peak signal power is 1 mW. (2 marks) h) Find the probability of error Pe of the received PCM signal. (2 marks) i) What shall we do to transmit this PCM signal using Unipolar NRZ over a channel which has a bandwidth of only 5 KHz?Explain. (2 marks) QUESTION 3 a) An audio signal of bandwidth 4 kHz is sampled at a rate of 25% above the Nyquist rate and quantized. The quantization error is not to exceed 0.1% of the signal peak amplitude. The resulting quantized samples are now coded and transmitted by 4-ary pulses. (i) Determine the minimum number of 4-ary pulses needed to encode each sample. (2 marks) (ii) Determine the minimum transmission bandwidth required to transmit this data with zero ISI. (2 marks) (iii) Determine the transmission bandwidth required if raised-cosine 4-ary pulses with 25% roll-off are used. (2 marks) b) An analog signal of bandwidth 10 kHz is sampled at a rate of 24 ksamples/s quantized into 256 samples and coded using M-ary multilevel pulses satisfying the Nyquist criterion with a roll-off factor r=0.2. A 30 kHz bandwidth is available to transmit the data. Determine the smallest acceptable value of M. (6 marks) c) A multilevel digital system sends one of 16 possible levels over a channel every 0.5 ms (i) What is the number of bits corresponding to each level? (2 marks) (ii) What is the bit rate?
A digital communication system transmits 5000 symbols alphanumeric information in 5 seconds using 8-bit ASCII coding. The system uses a multilevel pulse amplitude modulation (PAM) waveform with amplitude levels M=16 to transmit the information through a physical channel. Analyze the communication system by considering the following principles: (i) Calculate the effective transmitted data rate. (ii) Determine the number of bits per symbol. (iii) Calculate the symbol rate. (iv) Determine the minimum bandwidth required to prevent Inter-Symbol-Interference (ISI). (v) Describe how the required bandwidth of the digital communication system can be reduced. Support your answer with an example. (b) With the help of a block diagram, explain and analyze the generation and detection of phase shift keying (PSK) digital carrier modulation scheme.
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