Recent questions and answers in Digital Communications

A wireless digital transmission scheme is using $16$-QAM over an additive white Gaussian noise channel and a maximum-likelihood receiver. Consider the information bit rat...

A QPSK modulated signal from an additive white Gaussian noise (AWGN) channel is received with an $E_{b} / N_{o}=8.4 \mathrm{~dB}$ at the input of a coherent QPSK demodula...

Let the relevant bandwidth $(B)$ of a digital communication system be $1 ~\text{MHz}$ and $k T=-174 \mathrm{~dBm} / \mathrm{Hz}$, where $k$ is Boltzmann's constant and '$...

The average bit error rate at the input of a $(7,4,1)$ Hamming decoder is $0.10$. The probability that the decoder will fail to decode a received word correctly is $\_\_\...

​​​​​The information bit sequence $\{111010101\}$ is to be transmitted by encoding with Cyclic Redundancy Check $4$ (CRC-$4$) code, for which the generator polynomial is ...

Consider the two quadrature amplitude modulation $\text{(QAM)}$ constellations below. Suppose that the channel has additive white Gaussian noise channel and no intersymbo...

Consider two communication systems $C_{1}$ and $C_{2}$ that use pulse amplitude modulation $\text{(PAM)}$, $P A M_{1}$ and $P A M_{2}$. Let the distance between any two p...

The line code that has zero $\text{dc}$ component for pulse transmission of random binary data isNon-return to zero $\text{(NRZ)}$Retrun to zero $\text{(RZ)}$Alternate Ma...

In a digital communication system employing Frequency Shift Keying $\text{(FSK)}$, the $0$ and $1$ bit are represented by sine waves of $10 \; \mathrm{kHz}$ and $25 \; \m...

The peak-to-peak input to an $8$-bit $\text{PCM}$ coder is $2$ volts. The signal power-to-quantization noise power ratio (in $d\text{B}$) for an input of $0.5 \cos \left(...

Four independent messages have bandwidths of $100 \mathrm{~Hz}, 200 \mathrm{~Hz}$, and $400 \mathrm{~Hz}$, respectively. Each is sampled at the Nyquist rate, and the samp...

Input to a linear delta modulator is a sinusoidal signal whose frequency can vary from $200 \mathrm{~Hz}$ to $4000 \mathrm{~Hz}$. The input is sampled at eight times the ...

In the figure, the output of the oscillator, $\mathrm{V}_{1}$ has $10 \mathrm{~V}$ peak amplitude with zero DC value. The transfer characteristic of the Schmitt inverter ...

For a bit-rate of $8 \; \mathrm{kbps}$, the best possible values of the transmitted frequencies in a coherent binary FSK system are$16 \; \mathrm{kHz}$ and $20 \; \mathrm...

A discrete memoryless source generates either $0$ or $1$ at a rate of $160 \; \mathrm{Kbps}; 0$ is generated three times more frequently than $1.$ A coherent binary PSK m...

In a $\text{PCM}$ system with uniform quantisation, increasing the number of bits from $8$ to $9$ will reduce the quantisation noise power by a factor of$9$$8$$4$$2$

Compression in $\text{PCM}$ refers to relative compression ofhigher signal amplitudeslower signal amplitudeslower signal frequencieshigher signal frequencies

For a given data rate, the bandwidth $\mathrm{B}_{p}$ of a $\text{BPSK}$ signal and the bandwidth $\text{B}_{0}$ of the $\mathrm{OOK}$ signal are related as$\mathrm{B}_{p...

The pulse rate in a $\text{DM}$ system is $56,000$ per sec. The input signal is $5 \cos (2 \pi \; 1000 \; t)+2 \cos (2 \pi \; 2000 \; t) \; \mathrm{V}$, with $t$ in sec. ...

At a given probability of error, binary coherent $\text{FSK}$ is inferior to binary coherent $\text{PSK}$ by$6 \mathrm{~dB}$$3 \mathrm{~dB}$$2 \mathrm{~dB}$$0 \mathrm{~dB...

If $E_{b^{\prime}}$ the energy per bit of a binary digital signal, is $10^{-6}$ watt-sec and the one-sided power spectral density of the white noise, $\mathrm{N}_{0}=10^{...

The input to a linear delta modulator having a step-size $\Delta=0.628$ is a sine wave with frequency $f m$ and peak amplitude $E_{m}$. If the sampling frequency $f_{s}=4...

If $\text{S}$ represents the carrier synchronization at the receiver and $\rho$ represents the bandwidth efficiency, then the correct statement for the coherent binary $\...

A signal is sampled at $8 \; \mathrm{kHz}$ and is quantized using $8$-bit uniform quantizer. Assuming $\mathrm{SNR}_q$ for a sinusoidal signal, the correct statement for ...

In a $\text{PCM}$ system, if the code word length is increased from $6$ to $8$ bits, the signal to quantization noise ratio improves by the factor$8 / 6$$12$$16$$8$

Consider a binary digital communication system with equally likely $0$'s and $1$'s. When binary 0 is transmitted the voltage at the detector input can lie between the lev...

Choose the correct one from among the alternatives $\mathrm{A}, \mathrm{B}, \mathrm{C}, \mathrm{D}$ after matching an item from Group $1$ with the most appropriate item i...