GATE ECE
Communications
Noise In Digital Communication
Previous Years Questions

## Marks 1

A sinusoidal message signal is converted to a PCM signal using a uniform quantizer. The required signal to quantization noise ratio (SQNR) at the outp...
A binary baseband digital communication system employs the signal $$p\left( t \right) = \left\{ {\matrix{ {{1 \over {\sqrt {{T_s}} }},} & {0... A sinusoidal signal of amplitude A is quantized by a uniform quantizer. Assume that the signal utilizes all the representation levels of the quantizer... The capacity of a Binary Symmetric Channel (BSC) with cross - over probability 0.5 is ______ . Consider the pulse shape s(t) as shown. The impulse response h(t) of the filter matched to this pulse is ... ## Marks 2 A digital communication system uses a repetition code for channel encoding/decoding. During transmission, each bit is repeated three times (0 is trans... An analog pulse s(t) is transmitted over an additive white Gaussian noise (AWGN) channel. The received signal is r(t) = s(t) + n(t), where n(t) is add... Consider a binary, digital communication system which uses pulses g (t) and − g (t)for transmitting bits over an AWGN channel. If the receiver uses a ... The input X to the Binary Symmetric Channel (BSC) shown in the figure is ‘1’ with probability 0.8. The cross-over probability is 1/7. If the received... A source emits bit 0 with probability$${1 \over 3}$$and bit 1 with probability$${2 \over 3}$$. The emitted bits are communicated to the receiver. T... Consider a discrete-time channel Y = X + Z, where the additive noise Z is signal- dependent. In particular, given the trasmitted symbol$$X\, \in \,\{...
Consider a communication scheme where the binary valued signal X satisfies P{X = + 1} = 0.75 and P {X = - 1} = 0.25. The received signal Y = X + Z, wh...
Coherent orthogonal binary FSK modulation is used to transmit two equiprobable symbol waveforms $${s_1}\,(t)\, = \,\alpha \,\,\cos \,\,\,2\,\pi {f_1}... Let U and V be two independent zero mean Gaussian random variables of variances$${{1 \over 4}}$$and$${{1 \over 9}}$$respectively. The probability ... A BPSK scheme operating over an AWGN channel with noise power spectral density of N02, uses equi-probable signals$$${s_1}\left( t \right) = \sqrt ... A binary symmetric channel (BSC) has a transition probability of 1/8. If the binary transmit symbol X is such that P(X =0) = 9/10, then the probabi... A four phase and an eight-phase signal constellation are shown in the figure below. For the constraint that the minimum distance between pairs of ... A four phase and an eight-phase signal constellation are shown in the figure below. Assuming high SNR and that all signals are equally probable, ... Consider a base band binary PAM receiver shown below. The additive channel noise $$n(t)$$ is white with power spectral density $${S_N}\left( f \right)... Consider a base band binary PAM receiver shown below. The additive channel noise$$n(t)$$is white with power spectral density$${S_N}\left( f \right)... The amplitude of random signal is uniformly distributed between $$-$$5V and 5V If the signal to quantization noise ratio required in uniformly quanti... The amplitude of random signal is uniformly distributed between $$-$$5V and 5V If the positive values of the signal are uniformly quantized with a st... Consider a Binary Symmetric Channel (BSC) with probability of error being 'p'. To transit a bit, say 1, we transmit a sequence of three 1s. The receiv... During transmission over a certain binary communication channel, bit errors occurs independently with probability p. The probability of at most one bi... An input to a 6-level quantizer has the probability density function f(X) as shown in the figure. Decision boundaries of the quantizer are chosen so a... An input to a 6-level quantizer has the probability density function f(X) as shown in the figure. Decision boundaries of the quantizer are chosen so a... Two 4-ray signal constellations are shown. It is given that $${\phi _1}$$ and $${\phi _2}$$ constitute an orthonormal basis for the two constellations... Two 4-ray signal constellations are shown. It is given that $${\phi _1}$$ and $${\phi _2}$$ constitute an orthonormal basis for the two constellations... In the following figure the minimum value of the constant “C”, which is to be added to y1(t) such that y1(t) and y2(t) are different, is ... Let $$g\left( t \right){\mkern 1mu} {\mkern 1mu} \,\,\,\,\,{\mkern 1mu} = {\mkern 1mu} {\mkern 1mu} p\left( t \right){}^ * p\left( t \right)$$ where... A signal as shown in figure is applied to a matched filter. Which of the following does represent the output of this matched filter? ... A symmetric three-level midtread quantizer is to be designed assuming equiprobable occurrence of all quantization levels. The quantization noise power... A symmetric three-level midtread quantizer is to be designed assuming equiprobable occurrence of all quantization levels. If the input probability de... Consider a binary digital communication system with equally likely $$0’s$$ and $$1’s$$. When binary $$0$$ is transmitted the voltage at the detector i... If Eb, the energy per bit of a binary digital signal, is 10-5 watt-sec and the one-sided power spectral density of the white noise, N0 = 10-6 W/Hz, th... A sinusoidal signal with peak-to-peak amplitude of 1.536V is quantized into 128 levels using a mid-rise uniform quantizer. The quantization-noise powe... During transmission over a communication channel, bit errors occur independently with probability 'p'. If a block of n bits is transmitted, the probab... The peak-to-peak input to an 8-bit PCM coder is 2 volts . The signal power - to -quantization noise power ratio (in dB) for an input of 0.5 $$\cos \le... The input to a matched filter is given by$$$S\left( t \right) = \left\{ {\matrix{ {10\sin \left( {2\pi \times {{10}^6}t} \right),} & {0 <...
A signal having uniformly distributed amplitude in the interval ( -V, +V ) is to be encoded using PCM with uniform quantization. The signal - to - qua...
In a digital communication system, transmissions of successive bits through a noisy channel are assumed to be independent events with error probabilit...
Companding in PCM systems leads to improved signal - to - quantization noise ratio. This improvement is for
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