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GATE EC : Communications Champion Quiz 4

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Question 1

A speech signal, band limited to 5 KHz with peak to peak between +10 V to – 10 V and the signal is sampled at Nyquist rate and the bits 0 and 1 are transmitted using bipolar pulses. What is minimum bandwidth for distortion free transmission …. (in KHz)

Question 2

A sinusoidal signal of 2 kHz frequency is applied to a delta modulator. The sampling rate and step-size Δ of the delta modulator are 20, 000 sample per second and 0.1 V, respectively. To prevent slope overload, the maximum amplitude of the sinusoidal signal (in Volts) is

Question 3

In the output of a DM speech encoder, the consecutive pulses are of opposite polarity during time interval t₁ ≤ t ≤ t₂. This indicates that during this interval

Question 4

In a PCM system, if the code word length is increased from 6 to 8 bits, the signal to quantization noise ratio improves by the factor

Question 5

The modulation scheme commonly used for transmission from GSM mobile terminals is

Question 6

A source produces binary data at the rate of 10 kbps. The binary symbols are represented as shown in Figure.
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The source output is transmitted using two modulation schemes, namely Binary PSK (BPSK) and Quadrature PSK (QPSK). Let B1 and B2 be the bandwidth requirements of BPSK and QPSK respectively. Assuming that the bandwidth of the above rectangular pulses is 10 kHz, B₁ and B₂ are

Question 7

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

Question 8

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 bit Y= 0, the conditional probability that '1' was transmitted is ______.
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Question 9

The following waveform is to be quantized with a maximum of ± 0.5 Volts/sample error. What should be the space between quantization levels.

Question 10

A communication system operates in an AWGN channel and employs BPSK modulation. Find average BER if Eb / No = 9 where Eb is signal energy per bit and No is noise power density and erf(3) = 0.99997

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