GATE Communications: Digital Communications – Previous Year Questions
27 GATE previous year questions on Digital Communications (Communications, Electronics and Communication Engineering) with answers and explanations, from every paper.
- GATE 2017 EC Q32 – Which one of the following statements about differential pulse code modulation (DPCM) is true?
- GATE 2017 EC Q33 – In a digital communication system, the overall pulse shape p(t) at the receiver before the sampler has the Fourier transform P(f). If the symbols are…
- GATE 2017 EC Q60 – In binary frequency shift keying (FSK), the given signal waveforms are u 0(t) = 5(20000 t); 0 t T, and u 1(t) = 5(22000 t); 0 t T, where T is the…
- GATE 2015 EC Q60 – The transmitted signal in a GSM system is of 200 kHz bandwidth and 8 users share a common bandwidth using TDMA. If at a given time 12 users are…
- GATE 2015 EC Q62 – A source emits bit 0 with probability 13 and bit 1 with probability 23. The emitted bits are communicated to the receiver. The receiver decides for…
- GATE 2016 EC Q31 – Consider binary data transmission at a rate of 56 kbps using baseband binary pulse amplitude modulation (PAM) that is designed to have a raised-cosine…
- GATE 2016 EC Q59 – A digital communication system uses a repetition code for channel encoding/decoding. During transmission, each bit is repeated three times (0 is…
- GATE 2016 EC Q60 – 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…
- GATE 2018 EC Q27 – A binary source generates symbols X\-1,1\ which are transmitted over a noisy channel. The probability of transmitting X=1 is 0.5. Input to the…
- GATE 2018 EC Q50 – A random variable X takes values -0.5 and 0.5 with probabilities 14 and 34, respectively. The noisy observation of X is Y=X+Z, where Z has uniform…
- GATE 2019 EC Q44 – A single bit, equally likely to be 0 and 1, is to be sent across an additive white Gaussian noise (AWGN) channel with power spectral density N 0/2.…
- GATE 2019 EC Q56 – A voice signal m(t) is in the frequency range 5 kHz to 15 kHz. The signal is amplitude-modulated to generate an AM signal f(t)=A(1+m(t))2 f ct, where…
- GATE 2019 EC Q57 – A random variable X takes values -1 and +1 with probabilities 0.2 and 0.8, respectively. It is transmitted across a channel which adds noise N, so…
- GATE 2020 EC Q22 – A digital communication system transmits a block of N bits. The probability of error in decoding a bit is . The error event of each bit is independent…
- GATE 2020 EC Q58 – In a digital communication system, a symbol S randomly chosen from the set \s 1,s 2,s 3,s 4\ is transmitted. It is given that s 1=-3, s 2=-1, s 3=+1…
- GATE 2021 EC Q34 – A 4 kHz sinusoidal message signal having amplitude 4 V is fed to a delta modulator (DM) operating at a sampling rate of 32 kHz. The minimum step size…
- GATE 2021 EC Q62 – A message signal having peak-to-peak value of 2 V, root mean square value of 0.1 V and bandwidth of 5 kHz is sampled and fed to a pulse code…
- GATE 2021 EC Q63 – Consider a polar non-return to zero (NRZ) waveform, using +2 V and -2 V for representing binary '1' and '0', respectively, is transmitted in the…
- GATE 2022 EC Q35 – A symbol stream contains alternate QPSK and 16-QAM symbols. If symbols from this stream are transmitted at the rate of 1 mega-symbols per second, the…
- GATE 2022 EC Q63 – Consider a channel over which either symbol x A or symbol x B is transmitted. Let the output of the channel Y be the input to a maximum likelihood…
- GATE 2024 EC Q14 – A digital communication system transmits through a noiseless bandlimited channel [-W,W]. The received signal z(t) at the output of the receiving…
- GATE 2024 EC Q45 – A source transmits a symbol s, taken from \-4,0,4\ with equal probability, over an additive white Gaussian noise channel. The received noisy symbol r…
- GATE 2025 EC Q41 – A source transmits symbol S that takes values uniformly at random from the set \-2,0,2\. The receiver obtains Y=S+N, where N is a zero-mean Gaussian…
- GATE 2026 EC Q22 – Consider a discrete memoryless source with an alphabet of four source symbols. s(t) is a multi-level (-1, 0, +1, +2) signal representing a long…
- GATE 2026 EC Q32 – A wireless digital transmission scheme is using 16-QAM over an additive white Gaussian noise channel and a maximum-likelihood receiver. Consider the…
- GATE 2026 EC Q44 – A QPSK modulated signal from an additive white Gaussian noise (AWGN) channel is received with an E b/N o=8.4 dB at the input of a coherent QPSK…
- GATE 2026 EC Q63 – 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…