Communications: notes and questions
Notes for each topic, a formula sheet, practice questions and 50 past GATE questions from 11 papers (2018–2026), 48 of them solved step by step.
- previous-year questions
- 50previous-year questions
- solved step by step
- 48solved step by step
- GATE papers, 2018–2026
- 11GATE papers, 2018–2026
- topics with notes
- 5topics with notes
Foundation
Learn the subject one topic at a time. Each topic has notes, the key formulas and practice questions.
Topic notes and formulas
Notes on every topic, with the key formulas and practice.
- GATE EC only
Random processes, power spectral density and noise
A random process is a signal whose value at each time is a random variable, so it is described by averages rather than by a single waveform.
6 practice questions
Amplitude and angle modulation, receivers and multiplexing
Analog modulation places a message signal on a high-frequency carrier for transmission, and a receiver recovers it.
6 practice questions
- GATE EC only
Information theory: entropy, source coding and channel capacity
Information theory measures how much uncertainty a source carries (entropy), how compactly it can be written down (source coding) and how fast data can be sent reliably over a noisy channel (channel capacity).
5 practice questions
PCM, digital modulation and detection
This topic covers how an analogue signal becomes bits (sampling, quantisation, PCM, DPCM, delta modulation), how pulses are shaped to avoid inter-symbol interference, how bits ride on a carrier (ASK, PSK, FSK, QAM), and how the receiver decides which symbol was sent (matched filter, MAP, ML).
5 practice questions
- GATE EC only
Error detection and correction
Error detection and correction adds controlled redundancy to the data so that the receiver can notice, and sometimes repair, bits flipped by the channel.
5 practice questions
GATE
Past GATE questions on Communications by topic and year, the full papers, practice and the GATE syllabus.
50 questions, by topic and year
How many questions each topic had in the EC and IN papers of each year. This shows what was asked, not what will be asked. We placed each question under a topic ourselves; the exam paper does not label topics.
| Topic | 2018 | 2020 | 2022 | 2023 | 2024 | 2025 | 2026 | Total |
|---|---|---|---|---|---|---|---|---|
| Random processes | 1 | 1 | · | 2 | 1 | 1 | · | 6 |
| Analog modulation | 3 | 2 | 3 | 1 | 2 | 2 | 2 | 15 |
| Information theory | · | 1 | 2 | 1 | 1 | 3 | 1 | 9 |
| Digital communication | 3 | 1 | 3 | · | 3 | 1 | 4 | 15 |
| Error control | 1 | · | 1 | · | 1 | 1 | 1 | 5 |
Solved papers
27 practice questions
The GATE syllabus for Communications, paper by paper
Verbatim from the GATE 2027 syllabus PDFs: EC Section 7, “Communications”, and the communication part of IN Section 10, “Communication and Optical Instrumentation”. IN lists modulation, PCM, multiplexing and digital modulation but not random processes, information theory or error control, which are marked EC only. EE's syllabus has no communications: its only “modulation” is pulse width modulation, under Power Electronics.
Show the GATE EC wordingHide the GATE EC wording
Random Processes: Autocorrelation and power spectral density, properties of white noise, filtering of random signals through LTI systems. Analog Communications: Amplitude modulation and demodulation, angle modulation and demodulation, spectra of AM and FM, super heterodyne receivers. Information Theory: Entropy, source coding, mutual information and channel capacity theorem. Digital Communications: PCM, DPCM, digital modulation schemes (ASK, PSK, FSK, QAM), bandwidth, inter- symbol interference, MAP, ML detection, matched filter receiver, SNR and BER. Fundamentals of error correction, Hamming codes, CRC.
Show the GATE IN wordingHide the GATE IN wording
Amplitude and frequency modulation and demodulation, pulse code modulation, frequency and time division multiplexing; amplitude, phase, frequency, quadrature amplitude, pulse shift keying for digital modulation and demodulation; functional architectures of transmitters and receivers
Preparing in Kolkata? See IAE Academy’s GATE EC coaching and GATE IN coaching.
IF YOU WOULD RATHER TALK IT THROUGH