Basic Digital Communication

Basic Digital Communication is a clear, mathematical course on digital communication systems: how a message becomes bits, how bits become waveforms, and how a receiver recovers them from a noisy channel. Every topic has original drawings, typeset formulas with each symbol explained, worked examples with real numbers and practice questions with tap-to-reveal answers.

What the app covers

• Overview: the block diagram of a digital communication system, bit rate and symbol rate, bandwidth efficiency, SNR, Eb/N0 and bit error rate

• Signals and Spectra: the Fourier transform, a table of transform pairs and properties, energy and power, power spectral density, bandwidth definitions, white Gaussian noise and thermal noise

• Sampling: the sampling theorem, spectra of sampled signals, aliasing and anti-aliasing filters, natural and flat-top sampling and the aperture effect

• Quantisation and PCM: uniform quantisation, quantisation noise, SQNR with worked examples, μ-law and A-law companding, PCM systems and T1/E1, DPCM and prediction gain, delta modulation, slope overload and granular noise

• Information Theory: information and entropy, source coding and the Kraft inequality, Huffman coding step by step, mutual information, the binary symmetric channel, channel capacity, the Shannon–Hartley theorem and the Shannon limit

• Baseband Transmission: line codes (NRZ, RZ, AMI, Manchester) and their spectra, intersymbol interference, the Nyquist criterion, raised-cosine pulses and eye diagrams

• Detection in Noise: decision thresholds, the Q-function with tables, the matched filter and correlation receiver, bit error rates of polar, unipolar and orthogonal signalling

• Digital Modulation: I/Q signals and signal space, ASK, FSK, MSK, BPSK, DPSK, QPSK, M-PSK and QAM, with constellations, bandwidth and BER curves compared

• Channel Coding: code rate and Hamming distance, parity and Hamming codes with syndrome decoding, CRC, convolutional codes and Viterbi decoding on a trellis

• Spread Spectrum and OFDM: DSSS and processing gain, frequency hopping, CDMA with Walsh codes, OFDM subcarriers, the FFT and the cyclic prefix

• Quick Reference: all the main formulas on one page

Made for studying

• Original drawings: block diagrams, spectra, waveforms, eye diagrams, constellations, BER curves and trellises

• Formulas typeset clearly, with every symbol explained

• Worked examples and practice questions in every topic

• Search across all topics

• Previous and Next buttons to work through a section in order

• Dark mode

• Works offline, with no account needed

• Available in 8 languages: English, Español, Português, Français, Deutsch, العربية, हिन्दी and Bahasa Indonesia

For engineering students taking a course in digital communication or communication systems, and for anyone preparing for exams in this subject. Content is checked against standard textbooks, ITU-T and IEEE standards and open university course notes.

This app is an independent study aid. It is not affiliated with any textbook publisher, university or standards body.