Communication Systems

Moving information through noisy channels. Analog and digital communication: system fundamentals and noise, AM, FM and PM, sampling and digital baseband, ASK/FSK/PSK and QAM, Shannon's capacity limits, and error detection and correction codes — with BER and coding simulations.

• Communication Systems — Every communication system moves information from a source to a destination through a noisy channel. Learn the block diagram (source, transmitter, channel, receiver), analog vs digital communication, frequency bands and wavelength, bandwidth, decibels and dBm, noise (thermal kTB, noise figure), SNR and receiver sensitivity.
• Amplitude Modulation (AM) — AM varies a carrier's amplitude with the message. Learn the AM equation, modulation index, spectrum (carrier + sidebands), bandwidth, power distribution and efficiency, DSB-SC and SSB, envelope and coherent detection, over-modulation, and the superheterodyne receiver.
• Frequency & Phase Modulation (FM/PM) — Angle modulation varies the carrier's frequency or phase. Learn FM and PM equations, frequency deviation and modulation index β, narrowband vs wideband FM, Carson's rule bandwidth, Bessel sidebands, noise advantage and pre-emphasis, FM generation (VCO) and demodulation (PLL, discriminator).
• Digital Communication — Digital systems convert information to bits and bits to waveforms. Learn sampling and PCM (bit rate, quantisation SNR), line coding (NRZ, Manchester), pulse shaping and inter-symbol interference, Nyquist bandwidth and raised-cosine filters, Eb/N0, bit-error rate and eye diagrams — with a BER simulation.
• ASK, FSK & PSK — Digital modulation maps bits onto a carrier's amplitude, frequency or phase. Learn ASK/OOK, binary and M-ary FSK (and GFSK/MSK), BPSK, QPSK and differential PSK; constellation diagrams; bandwidth; BER comparisons; coherent vs non-coherent detection; and where each is used.
• QAM — Quadrature amplitude modulation varies both amplitude and phase to pack many bits per symbol. Learn I/Q representation, square constellations (16-, 64-, 256-, 1024-QAM), spectral efficiency, symbol error rate and required SNR, EVM, adaptive modulation, and OFDM with QAM in Wi-Fi, LTE/5G and cable.
• Shannon Theory — Information theory sets the ultimate limits. Learn information and entropy, source coding (Huffman), channel capacity C = B log₂(1 + SNR), the Shannon limit Eb/N₀ ≥ −1.6 dB, bandwidth vs power trade-offs, and how modern codes approach capacity.
• Error Detection — Detecting corrupted data. Learn parity bits, checksums (Internet checksum), cyclic redundancy checks (polynomial division, generator polynomials, burst-error detection, CRC-16/32), undetected error probability, and ARQ retransmission (stop-and-wait, go-back-N, selective repeat).
• Error Correction (FEC) — Forward error correction fixes errors without retransmission. Learn Hamming distance and correction capability, linear block codes (generator and parity-check matrices, syndrome decoding), Hamming(7,4), Reed–Solomon, convolutional codes and Viterbi decoding, interleaving, coding gain, and modern LDPC and polar codes — with a Python Hamming decoder.