Digital Communications
Syllabus
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1.- Introduction
Definition of communication systems, classification in analog and digital communication systems. Advantages of digital communication systems. Main functional block of a digital communication system. Review of some basic communication theory. Realistic constraints to be taken into account. Main objectives of this course.
2.- Pulse amplitude (linear) modulations
Baseband PAM modulations
Generation of a PAM signal: transmission filters and constellations. Power spectral density. Equivalent discrete channel transmitting through an additive white Gaussian channel as well as through a linear channel. Relationship between transmission rate and signal bandwidth when ISI is considered.
Bandpass PAM modulations
Generation of a bandpass PAM signal using quadrature carriers: transmission filters, modulators, and constellations. Complex notation used to represent bandpass PAM signals. Power spectral density. Equivalent discrete channel transmitting through an additive white Gaussian channel as well as through a linear channel. Relationship between transmission rate and signal bandwidth when ISI is considered.
3.- Angle modulations
Phase modulations
Phase shift keying (PSK) modulation. Quadrature Phase Shift Keying (QPSK) modulation. Offset Quadrature Phase Shift Keying (OQPSK) modulation. Differential PSK modulations.
Non-linear modulations
Continuous Phase Frequency Shift Keying (CPFSK) modulation. Minimum Shift Keying (MSK) modulation. Continuous Phase Modulation (CPM).
4.- Design of receivers in the presence of intersymbol interference (ISI)
Design of memoryless symbol-by-symbol detectors
Optimal delay for decision. ISI level. Re-design of decision regions.
Optimal detection under ISI
Maximum likelihood sequence detection. Viterbi algorithm.
Sub-optimal detection under ISI
Linear channel equalizers. Zero Forcing (ZF) design criterion. Minimum Mean Squared Error (MMSE) criterion
5.- Multipulse modulations
Multicarrier modulations. Frequency Division Multiplex (FDM) modulation. Orthogonal Frequency Division Multiplex (OFDM) modulation. Spread spectrum modulations: Direct Sequence Spread Spectrum (DS-SS) and Frequency Hopping Spread Spectrum (FH-SS).
6.- Channel coding for error prediction
Introduction and basic definitions
Linear block codes
Generating and parity check matrices. Syndrome based decoding. Performance analysis using soft and hard output.
Convolutional codes
Representations of convolutional codes. Trellis diagram and Viterbi algorithm. Performance analysis.
Trellis coded modulation (TCM codes)
Joint design of convolutional encoder and constellation. Bit assignment procedure: Ungerboeck rules.