6.450 Principles of Digital Communications I (Fall 2006, MIT OCW). Taught by Professor Lizhong Zheng and Professor Robert Gallager, this course serves as an introduction to the theory and practice behind many of today's communications systems. Topics covered include: digital communications at the block diagram level, data compression, Lempel-Ziv algorithm, scalar and vector quantization, sampling and aliasing, the Nyquist criterion, PAM and QAM modulation, signal constellations, finite-energy waveform spaces, detection, and modeling and system design for wireless communication.
(from ocw.mit.edu)

Lecture 10 - Degrees of Freedom, Orthonormal Expansions, and Aliasing