This ebook provides a unique pedagogical approach to teaching the fundamentals of communication systems using interactive graphics and in-line questions. The material opens with describing the transformation of bits into digital baseband waveforms. Double-sideband suppressed carrier modulation and quadrature modulation then provide the foundation for the discussions of Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), M-ary Quadrature Amplitude Modulation (M-QAM), M-ary Phase Shift Keying (MPSK), and the basic theory of Orthogonal Frequency Division Multiplexing (OFDM). Traditional analog modulation systems are also described. Systems trade-offs, including link budgets, are emphasized. Interactive graphics allow the students to engage with and visualize communication systems concepts. Interactivity and in-line review questions enables students to rapidly examine system tradeoffs and design alternatives. The topics covered build upon each other culminating with an introduction to the implementation of OFDM transmitters and receivers, the ubiquitous technology used in WiFi, 4G and 5G communication systems.