Communication Systems introduces Fourier transform, convolution and definitions of autocorrelation and power spectral density. It also introduces concepts of probability, random variables, and stochastic processes and their applications to the analysis of linear systems. Innovatively, this introductory text treats the modulation process using stochastic processes. In addition, the book covers speech coding, amplitude modulation, quadrature modulation, angle modulation, mobile cellular systems, propagation channels and more. The book also includes five appendices which cover topics such as Fourier series and transforms, Hilbert transform, formulas, and cellular systems. The authors' extensive academic and professional experience make this a reality-based teaching and learning resource.