You can download Digital and Analog Communication Systems 8th edition by Leon W. Couch free in pdf format.
For junior- to senior-level introductory communication systems courses for undergraduates, or an introductory graduate course. A useful resource for electrical engineers.
This revision of Couch’s authoritative text provides the latest treatment of digital communication systems. The author balances coverage of both digital and analog communication systems, with an emphasis on design. Readers will gain a working knowledge of both classical mathematical and personal computer methods to analyze, design, and simulate modern communication systems. MATLAB is integrated throughout.