The third edition of this hands-on textbook pursues the focus on the principles of wireless sensor networks (WSNs), their applications, their protocols and standards, and their analysis and test tools; a meticulous care has been accorded to the definitions and terminology. To make WSNs felt and seen, the adopted technologies as well as their manufacturers are presented in detail. In introductory computer networking books, chapters sequencing follows the bottom up or top down architecture of the seven layers protocol. This book is some more steps after, both horizontally and vertically, the view and understanding are getting clearer, chapters ordering is based on topics significance to the elaboration of wireless sensor networks (WSNs) concepts and issues. This book is intended for a wide audience, it is meant to be help and motivate, for both the senior undergraduates, postgraduates, researchers, and practitioners; concepts and WSNs related applications are laid out, research and practical issues are backed by appropriate literature, and new trends are put under focus. For senior undergraduate students, it familiarizes with conceptual foundations, applications and practical projects implementations. For graduate students and researchers, energy-efficient routing protocols, transport layer protocols and cross-layering protocols approach are presented. Testbeds and simulators provide a must follow emphasis on the analysis methods and tools for WSNs. For practitioners, besides applications and deployment, the manufacturers and components of WSNs at several platforms and testbeds are fully explored.