The IoT is a conglomeration of many disparate devices autonomously producing and/or consuming data on the very far edge of layers of networks and protocols. It is important to understand the constraints in building communication systems for the IoT or any form of networking. The internet of things will combine personal area networks, local area networks, and long-range wide area networks into a web of communication channels. Most of what makes the IoT possible is built around communication fabric; therefore, this chapter is dedicated to reviewing the fundamentals of network and communication systems. We will now focus on communication and signaling systems. We will explore the range, energy, and limitations of communication systems and how the architect will use these tools to develop a successful IoT solution.