Information Communication

A signal doesn’t do any good if it can’t get from one point to another, and while wired, direct connections and communications are important and challenging, wireless communication in the modern era is even more important and even more challenging. In this final chapter, Dr. Johnson reviews information communication, teaching the basic principles and challenges faced with both wired communication and wireless communication. While there is a great deal of overlap between the two, with wireless you need to consider the medium more carefully, line of sight, or even things such as bouncing signals off the ionosphere. Wireless signals tend to have higher levels of interference and lower signal strength, both of which are highly reliant on the environment, obstacles, and distance.

He also discusses the differences between analog and digital communication channels and explains why digital communication is better. We learn about the theoretical and real data capacities of channels and frequencies and how modulation works, where we modify a carrier wave to carry actual information.

An entire section is devoted to the Huffman Code, a variable length binary representation of the English alphabet that not only minimizes entropy but also is partially self-synchronizing. We learn about error correction coding and Shannon's Noisy Channel Coding Theorem which states that we can correct all errors in a data channel...we don’t know how to actually do this yet, but there are many imperfect error correction algorithms available. This and other subtleties of coding are discussed, perhaps to further emphasize how complicated communication systems truly are and how there is always room for improvement.