Energy Fundamentals of Radio

Chapter 5Understanding the Shannon Limit

For a practicing engineer seeking to broaden their understanding of communications, there is perhaps no better place to start than with the Shannon capacity limit. This may be news to engineers who experience communications theory only through harsh, uncompromising performance specifications on their designs. The author was years into his own circuit design training before he even heard of the Shannon limit. Nevertheless, those important specifications that can make circuit design so difficult are often grounded in this esoteric, but simple, information theoretic result.¹

Completely on the other side of the spectrum, you have communications theorists and system architects who are divorced from physical implementation details. For this crowd, the Shannon limit was practically the first thing they learned. Maximizing capacity in the network is the prime directive, and it drives all sorts of top-level decisions, such as what modulation strategies to support, how to allocate spectral resources and/or time slots to multiple users, etc. What is usually missing from discussions among this set is the difficulty of implementing their network architectures in physical hardware. To be more precise: the more ambitious your performance goals in terms of network capacity, the more energy your network will consume. If we are careful, we can augment the theorists’ innate understanding of Shannon capacity with an appreciation for the energy costs that ...