Energy Fundamentals of Radio

Chapter 12Energy and the Shannon Limit

For much of the history of communications systems since Shannon’s famous paper, the energy required to run communications networks has been a relative afterthought.¹ It is not difficult to see how this state of affairs came about. Data traffic in our communications infrastructure has been rising exponentially for decades. By this point in this book, we are wise to the fact that rising data traffic also means rising energy consumption. Only now, at the time of this writing, are the costs associated with this energy so high that they meaningfully affect the short-term profits of cellular carriers. Before this key threshold is crossed, energy is of concern only to the academic. After this threshold is crossed, energy-aware engineering becomes a high-stakes practice. The criticality only increases going forward: data traffic continues to compound at an annual rate of 20–30%, a veritable rocket ship.

For the modern network architect this means that all networks going forward are energy constrained. The challenge before was to deliver high data capacity given a scarcity of spectral resources; the challenge now is to deliver maximum data capacity given scarce spectral resources and scarce energy resources. The purpose of this chapter is to put spectrum and energy on equal footing.

12.1 An Energy Scaling Rule for Wireless Links

We are in position to complete the energy scaling rule for radio links that we started in Section 8.5. Deriving a concrete ...