Three pillars of modern wireless. Cellular networks that connect every pocket on the planet. Satellites that bounce internet, television, navigation, and weather data off mirrors moving 7 km/s overhead. Wireless sensor networks that quietly count temperature, soil moisture, vibration, and footsteps at scales nothing else can match. Each of these is a multi-billion-dollar industry, each rests on the same physics from earlier chapters, and each one is a juicy target for hardware-security work.
This chapter pulls together everything we have learned. Modulation and SNR live in Chapter 7 and Chapter 12. Antennas, propagation, and the Friis equation live in Chapter 13. Sensor-node hardware and radios live in Chapter 21. We are now going to push those tools across three concrete systems and see how the same equations turn into very different engineering tradeoffs depending on whether the link is six meters from a phone to a tower, six hundred kilometers to a Starlink satellite, or six millimeters from a soil-moisture probe to a battery-powered gateway in a vineyard.
The chapter is long because it covers three subjects, but the through-line is consistent: path loss, capacity, latency, and energy are the four knobs every wireless engineer turns. Every architectural decision (cell size, orbit altitude, sleep cycle) is a tradeoff among those four. Once you see that, the rest of the material organizes itself.