Chapter 1. Introduction
Setting the Scene
Broadcast radio and, later, broadcast TV have defined wireless for two generations. The ability for radio waves and TV signals to go anywhere and be heard and seen by anyone has provided huge benefits to the general public since the early twentieth century. If you are the receiver this broadcast capability is very attractive, but sometimes for the sender these broadcast qualities can be a major disadvantage.
The military were the first to address the disadvantage of being heard by everyone. To protect communications over radio, the military adapted secret codes that had for many years been used to protect written messages. Techniques such as spread spectrum transmission were invented to try to prevent unwanted ...