Overview

The growth of wireless communications in the last two decades of the twentieth century has been astounding. Despite impressive advances in wired (wireline) communications technology in the same period (e.g., in fiber-optic technology), wireless is now a permanent and prominent feature of the telecommunications landscape. People gladly pay to be free to communicate on the go without being tied down to fixed locations.

Long before the telephone was invented, wireless communications existed in a sense people shouting to each other over the air between them did not use wires to communicate. However, with the invention of the telephone, electrical signals carried the sound on wires, and thus began the rise of wired telecommunications. Long distance telecommunications was born. While telephony with wirelines greatly increased the range over which telecommunications was possible, it tied users to fixed locations (where the phones were located), and mobility was traded off for range. Mobile telephone systems, when they appeared, regained some of the mobility lost by wireline telephony, without sacrificing range in the end-to-end sense. ^[1] Since only the segment from mobile phone to base station is wireless and then it plugs into the global phone network, the corresponding party could be very far away, such as on the other side of the globe.

However, wireless links are generally of lower quality and less reliable than wired links. Why? Fundamentally, the wireless communications medium is more difficult than wired communications media. As the signals propagate through the air, they are neither guided by the...