Chapter 7. The New World of Wireless
If the technology of wireless has been around for a long time, then what is so new about it? What is new are the myriad of applications which lend themselves to wireless communications as a result of the tremendous advances made in RF and digital electronics. It took 30 years for the cellular phone to go from concept to serious market penetration, and most of that time was spent waiting for the advent of low cost semiconductor technology to make it financially feasible.
This chapter is a snapshot of the wireless world today (circa 1999), a world which is in constant transition. Newer technologies continue to replace older, less efficient ones while new applications for existing technology pop up everyday. New markets are evolving for this technology as developing countries seek basic local telephone service and turn to wireless to provide it. The regulatory landscape is in flux as regulators seek to address the many challenges—from efficient use of the available spectrum to the coordination of wireless emergency services.
This chapter is divided into two sections: fixed wireless applications and mobile telephony. Fixed wireless, as the name implies, is used to describe any wireless system in which all the parties communicating are stationary. There are many, many fixed wireless applications, only a few of which are covered here as a broad overview. One of these applications, point-to-point microwave communication, is just an enhancement of systems which have been around for years. Most of the enhancement is a result of converting the older, analog technology to the newer, digital technology, the result being that the new (digital) systems can take advantage of digital signal processing (DSP) to cram much more information into a given bandwidth.
Another fixed wireless application, wireless local loop (WLL), in which local telephone service (in the United States) is provided by somebody other than the incumbent local phone company, is a direct result of the FCC opening up the local telephone monopoly to competition.
In this chapter, you will learn about the main topologies used to construct wireless systems. You will also be introduced to a new modulation technique, called spread spectrum, which allows wireless service providers to cram even more users into a given bandwidth.
The section on mobile telephony begins by discussing the plethora of choices available to consumers for these services. You will learn how a generic cellular system works and be exposed to new concepts like handoff, frequency reuse, and air interface. You will also learn about the different technologies which service providers employ to maximize call capacity (and therefore profits).
Today, the demand for wireless connectivity all over the world has outpaced the supply (which should give you a clue as to where to invest). I have heard it said that 25% of the people on the planet die without ever making a phone call. Ignoring for the moment those people who actually have nobody to call, wireless technology offers the fastest and most cost effective way to allow these people to "reach out and touch someone." The world is just beginning to feel the enormous impact of wireless communications. Increased bandwidth demand for everything from wireless Internet access to wireless videoconferencing will ensure that every megahertz of spectrum is fully utilized.