The Wireless Internet Explained
Learn to understand technologies and standards of wireless computing as they relate to the Internet.
TABLE OF CONTENTS The Wireless Internet Explained
Chapter 2: Air Interfaces
Overview
This chapter begins with an overview of the dilemma of how to assign ownership of spectrum over a particular area. As a consequence of multiple conflicting requirements, it is possible to divide spectrum according to both frequency and territory, and both will be discussed.
Unfortunately, it is not possible to use one common mechanism for transmitting all wireless communications. We will look at some of the needs and differentiating components of an air interface. Using these metrics, we will give an overview of some of the most common wireless standards in operation today, both for terrestrial and satellite communications.
2.1 Air ownership
The biggest problem with air is ownership. You may think the air on your property belongs to you. After all, most other things, such as buildings and trees, do. And chances are, if you have some cables or other media for communication, then those belong to you too. Or at least you have some discretion over them.
There are at least two reasons why air space is approached differently, particularly when it comes to radio transmission.
One problem with dividing along territorial lines is shown in Figure 2.1. Air transmissions do not respect artificial property boundaries. Instead they cover a range whose shape depends a lot on the obstructions it encounters but which usually approximates a circle. If you assume four neighboring lots, you can see that you cannot map the range to the land. Either it only covers a fraction of it or else it will...
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