TABLE OF CONTENTS The basic task of a wireless communication system is to transfer information originating at one terminal to one or more other terminals. However, by using characteristics of the transmitted signal itself, another use has been added for wireless systems. It involves estimating how far one terminal is from another, or where that terminal is located. The uses for wireless distance measurement and location is varied and their numbers are constantly growing. They are included in areas of personal safety, industrial monitoring and control, and a myriad of commercial applications. The methods used for getting location information from a wireless link are also varied. Complexity, accuracy, and environment, are among the factors that play a role in determining the type of distance measuring system to apply for a particular use, although there may be several competing methods employed for the same type of application.
Perhaps the epitome of wireless location is the global positioning system (GPS). Although this book covers briefly the workings of that system, most of it is concerned with wholly on earth technologies. GPS remains a prime example of the relatively high positioning accuracy obtainable through very long distance wireless links. However, it is not a solution for everyone. GPS is well-priced for some applications, but overly expensive and complex for others. Also, GPS performance deteriorates in indoor use and in urban environments.
Distance measuring and location are two closely related concepts. Distance measuring can be considered as determining the radius of a...
