In general use, the term mobile is loosely defined. At a minimum, it implies that the noun with which it is paired is capable of moving easily. A mobile computer is a computer that is not confined to a desk by several large pieces of equipment and numerous wires. Current usage, however, is beginning to imply a greater degree of freedom. For example, a cordless phone is one that can only be used near its base station in the home, whereas a mobile phone can be used anywhere. These phones would not be considered mobile if they had to be plugged in wherever they were being used. On the same note, a mobile phone would not be considered truly mobile if the call was dropped every time it moved into a new cell site. When coupled with communications devices, mobility usually implies radio technology.
It is important to note the difference between mobility and nomadicity. In this book, the latter refers to the ability to move from one location to another and start communications. Nomadicity can best be described by the laptop user who moves from one location to another, plugs in the laptop, obtains an Internet connection, and starts communicating. The user, however, will need to terminate and restart sessions and applications as a result of the move.
The common use of the term mobile computing implies nomadic computing. When a businessperson uses their laptop in the office, shuts it down, takes it home, and uses it at homethis is nomadic. If the user is responsible for establishing a new connection everywhere they go this is nomadic. Our goal in the book is to facilitate a device that is always connected through the best available link.