"What got me into this business was the curiosity about how the dial telephone system worked."
Amos Joel
In 1970, when he was working as an electrical engineer at Bell Labs, in Murray Hill, New Jersey, Amos Joel (b. 1918) came up with an idea that worked so well that many of us use it today without noticing that anything has happened at all. Joel had invented the idea of the cellular mobile phone.
Cell phones existed prior to 1970, but they had problems. Since each call was made on a single channel, the number of simultaneous calls was limited to the number of available channels. Additionally, a cell phone user could not leave the base station area of coverage in which the call was initiated or the connection to the network would be lost.
Joel's cellular mobile communication system proposed providing phone service to a geographic area by dividing it up into many small, low-powered base stations or "cells." This network of cells could deal with a greater number of simultaneous calls by allocating a radio channel to a call in one cell and reusing the same radio channel in a number of other cells separated by enough distance to prevent interference. When a user traveled from the service area of one cell to another, the user's phone call would not be disrupted as each cell would "hand-off" to the other, switching cellular base stations and radio channels without anyone noticing.
The key ingredient? A microprocessor that could make all the decisions, identify the phone, find cellular base stations, and control the connection as users moved through the network. Today's cell phones support a number of additional services, such as text messaging, access to the Internet, and camera.
