AT&T Archives: Advanced Mobile Phone Service (AMPS)


1970 | 1980 | Móvil | Teléfono
Using simple graphics, this film, made in 1978, illustrates the concept of cellular telephony in easily-understood terms, which are instructive even today, since the basic idea of dividing a service area into a pattern of small cells remains the same.

As the film points out, the concept of using these small cells was developed at Bell Labs, and it was this idea that constituted the giant leap from earlier, less efficient mobile phone systems to today's modern cell service. What the film does not mention: the year the cellular idea was first proposed at the Labs, which was 1947.

In 1946, AT&T had introduced the first commercial mobile telephone service in St. Louis, Missouri. The equipment weighed nearly 80 pounds and was installed in a subscriber's motor vehicle. A single transmitter on a central tower provided service to the entire area, and only a handful of channels had to be shared by all subscribers. Before long, more channels were needed for mobile service to continue to grow. That's when Bell Labs engineer, D.H. Ring, proposed a solution.

In his 1947 memorandum, Ring outlined a hexagonal grid system composed of multiple low-power transmitters with automatic call handoff from one hexagon to another. The scheme would enable reuse of frequencies within a given area, dramatically increasing the mobile network's capacity. But at the time, the technology to implement Ring's proposal did not yet exist, and it would be another few decades before this scheme would be revisited by AT&T Bell Labs engineers Richard Frenkiel and Joel Engel. Their work would provide the basis for an AT&T proposal in 1971 to the Federal Communications Commission (FCC) for a cellular network. The FCC would later grant AT&T permission in 1977 to start conducting trials of a cellular system in the United States. The first commercial cellular system in the U.S., in Chicago, followed in 1983.

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