THE EARLY HISTORY OF CELLULAR TELEPHONE
Thursday, 12 April 2012Posted by
Crystal
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The system would initially be built covering the service area with hexagonal cells as large as possible while providing reliable coverage. The size of the largest cells would depend on terrain and, in the Technical Report, was conservatively estimated to be five miles in radius. (In the later trial system, covering the flatlands of Chicago, they were ten miles in radius.) An important contribution by Phil Porter was that the base stations would be placed at alternate corners of the cells, each base station having three directional antennas radiating into the three coterminous cells. Analyses indicated that sufficient spacing between co-channel cells to avoid interference could be achieved with a repeating pattern of seven cells, each assigned a unique set of channels. In addition to the voice channels, there would be paging and control channels to locate the mobile units by signal strength, assign the channels, and hand the call off to a new base station on a new channel when the mobile unit crossed a cell boundary.
It was recognized that the telephone traffic would not be uniform over the service area, and vehicular traffic density and population density were studied, first for greater Philadelphia and then extrapolated to other metropolitan areas. As the number of users, and their usage, increased, the cells with the highest traffic would reach the limit of the capacity of their assigned channels, and would be split to one-half the radius by adding intermediate base stations, requiring a redistribution of the channels to the cells. A second split to one-half the radius again would occur after even further growth. An essential algorithm was developed by Dick Frenkiel that allowed the growth to occur smoothly, without requiring quantum steps in system cost.
Following the filing of the Bell Laboratories Technical Report, interest further intensified. An annual Symposium on Microwave Mobile Communications was held at the Bureau of Standards in Boulder, Colorado. In November of 1973, a joint special issue of the IEEE Transactions on Communications and Transactions on Vehicular Technology was dedicated to cellular mobile radio. In January, 1979, an issue of the Bell System Technical Journal was devoted to the Advanced Mobile Phone Service.
The use of the word, “ultimately” to describe the deployment is appropriate. The opposition by the television broadcasters and the manufacturers continued, but, even after that was settled, thanks to the skills of Lou Weinberg, the regulatory guru on mobile radio at AT&T, and the spectrum was allocated, there was an additional long delay. This was an era when the FCC was committed to introducing competition into the telecommunications industry, and mobile telephone was a prime candidate. The FCC allocated one half of the spectrum, which came to called the “A” channels, to the radio common carriers, and the other half, the “B” channels, to the wireline telephone companies. The carriers were requested to submit detailed applications for assignment of the spectrum in the various metropolitan areas, including demonstrations of technical and financial qualifications. That split assignment created a classic example of the law of unintended consequences.
The wireline telephone companies were regulated utilities, chartered to provide service in specified areas. As a general rule, in any given geographical area, there was one wireline telephone company that was chartered to provide service. Even in cities such as Los Angeles, where both Pacific Telephone and General Telephone provided service, the boundaries between them were well defined. As a result, each application by a wireline telephone company for the B channels faced no competing application. But, in the major metropolitan areas, there were multiple competing applications for the A channels. The radio common carriers argued that, if the wireline telephone companies were allowed to begin offering service while the competing radio common carrier applications were being resolved, the wireline companies would capture the market and the radio carriers would not be able to catch up. The FCC agreed, and held up the wireline carrier applications until the radio carrier applications were resolved. After many years of attempting to resolve the competing applications, the FCC instituted a lottery for the A channels in order to break the logjam, and, in 1984, allowed commercial service. By that time, the breakup of the Bell System had taken place, and the makeup of the entire US telecommunications industry was vastly altered.
During this hiatus, the FCC did allow AT&T to build a trial system in the Chicago area, large enough, and with sufficient users, to test both the technical and market feasibility of the service. Chicago was chosen because the Bell Laboratories engineers responsible for the switching system were located there and could perform any early troubleshooting that would be required. When, in 1984, the FCC allowed commercial service, that system, operated by Illinois Bell, became the first commercial cellular telephone system in the United States.
That qualifier, “in the United States”, is necessary because the thirteen year delay only occurred in the US. By filing the Bell Laboratories Technical Report with the FCC, AT&T had put the design of the AMPS system into the public domain. Common carriers in other countries, most notably the Scandinavian countries and Japan, quickly implemented the system and began offering service.
Since this piece is intended for publication by a technical organization, I will leave it for others to expound on the irony that the FCC, in its commitment to the belief that competition would foster innovation, actually delayed innovation in the US for over a decade, while other countries allowed their citizens to enjoy the benefits of the technology developed here.
In the years since, cellular telephone has evolved in many ways. The transmission is now digital, and new bands of frequencies have been allocated. New data, messaging, and even video services have been developed. And the size, weight, and power requirements have been reduced to the point that portable units have replaced vehicle mounted units. But all of these advances still rely on the cellular concept of reusing frequencies in multiple small cells within a contiguous service area to achieve the necessary capacity within a limited spectrum.
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