The Lazy Person's Guide to mobile telephony

CHIPS, Summer, 2004 by Dale J. Long

In the last two installments of the Lazy Person's Guide, we reviewed the history and development of analog and digital telephone systems and looked at Voice over Internet Protocol (VoIP). In this issue, we will detach ourselves from the wired world and look at mobile telephony, which may well dominate the world's communication environment within the next 10 years.

Mobile telephony is a good example of the behavioral dilemmas associated with convenience technology. People want the freedom to take a telephone everywhere. Then they complain that they have less freedom because people can call them any time, day or night. Enabling or annoying, mobile telephony is here to stay. Let's take a look at what it is, how it developed and where it may go.

Cellular History

Cellular telephone technology is a hybrid of radio transmission, wide-area networking and traditional telephony. This type of technology is called "cellular" because the system uses base stations to divide a service area into multiple "cells." As a user travels from cell to cell, cellular calls are transferred, or "handed off" from base station to base station.

The cellular telephone is essentially a radio, albeit an extremely complex one. The roots of cellular telephone service stretch back to the mid-19th century. In 1843, chemist Michael Faraday, arguably the world's first expert on electro-magnetism, began exhaustive research into whether or not "space" could conduct electricity. He discovered that the atmosphere could, under certain conditions, conduct energy. His work became the basis for all future work in radio communications.

After Faraday, Dr. Mahlon Loomis of Virginia developed a method of transmitting and receiving telegraphic messages by using the Earth's atmosphere as a conductor. His system used kites linked to the ground with copper wires, laced with copper screens. Between 1866 and 1873 he conducted several demonstrations where he transmitted messages without wires at distances of 14 to 18 miles. A generation before Marconi gained fame for his work with radios, Loomis was the first person to build complete antenna and ground systems, the first to successfully transmit wireless telegraph signals, the first to conceive the idea of transmission traveling in "waves" from his antenna, and he was the first person awarded a patent for wireless telegraphy. Unfortunately, Loomis never gained any significant recognition for his work and many contemporaries thought him a crackpot and fraud. However, Loomis undoubtedly inspired at least some of what came afterward.

The first mobile telephone was installed in a car by the Detroit Police Department in the early 1920s. The basic concept of cellular telephone service began to take shape in 1947 when researchers tried to improve the range of crude mobile car phones by using small service areas (cells) that shared the same frequencies. But the technology needed to support the concept did not exist at the time.

Another problem was prevailing policy. The Federal Communications Commission (FCC) considered mobile phones a type of two-way radio. In 1947, AT&T asked the FCC to allocate a large band of radio frequencies for cellular use. This would allow mobile phone service on a large enough scale to give AT&T an incentive to research cellular technology for commercial use. But the FCC decided to limit cellular phone frequencies so that only 23 cellular phone conversations could occur simultaneously in the same service area. That wasn't much of an incentive.

In 1968, the FCC reconsidered, and said it would increase mobile telephone frequencies if new technology improved the process. AT&T Bell Labs proposed the cellular telephone system we know today. In 1973, Dr. Martin Cooper, a former general manager at Motorola, set up a base station in New York with the first working prototype of a cellular telephone, the Motorola Dyna-Tac. Dr. Cooper is generally considered both the inventor of the first portable handset and the first person to make a call on a portable cell phone.

In 1977, public cellular telephone testing began in Chicago with 2,000 customers. However, because of the high cost of providing the infrastructure, cellular service did not progress beyond the testing stage until the Cellular Technology Industry Association issued practical guidance for cellular telephone providers in 1988. At that point the research and development framework was in place and demand was becoming strong enough to drive commercial development.

Cellular Evolution

The first cellular services used analog signals operating at 800 megahertz (MHz). While these early analog phones worked, they suffered from short battery life because of the power required to transmit the continuous wave used in analog systems. Advances in control systems allowed analog systems to carry 56 calls within a cell, instead of the original 23. Modern cell phones have mostly moved to digital transmission.

Unlike analog, which broadcasts a continuous stream, digital cellular systems sample pieces of the wave, divide it into chunks, and send it in bursts of data. Digital systems make better use of bandwidth, are somewhat more secure and use a lot less power when broadcasting. In addition to the digital shift, a change from nickel-cadmium to lithium-ion batteries significantly increased the average talk/standby time for cell phones.