Cellular technology is the use of wireless communication, most commonly associated with the mobile phone. The term cellular comes from the design of the system, which carries mobile phone calls from geographical service areas that are divided into smaller pockets, called cells. Each cell contains a base station that accepts and transfers the calls from mobile phones that are based in its cell. The cells are interconnected by a central controller, called the mobile telecommunications switching office (MTSO). The MTSO connects the cellular system to the conventional telephone network and it also records call information so users can be charged appropriately. In addition, the MTSO system enables the signal strength to be examined every few seconds—automatically by computer—and then be switched to a stronger cell if necessary. The user does not notice the "handoff" from one cell to another.
Traditional cellular technology uses analog service. This type of service transmits calls in one continuous stream of information between the mobile phone and the base station on the same frequency. Analog technology modulates (varies) radio signals so they can carry information such as the human voice. The major drawback to using analog service is the limitation on the number of channels that can be used.
Digital technology, on the other hand, uses a simple binary code to represent any signal as a sequence of ones and zeros. The smallest unit of information for the digital transmission system is called a bit, which is either one or zero. Digital technology encodes the user's voice into a bit stream. By breaking down the information into these small units, digital technology allows faster transmission of data and in a more secure form than analog.
Prior to the late 1940s, when the mobile phone was in its early stages of development, it worked like a two-way radio, using one frequency to send a user's voice back and forth. At that time, the Federal Communications Commission (FCC) limited the number of radio frequencies available for transmitting signals from a mobile phone to one transmission antenna per city. (The FCC is the government department in charge of regulating anything that goes out over the airwaves, such as telephone, television, and radio.) Approximately two dozen calls only could be placed in each city at a single time. Mobile phone users often had to wait up to a half hour to place a call. Because of the limited number of available frequencies, which allowed so few people to use the technology at one time, communication companies did not want to devote resources to researching a system that would not be widely used. They did not want to spend development money on a project that had such great limits.
Analog: A method in which one type of data is represented by another varying physical quantity.
Cell: Broadcasting zone in a geographical service area containing a base station that accepts and transfers calls from mobile phones that are based in the cell.
Digital: The opposite of analog, it is a way of showing the quantity of something directly as digits or numbers.
During this time, communication researchers had begun to develop the cellular phone system. They theorized that by establishing service areas divided in cells and then splitting the cells into smaller geographical areas and implementing frequency reuse (where the same channel may be used for communication in cells located far apart enough to keep interference low), base stations could handle increased calls. This increase would then improve the useability of the mobile phone for consumers. However, following through on that theory was not yet possible, as the technology was still in its earliest stages.
Almost twenty years later, in 1968, the FCC reconsidered its earlier position on radio frequency limitations. In an attempt to encourage communication companies to develop better cellular systems, the FCC decided to increase the number of available radio frequencies.
In 1977, two communication companies, AT&T and Bell Labs, began the experimental use of a cellular system. By 1979, the first commercial cellular system debuted in Tokyo, Japan. In 1982, the FCC realized the incredible potential cellular communication had and authorized commercial cellular service in the United States. The first commercial analog cellular service, Advanced Mobile Phone Service (AMPS), was made available to the public in 1983 by the communication company Ameritech. Five years later, the popularity of the mobile phone skyrocketed and the number of users went beyond one million. The need to improve the constantly busy radio frequencies, however, became all too apparent for the communication companies.
Fortunately, in 1987, the FCC announced that communication companies could develop new technologies as an alternative to the then-current standard of AMPS. The FCC sought an improvement in and enlargement of cellular service. By 1991, the Telecommunications Industry Association (TIA) responded by creating personal communication services (PCS) technology. This new technology generally employed the use of all-digital wireless communication. The FCC announced in 1994 that it would allocate a spectrum (range of frequencies of sound waves) specifically for the PCS technology, which helped push the speed of the development of digital service.
The development of cellular/digital technology is playing an increasing importance in today's business markets. More employees are spending additional time away from their offices, thereby increasing the necessity of mobile communication technologies such as the hand-held phone, notebook computers, pagers, personal digital assistants, and palmtop computers.
[ See also Telephone ]