America Discovers New Ways to Communicate - Mobile Phones

The cell phone is the only information technology present since the mid-1980s that has outpaced the Internet in terms of use. The development of the modern cell phone began in the mid-1940s, nearly twenty years before scientists even conceived of an Internet. In 1946 the Bell System introduced the first commercial radio-telephone service in St. Louis, Missouri. The radio-telephone, typically mounted under the front dashboard of a car or truck, received incoming telephone calls via radio waves transmitted from a large tower planted on a downtown building. A bell rang and a light went off on the radio-telephone to signify an incoming call. When the person using the radiotelephone answered, his or her side of the conversation was transmitted to one of several receiving stations around the city that were all open to the same frequencies. Both the incoming and outgoing signals were relayed through a switchboard and routed into the national phone system. From the start, this system had a number of limitations. Calls had to be routed through a live switchboard operator, both parties involved in a conversation could not talk at once, and only three conversations could take place citywide at any given time with the bandwidth restrictions.

History and Development

The idea for the modern mobile cellular phone network was first posited in 1947 by D. H. Ring at Bell Laboratories in an internal memorandum. The memo proposed a system that would overcome many of the flaws inherent in the radio-telephone. The plan called for a network of low-powered cellular towers that could receive and transmit telephone calls via radio waves to and from mobile phones. Each tower would have a three-mile broadcast radius. As the user of the mobile phone traveled across these cells, the call was to be automatically routed from one tower to the next and the phone would switch frequencies. To accommodate more customers using a limited number of frequencies, towers that were out of range of one another were to send and receive radio signals of the same frequency. That way two people three miles apart or more could carry on separate conversations using the same frequency without interfering with one another's reception.

In order to implement this vision on a large scale and make a profit, AT&T would require more frequencies on the radio spectrum than the Federal Communications Commission (FCC) then allowed for two-way radio communications. The radio spectrum is essentially a long ribbon of frequencies that stretch from 3 kilohertz to 300 gigahertz. Only one device in an area, be it a radio station or a television station, can use a particular part of this ribbon to broadcast or else interference will arise. The FCC regulates what type of devices can operate over various sections of the radio spectrum. Cell phones generally eat up a big part of each spectrum because each cell phone requires two signals at two different frequencies—one signal for the incoming signal and one for the outgoing signal. With the limits the FCC imposed in 1947, only twenty-seven cellular phone conversations could take place in a metropolitan area equipped with Bell Lab's proposed cellular system. When AT&T approached the FCC and asked them for additional room on the radio spectrum, the FCC held fast and did not grant them additional frequencies.

Over the next twenty years, mobile phone technology did not show rapid advances. The Richmond Radiotelephone Company in 1948 implemented the first automated radio-telephone service that did not require a live switchboard operator. In 1964 the Bell System rolled out the Improved Mobile Telephone Service to replace their aging radio-telephone network. This system allowed for both people to talk at once during a call. The bandwidth each phone occupied on the radio spectrum was narrowed, so more than a few people in a city could use it.

Technological Developments after 1960

AT&T once again approached the FCC in 1958, this time asking for 75 megahertz of spectrum located in the 800 megahertz range of the radio spectrum. At the time, hardly anyone in the United States used this part of the spectrum for broadcasting. The FCC did not review the proposal until 1968. They then considered it for two years and made a tentative decision to let AT&T use that part of spectrum for two-way radio in 1970. Meanwhile, the Bell System, Motorola, and several other companies began engineering the technologies necessary for the cell phone network. In 1969 the Bell System installed the first cell phone system aboard a train. The system consisted of a set of payphones placed on the Metroliner trains that ran between New York City and Washington, D.C. Cell phone towers were set up along the track. As the train sped along, telephone conversations were routed from tower to tower just as described in the 1947 memo. Four years after this first cellular phone went into use, Martin Cooper at Motorola developed the first personal, handheld cellular phone. Motorola erected a single prototype cellular tower in New York to test the phone. Cooper made his first call to his rival at Bell Labs, who was attempting to create a similar device.

In 1978 the FCC allowed AT&T to test an analog cellular telephone service. AT&T chose Chicago, Illinois, for their trial run, and set up ten cellular towers, which covered 21,000 square miles of the Chicagoland area. Customers who wanted to use the service leased large, car-mounted telephones. The trial run was a success, and Ameritech, the regional Bell in metropolitan Chicago, launched the first commercial cellular service in 1983. Two months after Ameritech began service, Motorola offered service as well in the Washington-Baltimore area. Most people had carmounted phones. The alternatives were large portable phones that were so big they had to be carried around in a suitcase. At first, none of the cellular systems being put in place were compatible with one another and roaming outside of the calling area was not a possibility.

In the late 1980s the Telecommunications Industry Association established some basic standards for cell-phone companies. The standards paved the way for a continuous, cross-country network that everyone could use regardless of which company was providing the service (often times with extra roaming charges). The first standard was for analog phones. Analog phones process signals in much the same way as car radios or traditional phones do. When a person speaks into the cell phone, the microphone turns the signal into a continuous stream of electrical impulses, which travels out from the phone's antennae and to the cellular tower. Both these outgoing signals and the incoming signals on modern analog phones take up 30 kilohertz of space on the radio wave spectrum.

Modern Cell-Phone Networks

By 1990 the number of people using cell phones increased dramatically to over five million subscribers, according to the U.S. Census. (See Table 2.1.) With the analog standard and the frequency limitations imposed by the FCC, less than one hundred people in each network were able to use one cellular tower at once. If the number of cell phones maintained the same rate of growth, then cell-phone companies would soon require new technologies that allowed more cell-phone conversations to take place in a given area. The cell-phone companies' solution was to adopt digital technology.

A digital signal is a signal that is broken down into impulses representing ones and zeros. When a digital cell phone receives a digital signal, a chip inside the phone known as a digital signal processor (DSP) reads these ones and zeros and then constructs an analog signal that travels to the phone's speaker. Conversely, the DSP also processes analog signals coming from the phone's microphone, converting them into ones and zeros, before sending the signal to a cell tower. By breaking down the signal into ones and zeros, more telephone calls can be handled by one frequency. The process is analogous to breaking down and cutting up boxes to allow more to fit inside a trash can. The first digital system widely used by the cell phone companies was the time division multiple access (TDMA) method. Figure 2.4 and Figure 2.5 show the difference between the older, frequency division multiple access (FDMA) and TDMA. FDMA requires each phone to use a different frequency. TDMA allows three cell-phone conversations to be contained in the same thirty-kilohertz-wide band that held only one analog conversation. By the early 1990s cellular companies were erecting digital cellular towers enabled with TDMA across the country.

By 1995 the number of cell-phone users had grown to nearly thirty-four million people by U.S. Census estimates, and the TDMA systems were looking as if they might hit capacity as well. In response, the FCC auctioned off more frequency bands in the radio wave spectrum in the 1850 megahertz to the 1900 megahertz range. Services set up on these bands were known as personal communications services (PCS). PCS networks were designed for handheld mobile phones instead of car phones and had smaller cells than the original cellular network. The PCS networks also employed an updated version of TDMA and a newer technology known as code division multiple access (CDMA). Both could pack up to eight calls into one frequency band. With so many bands available, cell-phone companies introduced a multitude of features standard into their phones, such as the ability to send instant messages, surf the Web, play games, send e-mail, and check the identity of callers.

Issues and Concerns

Though cell phones have brought a great deal of convenience to modern life, they have become a source of trouble as well. Many believe that cell phones contribute to automobile accidents because drivers cannot concentrate on the road appropriately while speaking on a cell phone. While Congress continued to debate whether or not to institute a nationwide ban of handheld cell-phone use in automobiles, many states already had laws in place by late 2004. Figure 2.6 displays the states that had instituted cell phone driving laws as of July 2004. As can be seen, Washington, D.C., New Jersey, and New York all had full bans on the use of handheld cell phones while driving. Maine banned teen drivers from talking on cell phones while driving. Seven states banned cell phones just for drivers of school buses. In addition, cell-phone restrictions for drivers were being considered by the legislatures of Iowa, Hawaii, Louisiana, and North Carolina in 2004.

As cell-phone makers add such features as Internet access and video games, many believe cell phones are also becoming a bigger distraction and a source of potential trouble for children. In "Cell Phones and Kids: Do They Mix?," an MSNBC article published August 20, 2004, Bob Sullivan outlined some of the concerns parents face with regards to kids and cell phones. While parents have a fairly easy time monitoring what children do on the computer, cell phones are a different story. Given the portable nature of cell phones, children can easily play games or surf the Internet from any location, without their parents' knowledge. In addition, cell-phone Internet browsers have no parental controls, and cell-phone games do not have content ratings. The best way to monitor children's cell-phone use, Sullivan concluded, is to check the activity reported on monthly bills.

Finally, some health concerns associated with cell-phone use emerged at the beginning of the twenty-first century. In "Nerve Cell Damage in Mammalian Brain after Exposure to Microwaves from GSM Mobile Phones" (Environmental Health Perspectives, June 2003), Lief Salford and his colleagues at Lund University in Sweden demonstrated that cell-phone radiation caused brain damage in rats. The scientists mounted a European cell phone to the side of the rats' cage for two hours a day for fifty days to emulate the amount of exposure a habitual cell-phone user would receive. The rats' brains showed significant blood vessel leakage as well as areas of damaged neurons.