Portions of the following information are drawn from previous postings on the NPTalk discussion list. The cellular phone is a little tool that has, in a short amount of time, had a major impact on information and communications technology development around the globe. Strangely enough, the technology has been around a lot longer than you might think. Keep in mind that cellular phones themselves are basically transmitters and receivers of radio signals. Radio signals are carried as a series of waves, and are one form of radiation that makes up what is called the electromagnetic spectrum. There are also microwaves, infrared waves, the visible spectrum of color, ultraviolet rays, X-rays, and gamma rays. Radio waves are carried as a set of cycles (also known as its frequency). The frequency is measured in terms of one cycle per second, also called a Hertz (Hz), 1000 cycles per second is a kilohertz (kHz), and 1 million cycles per second is a megahertz (MHz). Way back when, instead of counting the number of cycles per second, the frequency of a radio waves used to be measured by assessing the distance between the topmost portion of two back-to-back cycles of waves-or the wavelength-in terms of meters. The short way of saying, in math terms, is: wavelength = 300 / frequency of wave or signal in MHz So, the higher the frequency of a radio signal, the shorter its wavelength (traditionally the distance between the top parts of two successive wave cycles) will be. One other term to keep in mind is something called bandwidth, which is the difference between an upper and lower frequency within a particular range of radio frequencies. Subsequently, the antenna needed to send and receive waves at a lower frequency must be larger than those for higher frequencies. With all of this transmission taking place at the lower end of the radio spectrum, there is not a lot of room for activity to occur. It seems that some 80 years ago, the Detroit, Michigan police were using mobile car radios at 2 MHz-their first major non-laboratory use in America. Only one small hitch: the crime rate forced such frequent use that there was no room to grow. Over the next two decades, more police units began using the frequency between 30 and 40 MHz, and the private and public demand for mobile radio units picks up. In 1945, St. Louis, Missouri was home to the first mobile telephone system available to the public. It utilized three channels at 150 MHz, instead of the six offered at the time by the United States Federal Communications Commission spaced apart at 60kHz intervals, thanks to equipment not able to counter interference among signals. Now skip ahead about two years. Enterprising science folks had an idea: what if, instead of trying to transmit numerous signals within large areas that bump up and interfere with one another, one simply established an entity that would serve as the base for a particular signal frequency in a smaller area, that could repeatedly transmit that signal to another station assigned another frequency, such that frequencies themselves could carry multiple loads of traffic? It took two years to figure this out, but only a few months for AT&T to try and put a lock on the idea, when, in 1947, it asked the FCC to open up a big chunk of existing radio frequencies to allow for deployment of mobile phone service. In a decision it would soon grow to regret, the FCC opted to put major constraints on the range of frequencies available for the service, meaning that only the equivalent of about 20 conversation could occur in a given area (or "cell") at once. Twenty-one years later, the FCC freed its mind somewhat, and said that it would open up more of the public's radio airwave for mobile phones if the underlying technology actually worked. AT&T and the Bell Laboratories concocted an approach consisting of these little broadcast towers, using a limited number of allowable frequencies, which could individually provide service to a radius of a few miles. When a mobile phone passed from cell to cell (the service area covered by a tower), the call itself would be transferred to that new cell. Thirty years after it proposed its first cell phone system, AT&T and the Bell Labs were finally able to build a prototype system, with a public demonstration in Chicago over the course of the next year, and a separate Motorola/American Radio public demonstration in the Washington, DC/Baltimore, Maryland area. Although the first commercial service started in Tokyo in 1979, it would not be until 1982 that the U.S. had its first commercial cell phone network, operated by Ameritech in Chicago. In five years, one million users filled the airwaves, clogging the system again. Without increasing the available bandwidth, and not desiring to split the existing cells to handle more capacity, the FCC, in 1987, let those entities with licenses in the cellular spectrum attempt to experiment with services at the frequency within 800 MHz. Everything in cellular service in the United States at that point in time relied upon analog radio signals. This means that the signals are sent in a continuous wave, such that the moment a user's cell phone is in operation, it sends out an identifier signal that attempts to find an open channel for communications. Analog service is limited in the number of channels open to users, much like regular FM radio service. How Radio Signals Work An electrical device called an oscillator generates carrier signals. The modulating signal, meanwhile, is generated from the voice or music that is picked up by a microphone, which converts it into an electrical signal, which is then amplified. This amplified signal, in the form of an electromagnetic wave, is then shot, at the speed of light (roughly 186,282 miles per second) into a layer of space called the ionosphere, through a transmitting antenna. Radio transmissions are encoded to make it easier to carry data-- voice or images, for example-over a significant distance. This is done in one of two ways. First, you can interrupt a transmission at certain points-- like the "dot-dash-dot" signals used in Morse code. The second method is called modulation. Modulation involves the addition of frequencies (also known as sidebands) to the main (or carrier) signal, by infusing it with a modulated signal. The sidebands themselves contain the actual information that is being sent. A receiving antenna picks up part of the electromagnetic wave signal, and reconverts it into electrical signals that are sent to a receiver. Usually, the signals at this point are combined with a signal frequency generated by an oscillator on the receiving end, and this produces an intermediate frequency. One of the two incoming frequencies goes to another amplifier, while the tuner dial on your radio receiver adjusts the oscillator-generated frequency. If the incoming signal is beyond the sensitivity of your radio receiver, it will amplify the signal's overall frequency, as long as the receiver is tuned to that frequency. This amplified signal is, through some circuitry, is then stripped into the signal wave (with the voice or music) and the accompanying carrier wave, which is ultimately what you hear. There are two types of modulation you are most familiar with, especially when you listen to programs on your radio in the car or at home: amplitude modulation (AM) and frequency modulation (FM). Amplitude modulation is when a carrier wave is encoded by modifying its strength in accordance with a modulating signal, but the frequency itself is held constant. The modulated signal breaks up a part of the carrier signal into sidebands that fall above and below the carrier wave's frequency, to an amount equal to the modulating signal's highest frequency. On your radio, a device called a rectifier converts the modulating signal into a receivable frequency, stripping out the carrier signal. A lot of power is necessary for AM radio signals to be transmitted because it is literally transmitting two sets of frequencies. Another flavor of AM is called single sideband modulation (SSB). This is when a modulated signal only carries one sideband and no carrier signal. In order to receive the signal, and receiver has to generate a wave at the same frequency as the carrier signal that would normally be sent. SSB is used by amateur (ham) radio broadcasts and telegraph over land and submarine cable. Frequency modulated (FM) radio signals rely upon a modulated signal is shot through a carrier signal. While the signal strength (amplitude) is held constant, the resulting change in the carrier signal, at any given moment, is directly proportional to the modulated frequency over time. FM has an advantage over AM in that it sounds better, thanks to the decreased amount of distortion. Think of all that static and those weird "whoosh" noises you hear on AM radio stations; one major cause is the change in amplitude. Since FM stations hold signal amplitude constant, they are less sensitive to noise. This is why more music, and the audio part of television signals, are carried through FM. To give you a better idea of how radio frequencies interact with one another and affect you, consider these figures:

• 535 kHZ-1.7 MHz (AM Radio)
• 5.9-26.1 MHz (Short wave radio)
• 26.96-27.41 MHz (Citizens Band (CB) radio)
• 54-88 MHz (Television channels 2-6)
• 88-108 MHz (FM Radio)
• 174-220 MHz (Television channels 7-13)
• 40 MHz (Alarm systems and garage door openers)
• 40-50 MHz (Regular cordless phone)
• 49 MHz (Baby monitor)
• 72 MHz (Radio-controlled model airplane)
• 75 MHz (Radio-controlled car)
• 215-220 MHz (Devices used to track animals in the wild)
• 145-437 MHz (MIR space station)
• 824-849 MHz (Cell phones used today)
• 900 MHz (Next generation cordless phones)
• 960-1215 MHz (Air traffic control radar)
• 1227-1575 MHz (Global Positioning System-- system of 24 satellites and a network of ground stations on earth that transmit receivable signals that can pinpoint and exact location)
• 2290-2300 MHz (Deep space radio signals)

There is, however, a disadvantage to FM. Look on your radio dial (for those of you using one of those digital displays, scan through the stations on your radio). You will see a big difference in the number of stations listed. FM stations are larger than AM in terms of bandwidth. While this means less of an issue with interference from other stations, it also means that there is less room on the FM dial for more stations. Who Invented the Cellular Phone? Keep in mind this stuff that we take for granted came about through a lot of work by different folks, including of James Maxwell (the math behind electromagnetic waves), Heinrich Hertz (that neat unit of frequency and the means for creating and detecting electromagnetic waves), and Guglielmo Marconi (using electromagnetic waves in wireless communications). In fact, take a quick leap back to 1895, and you would find Marconi demonstrating the first use of wireless telegraph. Six years later, the, the letter "S" was sent as a translatlantic transmission via Morse code. Three years later, Sir John Fleming picked up radio waves using the first vacuum electron tube, and by 1906, Lee de Forest was able to amplify radio waves thanks to his audion. That same year, Reginald Fessenden and Ernst Alexanderson conducted their experiments in transmitting voice via radio waves; Fessenden is particularly noteworthy for his work in the area of AM transmissions. Seven years later, Edwin Armstrong received a patent for the regenerative receiver circuit, the crucial piece for enabling long-range radio reception. By 1920, KDKA in Pittsburgh, Pennsylvania was operating as the first commercial radio broadcasting station, only one year before mobile car radios were in use by the Detroit, Michigan Police Department. By 1935, FM radio itself came into existence, thanks again to work pioneered by Armstrong, who also built the first FM station in 1939. AT&T and Southwestern Bell, on June 17, 1946, deployed a mobile radio telephone network service in St. Louis, Missouri, the first in the United States. The next year, AT&T's Bell Labs research unit proposed the idea for a cellular network. They only lacked one small piece of the equation: a way to make such a network feasible. By this time, however, early mobile radio telephones were in limited public use in the United States. As we pointed out previously, it would not be until the 1960s that analog cellular phones would be developed, right around the time that FM radio stations started to become popular in the U.S. The first analog cell phones availble to the public were made available in Japan in late 1979; in Scandinavia in 1981; in the U.S. in late 1983 by Motorola; and then chunks of Europe in the late 1980s. Competition for the development of true cellular communications system was pretty fierce during the 1960s and 1970s, especially between Motorola and the AT&T-affiliated Bell Laboratories. Cellular communications, pretty much until 1983, consisted of a bunch of radio car phones serviced by one antenna in selected metropolitan markets. Thanks to a number of developments in both technology and policy during the 1980s and early 1990s, cellular telephone service was expanded to reach more citizens than anyone could have expected. There is a problem, however, in pinpointing exactly who invented the cell phone itself. Conventional wisdom usually presents two candidates as deserving the credit: Dr. Martin Cooper and Dr. Henry T. Sampson. This gets really interesting when you take stock of what each is credited with. The first working cellular phone for commercial use-- still a car phone-- is generally credited to Motorola, which demonstrated it on October 13, 1983, in Chicago. They would design and produce a true portable cellular phone in 1984, and over the course of the year between, Motorola locked up over 250 patents related to the design for a comprehensive cellular phone network-- down to how the phone itself would look. Keep in mind that the Federal Communications Commission opted, between 1947 and the early 1980s, to only release up to 24 frequencies for cellular services. One of the major reasons for their hesitancy was an attempt to address AT&T's desire to open up new frequencies allocated to cellular services, which would only be devoted to mobile car radio phones (which was their specialty). Other entities, such as Motorola, wanted a wider spectrum opened up to other devices-- especially portable handheld units (which was their specialty). Until 1983, cell phones literally each took up a selected frequency, you could only have that many calls active at any one time. This means users could expect to wait a half-hour just to get a dial tone-- assuming they managed to endure the five to ten year wait to even receive the service in the first place. We should also point out that these earlier cell phones were not exactly portable, often coming in 30-pound suitcases that went into a car's trunk area. Enter Dr. Cooper, who was born in 1929 in Chicago, Illinois, and is widely credited as the "father of the cell phone." He earned a degree in electrical engineering from the Illinois Institute of Technology, served in the U.S. Navy for four years on combat ships and a submarine, before ultimately landing at Motorola in 1954, where he helped develop the first handheld police radios for the Chicago Police Department in 1967, before heading up the research efforts on cellular technology. During 1973, Dr. Cooper was a project manager for Motorola. On April 3 of that year, he and his team set up a cellular base station with a small antenna box on the roof of what is now the Alliance Capital Building in New York City, and from outside the Manhattan Hilton, he placed what is considered the first handheld cellular call, not-so-coincidentally to Joel Engel, the chief researcher at Bell Laboratories. The phone used was the Dyna-Tac phone. This was a unit that weighed 2.5 pounds, measured 9 x 5 x 1.75 inches, and after a charging period of 10 hours, allowed a user to dial or receive or talk on a phone conversation for a then-unheard of 35 minutes. Now we'll introduce Henry Thomas Sampson, an African-American who was born in 1934 in Jackson, Mississippi. Sampson received his undergraduate science degree in 1956 from Purdue University; a masters in engineering in 1961 from the University of California, Los Angeles; a masters in nuclear engineering in 1965 and a doctorate in the same field in 1967 from the University of Illinois Urbana-Champaign. Between 1956 and 1961, Sampson was a chemical engineer at the China Lake, California facilities of the U.S. Naval Weapons Center, worked at the Atomic Energy Commission, and eventually landed at the Aerospace Corporation, located in El Segundo, California. During that time, he worked on a number of projects that ultimately led to his patents for solid rocket motor technology and processes to convert of nuclear energy into electricity. Most noteworthy, however, is the July 6, 1971 patent (#3,591,860) held by both Sampson and Professor George Hunter Miley of the University of Illinois Urbana-Champaign, for something called a "gamma electric cell." This was a power source for high-voltage, low-current applications that could also be used to detect radiation, without requiring another energy source, and without leaking significant amounts of power, unlike previous designs. It is unclear how and to what degree the model of their device detected FM radio wave, but it is, without much doubt, a patent which is cited as crucial to the ultimate design of the cell phones we know and love (or hate) today. So the upshot is probably this: it might be safe to say that Dr. Cooper is the inventor of the first portable handheld cellular phone, and the first person to make a call on such a phone, while Drs. Sampson and Miley, invented, if not an actual working unit, then a pretty important element central to cellular technology without which we would not have the cellular phones and wireless applications around us today. The discouraging part is that the citations of Dt. Cooper's accomplishments are much easier to locate both on- and offline, and are widely considered the starting point of cellular communications as we know them today. The contribution of Drs. Sampson and Miley are either not widely known, nor actively promoted. What's Next? Recognizing the congestion taking place yet again, the FCC took a bold step and by 1994- after development and testing of a new standard by the cellular industry-- allocated a new spectrum for something called Personal Communication Services, or PCS. This allowed for a range of wireless services to be provided in the 1.9 GHz (gigahertz, or 1900 MHz) range, potentially enabling all-digital, versus analog, technology. This time there are two small hitches: First, there was no standard established in terms of the multiple ways digital cellular could be developed, leading to a lot of inconsistency in quality and a number of networks that had a limited service range. Second, even though interest in digital technology was growing rapidly by commercial providers, more than half of the existing cellular phones in the entire world were using analog services, thanks to the way the networks were built out. Currently there are three basic flavors of digital wireless technology standards in use:

• Code Division Multiple Access (CDMA IS-95), which breaks up voice streams and assigns them specific codes within the same general spectrum. This is the outgrowth of military technology during World War II used to prevent outside interference in radio transmissions, and has been used in the US since 1996 by Air Touch, Sprint PCS, and Verizon.
• Time Division Multiple Access (TDMA), used since 1994 by AT&T Wireless, Bell South and Southwestern Bell, which divides existing wireless frequencies into time slots shared by users at regular intervals
• Global System for Mobile Communications (GSM), is a standard first implemented in Europe in 1987, and in the U.S. in 1995, which combines analog and digital approaches. It uses more channels of larger size than available under the old analog standards. It is this standard-- used by companies like Pacific Bell, BellSouth, Sprint Spectrum, and Western Wireless- that is the only one of the three wireless approaches that allows for advanced data services including Internet, faxing, messaging, and wireless LANs, and that also allows wireless calling between North America and Europe.

Why would anyone want digital wireless technology anyway? Well, digital services work by creating a sample version of an analog sound wave (like your voice), cutting that sample into smaller bits of data which are sent out in an encoded manner, such that voice, text, or other information types can be sent and received with a greater insurance of speed and security than the open radio waves of an analog service. Resources Comparison of Radio Frequencies (HowStuffWorks.com) http://www.howstuffworks.com/radio-spectrum.htm Chart of the Electromagnetic Spectrum http://sss-mag.com/spectrum.html About.com guide to Inventors http://inventors.about.com Patent Information for Gamma-Electric Cell http://www.delphion.com/details?&pn=US03591860__ Ryan Turner OMB Watch