History of Cellular Phones. Cellular
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- Individual Inventors Inventors
- - increase frequencies allocation - split existing cells - improve the technology
- Wireless PCS Technology
- Wireless Standards Analog Service
- Digital Service
| History of Cellular Phones.
Cellular: A type of wireless communication that is most familiar to mobile phones users. It's called 'cellular' because the system uses many base stations to divide a service area into multiple 'cells'. Cellular calls are transferred from base station to base station as a user travels from cell to cell. The basic concept of cellular phones began in 1947, when researchers looked at crude mobile (car) phones and realized that by using small cells (range of service area) with frequency reuse they could increase the traffic capacity of mobile phones substantially. However at that time, there wasn’t technology that developed. Anything to do with broadcasting and sending a radio or television message out over the airwaves comes under Federal Communications Commission (FCC) regulation. A cell phone is a type of two-way radio. In 1947, AT&T (a telecommunications company) proposed that the FCC allocate a large number of radio-spectrum frequencies so that widespread mobile telephone service would become feasible and AT&T would have a incentive to research the new technology. We can partially blame the FCC for the gap between the initial concept of cellular service and its availability to the public. The FCC decided to limit the amount of frequencies available in 1947, the limits made only twenty-three phone conversations possible simultaneously in the same service area - not a market incentive for research. The FCC reconsidered its position in 1968, stating "if the technology to build a better mobile service works, we will increase the frequencies allocation, freeing the airwaves for more mobile phones." AT&T and Bell Labs proposed a cellular system to the FCC of many small, low-powered, broadcast towers, each covering a 'cell' a few miles in radius and collectively covering a larger area. Each tower would use only a few of the total frequencies allocated to the system. As the phones travelled across the area, calls would be passed from tower to tower.
"People want to talk to other people - not a house, or an office, or a car. Given a choice, people will demand the freedom to communicate wherever they are, unfettered by the infamous copper wire”. Martin Cooper added, "As I walked down the street while talking on the phone, sophisticated New Yorkers gaped at the sight of someone actually moving around while making a phone call. Remember that in 1973, there weren't cordless telephones, let alone cellular phones. I made numerous calls, including one where I crossed the street while talking to a New York radio reporter - probably one of the more dangerous things I have ever done in my life." Martin Cooper's role in conceiving and developing the first portable cellular phone directly impacted his choice to found and lead ArrayComm, a wireless technology and systems company founded in 1992. ArrayComm's core adaptive antenna technology increases the capacity and coverage of any cellular system, while significantly lowering costs and making speech more reliable. ArrayComm has also used its adaptive antenna technology to make the Internet "personal" by creating the i-BURST Personal Broadband System, which delivers high-speed, mobile Internet access that consumers can afford.
Martin Cooper demonstrates the first portable cellular telephone. ArrayComm By 1977, AT&T and Bell Labs had constructed a prototype cellular system. A year later, public trials of the new system were started in Chicago with over 2000 trial customers. In 1979, in a separate venture, the first commercial cellular telephone system began operation in Tokyo. In 1981, Motorola and American Radio telephone started a second U.S. cellular radio-telephone system test in the Washington/Baltimore area. By 1982, the slow-moving FCC finally authorized commercial cellular service for the USA. A year later, the first American commercial analog cellular service or AMPS (Advanced Mobile Phone Service) was made available in Chicago by Ameritech. Despite the incredible demand, it took cellular phone service 37 years to become commercially available through the world. Consumer demand quickly outstripped the 1982 system standards. By 1987, cellular telephone subscribers exceeded one million and the airways were crowded. Three ways of improving services existed: - increase frequencies allocation - split existing cells - improve the technology The FCC did not want to handout any more bandwidth, and building/splitting cells would have been expensive and would have added bulk to the network. To stimulate the growth of new technology, the FCC declared in 1987 that cellular licensees could employ alternative cellular technologies in the 800 MHz band. The cellular industry began to research new transmission technology as an alternative. Wireless PCS Technology PCS (Personal Communication Services): Used to describe a newer class of wireless communications services recently authorized by the FCC. PCS systems use a different radio frequency, the 1.9 GHz band, than cellular phones and generally use all-digital technology for transmission and reception. After the Federal Communications Commission (FCC) declared in 1987 that cellular licensees could employ alternative cellular technologies in the 800 MHz band, the cellular industry began to research new transmission technology as an alternative to AMPS (Advanced Mobile Phone Service) that had been the industry standard since 1978. In 1988, the Cellular Technology Industry Association (CTIA) was established to work with the cellular service operators and researchers to identify new technology requirements and set goals. They wanted the new products and services introduced by 1991, a 1000% percent increase in system capacity with both AMPS (analog) and digital capability during transmission, and new data features such as fax and messaging services. The Telecommunications Industry Association (TIA) created a standard specification based on the requirements the CTIA had recommended. The TDMA Interim Standard 54 or TDMA IS-54 was released in early 1991. The technology was tested that same year in Dallas and Sweden. In 1994, the FCC announced it was allocating spectrum specifically for PCS technologies at the 1900 MHz band. Three major standards have been released since 1991. All of these new digital wireless standards are currently being used in PCS. Wireless Standards Analog Service: A method of modulating radio signals so that they can carry information such as voice or data. Analog cellular phones work like a FM radio. The receiver and transmitter are tuned to the same frequency, and the voice transmitted is varied within a small band to create a pattern that the receiver reconstructs, amplifies and sends to a speaker. The drawback of analog is the limitation on the number of channels that can be used. Digital Service: A method of encoding information using a binary code of 0s and 1s. Most newer wireless phones and networks use digital technology. In digital, the analog voice signal is converted into binary code and transmitted as a series of on and off transmissions. One of digital's drawbacks, is that there are three digital wireless technologies, CDMA, TDMA and GSM. Phones that work with one technology may not work on another. TDMA IS-136 (Time Division Multiple Access) is an update to TDMA IS-54, also called Digital AMPS or D-AMPS. Released in 1994, TDMA IS-136 uses the frequency bands available to the wireless network and divides them into time slots with each phone user having access to one time slot at regular intervals. TDMA IS-136 exists in North America at both the 800 MHz and 1900 MHz bands. Major US carriers using TDMA are AT&T Wireless Services, Bell South and Southwestern Bell. CDMA IS-95 (Code Division Multiple Access) is based on a form of spread spectrum technology that separates voice signals by assigning them digital codes within the same broad spectrum. CDMA type technology dates back to the 1940s, when spread spectrum technology was used in military communications systems because it was resistant to interference from enemy signals. The Qualcomm corporation began developing a CDMA wireless system in the late 1980s that was accepted as a standard in 1993 and went into operation by 1996. CDMA also exists at both the 800 MHz and 1900 MHz bands. The major US carriers using CDMA are Air Touch, Bell Atlantic/Nynex, GTE, Primeco and Sprint PCS. GSM (Global System for Mobile Communications) is based on a improved version of TDMA technology. In 1982, the Conference of European Posts and Telecommunications (CEPT) began the process of creating a digital cellular standard that would allow users to roam from country to country in Europe. By 1987, the GSM standard was created based on a hybrid of FDMA (analog) and TDMA (digital) technologies. GSM engineers decided to use wider 200 kHz channels instead of the 30 khz channels that TDMA used, and instead of having only 3 slots like TDMA, GSM channels had 8 slots. This allowed for fast bit rates and more natural-sounding voice-compression algorithms. GSM is currently the only one of the three technologies that provide data services such as email, fax, internet browsing, and intranet/LAN wireless access. Download 17.59 Kb. Share with your friends:
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