ব্যবহারকারী:ইবুঙো চাউবা/খেলাঘর

Predecessorsedit[সম্পাদনা]

In 1908, Professor Albert Jahn and the Oakland Transcontinental Aerial Telephone and Power Company claimed to have developed a wireless telephone. They were accused of fraud and the charge was then dropped, but they do not really seem to have proceeded with production. In 1917, the Finnish inventor Eric Tigerstedt successfully filed a patent for a "pocket-size folding telephone with a very thin carbon microphone". Beginning in 1918, the German railroad system tested wireless telephony on military trains between Berlin and Zossen. In 1924, public trials started with telephone connection on trains between Berlin and Hamburg. In 1925, the company Zugtelephonie AG was founded to supply train-telephony equipment and, in 1926, telephone service in trains of the Deutsche Reichsbahn and the German mail service on the route between Hamburg and Berlin was approved and offered to first-class travelers.

Fiction anticipated the development of real-world mobile telephones. In 1906, the English caricaturist Lewis Baumer published a cartoon in Punch entitled "Forecasts for 1907" in which he showed a man and a woman in London's Hyde Park each separately engaged in gambling and dating on wireless-telegraphy equipment. Cartoonist W. K. Haselden published The Pocket Telephone: When Will It Ring? in 1919, depicting six awkward possibilities. In 1923, Ilya Ehrenburg casually listed "pocket telephones" among the achievements of contemporary technology in a story in his collection Thirteen Pipes (Russian: Тринадцать трубок). In 1926, the artist Karl Arnold drew a visionary cartoon about the use of mobile phones in the street, in the picture "wireless telephony", published in the German satirical magazine Simplicissimus. The popular American cartoon detective Dick Tracy acquired a two-way, atomic-battery-powered wrist radio in 1946, upgraded to a wrist TV in 1964.

The Second World War (1939-1945) saw the military use of radio-telephony links. Hand-held radio transceivers have been available since the 1940s. Mobile telephones for automobiles became available from some telephone companies in the 1940s. Early devices were bulky, consumed large amounts of power, and the network supported only a few simultaneous conversations. (Modern cellular networks allow automatic and pervasive use of mobile phones for voice- and data-communication.)

In the United States, engineers from Bell Labs began work on a system to allow mobile users to place and receive telephone calls from automobiles, leading to the inauguration of mobile service on 17 June 1946 in St. Louis, Missouri. Shortly after, AT&T offered Mobile Telephone Service. A wide range of mostly incompatible mobile-telephone services offered limited coverage areas and only a few available channels in urban areas. As calls were transmitted as unencrypted analog signals, anyone with radio equipment that could receive those frequencies could eavesdrop. The commercial introduction (in Japan in 1979) of cellular technology, which allowed re-use of frequencies many times in small adjacent areas covered by relatively low-powered transmitters, made widespread adoption of mobile telephones economically feasible.

In the USSR, Leonid Kupriyanovich, an engineer from Moscow, developed and presented a number of experimental pocket-sized communications radios in 1957–1961. The weight of one model, presented in 1961, was only 70 g and could fit in a palm. However, in the USSR the decision at first to develop the system of the automobile "Altai" phone was made^{[by whom?]}.

In 1965, the Bulgarian company "Radioelektronika" presented a mobile automatic phone combined with a base station at the Inforga-65 international exhibition in Moscow. Solutions of this phone were based on a system developed by Leonid Kupriyanovich. One base station, connected to one telephone wire line, could serve up to 15 customers.

Advances in mobile telephony can be traced in successive generations from the early "0G" services like MTS and its successor Improved Mobile Telephone Service, to first-generation (1G) analog cellular networks (1979–), second-generation (2G) digital cellular networks (1991–), third-generation (3G) broadband data services (launched commercially in 2001) to the fourth-generation (4G) native-IP networks (launched in 2006 in South Korea). 5G began deployment in 2019.

Radio Common Carrier or RCC was a service introduced in the 1960s by independent telephone companies to compete against AT&T's IMTS. RCC systems used paired UHF 454/459 MHz and VHF 152/158 MHz frequencies near those used by IMTS. RCC based services were provided until the 1980s when cellular AMPS systems made RCC equipment obsolete.

Some RCC systems were designed to allow customers of adjacent carriers to use their facilities, but equipment used by RCCs did not allow the equivalent of modern "roaming" because technical standards were not uniform. For example, the phone of an Omaha, Nebraska–based RCC service would not be likely to work in Phoenix, Arizona. Roaming was not encouraged, in part, because there was no centralized industry billing database for RCCs. Signaling formats were not standardized. For example, some systems used two-tone sequential paging to alert a mobile of an incoming call. Other systems used DTMF. Some used Secode 2805, which transmitted an interrupted 2805 Hz tone (similar to IMTS signaling) to alert mobiles of an offered call. Some radio equipment used with RCC systems was half-duplex, push-to-talk LOMO equipment such as Motorola hand-helds or RCA 700-series conventional two-way radios. Other vehicular equipment had telephone handsets and rotary dials or pushbutton pads, and operated full duplex like a conventional wired telephone. A few users had full-duplex briefcase telephones (radically advanced for their day)

At the end of RCC's existence, industry associations were working on a technical standard that would have allowed roaming, and some mobile users had multiple decoders to enable operation with more than one of the common signaling formats (600/1500, 2805, and Reach). Manual operation was often a fallback for RCC roamers.

Early generationsedit[সম্পাদনা]

Newer technology has been developed and rolled out in a series of waves or generations. The "generation" terminology only became widely used when 3G was launched, but is now used retrospectively when referring to the earlier systems.

1G – Analog cellularedit[সম্পাদনা]

Main article: 1G

The first automatic analog cellular systems ever deployed were NTT's system first used in 1979 for car phones in Tokyo (and later the rest of the country of Japan), and the cellular systems released by Comvik in Sweden in September, NMT in the other Nordic countries in October of 1981.

The first analog cellular system widely deployed in North America was the Advanced Mobile Phone System (AMPS). It was commercially introduced in the Americas on 13 October 1983, Israel in 1986, and Australia in 1987. AMPS was a pioneering technology that helped drive mass market usage of cellular technology, but it had several serious issues by modern standards. It was unencrypted and easily vulnerable to eavesdropping via a scanner; it was susceptible to cell phone "cloning" and it used a Frequency-division multiple access (FDMA) scheme and required significant amounts of wireless spectrum to support.

On 6 March 1983, the DynaTAC 8000X mobile phone launched on the first US 1G network by Ameritech. It cost $100M to develop, and took over a decade to reach the market. The phone had a talk time of just thirty minutes and took ten hours to charge. Consumer demand was strong despite the battery life, weight, and low talk time, and waiting lists were in the thousands.

Many of the iconic early commercial cell phones such as the Motorola DynaTAC Analog AMPS were eventually superseded by Digital AMPS (D-AMPS) in 1990, and AMPS service was shut down by most North American carriers by 2008.

In February 1986, Australia launched its Cellular Telephone System by Telecom Australia. Peter Reedman was the first Telecom Customer to be connected on 6 January 1986 along with five other subscribers as test customers prior to the official launch date of 28 February.

2G – Digital cellularedit[সম্পাদনা]

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Main articles: 2G, 2.5G, and 2.75G

In the 1990s, the 'second generation' mobile phone systems emerged. Two systems competed for supremacy in the global market: the European developed GSM standard and the U.S. developed CDMA standard. These differed from the previous generation by using digital instead of analog transmission, and also fast out-of-band phone-to-network signaling. The rise in mobile phone usage as a result of 2G was explosive and this era also saw the advent of prepaid mobile phones.

Handheld mobile phoneedit[সম্পাদনা]

Prior to 1973, mobile telephony was limited to phones installed in cars and other vehicles. The first portable cellular phone commercially available for use on a cellular network was developed by E.F. Johnson and Millicom, Inc. It was introduced by Millicom subsidiary Comvik in Sweden in September 1981.

Motorola was the first company to produce a handheld mobile phone. On 3 April 1973, Martin Cooper, a Motorola researcher and executive, made the first mobile telephone call from handheld subscriber equipment, placing a call to Dr. Joel S. Engel of Bell Labs, his rival. The prototype handheld phone used by Dr. Cooper weighed 2 kilograms (4.4 lb) and measured 23 by 13 by 4.5 centimetres (9.1 by 5.1 by 1.8 in). The prototype offered a talk time of just 30 minutes and took 10 hours to re-charge. Commonly referred to as “the Brick,” it was not commercially launched until October 1983, and only then in the U.S.

John F. Mitchell, Motorola's chief of portable communication products and Cooper's boss in 1973, played a key role in advancing the development of handheld mobile telephone equipment. Mitchell successfully pushed Motorola to develop wireless communication products that would be small enough to use anywhere and participated in the design of the cellular phone.

Emergence of automated servicesedit[সম্পাদনা]

The first fully automated mobile phone system for vehicles was launched in Sweden in 1956. Named MTA (Mobiltelefonisystem A), it allowed calls to be made and received in the car using a rotary dial. The car phone could also be paged. Calls from the car were direct dial, whereas incoming calls required an operator to locate the nearest base station to the car. It was developed by Sture Laurén and other engineers at Televerket network operator. Ericsson provided the switchboard while Svenska Radioaktiebolaget (SRA) and Marconi provided the telephones and base station equipment. MTA phones consisted of vacuum tubes and relays, and weighed 40 kilograms (88 lb). In 1962, an upgraded version called Mobile System B (MTB) was introduced. This was a push-button telephone, and used transistors and DTMF signaling to improve its operational reliability. In 1971 the MTD version was launched, opening for several different brands of equipment and gaining commercial success. The network remained open until 1983 and still had 600 customers when it closed.

In 1958, development began on a similar system for motorists in the USSR named "Altay". The main developers of the Altay system were the Voronezh Science Research Institute of Communications (VNIIS) and the State Specialized Project Institute (GSPI). In 1963, the service started in Moscow, and by 1970, was deployed in 30 cities across the USSR. Versions of the Altay system are still in use today as a trunking system in some parts of Russia.

In 1959, a private telephone company in Brewster, Kansas, US, the S&T Telephone Company, (still in business today) with the use of Motorola Radio Telephone equipment and a private tower facility, offered to the public mobile telephone services in that local area of NW Kansas. This system was a direct dial up service through their local switchboard, and was installed in many private vehicles including grain combines, trucks, and automobiles. For some as yet unknown reason, the system, after being placed online and operated for a very brief time period, was shut down. The management of the company was immediately changed, and the fully operable system and related equipment was immediately dismantled in early 1960, not to be seen again.^{[citation needed]}

In 1966, Bulgaria presented the pocket mobile automatic phone RAT-0,5 combined with a base station RATZ-10 (RATC-10) on Interorgtechnika-66 international exhibition. One base station, connected to one telephone wire line, could serve up to six customers.

One of the first successful public commercial mobile phone networks was the ARP network in Finland, launched in 1971. Posthumously, ARP is sometimes viewed as a zero generation (0G) cellular network, being slightly above previous proprietary and limited coverage networks.^{[citation needed]}

Cellular conceptedit[সম্পাদনা]

European mobile radio networksedit[সম্পাদনা]

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In Europe, several mutually incompatible mobile radio services were developed.

In 1966, Norway had a system called OLT which was manually controlled. Finland's ARP, launched in 1971, was also manual as was the Swedish MTD. All were replaced by the automatic NMT, (Nordic Mobile Telephone) system in the early 1980s.

In July 1971, Readycall was introduced in London by Burndept after obtaining a special concession to break the Post Office monopoly to allow selective calling to mobiles of calls from the public telephone system. This system was available to the public for a subscription of £16 month. A year later the service was extended to two other UK towns.

West Germany had a network called A-Netz launched in 1952 as the country's first public commercial mobile phone network. In 1972, this was displaced by B-Netz which connected calls automatically.

Other servicesedit[সম্পাদনা]

In 1969, Penn Central Railroad equipped commuter trains along the 360 kilometres (220 mi) New York-Washington route with special pay phones that allowed passengers to place telephone calls while the train was moving. The system re-used six frequencies in the 450 MHz band in nine sites.

In the UK, Channel Islands and elsewhere the "Rabbit" phone system was briefly used, being a hybrid of "cell" base stations and handsets. One major limitation was that you had to be less than 300 feet (closer with buildings) from a base due to power limitations on a portable device. With modern technology a similar variant is being considered for Apple's new 4G "smart watch" so they can be used in large events in a broadly similar way to a femtocell

Early servicesedit[সম্পাদনা]

MTSedit[সম্পাদনা]

In 1949, AT&T commercialized Mobile Telephone Service. From its start in St. Louis, Missouri, in 1946, AT&T introduced Mobile Telephone Service to one hundred towns and highway corridors by 1948. Mobile Telephone Service was a rarity with only 5,000 customers placing about 30,000 calls each week. Calls were set up manually by an operator and the user had to depress a button on the handset to speak and release the button to listen. The call subscriber equipment weighed about 80 pounds (36 kg)

Subscriber growth and revenue generation were hampered by the constraints of the technology. Because only three radio channels were available, only three customers in any given city could make mobile telephone calls at one time. Mobile Telephone Service was expensive, costing US$15 per month, plus $0.30–0.40 per local call, equivalent to (in 2012 US dollars) about $176 per month and $3.50–4.75 per call.

In the UK, there was also a vehicle-based system called "Post Office Radiophone Service," which was launched around the city of Manchester in 1959, and although it required callers to speak to an operator, it was possible to be put through to any subscriber in Great Britain. The service was extended to London in 1965 and other major cities in 1972.

IMTSedit[সম্পাদনা]

AT&T introduced the first major improvement to mobile telephony in 1965, giving the improved service the obvious name of Improved Mobile Telephone Service. IMTS used additional radio channels, allowing more simultaneous calls in a given geographic area, introduced customer dialing, eliminating manual call setup by an operator, and reduced the size and weight of the subscriber equipment.

Despite the capacity improvement offered by IMTS, demand outstripped capacity. In agreement with state regulatory agencies, AT&T limited the service to just 40,000 customers system wide. In New York City, for example, 2,000 customers shared just 12 radio channels and typically had to wait 30 minutes to place a call.