History of mobile phones
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Mobile rigs, such as ham radio gear installed in automobiles were the predecessor of mobile phones, along with taxicab radios, two way radios in police cruisers, and the like. A large community of mobile radio users, known as the mobileers, popularized the technology that would eventually give way to the mobile phone. Originally, mobile phones were permanently installed in vehicles, but later versions such as the so-called "bag phones" were equipped with a cigarette lighter plug so that they could also be carried, and thus could be used as either mobile or as portable phones.
What was possibly the first real mobile phone, in the sense that it was connected to the telephone network, was tested by the Swedish police in 1946, for use in police cruisers. A half dozen calls could be made before the police car's battery ran out. Radiophones began to be publicly available, in the US, at the end of the 1940s[1] though the distinction between such phones and a two way radio becomes blurry since special systems are required to "patch" into the phone network with the assistance of human operators. Recognisable mobile phones with direct dialling have existed at least since the 1950s
Modern mobile telephony is often considered to have started on April 3, 1973, when Martin Cooper – then an employee of Motorola – placed the first call to the company's rival AT&T's Bell Labs, while walking the streets of New York City. Motorola (Motor-ola) has a long history of making automotive radio, especially two-way radios for taxicabs and police cruisers.
Mobile phones began to proliferate through the 1980s with the introduction of "cellular" phones based on cellular networks with multiple base stations located relatively close to each other, and protocols for the automated "handover" between two cells when a phone moved from one cell to the other. At this time analog transmission was in use in all systems. Mobile phones were somewhat larger than current ones, and at first, all were designed for permanent installation in cars (hence the term car phone). Soon, some of these bulky units were converted for use as "transportable" phones the size of a briefcase. Motorola introduced the first truly portable, hand held phone. These systems (NMT, AMPS, TACS) later became known as first generation mobile phones.
In September 1981 the first cell phone network with automatic roaming was started in Saudi Arabia; it was an NMT system. One month later the Nordic countries started an NMT network with automatic roaming between countries.
In the 1990s, second generation (2G) mobile phone systems such as GSM, IS-136 ("TDMA"), iDEN and IS-95 ("CDMA") began to be introduced. The first digital cellular phone call was made in the United States in 1990, in 1991 the first GSM network opened in Europe. 2G phone systems were characterised by digital circuit switched transmission and the introduction of advanced and fast phone to network signalling. In general the frequencies used by 2G systems in Europe were higher though with some overlap, for example the 900 MHz frequency range was used for both 1G and 2G systems in Europe and so such 1G systems were rapidly closed down to make space for 2G systems. In America the IS-54 standard was deployned in the same band as AMPS, and displaced some of the existing analog channels.
Coinciding with the introduction of 2G systems were trends which meant that the larger "bricks" disappeared and tiny 100–200g hand-held devices became the norm. These trends included technology improvements such as better battery technologies and lower power electronics, but also are largely related to the higher density of cellular sites caused by increasing usage levels.
Not long after the introduction of 2G networks, projects began to develop 3G systems. Inevitably there were many different standards with different contenders pushing their own technologies. Quite differently from 2G systems, however, the meaning of 3G has been standardised in the IMT-2000 standardisation process. This process did not standardise on a technology, but rather on a set of requirements (2Mb/s maximum data rate indoors, 384Kb/s outdoors, for example). At that point, the vision of a single unified worldwide standard broke down and several different standards have been introduced.
During the development of 3G systems, 2.5G systems such as CDMA2000 1x and GPRS were developed as extensions to existing 2G networks. These provide some of the features of 3G without fulfilling the promised high data rates or full range of multimedia services. E.g. CDMA2000-1X delivers theoretical maximum data speeds of up to 307 kbit/s. Just beyond these is the EDGE system which in theory covers the requirements for a 3G system, but is so narrowly above these that any practical system would be sure to fall short.
At the beginning of the 21st century, 3G mobile phone systems such as UMTS and CDMA2000 1xEV-DO have now begun to be publicly available. The final success of these systems is still to be determined.
