In the Soviet Union (USSR), the first work devoted to this subject was published in 1935 by Dmitry Ageev.
The technology of CDMA was used in 1957, when the young military radio engineer Leonid Kupriyanovich in Moscow made an experimental model of a wearable automatic mobile phone, called LK-1 by him, with a base station.
In 1958, Kupriyanovich made the new experimental "pocket" model of mobile phone.
To serve more customers, Kupriyanovich proposed the device, which he called "correlator." In 1958, the USSR also started the development of the "Altai" national civil mobile phone service for cars, based on the Soviet MRT-1327 standard.
In 1963 this service started in Moscow, and in 1970 Altai service was used in 30 USSR cities. == Uses == Synchronous CDM (code-division 'multiplexing', an early generation of CDMA) was implemented in the Global Positioning System (GPS).
In 1963 this service started in Moscow, and in 1970 Altai service was used in 30 USSR cities. == Uses == Synchronous CDM (code-division 'multiplexing', an early generation of CDMA) was implemented in the Global Positioning System (GPS).
In CDMA cellular, the base station uses a fast closed-loop power-control scheme to tightly control each mobile's transmit power. In 2019, schemes to precisely estimate the required length of the codes in dependence of Doppler and delay characteristics have been developed.
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