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2012/11/29 11:10:16

CDMA (Code Division Multiple Access is Code-division multiple access)

CDMA (engl. Code Division Multiple Access is code-division multiple access) is technology of mobile communication with channels of one frequency band, but excellent from each other code modulation.

Capability transfer large volumes of information it was put by developers of the American company Qualcom "by default", unlike the GSM standard where data transmission is so-called "superstructure" in a telephone system.

Over 250 operators in 99 countries of the world use CDMA technologies with the different frequency ranges (450/800/900/2000 MHz). The number of subscribers of CDMA EV-DO networks approaches 100 million.

In Russia the CDMA technology develops with the frequency range of 450 MHz as it is recognized as the most suitable standard for step-by-step "digitalization" of NMT-450i networks.

CDMA 450 MHz (IMT-MC-450) is the technology complex of new generation uniting the highest transmission quality of the speech and exclusively high data transfer rates.

Advantages of the CDMA standard 450 MHz

  • Pure sounding of the speech
  • Lack of extraneous noises and high confidentiality level of a talk — initially the standard was developed for the U.S. Armed Forces. Decrypt a signal without knowledge of the code impracticablly.
  • The increased capacity of network providing implementation of unlimited accesses both in voice traffic, and in a data transmission traffic
  • There is no strict number of channels. With increase in loading losses in data transmission packets increase, but at the same time there is no break of connections.
  • The high data transfer rate allowing to implement a full-fledged work on the Internet and to use all opportunities of business solutions of the class "remote office" as using the mobile phone, and having connected it to the computer.
  • Much higher level of security of cell phones in comparison with devices of other standards (peak capacity of the modern GSM phones is about 1.0 W while this indicator of CDMA phones does not exceed 0.2 W that, including, well affects also work duration without recharge).

FH-CDMA

Code-division multiple access of channels (with a jump on frequency). Abbreviation of Frequency Hopping Code Division Multiple Access. The main advantages of FH-CDMA technology — high noise immunity and small sensitivity to dispersion of capacities of subscriber devices.