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Cellular telephone system, used to describe a mobilewireless telephoneApplication, which divides a given region into sub regions, called cells.Cellular mobile telephone systemIt was in the early 1970sBell Lab After giving the concept and related theory of cellular system coverage cell, the system has developed rapidly.
In the past, cellular phones have always been used as a means of ground communication. After boarding, before takeoff and during the whole flight, the cellular phones carried by passengers must be turned off, and communication with any aspect will be temporarily interrupted.This situation will certainly bring inconvenience to work.To this end, AirCell in the United States conceived the idea of developing an airborne cellular telephone system in the early 1990s. Today, AirCell's airborne cellular telephone system has been developed and is installing cellular network ground stations in 150 important locations in the United States to provide airborne cellular communications covering the whole country.
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The AirCell airborne cellular telephone system operates in the 800MHz frequency band. The AirCell airborne cellular telephone system receives airborne cellular telephone and data through the AirCell base station antenna, and then sends these data to the telephone network through the existing cooperative ground cellular stations.Among the 150 websites covering the country, each website is 165 miles apart and covers a diameter of 200 miles.At present, the AirCell system provides five communication channels in each base station.However, when communication services increase, the total number of channels in each base station can increase to 98.If the traffic volume increases beyond the channel capacity, base stations can also be added in high traffic areas.The standard 30KHz cellular frequency modulation (FM) channel is used when the AirCell system is talking.In addition to calls, it can also transmit data with a data rate of 9.6 Kbps
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first generationCellular mobile telephone system: Refers to the analog cellular mobile telephone system, which is mainly characterized by the transmission of analog signals through wireless channels.
The second generation cellular mobile phone system: the index word cellular mobile phone system, which is characterized by direct transmission and processing of digital information, has the advantages of all digital systems and greatly improves the frequency utilization.
GSM was originally the abbreviation of a mobile communication special research group established in Europe.This group has done a lot of work in cellular mobile communication in Europe, demonstrated eight different experimental schemes, and finally formulated a pan EuropeanDigital cellular mobile communication systemAnd named after the research group GSM.
