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The world moves the standard that the correspondence system(GSM, the Global System for Mobile communication) is draw up by the correspondence system that the Europe aims at with the 900 MHz wave band work.In order to imitating an enlargement ability of correspond by letter the system limited, so according to increment the business contents need of request but develop the item's technique.This technique provided nations to travel extensively,high quality words sound,high safety with enough capacity with develop the system service of the high class.Cooperating to complete through whole joint efforts of European nations should technical development, provide the suitable for different nation and culture traditional of of the integral whole turn the beehive correspondence system.
Although GSM just standard in an Europe, obtain global success.The GSM have many the one and only of characteristic, make it become nowadays extensively approve of the wireless correspondence standard.The GSM conduct and actions is develop in whole kind of correspondence standards of European regions, aim at of be of the European nation the standard is diverse,and permit sex to differ of condition, but this kind of condition existed still today.
GSM from descend to say a few composings:Exchange system(SS, the Switch System),the 基 station system(BSS, the Base Station System) to support system with operation.(OSS, the Operations and Support System)The BSS is received and dispatch the letter set(BTS, the Base Transceiver Satations) by the 基 station controller(BSC, the Base Satation Controller) and the 基 station to constitute.In the general structure, a few BTS conjunctions are on a BSC, and a few BSC conjunctions is in the commutation center.(MSC, the Mobile Switching Center)
The wireless channel of the GSM system has the bandwidth with 200 kHzs.The GSM system has already broken through in a few different wave bands, they respectively is the 900 MHzses,1800 MHzses and 1900 MHz 频 segment.The work still needs the frequency chart to carry on a certain degree to frequency chart to tidy up before use in the GSM the letter way of the 1800 MHzs and the 1900 MHz 频 segment.However, the frequency chart with 900 MHzs is use by a kind of emulation system that is called to expand to all connect into the correspondence system(ETACS, the Enhanced Total Access Communication System), it take up of the letter way bandwidth is a 25 kHzs.So, when the GSM system leads to go into that 频 segment, need to carry on reallocate to the letter way to accept GSM system.

Keyword GSM;Correspond by letter system; The PDU code; Wireless correspondence system

GSM communications system design Summary Global system for mobile communications (GSM,Global System for Mobile communication) is the European 900MHz band for the communications system to the standards. The communications system simulation capacity expansion limited, and therefore the need for increased operational requirements of the development of the technology. This technology provides international roaming, high-quality voice, high security and sufficient capacity for the development of advanced systems. After all European countries to work together to complete the technology development cooperation provided for in different countries and cultural integration between traditional cellular communications systems. While GSM is a European standard, but to achieve global success. GSM has many unique characteristics, widely recognized as the standard radio communications. GSM throughout Europe as a communication standard was developed and is against the standards varied between European countries, the situation of poor compatibility, but this situation still exists today. GSM posed by the several major modules : the exchange system (SS,Switch System), the base system (BSS,Base Station System) and operations support systems (OSS,Operations and Support System). BSS by phone signal controllers (BSC,Base Satation Controller) and base stations send letters Taiwan (BTS,Base Transceiver Satations). In general structure, several contracted with a BSC in, and several BSC link in the exchange center (MSC,Mobile Switching Center). GSM system with radio frequency 200kHz bandwidth. GSM system has been launched in several different bands, they are 900MHz, 1800MHz and 1900MHz frequency bands. Work on the GSM 1800MHz and 1900MHz band access in the use of spectrum is required before some degree of spectrum clearing. However, the 900MHz spectrum is known as a whole to expand access communications systems (ETACS,Enhanced Total Access Communication System) simulation system used in the occupied bandwidth to 25kHz. Therefore, when the introduction of the band GSM system, the need for access to a reallocation to accommodate GSM system. Keyword GSM; communications systems; PDU coding; Wireless communication systems