Telecom

GSM
GSM ( Global System for Mobile Communciations: orginally form Groupe special Mobile) is the most popular standard for mobile telephony systems in the world. The GSM association, its promoting industry trade organization of mobile phone carriers and manufactures, estimates that 80% of the global mobile market uses the standard. GSM is used by over 3 billion people across more than 212 countries and territories. Its ubiquity enables international roaming arrangements between mobile phone operators, providing subscribers the use of their phone in many parts of the world. GSM differs from its predecessor technologies in that both signaling and speed signaling and speech channels are digital. and thus GSM is considered a second generation 2G mobile phone system this also facilitates the wide-spread implementation of data communication applications into the system.


GSM-1800
GSM-1800 uses 1710-1785 MHz to send information from the mobile station to the base tranceiver station (uplink) and 1805-1880 MHz for the other direction (downlink), providing 374 channels (channel number 512 to 885). Duplex spacing is 95 MHz.

GSM-850 and GSM-1900
GSM-85 and GSM-1900 are used in the United States, Canada, and many other countries in the Americas.
 - GSM-850 use 824-849 MHz to send information from the mobile station to  the base station (uplink) and 869-894 MHz for the other direction (downlink). Channel numbers are 128 to 251.
GSM-850 is also sometimes called GSM-800 because this frequency range was known as the "800 MHz band" (for simplfication) when it was first allocated for AMPS in the United States in 1983.
The term Cellular is sometimes used to describe the 850 MHz band, because the original analog cellular mobile communication system was allocated in this spectrum.
GSM-1900 uses 1850-1910 MHz to send information from the mobile station to the base station (uplink) and 1930-1990 MHz for the other direction (downlink). Channel number are 512 to 810.



GPRS
General packet radio service (GPRS) is a packet oriented mobile data service available to users of the 2G cellular communication systems global system for mobile communications (GSM), as well as in the 3G systems. in 2G systems, GPRS provides data rates of 56-144 kbit/s.
GPRS data transfer is typically charged per megabyte of traffic transferred, while data communiation via traditional circuit switching is billed per minute of connection time, in dependent of whether the user actually is using the capacity or is in an idle state. GPRS is a best-effort packet switched service, as opposed to circuit switching, where a certain quality of service (QoS) is guaranteed during the connection for non-mobiles users.

0G
these early mobile telephone systems can be distinguished from earlier closed radiotelephone systems in that they were available as a commercial service that was part of the public switched telephone network, with their own telephone number, rather that part of a closed network such as a police radio or taxi dispatch system.

1G
1G refers to the first-generation of wireless telephone technology, mobile telecommunications. these are the analog telecommunications standards that were introduced in the 1980s and contiued until being replaced by 2G digital telecommunications. The main difference between two succeeding mobile telephone systems. 1G and 2G, is that the radio signals that 1G networks use are analog, while 2G networks are digital.
1G is only modulated to higher frequency, typically 150 MHz and up.

2G
2G is short for second-generation wireless telephone technology. second generation 2G cellular telecom networks were commercially launched on the GSM standard. Three primary benefits of 2G networks over their predecessors were that phone conversations were digitally encrypted, 2G system were significantty more efficient on the spectrum allowing for far greater mobile phone penetration levels, and 2g introduced data services for mobile, starting with SMS text messages.
2G technologies can be divided into TDMA-based and CDMA-based standards depending on the type of multiplexing used. The main 2G standards are:
- GSM
-CDMA
PDC
IDE
IS-136




3G or IMT-2000
IMT-2000 (International Moblie Telecommunications-2000), better know as 3G or 3rd Generation, is a family of standards of mobile telecommunications fulfilling specifications by international telecommunication union, which includes UMTS, and CDMA2000 as well as the non-mobile wireless standard. While the GSM EDGE standard also fulfils the IMT-2000 specification, EDGE phones are typically not branded 3G, Services include wide-area wireless voice telephone, video calls, and wireless data, all in a mobile environment. Compared to 2G and 2.5G service, 3G allows simultaneous use of speech and data service and higher data rates ( at least 200 kbit/s peak bit rate to fulfill to IMT-2000 specification). Tolday's 3G systems can offer practice of up to 14.0 Mbit/s on the downlink and 5.8 Mbit/s on the uplink.

4G
4G refers to the fourth generation of cellular wireless standards. It is a successor to 3G and 2G standards. The nomenclature of the generations generally refers to a change int the fundamental nature of the service. The first wast the move from analogue (1G) to digital (2G) transmission. this was followed by multi-media support. spread sectrum transmission and at least 200 kbit/s (3G) and now 4G. which refers to all IP packet switched networks, mobile ultra-broadband (gigabit speed) access and multi-carrier transmission.





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