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What is GSM mean and how is it different from CDMA?


This article is taken from here. Just want to share the info(s) =)


First off, GSM stands for Global Systems for Mobile communications. It is a type of cell phone network first developed in Europe. It is estimated that nearly 80% of the global cell phone community uses GSM networks. GSM technology operates on the four frequency bands across the globe. These are 850/900/1800/1900 mhz. Each country uses a different combination of these four bands, usually a maximum of two bands per country. The two frequency bands in use in the United States are 850 and 1900 mhz.



  • The two major GSM carriers in the US are AT&T and T-Mobile. Currently, T-Mobile operates exclusively on the 1900 mhz band. AT&T operates on both the 850 and 1900 mhz band.
CDMA is another type of cell phone network. It is essentially a digital radio system that allows phones to access the same frequencies at the same time. CDMA devices can only access frequencies that they have been programmed to access, significantly limiting roaming capabilities.
  • The major CDMA carriers in the US are Verizon, Sprint, Metro PCS and US Cellular. Each operates on their own frequency.
GSM networks are designed to share signals, allowing for roaming agreements between different carriers around the world. GSM phones all use SIM cards (Subscriber Identity Module), which can be removed from any phone and placed into any other GSM based phone. 

As most GSM tri-band phones are models designed for maximum compatibility across the world, the most common combination of frequency bands in a tri-band phone is 900/1800/1900 mhz. This means that if you travelled into an area which only has coverage on the 850 mhz band, you would be unable to make or receive calls. However, manufacturers are now releasing tri-band phones optimized for the American market, which support the 850/1800/1900 frequency bands. This enables users to have maximum compatibility in the United States as well as being able to use the phone abroad. Please check the frequency bands in the product descriptions to see which bands are supported. 

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