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From Free Knowledge Base- The DUCK Project: information for everyone
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The original cellular technology was based on an analog signal. During the 1990s the new PCS digital mobile phone technology was introduced. PCS stood for Personal Communication System, and Sprint being one of the first companies to adopt this started their digital phone division, called Sprint PCS. == [[AMPS]] =={{:AMPS}}== [[GSM]] ==[[GSM]] stands for Global System for Mobile Communications; it's the world's most prolific mobile standard. This is what you will find if you are, say for example, traveling in Europe. Most new phones on AT&T and T-Mobile actually adhere to both GSM and the newer UMTS (Universal Mobile Telecommunications System) standards. UMTS isn't an official part of the GSM standard, but it is what GSM carriers use for 3G data transmission.Phones using GSM can do both voice and data at the same time, which cannot be done with CDMA.Switching Providers: GSM phones use a removable Sim Card. If the phone is unlocked you can pop a SIM card out of a GSM phone and stick it in any other GSM phone, switching a phone from one provider to another.== [[CDMA]] ==[[CDMA]] stands for Code Division Multiple Access, including both CDMAOne or CDMA 2000. This is the most common standard in the United States of America throughout the 1990's and until present (2012).CDMA2000, based more directly on its predecessor includes a range of improvements over the original CDMAOne, key among them 3G data speeds.CDMA phones have a slightly more refined method for handing off calls from tower to tower, so they drop fewer calls as compared to GSM.Switching Providers: CDMA phones ship locked to one network, and can only be switched to another with the cooperation of both the old and new carriers.3G Data phones do not use SIM cards.4G Data phones utilize a SIM card. Verizon, for example, states, "''All Verizon Wireless 4G Certified Devices will need a Verizon Wireless Subscriber Identity Module (SIM) Card. 4G SIM Cards are required for Verizon Wireless 4G LTE service.''" See [http://support.verizonwireless.com/information/4gsim.html 4G SIM Information].== TDMA ==This is an outdated technology. The major TDMA carriers switched over to GSM. AT&T (including the former AT&T Wireless) and US Cellular were formerly on the TDMA standard. US Cellular actually went to CDMA.=== iDEN ===Sprint Nextel provided iDEN (Integrated Digital Enhanced Network) service across the United States, but its iDEN network was decommissioned on June 30, 2013. iDEN places more users in a given spectral space, compared to analog cellular and two-way radio systems, by using speech compression and time division multiple access (TDMA).== U.S. Providers and Technologies ==* Verizon - CDMA, UMTS* AT&T Mobility - GSM, UMTS, HSDPA* Sprint - CDMA, UMTS:* Nextel - iDEN* US Cellular - CDMA* T-Mobile - GSM, UMTS, GAN* Cricket Communications - CDMA* Virgin Mobile - CSMAA Mobile Virtual Network Operator (MVNO) is a cell phone company that doesn't own any wireless spectrum, but instead buys it from a network operator such as Sprint. Essentially, an MVNO is a marketing company that believes it can build a profitable business targeting niche markets such as Hispanics or teenagers. Prior to 2006, most MVNOs offered prepaid service, with TracFone and Virgin Mobile among the notable-name providers. == Roaming ==A CDMA-only phone from Verizon, Sprint, or US Cellular is only able to roam on other CDMA networks. This is fine in North America, but CDMA networks are rare in Europe and other countries. These three carriers offer phones with built-in GSM support for International traveling, but this feature is missing from their most popular handsets. The CDMA carriers offer a few models of "World Phones" which have SIM card slots for the installation of GSM SIM cards so these phones can operate on GSM networks. These phones require a second radio, so cost more to manufacturer. One example of such a World Phone is the [[BlackBerry Bold 9650]]. Currently (2012), there are no Verizon 4G LTE models that offer GSM support. The world phones are 3G phones when operated domestically.