Mobile Phone Network Technology Overview

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

This technology is mentioned for historical purposes. Although radio phones or a proto cell phone technology can be traced back to the 1950s, Advanced Mobile Phone System (AMPS) is considered the first true cell phone network commercially available to the United States, starting in 1978.

AMPS communication was unencrypted, so people to listen in on cell phone conversations with an ordinary police scanner. Phones were often cloned, causing issues of fraud and network abuse. AMPS was also a bandwidth hog, using a Frequency-division multiple access (FDMA) scheme that required significant amounts of wireless spectrum.

AMPS started to get phased out beginning in the 1990s when PCS digital was introduced.

Verizon Wireless operated an AMPS network, and on February 18, 2008, Verizon discontinued all AMPS service. The last of the AT&T AMPS network was shut down February 18, 2008.

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 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 - CSMA

A 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.

Using Another Provider's Phone With Verizon, Sprint, or US Cellular

The two leading digital mobile phone technologies in the United States, and some parts of the world, are CDMA and GSM. These are competing technologies, "CDMA vs GSM," that are not compatible nor interchangeable. They're the reason you can't use AT&T phones on Sprints' network or Verizon’s and vice versa.

CDMA (Code Division Multiple Access) and GSM (Global System for Mobiles) are shorthand for the two major radio systems used in cell phones. Both acronyms include the basis for a set of expanding technologies and standards.

As of this writing the CDMA standard is the most expansive in the United States, with the most towards and cells. However, in Europe and most of the rest of the digital world the GSM standard is dominant. Following that are less developed countries still using the aging AMPS analog standard.

Verizon's phones and network are CDMA, which doesn't use sim cards. The new G4 phones do have a SIM card tied to the owner.

G3 and earlier CDMA phones do not use sim cards, while GSM phones all do.

CDMA and GSM are different technologies that are incompatible with each other.

The term "unlocking" referring to an unlocked phone is used when discussing GSM and iDEN phones.

There are other CDMA providers besides Verizon, which include Sprint and US Cellular.

Verizon will only activate another Verizon phone. A non-Verizon CDMA phone's ESN number will not be in Verizon's database of phones, and therefore, Verizon will not activate it. Verizon will also blacklist a Bad Verizon ESN Number on a formerly valid Verizon phone for certain reasons, which brings attention to one important caveat when buying a used Verizon phone.

Mobile Broadband Data

Mobile broadband is also known as 3G, or third-generation cell-phone technology. Both GSM and CDMA have developed their own 3G technology solutions for delivering high-speed Internet access to mobile devices.

The CDMA-based mobile broadband technology is called EV-DO.

The GSM mobile broadband technology is called HSDPA.

Other Technologies and Related Termonology

WiMax

Sprint Nextel developed WiMax technology before Verizon's 4G LTE was available. WiMax is a high speed alternative to 4G LTE. However, Sprint Nextel has decided to abandoned WiMax and convert their networks to 4G LTE. (May 2012)

4G LTE

CDMA 3G is being replaced / upgraded to 4G LTE, a faster data technology. Unlike CDMA 3G (called 3G EV-DO), 4G LTE is supposed to become a global standard, which includes Europe and regions previously not 3G EV-DO compatible. Even though 4G LTE will eventually be more universal, carriers such as Verizon are still using incompatible radio frequencies which Europe. As of 2012, Verizon 4G devices are not world roam compatible.

AT&T and Verizon are each using 700 MHz to build their LTE networks. But they use different slivers of this frequency, and because the "bands" aren't harmonized, the specifications are different and devices built for AT&T won't work on Verizon's network and vice versa.

3G EV-DO

In North America, Verizon and Sprint have large network coverage for 3G EV-DO data technology.