CDMA
Code-Division Multiple Access.
CDMA is a digital wireless technology. It is a general type of technology, implemented in many specific technologies. But the term "CDMA" is also commonly used to refer to one specific family of technologies (IS-95 and CDMA2000) used in the US by Sprint and Verizon Wireless. This technology competes with GSM, used by AT&T and T-Mobile.
CDMA is a "spread spectrum" technology, which means that it spreads the information contained in a particular signal of interest over a much greater bandwidth than the original signal.
Unlike many competing technologies, CDMA has no hard limit for the number of users who may share one base station (tower). Instead, with CDMA, additional users can connect until the base station determines that call quality would suffer beyond a set limit.
CDMA (IS-95) systems have been in commercial operation since 1995. CDMA networks operate in the 800 and 1900 MHz frequency bands with primary markets in the Americas and Asia.
IS-95 CDMA technology has also been called cdmaOne and cdma2000.
GSM
Global System for Mobile Communication.
GSM is the dominant 2G digital mobile phone standard for most of the world. It determines the way in which mobile phones communicate with the land-based network of towers.
GSM is one of two major mobile phone technologies in the U.S. The other is CDMA. AT&T and T-Mobile use GSM. Sprint and Verizon use CDMA. GSM is more prevalent in most other parts of the world, and especially in Europe.
Although GSM and CDMA provide similar basic features and services to end-users, (such as voice calling, text messaging, and data services,) they operate very differently at many technical levels. This makes GSM phones completely incompatible with CDMA networks, and vice-versa.
The most visible feature of GSM are SIM cards. SIM cards are removable, thumbnail-sized smart cards which identify the user on the network, and can also store information such as phone book entries. SIM cards allows users to switch phones by simply moving their SIM card from one phone to the other.
WCDMA
(Wideband Code Division Multiple Access)
Wideband CDMA is a third-generation (3G) wireless standard which utilizes one 5 MHz channel for both voice and data, initially offering data speeds up to 384 Kbps. WCDMA is the 3G technology used in the US by AT&T and T-Mobile.
There are several newer technologies that offer much faster data speeds, such as HSDPA, HSUPA, and HSPA. These do not replace WCDMA, but rather build on and enhance WCDMA. Therefore any phone with HSDPA also includes WCDMA by definition.
WCDMA is also referred to as UMTS - the two terms are effectively interchangeable.
WCDMA is the 3G standard that most GSM carriers are moving to. Parts of the WCDMA standard are based on GSM technology. WCDMA networks are designed to integrate with GSM networks at certain levels. Most WCDMA phones include GSM as well, for backward compatibility.
WCDMA borrows certain technology ideas from CDMA, as the name implies, but is in fact very different and incompatible with phones and networks using "CDMA" technology.
In Europe and Asia, WCDMA is being deployed in the all-new 2100 MHz frequency band. In North America, WCDMA is being deployed in the existing 1900 MHz (PCS) and 850 MHz (cellular) bands, as well as the newer 1700 MHz (AWS) band.
3G
3G Stands for 3rd-generation. Analog cellular phones were the first generation. Digital phones marked the second generation (2G).
3G is loosely defined, but generally includes high data speeds, always-on data access, and greater voice capacity.
The high data speeds are possibly the most prominent feature, and certainly the most hyped. They enable such advanced features as live, streaming video.
There are several different 3G technology standards. The most prevalent worldwide is UMTS, which is based on WCDMA. (The terms WCDMA and UMTS are often used interchangeably.) UMTS is the 3G technology of choice for most carriers that used GSM as their 2G technology.
The other major standard is cdma2000, which is an evolution of CDMA 2G technology. There are several types of cdma2000, each offering different data rates and levels of compatibility with 2G CDMA. EV-DO Rev A is the most common today.
UMTS
Universal Mobile Telecommunications System.
A third generation (3G) mobile communications technology that promises data transmission speeds of up to 2 megabits per second (Mbps), although actual speeds may be significantly lower at first, due to network capacity restrictions.
UMTS uses WCDMA technology, and the two terms are often used interchangeably with each other.
PCS
(Personal Communications Services)
1. The FCC-licensed frequency band near 1900 MHz.
2. A marketing term used to describe a wide variety of two-way digital wireless service offerings operating at 1900 MHz.
