2G: 2G is short for second-generation wireless telephone technology. This means it is digital instead of analog. Three primary benefits of 2G networks over their predecessors were that phone conversations were digitally encrypted, 2G systems were significantly 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.

3G: 3G refers to the third generation of mobile telephony (cellular) technology. The third generation, as the name suggests, follows two earlier generations. GSM could deliver not only voice, but also circuit-switched data at speeds up to 14.4 Kbps. But to support mobile multimedia applications, 3G had to deliver packet-switched data with better spectral efficiency, at far greater speeds. 3G is designed to provide voice and high-speed mobile data using the cellular approach already proven to work in mobile phone networks.
3G provides accelerated data speeds and simultaneous voice and data capabilities 3G allows for speeds of up to 384 Kb/s downstream and 64 Kb/s upstream.

4G: 4G refers to the fourth generation of cellular wireless and is a successor to 3G and 2G standards.

SIM Cards: A SIM card or Subscriber Identity Module is a portable memory chip used in most models of cellular telephones. The SIM card makes it easy to switch to a new phone by simply sliding the SIM out of the old phone and into the new one. It can be thought of as a mini hard disk that automatically activates the phone into which it is inserted.

SMS: Short Message Service is a communication service standard in the GSM mobile communication system, using standardized communications protocols allowing the exchange of short text messages (up to 160 characters) between mobile devices. This service is also known as text messaging. Most SMS messages are mobile-to-mobile text messages, though the standard supports other types of broadcast messaging as well.

MMS: Multimedia Messaging Service is a standard used to send messages that include multimedia content (photos, videos) to and from mobile devices. MMS is widely used in GSM/GPRS networks.

GSM and CDMA: hough GSM and CDMA are different mobile offerings than provide the same general service it may be best to compare them side by side in order to realize the differences. Both are one of the three main digital technologies, with TDMA being the third.
GSM's high-speed wireless data technology (GPRS), usually offers a slower data bandwidth for wireless data connection than CDMA's high-speed technology (1xRTT, short for single carrier radio transmission technology), which has the capability of providing ISDN (Integrated Services Digital Network)-like speeds of as much as 144Kbps (kilobits per second). However, 1xRTT requires a dedicated connection to the network for use, whereas GPRS sends in packets, which means that data calls made on a GSM handset don't block out voice calls like they do on CDMA phones.
How do GSM and CDMA offerings work together, especially in densely populated areas, In theory, GSM and CDMA are invisible to one another and should "play nice" with one another. In practice, however, this is not the case. High-powered CDMA signals have raised the "noise floor" for GSM receivers, meaning there is less space within the available band to send a clear signal. This sometimes results in dropped calls in areas where there is a high concentration of CDMA technology. Conversely, high-powered GSM signals have been shown to cause overloading and jamming of CDMA receivers due to CDMA's reliance upon broadcasting across its entire available band.
GSM is mostly used in Europe and Asia while United States carriers are split in their offerings.

• Sprint and Verizon use CDMA
• AT&T and T-Mobile use GSM

GSM: Global System for Mobile Communications

• Dominant standard worldwide except the United States.
• Global market share = 80%
• GSM is a 2G technology
• GSM uses SIM cards: Enables you to carry all of your contact and calendar information over to a new handset simply by putting in the SIM card into the new mobile device.
• International Service: GSM is used in more than 74% of the markets across the globe, users of tri-band or quad-band handsets can travel internationally and still use their mobile devices.
• Data Transfer Methods: GSM is slower than CDMA.

CDMA: Code Division Multiple Access

• Dominant standard in the United States.
• Global market share = 20%
• CDMA is a 3G technology.
• CDMA does not use SIM cards: CDMA providers provide a service where user data, including phone numbers, schedules and other information on a database. This service makes it possible to not only swap over to a new handset with little trouble, but it also gives users the ability to recover contact date even if their phone is lost or stolen.
• International Service: CDMA does not offer multiband capability therefore can't readily be used in multiple countries.
• Data Transfer Methods: CDMA is faster than GSM
• With every mobile device CDMA is assigned a unique mathematical signature. It applies this signature to the original signal and transmits the modified signal. A receiver applies the inverse of the mathematical operation to recover the original signal.

GPRS: GSM was the most successful 2G cellular technology, but had slow data transfer rates. In order to address this issue GSM used another technology GPRS which stands for General Packet Radio System. GPRS technology enabled much higher data rates to be conveyed over a cellular network (GSM) that was voice centric.
GPRS became the first stepping stone on the path between 2G GSM cellular technology and the 3G CDMA systems With GPRS data rates up to 172 kbps could be achieved allowing web browsing and other data transfer related applications become possible. Though some data could be transferred using 2G GSM the rates were too slow for real data applications. It will be common to see GSM and GPRS linked together as GSM\GPRS. This simply means GSM networks are also capable of faster data rates for mobile applications.
GPRS is associated with GSM networks.

Edge: Enhanced Data rates for GSM Evolution (also known as EGPRS Enhanced GPRS) is a backward compatible digital mobile technology that allows improved data transmission rates, to standard GSM. Edge is considered a 3G radio technology. Edge is an upgrade to GSM/GPRS networks that provides more than 3 times the performance of standard GSM/GPRS networks. Edge/EGPRS is implemented as a bolt on enhancement for 2G and 2.5G GSM and GPRS networks, making it easier for existing GSM carriers to upgrade to it. EDGE/EGPRS is a superset to GPRS and can function on any network with GPRS deployed on it, provided the carrier implements the necessary upgrade.

HSDPA: High Speed Downlink Packet Access is a new protocol for mobile telephone data transmissions. It is a 3.5G technology and the standard to provide download speeds on a mobile device equivalent to a home DSL (Digital Subscriber Line) line. Though any data can be transmitted, applications with high data demands such as video and streaming music are the focus of HSDPA. HSDPA is associated with GSM networks. Theoretically, HSDPA speeds can reach 3.6 Mbps downstream and 348 Kbps upstream.

EVDO: Evolution Data Only or Evolution Data Optimized is a standard for high speed wireless broadband. It sometimes is referred to as CDMA2000 and is a 3G wireless standard. The biggest obstacle to implementing high speed wireless networks is the lack of bandwidth, only so much data can be transmitted across the available bandwidth. EVDO is an advanced CDMA technology developed to deal with this limitation. Therefore EVDO is associated with CDMA networks.
Traditional wireless networks create a physical path between receiving and sending devices, much like traditional telephone networks. EVDO instead adopts the same approach used for the internet. Each packet is sent independently of all the other packets. This saves bandwidth for use by other devices; when neither party on a phone call is speaking, the connection consumes no bandwidth because there are no packets to send.
EVDO has a theoretical throughput of 2.4 megabits per second. This is as fast as many residential DSL and cable broadband connections currently available in the United States. A significant advantage of EVDO over competing technologies is that it uses the same broadcasting frequencies as existing CDMA networks. The major EVDO deployments in the US are by Verizon and Sprint.
EVDO is a competing CDMA standard to WCDMA.

WCDMA: (Wideband Code Division Multiple Access) is the radio access scheme used for third generation cellular systems. The 3G systems to support wideband services like high-speed Internet access, video and high quality image transmission with the same quality as the fixed networks. Data rate of 384 Kbps with wide area coverage can be achieved while 2 Mbps can be achieved for local coverage.
WCDMA is a competing GSM standard to EVDO

UMTS: UMTS stands for Universal Mobile Telecommunications System. UMTS is a 3G technology and is designed for traditional phone tasks as voice mail, and paging but also Internet access, video and text messaging (SMS). One of the main benefits of UMTS is its speed. Current rates of transfer for broadband information are 2 Mbps a second. This speed makes it possible for streaming video and video conferencing on mobile devices.
UMTS is associated with the GSM standard technologies.

The following lists the different technologies that are associated with GSM and CDMA.

GSM

• GPRS: Provides higher data rates to traditional GSM 2G networks.
• EDGE: A turbo GPRS providing higher data rates for 3G networks.
• UMTS: Faster throughput for broadband applications. 3G network.
• HSDPA: Provides download speed equal to DSL. 3.5G network. HSDPA speeds can reach 3.6 Mbps downstream and 348 Kbps upstream.

CDMA

• EVDO: Provides download speed equal to DSL or cable modems. EVDO has a theoretical throughput of 2.4 megabits per second.