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2. iPhone 4 - Wikipedia

   en.wikipedia.org/wiki/IPhone_4

   An iPhone 4 A1332 with a micro-SIM card removed with a paper clip, showing its SIM card compartment. The GSM iPhone 4 uses a micro-SIM card, which is positioned in an ejectable tray, located on the right side of the device. The CDMA iPhone 4, however, the phone connects to the network using an ESN. All prior models have used regular mini-SIM ...

3. Comparison of mobile phone standards - Wikipedia

   en.wikipedia.org/wiki/Comparison_of_mobile_phone...

   GSM uses TDMA and FDMA for user and cell separation. UMTS, IS-95 and CDMA-2000 use CDMA. WiMAX and LTE use OFDM. Time-division multiple access (TDMA) provides multiuser access by chopping up the channel into sequential time slices. Each user of the channel takes turns to transmit and receive signals.

4. iPhone 4s - Wikipedia

   en.wikipedia.org/wiki/IPhone_4S

   There were no external differences between the iPhone 4 CDMA model and the iPhone 4s, with the exception of a SIM card slot on the iPhone 4s. [27] All changes were internal (slight external differences between the iPhone 4 GSM model and the iPhone 4s exist, as said differences existed between the CDMA and GSM models of the iPhone 4). [29] [30]

5. Cellular frequencies - Wikipedia

   en.wikipedia.org/wiki/Cellular_frequencies

   Cellular frequencies. Cellular frequencies are the sets of frequency ranges within the ultra high frequency band that have been assigned for cellular-compatible mobile devices, such as mobile phones, to connect to cellular networks. [1] Most mobile networks worldwide use portions of the radio frequency spectrum, allocated to the mobile service ...

6. UMTS - Wikipedia

   en.wikipedia.org/wiki/UMTS

   The Universal Mobile Telecommunications System (UMTS) is a 3G mobile cellular system for networks based on the GSM standard. Developed and maintained by the 3GPP (3rd Generation Partnership Project), UMTS is a component of the International Telecommunication Union IMT-2000 standard set and compares with the CDMA2000 standard set for networks based on the competing cdmaOne technology.

7. Code-division multiple access - Wikipedia

   en.wikipedia.org/wiki/Code-division_multiple_access

   Multiplexing. Code-division multiple access (CDMA) is a channel access method used by various radio communication technologies. CDMA is an example of multiple access, where several transmitters can send information simultaneously over a single communication channel. This allows several users to share a band of frequencies (see bandwidth).