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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.
The GSM standard does not include the 3G Universal Mobile Telecommunications System (UMTS), code-division multiple access (CDMA) technology, nor the 4G LTE orthogonal frequency-division multiple access (OFDMA) technology standards issued by the 3GPP. [16] GSM, for the first time, set a common standard for Europe for wireless networks.
In 3G, the most prevalent technology was UMTS with CDMA-2000 in close contention. All radio access technologies have to solve the same problems: to divide the finite RF spectrum among multiple users as efficiently as possible. GSM uses TDMA and FDMA for user and cell separation. UMTS, IS-95 and CDMA-2000 use CDMA. WiMAX and LTE use OFDM.
These phones include combination of GSM and CDMA technology. They can be used as a GSM or CDMA phone according to the user's preference. These handsets are also called global phones. An example of this is the Samsung SCH-A790. These dual-mode handsets are compatible with both GSM and CDMA networks and are essentially two phones in one device.
However, unlike TDMA, there are no time slots, and all CDMA radios can be active all the time to deliver up to 14.4 kbit/s data transmission speeds. With the evolution of CDMA to CDMA2000 and 1xRTT, the use of IS-95 CDMA Circuit Switched Data declined in favour of the faster data transmission speeds available with the newer technologies.
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.
CDMA frequency bands or frequency ranges are the cellular frequencies designated by the ITU for the operation of cdmaOne ... GSM frequency bands; UMTS frequency bands ...
The comparable technology in the context of GSM is GSM-1800, also known as "Digital Cellular System" (DCS). [10] GSM-1800 launched in Hong Kong in 1997. It can form dual band service with GSM at 900MHz. This frequency was inherited into UMTS, LTE, and 5G NR. Korea, which has never used GSM, runs CDMA on 1800 MHz. See CDMA frequency bands.