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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.
In reality, only one person is actually using the channel at a specific moment. This is analogous to time-sharing on a large computer server. Frequency-division multiple access (FDMA) provides multiuser access by separating the used frequencies. This is used in GSM to separate cells, which then use TDMA to separate users within the cell.
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.
GSM/UMTS were the most widespread 2G/3G wireless standards worldwide. Most countries used only the GSM family. A few countries, including China, the United States, Canada, Ukraine, Trinidad and Tobago, India, South Korea and Japan, used both standards. 3GPP2 had its last activity in 2013, [2] and the group has been dormant ever since.
Thomas Haug (first GSM president) and Philippe Dupuis (second GSM president) during a GSM meeting in Belgium, April 1992. In 1983, work began to develop a European standard for digital cellular voice telecommunications when the European Conference of Postal and Telecommunications Administrations (CEPT) set up the Groupe Spécial Mobile (GSM) committee and later provided a permanent technical ...
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.
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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.