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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.
Most 2G cellular systems, with the notable exception of IS-95, are based on TDMA. GSM, D-AMPS, PDC, iDEN, and PHS are examples of TDMA cellular systems.. In the GSM system, the synchronization of the mobile phones is achieved by sending timing advance commands from the base station which instruct the mobile phone to transmit earlier and by how much.
LTE (Long Term Evolution) is commonly marketed as 4G LTE, but it did not initially meet the technical criteria of a 4G wireless service, as specified in the 3GPP Release 8 and 9 document series for LTE Advanced. Given the competitive pressures of WiMAX and its evolution with Advanced new releases, it has become synonymous with 4G. It was first ...
The Universal Mobile Telecommunications System (UMTS) is a 3G mobile cellular system for networks based on the GSM standard. [1] 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.
With the introduction of digital transmission in TDMA-based systems like GSM, CSD provided almost direct access to the underlying digital signal, allowing for higher speeds. At the same time, the speech-oriented audio compression used in GSM actually meant that data rates using a traditional modem connected to the phone would have been even ...
The Qualcomm standard IS-95, marketed as cdmaOne. The Qualcomm standard IS-2000, known as CDMA2000, is used by several mobile phone companies, including the Globalstar network. [nb 1] The UMTS 3G mobile phone standard, which uses W-CDMA. [nb 2] CDMA has been used in the OmniTRACS satellite system for transportation logistics.
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 ...