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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.
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.
One of the key features of GSM is the Subscriber Identity Module, commonly known as a SIM card. The SIM is a detachable smart card [ 3 ] containing a user's subscription information and phone book. This allows users to retain their information after switching handsets.
For example, one version of the Nokia 6340i GAIT phone sold in North America can operate on GSM-1900, GSM-850 and legacy TDMA-1900, TDMA-800, and AMPS-800, making it both multi-mode and multi-band. As a more recent example the Apple iPhone 5 and iPhone 4S support quad-band GSM at 850/900/1800/1900 MHz, quad-band UMTS/HSDPA/HSUPA at 850/900/1900 ...
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 access method used for IS-54 is Time Division Multiple Access (TDMA), which was the first U.S. digital standard to be developed. It was adopted by the TIA in 1992. TDMA subdivides each of the 30 kHz AMPS channels into three full-rate TDMA channels, each of which is capable of supporting a single voice call.
In 2002, NTT DoCoMo's FOMA 3G network was the first commercial UMTS network – using a pre-release specification, [39] it was initially incompatible with the UMTS standard at the radio level but used standard USIM cards, meaning USIM card based roaming was possible (transferring the USIM card into a UMTS or GSM phone when travelling). Both NTT ...
A card with all 3 features is called a removable user identity card, or R-UIM. Thus, the R-UIM card can be inserted into CDMA, GSM, or UMTS handsets, and will work in all three cases. In 3G networks, it is a mistake to speak of a USIM, CSIM, or SIM card, as all three are applications running on a UICC card.