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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.
TDMA frame structure showing a data stream divided into frames and those frames divided into time slots. Time-division multiple access (TDMA) is a channel access method for shared-medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. [1]
Typical 2G standards include GSM and IS-95 with extensions via GPRS, EDGE and 1xRTT, providing Internet access to users of originally voice centric 2G networks. Both EDGE and 1xRTT are 3G standards, as defined by the ITU , but are usually marketed as 2.9G due to their comparatively low speeds and high delays when compared to true 3G technologies.
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 ...
Time-division multiplexing (TDM) is a method of transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line so that each signal appears on the line only a fraction of time according to agreed rules, e.g. with each transmitter working in turn.
The North American Standards IS-54 and IS-136 were also second-generation (2G) mobile phone systems, known as (Digital AMPS) and used TDMA with three time slots in each 30 kHz channel, supporting 3 digitally compressed calls in the same spectrum as a single analog call in the previous AMPS standard. This was later changed to 6 half rate time ...
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.
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.