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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.
An advanced form is dynamic TDMA (DTDMA), where an assignment of transmitters to time slots varies on each frame. Multi-frequency time-division multiple access (MF-TDMA) combines time and frequency multiple access. As an example, 2G cellular systems are based on a combination of TDMA and FDMA
In theory, CDMA, TDMA and FDMA have exactly the same spectral efficiency but practically, each has its own challenges – power control in the case of CDMA, timing in the case of TDMA, and frequency generation/filtering in the case of FDMA. For a classic example for understanding the fundamental difference of TDMA and CDMA, imagine a cocktail ...
For example, user A and user B both try to access a quiet link at the same time. Since they detect a collision, user A waits for a random time between 0 and 1 time units and so does user B. Let's say user A chooses a lower back-off time. User A then begins to use the link and B allows it to finish sending its frame. If user A still has more to ...
Frequency-division multiple access (FDMA) is a channel access method used in some multiple-access protocols. FDMA allows multiple users to send data through a single communication channel, such as a coaxial cable or microwave beam, by dividing the bandwidth of the channel into separate non-overlapping frequency sub-channels and allocating each sub-channel to a separate user.
Single-carrier FDMA (SC-FDMA) is a frequency-division multiple access scheme. Originally known as Carrier Interferometry , it is also called linearly precoded OFDMA ( LP-OFDMA ). Like other multiple access schemes (TDMA, FDMA, CDMA, OFDMA), it deals with the assignment of multiple users to a shared communication resource.
Multiple links can be created in limited spectrum through FDMA, TDMA, or SDMA. Some advanced forms of transmission multiplexing combine frequency- and time-division approaches like OFDM or CDMA. In cellular telephone communications, the air interface is the radio-frequency portion of the circuit between the cellular phone set or wireless modem ...
MF-TDMA ("Multi-frequency time-division multiple access") is a technology for dynamically sharing bandwidth resources in an over-the-air two-way communications network. See also [ edit ]