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Changing short description from "Channel access method for shared medium networks" to "Channel access method for networks using a shared communications medium" (Shortdesc helper) |
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TDMA is a type of [[time-division multiplexing]] (TDM), with the special point that instead of having one [[transmitter]] connected to one [[Receiver (radio)|receiver]], there are multiple transmitters. In the case of the ''[[uplink]]'' from a [[mobile phone]] to a [[base station]] this becomes particularly difficult because the mobile phone can move around and vary the ''timing advance'' required to make its transmission match the gap in transmission from its peers.
The simplest form of TDM/TDMA is fixed allocation TDMA. As the name implies, the M slots that make up each frame are pre-allocated to a long-term signal source. The multiplexing operation consists of providing each source with an opportunity to occupy one or more slots. The demultiplexing operation consists of recovering the signal from the slot or slots in which it is located and delivering the data to the corresponding place.1
Fixed allocation TDM is convenient to use when the source requirements are predictable, and the traffic is very heavy, because in this case, the time slots are almost always full. Because when this is not the case, TDM is not the best way to use the spectrum. If the owner of the slot is not sending data for a certain amount of time, the slot would be wasted.
TDMA is inherently superior to FDMA in the sense that the average delay of each packet using TDMA is less than using FDMA.
== Characteristics ==
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