Aikavälimultiplexointi

Aikavälimultiplexointi, often abbreviated as TDM (Time Division Multiplexing), is a technique used in telecommunications to allow multiple digital data streams to share a single communication channel. It works by dividing the time available on the channel into discrete slots. Each time slot is assigned to a specific data stream, and that stream can transmit its data during its allocated slot. The process then repeats cyclically, with each stream getting its turn to transmit.

This method is a form of multiplexing, which is the process of combining multiple signals into a single transmission medium. In TDM, the multiplexing is achieved by interleaving bits or bytes from different channels in a time-ordered sequence. When the combined signal reaches the receiving end, a demultiplexer separates the interleaved data back into its original streams, directing each stream to its intended destination.

TDM is widely used in digital telephony systems, such as the synchronous optical networking (SONET) and synchronous digital hierarchy (SDH) standards, as well as in older Time Division Multiple Access (TDMA) cellular systems. Its main advantage is that it can provide guaranteed bandwidth for each channel, as each stream has a dedicated time slot. However, it can be inefficient if some channels do not have data to transmit during their allocated slots, as those slots would be wasted. Variants like statistical time division multiplexing (STDM) aim to improve efficiency by allocating time slots dynamically based on demand.