Zeitmultiplexing

Zeitmultiplexing, or time-division multiplexing (TDM), is a method for transmitting multiple signals over a single transmission medium by dividing time into discrete intervals. Each input signal is assigned a specific time slot within a repeating frame, and the signals are sampled in rapid succession. At the receiving end, a corresponding clock regenerates the timing and reconstructs the original signals.

There are two main forms of TDM. In synchronous (or fixed-slot) TDM, every channel has a predetermined time slot in each frame, even if the channel is idle. This provides predictable framing but can waste bandwidth. In statistical (or asynchronous) TDM, time slots are allocated on demand based on traffic, improving efficiency for bursty data but requiring more complex control and synchronization.

TDM is widely used in digital telecommunications. It underpins traditional multiplexing schemes such as PDH and, in modern networks, contributes to the structure of SDH/SONET transport, where multiple tributary streams are carried in a high-capacity, time-mliced frame. Beyond voice, TDM supports multiplexed data and multimedia streams over fiber and other media. It is often contrasted with frequency-division multiplexing (FDM) and with packet-based approaches, which can offer greater flexibility for irregular data traffic.

Key advantages include straightforward demultiplexing, predictable latency for fixed-slot systems, and efficient use of a shared medium when traffic is steady. Limitations involve potential bandwidth waste in fixed-slot configurations, the need for precise timing and synchronization, and reduced efficiency for highly bursty or highly variable traffic without a statistical or adaptive variant.