TDMA Frame

One TDMA frame includes 8 basic timeslots, and each timeslot is a basic physical channel.

The Physical Channel is a combination of FDMA and TDMA, which is composed of the timeslot streams between the base station (BS) and the mobile station (MS). The positions of these timeslots do not change in different TDMA frames. The above diagram shows the complete structure of the TDMA frame, including the timeslot and burst sequence. It should be remembered that the TDMA frame is the “physical” frame repeated on the radio link.

Every TDMA frame includes 8 timeslots, which seize 60/13≈4.615ms altogether. Every timeslot contains 156.25 bit duration, which seize is 15/26≈0.557ms. Multiple TDMA frames constitute a Multi-frame, which has two types of structures including 26 or 51 coherent TDMA frames respectively. These multiframes should be used when different logical channels are mapping to one physical channel.

The period of the multiframe containing 26 frames is 120ms, which is used in the traffic channel and the associated control channel. In these frames, 24 bursts are used for the traffic and the remaining two are used for the signaling.

The period of the multiframe containing 51 frames is 3060/13≈235.385ms, which is used especially in the control channel.

Multiple multi-frames constitute a Super  frame, which is a coherent 51×26TDMA frames. That is to say, one super frame can contain either 51 26TDMA multi-frames or 26 51TDMA multi-frames. The period of all super frames is 1326 TDMA frames, i.e. 6.12 seconds.

Furthermore, multiple super frames constitute a Hyper  frame, which contains 2048 super frames and its period is 12533.76 seconds, i.e. 3 hours, 28 minutes, 53 seconds and 760 milliseconds. The hyper frame is used in encrypted voice and data. Each period of the hyper frame contains 2715648 TDMA frames, which are numbered in sequence from 0 to 2715647 successively. The frame number is transmitted in the synchronous channel, which is also a necessary parameter in the frequency hopping algorithm.