8 Time Slots and TDMA-Frames

3GPP43.052GSM Cordless Telephony System (CTS), Phase 1Lower Layers of the CTS Radio Interface, Stage 2Release 17TS

The time slot organisation is as specified in GSM 05.02 subclause 4.3.1.

The TDMA frames are organised in multiframes, superframes, and hyperframes. The hyperframe is the longest recurrent time period and consists of 26 x 51 x 2048 TDMA frames. The TDMA frames are numbered modulo this hyperframe, which means that the frame number FN ranges from 0 to FN_MAX= (26 x 51 x 2¹¹ ) -1 = 2715647. The CTS-FP keeps track of the frame numbering once initialised.

Two types of multiframes exist in the GSM-CTS system:

– a 26-multiframe with a duration of 120 ms, comprising 26 TDMA frames. This multiframe is used to carry TCH, SACCH, and FACCH (see clause 10);

– a 52-multiframe with a duration of 240 ms, comprising 52 TDMA frames. This multiframe is used to carry CTSBCH, CTSARCH, CTSAGCH and CTSPCH (see clause 10), and is indicated as CTSBCH multiframe.

NOTE: GSM-CTS uses a scheme slightly different from the GSM-based frame structure in that instead of 51‑multiframes, 52-multiframes are used. The reason for this choice is that the bursts of the CTSBCH have a frame distance that coincides with the idle frames of a TCH/F connection; it is therefore possible to support in the CTS-FP a speech connection and the CTSBCH transmission in parallel on the same timeslot, which allows the realisation of the CTS-FP hardware with a state of the art chipset for a GSM‑MS supporting only a single timeslot.