5A.1 Frame structure

25.2213GPPPhysical channels and mapping of transport channels onto physical channels (TDD)Release 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

The TDMA frame has duration of 10 ms and is divided into 2 sub-frames of 5ms. The frame structure for each sub-frame in the 10ms frame length is the same.

Figure 18B: Structure of the sub-frame for 1.28Mcps TDD option

Time slot#n (n from 0 to 6): the n^th traffic time slot, 864 chips duration;

DwPTS: downlink pilot time slot, 96 chips duration;

UpPTS: uplink pilot time slot, 160 chips duration;

GP: main guard period for TDD operation, 96 chips duration;

In Figure 18B, the total number of traffic time slots for uplink and downlink is 7, and the length for each traffic time slot is 864 chips duration. Among the 7 traffic time slots, time slot#0 is always allocated as downlink while time slot#1 is always allocated as uplink. The time slots for the uplink and the downlink are separated by switching points. Between the downlink time slots and uplink time slots, the special period is the switching point to separate the uplink and downlink. In each sub-frame of 5ms for 1.28Mcps option, there are two switching points (uplink to downlink and vice versa).

Using the above frame structure, the 1.28Mcps TDD option can operate on both symmetric and asymmetric mode by properly configuring the number of downlink and uplink time slots. In any configuration at least one time slot (time slot#0) has to be allocated for the downlink and at least one time slot has to be allocated for the uplink (time slot#1).

In case of entire carrier dedicated to MBSFN, no uplink timeslot is used, and DwPTS, UpPTS and GP(96 chips duration) are combined into one short timeslot, the duration of which is 0.275ms.

In a multi-frequency cell the traffic time slots allocated for uplink and downlink pair(s) for one UE should be on the same carrier.

Examples for symmetric and asymmetric UL/DL allocations are given in figure 18C.

Symmetric DL/UL allocation

Asymmetric DL/UL allocation

Entire carrier dedicated to MBSFN

Figure 18C: 1.28Mcps TDD sub-frame structure examples

Note 1: In a multi-frequency cell, it is suggested the switching point configuration on secondary frequencies to be the same as that on primary frequency.