LTE: TDD Timing Calculator

Uplink/Downlink Config  0 1 2 3 4 5 6                          ttiBundling                        

pdschSF       dci0SF       phichSF        puschSF      ulIndex      Iphich
0 1 2 3 4 5 6 7 8 9           0 1 2 3 4 5 6 7 8 9           0 1 2 3 4 5 6 7 8 9           0 1 2 3 4 5 6 7 8 9           01 10 11           0 1

Select type Display_UL_DL_Configuration Uplink_AckNack_SF PUSCH_for_DCI0 PUSCH_for_PHICH PHICH_SF        

There have been many requests to post some sort of timing calculator for TDD. With TDD, it is often troublesome to refer to multiple tables from different specifications to calculate the subframe in which a specific procedure happens, for instance, the uplink HARQ-ACK timing.

I tried to include the most important timing calculations as of now. I will work to enhance this tool further when I find time.

How this tool works?

The intended purpose or the functionality needs to be selected first (from “Select Type” drop-down). It is mandatory to select UL/DL Configuration for any type of calculation. The purpose of each type of calculation is explained below.

Display_UL_DL_Configuration:

This option just displays uplink/downlink subframe configuration and Downlink-to-Uplink switch-point periodicity from Table 4.2-2 of 3GPP TS 36.211.

Uplink_AckNack_SF:

This option is to calculate the subframe in which HARQ feedback is transmitted in the uplink upon detection of a PDSCH transmission or a PDCCH indicating SPS release in the subframe which is selected from the drop-down labelled as “pdschSF”.

The timing is calculated from Table 10.1.3.1-1 in 3GPP TS 36.213.

PUSCH_for_DCI0:

The purpose here is to calculate the subframe in which PUSCH is transmitted upon detection of PDCCH with uplink DCI format in the subframe which is selected from the drop-down labelled as “dci0SF”.

The timing of PUSCH is calculated from Table 8-2 in 3GPP TS 36.213. For UL/DL Configuration 0, the timing also depends on UL Index received in the corresponding DCI which is selected from the drop-down labelled as “ulIndex”.

In case if TTI Bundling is used, the indicated PUSCH subframe is the first subframe in the bundle.

PUSCH_for_PHICH:

The purpose here is to calculate the subframe in which PUSCH is transmitted upon detection of PHICH in the subframe which is selected from the drop-down labelled as “phichSF”.

In case if TTI bundling is not used, the timing of PUSCH is calculated from Table 8-2 in 3GPP TS 36.213.

In case if TTI Bundling is used, the calculations are done using Table 8-2 and Table 8-2a in 3GPP TS 36.213. The indicated PUSCH subframe is the first subframe in the bundle.

For UL/DL Configuration 0, the timing of PUSCH also depends on I_PHICH value which is selected from the drop-down labelled as “Iphich”.

PHICH_SF:

This option is to calculate the subframe in which HARQ feedback is received (on PHICH) for PUSCH transmission in the subframe which is selected from the drop-down labelled as “puschSF”.

When TTI Bundling is used, select puschSF such that it is the last subframe in the PUSCH bundle.

The timing is calculated from Table 9.1.2-1 in 3GPP TS 36.213 but it is same as using Table 8.3-1 and I_PHICH.

Reference: 3GPP TS 36.211 and 3GPP TS 36.213