14.9s Downlink power control

25.3313GPPProtocol specificationRadio Resource Control (RRC)Release 17TS

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

14.9.1 Generalities

This function is implemented in the UE in order to set the SIR target value on each CCTrCH used for the downlink power control. This SIR value shall be adjusted according to an autonomous function in the UE in order to achieve the same measured quality as the quality target set by UTRAN. The quality target is set as the transport channel BLER value for each transport channel as signalled by UTRAN.

When transport channel BLER is used the UE shall run a quality target control loop such that the quality requirement is met for each transport channel, which has been assigned a BLER target.

The UE shall set the SIR target when the physical channel has been set up or reconfigured. It shall not increase the SIR target value before the power control has converged on the current value. The UE may estimate whether the power control has converged on the current value, by comparing the averaged measured SIR to the SIR target value.

NOTE: The power control function for F-DPCH is specified in [29].

14.9.2 Downlink power control in compressed mode

In compressed mode, the target SIR needs to be changed in several frames compared to normal mode. For this purpose, four values DeltaSIR1, DeltaSIRafter1, DeltaSIR2 and DeltaSIRafter2 are signalled by the UTRAN to the UE (see subclause 10.3.6.33).

For each frame, the target SIR offset during compressed mode, compared to normal mode is:

SIR = max (SIR1_compression, … , SIRn_compression) + SIR1_coding + SIR2_coding

where n is the number of TTI lengths for all TrChs of the CCTrCh, F_iis the length in number of frames of the i-th TTI and where SIR_coding fulfils:

– SIR1_coding= DeltaSIR1 if the start of the first transmission gap in the transmission gap pattern is within the current frame.

– SIR1_coding= DeltaSIRafter1 if the current frame just follows a frame containing the start of the first transmission gap in the transmission gap pattern.

– SIR2_coding= DeltaSIR2 if the start of the second transmission gap in the transmission gap pattern is within the current frame.

– SIR2_coding= DeltaSIRafter2 if the current frame just follows a frame containing the start of the second transmission gap in the transmission gap pattern.

– SIR1_coding= 0 and SIR2_coding= 0 otherwise.

and SIRi_compression is defined by :

– SIRi_compression = 3 dB for downlink frames compressed by reducing the spreading factor by 2.

– SIRi_compression = 0 dB in all other cases.

Several compressed mode patterns applying to the same frames should be avoided as much as possible.

In case several compressed mode patterns are used simultaneously, a SIR offset is computed for each compressed mode pattern and the sum of all SIR offsets is applied to the frame.