Difference between SRS Tx port switching: 1T2R and 1T4R

Hainm · July 24, 2021, 3:00am

Hi Experts.
Sharing difference between SRS Tx port switching: 1T2R and 1T4R.

UE in b3+n78: support 1T4R, UE will be allocated 04 SRS resources in 02 slots, 7 & 17
UE in b3+n41: support 1T2R, UE will be allocated 02 SRS resources in same slot

Indraparin · August 4, 2021, 12:21pm

Thanks for sharing @Hainm !
What are the impact on performance?

Hainm · August 4, 2021, 12:22pm

1T4R is better, UE may be scheduled more layers than 1T2R.

Indraparin · August 4, 2021, 12:23pm

I think DL layer depends on maxNumberMIMO-LayersPDSCH, this srs switching I think more related to SRS beam weighting.

RFSpecialist · August 4, 2021, 12:23pm

SRS 1T4R or 1T2R are well explained here:

SRS are transmitted from 4 RX antenna.

Hainm · August 4, 2021, 12:24pm

SRS beam weight of 1T4R has better than 1T2R, so gnb easier to allocate more layers to UE.

From this site examples, 1T2R has 02 SRS resource, 1T4R has 04 SRS resources.

Same as seen in Probe.

RFSpecialist · August 4, 2021, 12:25pm

With 1T2R there cannot be 4 MIMO layers, just 2.

ankgitm · August 4, 2021, 12:25pm

SRS used for AoA calculation as well and assignment of weights to Antenna elements.