A UE receives configurations of first and second configured SRS resource sets for non-codebook based transmission. The UE receives DCI containing a first SRI field and a second SRI field. The first SRI field indicates an SRS resource of a first indicated SRS resource set. The second SRI field indicates an SRS resource of a second indicated SRS resource set. A size of the first SRI field is based on a first maximum number of layers, a second maximum number of layers, a third maximum number of layers, a first number of SRS resources in the first indicated SRS resource set, and a second number of SRS resources in the second indicated SRS resource set. A size of the second SRI field is based on the third maximum number of layers and the second number of SRS resources in the second indicated SRS resource set.