A method of performing uplink transmission by a user equipment, UE, in a wireless communication system, the method comprising: receiving, from a base station configuration information for a sounding reference signal, SRS, wherein the configuration information includes i) SRS resource information and ii) spatial relation information that specifies a relation between a first SRS and a second SRS that is a reference for spatial beamforming of the first SRS; and transmitting, to the base station the first SRS on a SRS resource indicated by the SRS resource information, wherein the first SRS is transmitted by applying, to the first SRS, a first spatial beamforming that is identical to a second spatial beamforming used for transmission of the second SRS, based on the spatial relation information, wherein the method further comprises: receiving, from the base station downlink control information, DCI, for scheduling uplink transmission, wherein the DCI includes an SRS resource indication, SRI, wherein based on a plurality of SRS resources in an SRS resource set being configured by the SRS resource information, the SRI in the DCI is associated with the SRS resource on which the first SRS is transmitted and characterized in that the method further comprises: determining a bit width of an SRI field carrying the SRI in the DCI, wherein the bit width is determined based on (i) a number of SRS resources in the SRS resource set configured for the UE and (ii) a maximum number of layers supported for the uplink transmission. receiving, from a base station configuration information for a sounding reference signal, SRS, wherein the configuration information includes i) SRS resource information and ii) spatial relation information that specifies a relation between a first SRS and a second SRS that is a reference for spatial beamforming of the first SRS; and transmitting, to the base station the first SRS on a SRS resource indicated by the SRS resource information, wherein the first SRS is transmitted by applying, to the first SRS, a first spatial beamforming that is identical to a second spatial beamforming used for transmission of the second SRS, based on the spatial relation information, wherein the method further comprises: receiving, from the base station downlink control information, DCI, for scheduling uplink transmission, wherein the DCI includes an SRS resource indication, SRI, wherein based on a plurality of SRS resources in an SRS resource set being configured by the SRS resource information, the SRI in the DCI is associated with the SRS resource on which the first SRS is transmitted and characterized in that the method further comprises: determining a bit width of an SRI field carrying the SRI in the DCI, wherein the bit width is determined based on (i) a number of SRS resources in the SRS resource set configured for the UE and (ii) a maximum number of layers supported for the uplink transmission. receiving, from the base station downlink control information, DCI, for scheduling uplink transmission, wherein the DCI includes an SRS resource indication, SRI, wherein based on a plurality of SRS resources in an SRS resource set being configured by the SRS resource information, the SRI in the DCI is associated with the SRS resource on which the first SRS is transmitted and characterized in that the method further comprises: determining a bit width of an SRI field carrying the SRI in the DCI, wherein the bit width is determined based on (i) a number of SRS resources in the SRS resource set configured for the UE and (ii) a maximum number of layers supported for the uplink transmission.