 to the SRSs indicated in the SRI. The device should then transmit the precoded signal using the same antenna configuration and mapping that was used for the SRS transmission (indicated by the SRI). The use of multiple SRSs for codebook-based PUSCH transmission assumes that the UE transmits multi-port SRSs over separate and relatively wide beams. These beams may cor- respond to different UE antenna panels with different directions, where each panel includes a set of antenna elements corresponding to the antenna ports of each multi-port SRS (see Fig. 4.89). The SRI received from the network determines which beam should be used for the transmission, while the precoder information (number of layers and preco- der) determines how the transmission should be done within the selected beam. Codebook-based precoding is typically used when uplink/downlink reciprocity cannot be achieved and when uplink measurements are needed in order to determine a suitable uplink precoding [6,9,14]. In contrast to codebook-based precoding, which is based on network measurements and selection of uplink precoder, non-codebook-based precoding is based on device 640 Chapter 4 gNB Indicates to the UE the desired beam direction (SRS gNB Indicates to the UE the desired beam/precoder index), rank, and transmit precoding for the uplink direction and rank (all included in SRS indices) UE transmits multiple SRSs UE transmits multiple SRSs in different beam directions in different beam directions ((HII)) SRS3 / UE transmits as indicated by UE transmits uplink to match the direction of the the gNB indicated SRSs Codebook-based uplink transmission Non-codebook-based uplink transmission Figure 4.89 Codebook-based uplink transmission versus non-codebook-based uplink transmission [69]. measurements and precoder indications to the network. The concept of uplink non- codebook-based precoding is illustrated in Fig. 4.89. Based on downlink measurements con- ducted on configured CSI-RS resources, the UE selects a suitable uplink multi-layer preco- der. Non-cod