NR also offers new functionality such as non-codebook-based precoding for uplink and uplink beam management. For non-codebook-based precoding, multiple SRS signals (SRS resources) are transmitted by the UE using different precoding. gNB indicates the actual precoding for PUSCH transmission based on SRS measurements through signaling of the indices of the selected SRS resources (SRS resource index- SRI). For SRS used for beam management, the actual beam indication for PUSCH and PUCCH transmission is also accomplished by similar principles using SRI. Unlike LTE, the physical resource used for SRS in NR is configured in a UE-specific man- ner. In the time domain, SRS can be transmitted using one, two, or four OFDM symbols, which can be located in the last six symbols of a slot. Multiple SRS symbols can be utilized at the gNB to support uplink beam management or to provide coverage extension by coherent processing of multiple SRS symbol transmission. Similar to other reference signals in NR, SRS support periodic, semi-persistent, and ape- riodic transmission, where semi-persistent SRSs are transmitted based on MAC activation command. 3.5.8 Beam Management mmWave bands offer significantly more spectrum than the conventional sub-6 GHz bands currently used by LTE/LTE-A cellular systems and therefore the mmWave spectrum is con- sidered as a key enabler of multi-Gbps data rates for the NR system in certain deployment 3.5 NR Physical Layer Figure 3.5.16 Beam measurement and Beamformed reporting. Reference signal # 1 Beamformed Reference signal # 2 Beamformed Reference signal # K Beam measurements and reporting Index of the preferred reference signal (beam), beam quality scenarios. Such a spectrum, however, makes propagation conditions more severe than at the conventional lower frequencies. In particular, signals in the mmWave spectrum are subject to higher attenuation due to outdoor-to-indoor penetration losses, blockage, oxy- gen absorption, etc. To compensate for these impairments, highly directional multi-antenna transm