ing Scheme (MCS). PTRS is sparse in frequency and exists for one subcarrier every second or every fourth PRB depending on the scheduled BW. PTRS is not presented at low scheduled MCSs and bandwidths or for random access, System Information (SI), and paging messages. In this section, we've covered the downlink physical channels, PDCCH, PDSCH, and some of their aspects, together with the downlink physical channels such as CSI-RS, TRS, and PTRS. In the next section, we will cover the physical channels and signals in the uplink. Uplink physical channels and signals Uplink physical channels and signals Now, let's have a look at the physical uplink channels and signals. In previous chapters, we covered the PRACH and Sounding Reference Signals (SRS). In this section, we will learn the physical uplink control and data channels, and signals such as the Physical Uplink Shared Channel (PUSCH), PUSCH Demodulation Reference Signal (DMRS), and Physical Uplink Control Channel (PUCCH). Let's start with the PUSCH. The PUSCH The PUSCH carries data and also optionally Uplink Control Information (UCI). As we described before in previous chapters, the uplink waveform can be either Cyclic Prefix OFDM (CP-OFDM) or Discrete Fourier Transform-Spread-OFDM (DFT-s-OFDM). The waveform to be used is signaled to the device by the network. DFT-s-OFDM is only used for single-layer transmissions, and it is intended for power-limited scenarios. This waveform also supports intra-slot frequency hopping for more diversity. As in the downlink case, PUSCH mapping is done in the same order as in LTE; first, across the layers associated with the codeword, then across the subcarriers, and, finally, across the OFDM symbols. The PUSCH uses the same modulation as the downlink with the exception that Binary Phase Shift Keying (pi/2-BPSK) can be employed for DFT-s-OFDM. The intention is to provide more Peak-to- Average Power Ratio (PAPR) gain for the waveform. The uplink transmission can be either codebook-based or non-codebook-based, and the transmission can 