PUSCH

PUSCH is the uplink counterpart to PDSCH — the channel carrying user data from device to network, plus any uplink control information that can't fit on or isn't scheduled for PUCCH. The thing that makes uplink its own engineering problem is power. A handset has a small battery and a modest power amplifier, so the uplink is usually the coverage-limiting direction, and NR gives it two waveforms to cope.

By default PUSCH uses CP-OFDM, the same flexible waveform as downlink. But near the cell edge the network can switch a UE to DFT-s-OFDM (transform precoding), which has a much lower peak-to-average power ratio — that lets the amplifier run closer to its limit without distortion, extending uplink reach at the cost of some spectral flexibility. PUSCH can be scheduled per-grant via DCI, or configured grant-free for latency-sensitive traffic so the UE transmits on pre-allocated resources without asking first. Like PDSCH it carries DMRS and is protected by HARQ.