Question: Which of the following uplink physical signals in a 5G New Radio (NR) network is primarily used for channel sounding, to help the base station assess the uplink channel conditions?
Option 1: Demodulation Reference Signals (DM-RS): Used by the UE to aid in demodulating data transmitted on the Physical Uplink Shared Channel (PUSCH).
Option 2: Sounding Reference Signal (SRS): Utilized for measuring the uplink channel state information, enabling the gNodeB to optimize resource allocation and beamforming.
Option 3: Phase-Tracking Reference Signals (PT-RS): Employed to compensate for phase noise in high-reliability, low-latency communications, ensuring coherent demodulation.
Option 4: Uplink Control Information (UCI) Signals: Carrying control data such as ACK/NACK feedback and Channel State Information (CSI) reports.
Explanation: The correct answer is Option 2 because the Sounding Reference Signal (SRS) is specifically designed for channel sounding. It helps the base station (gNodeB) to estimate the uplink channel conditions, which is crucial for link adaptation, beamforming, and resource allocation optimization in 5G NR networks. While DM-RS aids in demodulation of specific uplink transmissions, PT-RS focuses on mitigating phase noise, and UCI Signals carry control information, SRS is uniquely defined for the purpose of channel sounding.