5G • RAN
SRS for Antenna Switching
SRS for Downlink Channel Sounding via Antenna Switching
SRS configuration enabling UEs with fewer TX than RX chains (e.g. 1T4R, 2T4R) to sound all receive antennas.
Technical Explanation
Many 5G smartphones have 4 receive antennas (4R) but only 1 or 2 transmit chains (1T or 2T). By dynamically switching transmit chains across all antenna ports across successive OFDM symbols, the UE transmits SRS from all 4 antennas, allowing the gNodeB to obtain full 4-port channel reciprocity for downlink 4x4 MIMO beamforming.
Key Functions
- Sounds all 4 receiver antennas on 1T4R and 2T4R mobile devices
- Switches RF chains between antennas within configured guard periods
- Enables full downlink reciprocity-based beamforming for multi-antenna handsets
Specifications
3GPP TS 38.214
Interfaces
Uu
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