5G • 5G-Advanced (Rel-18)
Multi-RTT Phase 2
Enhanced Multi-Cell Round-Trip Time Positioning
Measures round-trip time between a terminal and multiple base stations simultaneously, calculating precise 3D position without clock synchronization.
Technical Explanation
Traditional Time Difference of Arrival (TDoA) requires all base stations to maintain sub-nanosecond clock synchronization with each other. Multi-RTT (Round Trip Time) eliminates this requirement: the UE measures Rx-Tx time differences and the base stations measure their own Rx-Tx differences, canceling out clock offsets and delivering robust 3D positioning.
Key Functions
- Calculates 3D spatial coordinates without requiring atomic clock synchronization across towers
- Combines downlink PRS and uplink SRS round-trip transmission timing measurements
- Eliminates clock bias errors between unsynchronized private network base stations
- Delivers resilient 1-meter positioning in challenging indoor and subterranean deployments
Specifications
3GPP TR 38.857, TS 38.215 (Rel-18)
Interfaces
Uu (PRS/SRS)LPP
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