5G • RAN
High Speed Flag
High Speed Configuration for PRACH
Configuration parameter enabling restricted cyclic shift sets for PRACH in high Doppler environments.
Technical Explanation
When highSpeedFlag is set to true (restricted sets Type A or Type B), high Doppler shifts cause frequency-domain offsets that distort cyclic shift detection. The gNodeB configures restricted sets of cyclic shifts that omit shifts vulnerable to Doppler-induced false alarms for velocities up to 500 km/h.
Key Functions
- Selects restricted cyclic shift sets immune to Doppler aliasing
- Prevents false preamble detection at high vehicular speeds
- Essential for high-speed train corridors and railway deployments
Specifications
3GPP TS 38.211
Interfaces
Uu
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