5G • RAN
PRACH Short Formats
Short Preamble Formats (A, B, C series)
Short preamble formats (sequence length 139) spanning 2 to 12 OFDM symbols for micro cells and TDD systems.
Technical Explanation
Short PRACH formats (A1-A3, B1-B4, C0, C2) use a 139-length sequence with SCS matching the data channel (15, 30, 60, or 120 kHz). Spanning just a few OFDM symbols within a single slot, they fit neatly into TDD uplink slots and allow fast beam sweeping across multiple PRACH occasions.
Key Functions
- Fit inside flexible TDD uplink slots without consuming full subframes
- Support multi-beam PRACH sweeping in mmWave and massive MIMO
- Offer sequence length 139 with subcarrier spacing up to 120 kHz
Specifications
3GPP TS 38.211
Interfaces
Uu
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