5G Numerology (SCS)
5G Flexible OFDM Numerology & Subcarrier Spacing
The scalable OFDM subcarrier spacing (15 kHz × 2^μ) that enables 5G to adapt its slot duration and latency to different frequencies and services.
Technical Explanation
Unlike 4G LTE which has a fixed 15 kHz Subcarrier Spacing (SCS) and 1 ms subframe/slot, 5G NR introduces flexible numerology parameterized by μ (mu = 0, 1, 2, 3, 4): • μ=0: 15 kHz SCS, Slot duration 1.0 ms (FR1, Low-band coverage) • μ=1: 30 kHz SCS, Slot duration 0.5 ms (FR1, C-band n78 / Mid-band standard) • μ=2: 60 kHz SCS, Slot duration 0.25 ms (FR1/FR2) • μ=3: 120 kHz SCS, Slot duration 0.125 ms (FR2 mmWave) • μ=4: 240 kHz SCS, Slot duration 0.0625 ms (FR2 SSB Beam Sweeping) As SCS doubles, slot duration halves, enabling low-latency scheduling for URLLC and overcoming phase noise at mmWave.
Key Functions
- Scalable time-frequency grid matching spectrum constraints
- Ultra-short slot durations for sub-millisecond URLLC latency
- Robustness against Doppler spread in high-speed rail and phase noise in mmWave
- Support for mini-slots (non-slot based scheduling) of 2, 4, or 7 symbols