GSCN Calculator
Compute Global Synchronization Channel Number (GSCN) to SSB reference frequency per 3GPP TS 38.104 §5.4.3. GSCN is used during initial cell search on 5G NR.
Last verified 2026-04-15 against 3GPP TS 38.104 v18.3.0 §5.4.3 · Release 18
GSCN piecewise raster
| Range | Freq | Formula | GSCN range |
|---|---|---|---|
| A | 0 to 3 GHz | SS_ref = N*1200 + M*50 kHz, M in {1,3,5} | 2 to 7498 |
| B | 3 to 24.25 GHz | SS_ref = 3000 + N*1.44 MHz | 7499 to 22255 |
| C | 24.25 to 100 GHz | SS_ref = 24250.08 + N*17.28 MHz | 22256 to 26639 |
Worked examples
GSCN 7499 -> 3000 MHz (Range B lower bound) GSCN 7500 -> 3000 + 1 * 1.44 = 3001.44 MHz GSCN 22256 -> 24250.08 MHz (Range C lower bound) GSCN 22260 -> 24250.08 + 4 * 17.28 = 24319.2 MHz
GSCN on your Android with HiCellTek
HiCellTek RF Monitor displays the GSCN of every detected 5G NR cell along with SSB index, PCI and the derived SSB frequency.
Frequently asked questions
What is GSCN?
Global Synchronization Channel Number, used by the UE during initial cell search to step through candidate SSB center frequencies. Defined in 3GPP TS 38.104 §5.4.3.
How is GSCN different from NR-ARFCN?
NR-ARFCN addresses any frequency on the raster. GSCN addresses only SSB center frequencies, which are a sparser subset used for initial cell search.
What is the GSCN range?
2 to 26639 across three piecewise ranges covering 0 to 100 GHz.
Do I need GSCN for handover?
No, handover uses NR-ARFCN. GSCN is used for initial cell search only, where the UE does not yet know the carrier frequency.
Why is the raster sparser than NR-ARFCN?
To reduce the UE cell search time. A sparser SSB raster means fewer candidate frequencies to try during initial acquisition.
How does GSCN relate to SSB?
Each GSCN corresponds to the center frequency of a potential SSB (SS/PBCH block). The UE searches these frequencies for PSS and SSS during initial cell selection.