5G NR GSCN Calculator
Convert between Global Synchronization Channel Number (GSCN) and frequency for 5G NR SSB.
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Specifications
GSCN frequency mapping as defined by 3GPP protocols for SSB identification.
Runtime Log
Compliance Reference
TS 38.104 Compliance Suite
Derived from standard frequency mapping rules. This calculation module follows the 3GPP Technical Specifications Revision 17. Ensure to verify with local spectral regulations for regional deviations.
What is GSCN in 5G NR?
The Global Synchronization Channel Number (GSCN) is a signaling index used by 5G NR to identify the frequency of the SS/PBCH block (SSB). Unlike LTE, where the UE scans the entire frequency raster, 5G NR uses a coarser Synchronization Raster to speed up the cell search process.
GSCN values are defined across different frequency ranges (FR1 and FR2) with different granularities, ensuring that the User Equipment (UE) can quickly find the synchronization signal without exhaustive scanning.
Key Differences: GSCN vs ARFCN
- ARFCN:Used for the general Channel Raster. It defines the center frequency of the entire carrier.
- GSCN:Used specifically for the Synchronization Raster. it defines the center frequency of the SSB.
3GPP Technical Formulas
N = 1 to 2499, M ∈ {1, 3, 5}. Step size: 1.2 MHz.
Frequency = 3000 + N × 1.44 MHz. Step size: 1.44 MHz.
Frequency = 24250.08 + N × 17.28 MHz. Step size: 17.28 MHz.
Frequently Asked Questions
What is the range of GSCN values in 5G?
GSCN values range from 2 to 7498 for frequencies below 3 GHz, 7499 to 22255 for frequencies between 3 GHz and 24.25 GHz, and 22256 to 26639 for FR2 (mmWave) frequencies.
Why does 5G use GSCN instead of ARFCN for cell search?
Searching every ARFCN position would be extremely slow due to the fine channel raster (15/30/60 kHz). GSCN provides a much coarser 'Synchronization Raster', allowing the UE to find the SSB much faster during initial access.
Is GSCN the same for all bandwidths?
The GSCN identifies the SSB position, which always has a fixed bandwidth of 20 Resource Blocks (RBs). Regardless of the total carrier bandwidth (e.g., 20MHz or 100MHz), the GSCN points to the center of this 20 RB block.