Convert between 5G NR GSCN values and SSB center frequencies. Find the Synchronization Signal Block (SSB) frequency for any GSCN per 3GPP TS 38.104.
GSCN → SSB Frequency
SSB Center Frequency (MHz)
Frequency Range
NR-ARFCN of SSB center
Frequency → GSCN
Nearest valid GSCN
Exact SSB frequency (MHz)
Frequency Range
GSCN Reference Table (3GPP TS 38.104)
Range
GSCN
Formula
Step
0–3 GHz
2–7498
N×1200 + M×50 kHz (M=1,3,5)
~1.2 MHz
3–24.25 GHz
7499–22255
3000 MHz + N×1.44 MHz
1.44 MHz
24.25–100 GHz
22256–26639
24250.08 + N×17.28 MHz
17.28 MHz
Frequently Asked Questions
What is GSCN in 5G NR?
GSCN (Global Synchronization Channel Number) is a number used in 5G NR to identify the center frequency of a Synchronization Signal Block (SSB). Defined in 3GPP TS 38.104, GSCN values range from 2 to 26,639 and map to specific SSB center frequencies. Unlike NR-ARFCN, GSCN uses a coarser raster tuned for efficient SSB scanning during cell search.
Why does 5G NR use GSCN instead of a fixed raster?
5G NR uses GSCN for SSB placement to reduce the time a UE spends scanning for synchronization signals. While data channels use a fine frequency raster (NR-ARFCN), SSBs use a coarser synchronization raster (GSCN) with larger steps — roughly 1.2 MHz in sub-3 GHz, 1.44 MHz in 3–24.25 GHz, and 17.28 MHz in mmWave. This drastically reduces the number of candidate frequencies a device must check during initial cell search.
What is the SSB (Synchronization Signal Block)?
The SSB (Synchronization Signal Block) is a 5G NR signal block that carries the Primary Synchronization Signal (PSS), Secondary Synchronization Signal (SSS), and Physical Broadcast Channel (PBCH). It is periodically transmitted by gNBs and used by UEs to synchronize to the network and decode system information. The SSB center frequency is identified by the GSCN value.