What is GSCN in 5G?

Hi experts, what is GSCN in 5G?
Explanation please. Thanks.

Hi @Yasik_Ali.
It is “Global Synchronization Raster Channel” like ARFCN but it gives a range of freq to UE for initial search.

Requirement to configure 2 center frequencies for each 5G cell.
New Radio Absolute Radio Frequency Channel Number (NR-ARFCN).
Global Synchronisation Channel Number (GSCN).
NR-ARFCN is applicable to the channel bandwidth.
GSCN is applicable to the Synchronisation Signals / PBCH Block.
NR-ARFCN uses a fine raster to provide flexibility.
GSCN uses a coarse raster to reduce cell search times.
Requirement to know the selected SS/PBCH frequency in terms of both GSCN and ARFCN numbering.
3GPP has specified a ‘Global Frequency Raster’ for the NR-ARFCN
Each operating band uses a subset of the carriers belonging to the ‘Global Frequency Raster’
The ‘Global Frequency Raster’ has a resolution which depends upon the frequency range

image

The position of the SS/PBCH within the channel bandwidth can be configured
unlike 4G which always broadcasts the PBCH in the center of the channel.
The GSCN must be selected to ensure:
SS/PBCH is fully accommodated within the channel bandwidth.
subcarrier alignment is achieved between the SS/PBCH Block and the channel.
Hope this helps…

The raster step size for the GSCN depends upon the frequency range
1.2 MHz @ freq < 3 GHz
1.44 MHz @ freq > 3 GHz, < 24.25 GHz
17.28 MHz @ freq > 24.25 GHz

In LTE synchronization signals are transmitted at centre of carrier. But in NR, that is not the case. Here Synchronization signals (PSS+SSS+MIB) is transmitted at GSCN. The GSN specifies frequency range where UE searches for SS Block. The SS Block may be transmitted at other frequencies which are not included in GSCN. This can be done for NSA case.