What is NCGI (NR cell global identifier)

NCGI (NR Cell Global Identifier) Explained Technically

In the context of 5G New Radio (NR) cellular networks, NCGI (NR Cell Global Identifier) serves as a unique identifier for a specific cell within a Public Land Mobile Network (PLMN). It combines two crucial identifiers:

• PLMN-Id (Public Land Mobile Network Identifier): This 3-digit code identifies the mobile network operator (MNO) associated with the cell. It's a combination of the Mobile Country Code (MCC) and Mobile Network Code (MNC).
• NR Cell Identity (NCI): This unique 36-bit identifier differentiates individual NR cells within the same PLMN.

Purpose of NCGI:

• NCGI plays a vital role in enabling communication between user equipment (UE) and the network. It allows UEs to:
  • Identify the serving NR cell during cell discovery and initial network attachment.
  • Synchronize with the network and access downlink control channels for receiving network information and instructions.
  • Differentiate neighboring NR cells for potential handover procedures when moving around the network coverage area.

Benefits of NCGI:

• Unique Cell Identification: NCGI provides a globally unique identifier for NR cells, ensuring unambiguous identification within the vast landscape of cellular networks.
• Simplified Network Management: NCGI facilitates efficient network management by allowing operators to distinguish and manage individual NR cells within their network infrastructure.
• Improved Handover Performance: During handover procedures, NCGI helps UEs seamlessly switch between NR cells while maintaining connectivity with the network.

Comparison with Cell ID in Legacy Networks:

• In legacy cellular networks like 2G and 3G, a Cell ID (typically a 16-bit identifier) served a similar purpose of identifying individual cells.
• NCGI builds upon the concept of Cell ID but offers a more comprehensive and globally unique identifier due to the inclusion of the PLMN-Id. This becomes crucial in the context of 5G, where network densification and potential network slicing scenarios might involve numerous NR cells operating within close proximity.

NR Cell Identity (NCI):

• As mentioned earlier, NCI is a 36-bit code that forms a crucial part of the NCGI. The specific allocation and assignment of NCI values are typically defined by the network operator.
• However, certain network infrastructure vendors might also have a role in NCI assignment depending on the network deployment strategy.

Additional Information:

• NCGI is typically broadcasted on the NR Physical Broadcast Channel (NR-PBCH), allowing UEs to discover and identify nearby NR cells.
• Network messages transmitted on control channels might also reference NCGI to provide cell-specific information to UEs.

Conclusion:

NCGI plays a critical role in 5G NR cellular networks as a unique identifier for NR cells. By combining the PLMN-Id and NCI, NCGI enables UEs to identify the serving network, synchronize with the network, and participate in essential network procedures like cell discovery and handover. As 5G networks continue to evolve, NCGI remains a fundamental element for ensuring seamless and efficient user connectivity.