NR Cell Global Identity

In 5G, NR Cell Global Identifier (NCGI) is used to identify NR cells globally and similar to ECGI (EUTRA Cell Global Identifier ) in 4G LTE. The NCGI is constructed from the PLMN ID the cell belongs to and the NR Cell Identity (NCI) of the cell.

NCGI Key Pointers

• The NCI has a total size of 36 bits. These 36 bits are constitute of  gNB Identity (gNB ID) and the Cell Identity (CI)
• NR Cell Identity is broadcasted within SIB#1
• The gNB ID can be configured to use between 22 bits to 32 bits which leaves  14 bits and 4 bits for the CI respectively
• Allocating 22 bits for the gNB Id provides as total gNB ID 2^22=4194305  with a range from 0 to 4194304
  • This range is large enough to support the majority of Network Providers
  • A networks which planes a large numbers of small cells may require a larger gNB ID
  • Identities can be allocated such that from ID one shall be able to identify whether it is a Macro Cell or Small cell  e.g. gNB ID 0 to 50 000 could be used for Macro cells, while 50 001 to 250 000 can be used for Small cells
• By Allocating 22 bits for the gNB ID, 14 bits are left for Cell ID which provides 2^14= 16384 Cell IDs within one gNB with bits a range from 0 to 16383
  • The 16384 Cell IDs shall be large enough for single Base Station will support this number of cells although
  • While using CU/DU architecture for a gNB, no. of cells per gNB can become high  e.g. a single CU may support 250 DU and each DU could support 12 cells
  • While using CU/DU architecture for gNB, the Cell ID planning can be done such that DU information can be retrieve from it e.g. first 4 bits could be used to identify a sector, the next 3 bits could be used to identify the carrier and the remaining 7 bits could be used to identify the DU

NR Cell Global Identity and NR Cell Identity Structure

The NCGL and NCI structures are shown in following figure

•  NR Cell Identity: gNB Identity (gNB ID) + Cell Identity (CI)
  • Length: 36 bits
  • Range: 0 to 68719476735
• Maximum gNB ID – 32 bit
  • Range: 0 to 4294967295
• Minimum gNB ID – 22 bit
  • Range: 0 to 4194303
• Maximum Cell ID – 14 bits
  • Range: 0 to 16383
• Minimum Cell ID – 4 bit
  • Range: 0 to 15

NCGI Calculator

[CP_CALCULATED_FIELDS id=”12″]

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