5G NR Cell Global Identity (NCGI) Planning and Calculations

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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

Diagram show the Structure of NR Cell Global ID is made of PLMN , gNB ID and Cell ID

  •  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

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