In 5G NR (New Radio), the Physical Cell Identity (PCI) is calculated based on the synchronization signals transmitted by the gNB (5G base station). Specifically, the PCI is derived from the Primary Synchronization Signal (PSS) and the Secondary Synchronization Signal (SSS).
Understanding PCI Calculation
The PCI in 5G is a combination of two components:
- N_ID1: Derived from the Secondary Synchronization Signal (SSS).
- N_ID2: Derived from the Primary Synchronization Signal (PSS).
The total PCI value is given by:
PCI=3×NID1+NID2\text{PCI} = 3 \times N_{ID1} + N_{ID2}
Steps for Calculating PCI from SSS and PSS:
- Determine N_ID2 from PSS:
- The PSS is responsible for identifying the N_ID2 value. The PSS can have three possible values (0, 1, 2), corresponding to the three possible sequences for PSS.
- N_ID2 is directly derived from the PSS as follows:
- PSS sequence 0: N_ID2 = 0
- PSS sequence 1: N_ID2 = 1
- PSS sequence 2: N_ID2 = 2
- Determine N_ID1 from SSS:
- The SSS provides the N_ID1 value. There are 336 possible SSS sequences, so N_ID1 can take any value from 0 to 335.
- The SSS sequence is mapped directly to N_ID1.
- Calculate the PCI:
- Combine the N_ID1 and N_ID2 values using the formula:
PCI=3×NID1+NID2\text{PCI} = 3 \times N_{ID1} + N_{ID2}
- Example: If N_ID1 is 150 and N_ID2 is 2, then the PCI would be calculated as:
PCI=3×150+2=450+2=452\text{PCI} = 3 \times 150 + 2 = 450 + 2 = 452
Key Points to Remember:
- PSS helps in coarse synchronization and identifies the N_ID2, which is a number between 0 and 2.
- SSS helps in fine synchronization and identifies the N_ID1, which is a number between 0 and 335.
- The combination of N_ID1 and N_ID2 gives the unique PCI, which ranges from 0 to 1007, providing a unique identity to the cell within the network.
This calculation ensures that each cell in a 5G network can be uniquely identified, enabling devices to connect and communicate effectively.
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