PCI management is an important aspect as part of radio planning, PCI calculation and planning in 5G is similar to 4g and legacy radio technologies. The main requirements for PCI allocation and planning are to remain collision free and confusion free.
collision free: physical separation between cells using same PCI is great to ensure that a UE should never simultaneously receives same PCI from more than a single cell.
confusion free: physical separation between cells using same PCI is great to avoid ambiguity for the base stations. i.e any cell whose neighbours cant have same PCI which should create confusion for the base stations.
From above image, taken hexagonal cell layout with 3 sector example, PCI mod 3 satisfies between any/all neighbours whereas pci mod 4 satisfied only neighbours belonging to same base station and not with neighbours belonging to different base stations.
