PCI Planner (mod 3, mod 6, mod 30)
Avoid PCI collisions and confusion between neighbouring cells.
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PCI Planner (mod 3, mod 6, mod 30) by TheCalcTools
How the PCI Planner (mod 3, mod 6, mod 30) works
Choose LTE or NR and enter the PCIs of two neighbouring cells.
PCI = 3 × (SSS group) + PSS ID, so PCI mod 3 gives the primary synchronisation sequence and PCI ÷ 3 the secondary group.
Neighbours should avoid the same mod 3 (LTE RS/PSS), mod 6 (LTE CRS frequency shift on 1 antenna port) and mod 30 (UL reference signal group).
The formula
Worked example
Using the default values shown in the calculator:
| Technology | LTE (PCI 0–503) |
|---|---|
| PCI of cell A | 120 |
| PCI of cell B (neighbour) | 123 |
- PCI 120: PSS ID = 0, SSS group = 40, mod 6 = 0, mod 30 = 0.
- Cell B has PCI 123, so mod 3 is also 0. Result: mod 3 conflict (same PSS): risk of PSS/RS interference.
Result:
| Cell A: PSS ID (PCI mod 3) | 0 |
|---|---|
| Cell A: SSS group (PCI ÷ 3) | 40 |
| Cell A: PCI mod 6 | 0 |
| Cell A: PCI mod 30 | 0 |
| Conflict between A and B | mod 3 conflict (same PSS): risk of PSS/RS interference |
Frequently asked questions
Collision or confusion?
Collision: two neighbours share a PCI on the same frequency. Confusion: a cell has two neighbours with the same PCI, so handover targets are ambiguous. Both break handover.
Is mod 30 still relevant in NR?
NR uses different uplink reference signal rules, but many operators still keep mod-3 separation for SSB interference reasons. Follow your vendor’s PCI planning guide.
Sources and further reading
- 3GPP TS 36.211 / 36.213 / 36.101 (LTE)
- 3GPP TS 38.104: NR base station radio transmission and reception
- Wikipedia: Physical Cell ID
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