Hi there, Community!
This post brings you more details on the topic of PCI, PSS and SSS conflicts in LTE. Please see below.
Source: https://www.researchgate.net/figure/PCI-conflict-detection-based-on-handover-measurements-The-mobile-reports-a-new-candidate_fig2_4340405
BACKGROUND INFORMATION
There are 2 scenarios where the PCI, PSS or SSS can be conflict.
Scenario 1
The value of PCI is the same. Sector 2 of Site B pointing to the direction of Sector 1 of Site A with the same PCI value (201) and same PSS value (0). Normally when the PCI is the same, the PSS and SSS also will be the same. When this scenario happened UE will have problems to select correct cell, and this will lead to Network Entry failure (RACH failure).
Scenario 2
The value of PCI is different. but the PSS value is the same. See the RED dotted circle. Sector 2 of Site B pointing to the direction of Sector 1 of Site C with different PCI value; 201 and 252, but the PSS value is the same (0). When this scenario happened UE will have problems to select correct cell, and this will lead to Network Entry failure (RACH failure)
SOLUTION
We need to understand the formula of calculating PCI:
PCI = 3xSSS + PSS
How to get the value of PSS from the PCI?
PSS = PCI mod 3
The PCI range from 0 to 503. and SSS range from 0 to 167.
In order to have a proper RF planning, we should avoid to have the same PCI or PSS value as this will lead to Network Entry failure. Below is the correct planning of PCI which don't have PCI or PSS conflict.
SUGGESTIONS
1. Need to do a routine neighbor list audit to ensure there are no PCI or PSS conflicts.
2. The neighbor should be tabulated in the Map view (using Map Info) in either the PCI or PSS value.
