LTE/NR PCI Conflict , PCI Confusion,PCI Collision, Mod of PCIs- 3,4,6,30

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Dear readers as per above snap its easy to say PCI confusion and Collision coming under PCI conflict and reaspective reasons that mentioned in snap .

Each 5G/4G cell corresponds to a Physical Cell ID (PCI) and it is used to distinguish cells on the radio side. The PCI planning for 5G NR is very much similar to PCI planning for LTE and scrambling code planning for 3G UMTS. Bad or wrong planning can affect the synchronization procedure , demodulation, and handover signalling and degrade the network performs. PCI Planning should be simpler for NR compare to LTE because there are double as many PCIs available for allocation

While Planning PCI , below things need to follow strictly 

1. Nbr cell should not have same position of PSS 

2. Nbr Cell can use same SSS position 

3. Intra Cells of an eNB should not have same PCI in same carrier 

As PCI is derived from PSS and SSS so there should not be same position of PSS &SSS combination of cells on their different Antenna Port .

For example for Antenna Port-0 and Port-2 should not have same position of PSS&SSS in their respective frame other-wise their will be PCI conflict type case will arrise instead of different PCI 

In short reference symbol posion of Ports of antennas should not match for their respective frames 

Collision Mod:- Mod of PCIs:-Mod-3,Mod-6,Mod-30 ,Mod-4

These mods are derived from referense signal posion collision and its observed that such cases are 3 in LTE [Mod-3,6,30]and 3 in NR[Mod-3,4,30] 

I am writing reference signal means for LTE - Reference Signal and for NR- DMRS

5G does not have CRS, and it does not need to send “Reference Signal” like 4G, which makes reference signal interference is not applicable. 5G uses DMRS in Broadcast Channel (PBCH)

Mod-3 :- Reference signal/DMRS pattern is same in DL for every 3rd PCI [ Situation arise when Nbr cell every 3rd PCI collides on reference signal in DL ]

Note:- Mod-3 occurs in multiple antenna system , only in DL

Mod-4 :- If neighboring cell use PCI having same Mod 4 value, shall result in DMRS to DMRS interference

PCI Mod-4 rule is based on subs-carrier positions of DMRS for PBCH. The subcarriers are allocated to DMRS using ‘Mod-4’ computation

Note:- Mod-4 occurs in multiple antenna system , only in DL

Mod-6 :- Reference signal pattern is same in DL for every 6th PCI [ Situation arise when Nbr cell every 6th  PCI collides on reference signal in DL ]

Note:- Mod-6 occurs in single antenna system , Only in DL

Mod-30 :- Reference signal/DMRS pattern is same in UL for every 30th PCI [ Situation arise when Nbr cell every 30th PCI collides on reference signal in UL ]

Note:- Mod-30 occurs in multiple antenna system , Only in UL





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