Hello All.
Why there is only 504 PCIs in LTE?
Admin note: this post was updated with image below.
1 Like
This can help:
Depends how deep you want to look.
Each primary and secondary sync signal is a sequence, these are orthogonal and with certain length you can create only certain number of orthogonal sequences.
Primary are only 3, because UE has to scan for these on all possible frequencies which is time demanding if you would have many, once sync signal location is found by PSS the SSS can have way more sequences to run correlation to.
There is a relationship between length of sync signal and probability of successful decoding in particular SNR.
So as always an engineer trade off 
these decisions are documented in 3GPP papers.
Thank you all. But my question is why only 504 PCIs?
Why it’s not 505, 506…?
Why only 167 SSS & 0, 1, 2 PSS?
It was standard of design to limited.
When we will code or implemented a for particular they should limited.
When can identify with easy.
Orthogonality in regards of Zadoff-Chu sequence also took place.
It is more effective than previous UMTS’ Walsh codes.
Long story short: 3gpp says so 
1 Like