top button
Flag Notify
    Connect to us
      Site Registration

Site Registration

LTE: Why physical cell identity has been divided into PSS and SSS forms ?

+5 votes
2,210 views

As LTE PCI ranges from 0 to 504, why PCI has been divided into PSS and SSS ?

posted Apr 13, 2014 by Harshita

Share this question
Facebook Share Button Twitter Share Button LinkedIn Share Button

1 Answer

+1 vote

I have not very deep knowledge about it, but still I have something which I would like to share.

In lte, a physical cell can have max 3 sectors, each sector may have either one of the values {0,1,2}.
ZC-sequence is being used for PSS in lte. ZC-sequence has following properties:
1. A ZC sequence has constant amplitude.
2. ZC sequences of any length have ’ideal’ cyclic Auto-Correlation.
3. Two Sequences with M1 and M2 have constant cyclic
Cross-Correlation if M1 is relative prime to M2. Thisvalue achieves the minimum Cross-Correlation for any two sequences with ideal Auto-Correlation.

For PSS, ZC-Roots {29,34,25} are being used due to this 3 root index, PSS has three possible values which are nothing but 0, 1 or 2.

SSS tells about the group id of PCI. PCI = 3 * SSS + PSS.
SSS ranges from 0 to 167.

Please correct me if I am wrong.

answer Apr 15, 2014 by Vimal Kumar Mishra
PCI = 3 * PSS + SSS
commented Jan 9, 2017 by anonymous
Similar Questions
+1 vote
LTE: Why PSS and SSS are placed side by side ?

Why these two are placed side by side within "first time slot" of 0th and 5th sub frame of a radio frame ?
Is it due to any mathematical calculation or something else ?

+2 votes
How can we check the position of PSS and SSS?

I know PSS and SSS will occupy last and penultimate symbol simultaneously in slot#0 and slot#10. How can we ensure they are occupying that positions only? And what is the reason behind those particular positions?

+5 votes
LTE: Detection of PSS and SSS

I understand that according to the standard a 64 FFT is used by the UE for cell search for all Bandwidth configurations(see section 2.2.1 page 7 in the below document). Suppose we are transmitting at 20 MHz which means we do a 2048 FFT on the transmitter side for the whole resource grid, including the 6th and 7th symbols corresponding to PSS and SSS in Subframe 0 and 5. In this case how is it possible for UE to do cell search using 64-FFT. Although PSS and SSS use only the central 62 subcarriers, shouldn't the UE use the same FFT length used in the transmitter side ? Also, how is the DL resource grid processed by the UE ?Does the UE extract Symbols 6,7 of Subframes 0,5 and process it separately with 64-FFT(after low pass filtering) while using 2048 FFT for the rest of the symbols ?

http://cdn.rohde-schwarz.com/dl_downloads/dl_application/application_notes/1ma150/1MA150_0E_cell_searchselection_in_LTE.pdf

...