NR-Primary Synchronization Signal (PSS)
5G-NR Primary Synchronization Signal (PSS) is Physical Layer specific signal and help UE to get Radio Frame Boundary. It is type of an m-Sequence which is a special type of LFSR (Linear Feedback Shift Register) sequence provides the longest non-repeating sequence.
NR-PSS has following characteristics
- NR-PSS a m-Sequence made up of 127 Values
- PSS is mapped to 127 active sub carriers around the lower end of the system bandwidth
- It is used by UE for Downlink Frame Synchronization and provides Radio Frame Boundary i.e. Position of 1st Symbol in a Radio frame
- It is a critical factors determining Physical Layer Cell ID and provides N (2) ID value for calculation
PSS Sequence Generation:
As per the 3GPP TS 38.211 PSS Sequence is represented by d PSS (n) and it is determined by N (2) ID. It can be generated using following equation.
While comparing the NR PSS sequence with LTE PSS sequence, the major difference is the type of sequence used for generation. LTE PSS is use Zadoff-Chu sequence while NR PSS use m-Sequence. Below is the comparison for both NR PSS and LTE PSS generation equation.
Another difference is the LTE PSS is mapped to center 72 sub-carriers whereas NR PSS is mapped to 127 active sub-carriers.