PSS (Primiary Synchronization Signal)

PSS is a specific physical layer signal that is used for radio frame synchronization. It has characterstics as listed below.

• Mapped to 127 active sub carriers around the center of SSB block located at subcarrier 56~182 (Refer to the structure of SSB)
• Placed at the first OFDM symbol (symbol 0) within a SSB Burst
• Made up of 127 m-Sequence Values
• Used for Downlink Frame Synchronization
• One of the critical factors determining Physical Cell ID

Comparision to LTE PSS

Following is the PSS sequence generation formula for NR PSS and LTE PSS. As you see here, NR PSS is a kind of m-Sequence whereas LTE PSS is a kind of Zadoff-chu sequence.

Sequence Generation Algorithm

NR PSS sequence is generated by the following formula. Unless you are the one who need to implement this, you may not need to understand every details of this formula. But at least it would be good to know of the major factors to determine the sequence. Followings are some highlights about this sequence.

• The sequence is determined by NID(2) as in LTE.

Reference

[1] 38.211 NR;Physical channels and modulation(Release 15)