What is the difference between PSS and SSS in 5G NR?

Both live in the SSB but do different jobs. The PSS is one of three length-127 m-sequences and carries N_ID_2 (0, 1 or 2), giving the UE OFDM symbol timing. The SSS is a Gold-like sequence with 336 possibilities and carries N_ID_1 (0–335). The UE detects PSS first to lock timing, then SSS to resolve the cell-ID group.

How is the PCI calculated from PSS and SSS?

The physical cell ID is PCI = 3 × N_ID_1 + N_ID_2. N_ID_2 (0–2) comes from the PSS and N_ID_1 (0–335) from the SSS, so the full range is 0 to 1007 — that is 336 × 3 = 1008 distinct IDs.

What does a 5G UE read from the MIB versus SIB1?

The MIB is a tiny 24-bit message carried in PBCH inside the SSB. It gives the system frame number, the common subcarrier spacing, the k_SSB offset, the DMRS Type-A position and pdcch-ConfigSIB1 — essentially the pointer to where CORESET#0 and the Type0-PDCCH common search space sit. The UE then monitors that search space for a DCI scrambled with SI-RNTI, decodes the PDSCH it points to, and that PDSCH carries SIB1 (PLMN list, cell access info, TAC, cell identity, scheduling for the other SIBs).

Cell Search Visualizer

Watch a 5G UE acquire a cell from scratch — PSS (m-sequence, 3 candidates) then SSS (Gold-like, 336 candidates), PCI computation, PBCH/MIB decoding and finally SIB1 via the Type0-PDCCH common search space. Per 3GPP TS 38.211 §7.4 and TS 38.213 §13.

PCI (0..1007)

N_ID_1

166 (0..335)

N_ID_2

2 (0..2)

SSB time-frequency grid — 4 OFDM symbols × 240 subcarriers (downsampled to 60 cols)

Symbol 0

PSS

Symbol 1

PBCH

Symbol 2

SSS

Symbol 3

PBCH

PSSSSSPBCHDMRS

Step 1 / 5

S1PSS detection

Channel	PSS on symbol 0 of SSB, subcarriers 56..182
Sequence	BPSK-modulated m-sequence of length 127 (TS 38.211 §7.4.2.2)
Generator	x(i+7) = (x(i+4) + x(i)) mod 2; init [1,1,1,0,1,1,0]
Cyclic shift	m = 43·N_ID_2 → m(0)=0, m(1)=43, m(2)=86
Candidates tested	3 (N_ID_2 = 0, 1, 2)
Detection method	Time-domain correlation with all 3 PSS sequences
Output	N_ID_2 = 2

What the UE knows after this step

•N_ID_2 = PCI mod 3
•→ 2
•OFDM symbol boundary locked
•Coarse frequency offset estimated

About 5G initial cell search

When a UE powers on or loses coverage, it performs initial cell search to acquire timing, frequency, the Physical Cell ID (PCI) and the Master Information Block. 5G NR packages these signals into a Synchronization Signal Block (SSB) — 4 OFDM symbols wide and 240 subcarriers (20 PRBs) tall, broadcast periodically (typically every 20 ms) and optionally beam-swept with up to L = 4 / 8 / 64 beams in FR1 / FR2.

The UE first correlates against the 3 possible PSS sequences (m-sequences with cyclic shifts 0, 43 and 86). That yields N_ID_2 and OFDM symbol timing. It then correlates against the 336 possible SSS Gold-like sequences to resolve N_ID_1, giving PCI = 3·N_ID_1 + N_ID_2 . PBCH is decoded next (its DMRS v-shift is PCI mod 4) to extract the 24-bit MIB, which tells the UE where Type0-PDCCH common search space lives so it can go fetch SIB1.

Who uses this visualizer?

RAN developers use it to teach PHY layer bring-up. Field engineers use PSS (mod 3), DMRS (mod 4 / 30) planning insights when debugging interference. Students use it to anchor the abstract TS 38.211 equations to a concrete frame picture.

Related tools

How to use the Cell Search Visualizer

Enter a PCI. Type a physical cell ID from 0 to 1007; the tool immediately splits it into N_ID_1 and N_ID_2.
Look at the SSB grid. See where PSS, SSS, PBCH and the PBCH DMRS land across the 4 OFDM symbols and 240 subcarriers — the DMRS v-shift tracks PCI mod 4.
Walk the five stages. Step from PSS detection to SSS detection, PCI computation, PBCH/MIB decode, and finally SIB1 acquisition.
Check what the UE knows. After each stage, read the side panel listing exactly what timing and identity information the UE has resolved so far.
Try a few PCIs. Change the PCI to watch how the SSS index, DMRS shift and the highlighted resource elements move.

Frequently asked questions

What is the difference between PSS and SSS in 5G NR?: Both live in the SSB but do different jobs. The PSS is one of three length-127 m-sequences and carries N_ID_2 (0, 1 or 2), giving the UE OFDM symbol timing. The SSS is a Gold-like sequence with 336 possibilities and carries N_ID_1 (0–335). The UE detects PSS first to lock timing, then SSS to resolve the cell-ID group.
How is the PCI calculated from PSS and SSS?: The physical cell ID is PCI = 3 × N_ID_1 + N_ID_2. N_ID_2 (0–2) comes from the PSS and N_ID_1 (0–335) from the SSS, so the full range is 0 to 1007 — that is 336 × 3 = 1008 distinct IDs.
What does a 5G UE read from the MIB versus SIB1?: The MIB is a tiny 24-bit message carried in PBCH inside the SSB. It gives the system frame number, the common subcarrier spacing, the k_SSB offset, the DMRS Type-A position and pdcch-ConfigSIB1 — essentially the pointer to where CORESET#0 and the Type0-PDCCH common search space sit. The UE then monitors that search space for a DCI scrambled with SI-RNTI, decodes the PDSCH it points to, and that PDSCH carries SIB1 (PLMN list, cell access info, TAC, cell identity, scheduling for the other SIBs).

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