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5G NR PUCCH Resource Grid Visualizer 

This tool visualizes the Physical Uplink Control Channel (PUCCH) resource allocation in 5G NR. The grid shows how UCI (Uplink Control Information) and DMRS (Demodulation Reference Signal) occupy Resource Elements (REs) across OFDM symbols and subcarriers. A constellation plot (top-right) shows the modulation per format: Format 0 displays 12 cyclic-shift phase states; Formats 1–4 show UCI and DMRS constellation points. Hover over an RE to see its value overlaid as a vector on the constellation.

PUCCH Formats

Format 0 (Short): Sequence-based, 1–2 symbols. No QAM modulation; information is encoded via cyclic shift of a base sequence (12 possible phases). initialCyclicShift selects the cyclic shift. Intra-slot frequency hopping supported when nrofSymbols=2 (TS 38.211 §6.3.2.3.2).

Format 1 (Long): 4–14 symbols. TDM: DMRS and UCI strictly alternate — even-indexed symbols within the allocation are DMRS, odd-indexed are UCI (TS 38.211 Table 6.3.2.4.1-1). additionalDMRS (nrofSymbols≥5) doubles DMRS density to consecutive pairs every 4 symbols.

Format 2 (Short): 1–2 symbols. FDM: DMRS and UCI occupy the same symbol but different subcarriers (every 3rd subcarrier is DMRS, TS 38.211 §6.3.2.5). UCI and DMRS use QPSK. additionalDMRS is not applicable to Format 2.

Format 3 (Long): 4–14 symbols, multiple PRBs. TDM: DMRS positions are defined by a fixed lookup per nrofSymbols (TS 38.211 Table 6.3.2.6.1-1). additionalDMRS selects a denser pattern (Table 6.3.2.6.1-2). UCI: π/2-BPSK or QPSK; DMRS: low-PAPR sequence.

Format 4 (Long): 4–14 symbols, 1 PRB only, with Pre-DFT OCC (Orthogonal Cover Code). DMRS uses the same TDM lookup as Format 3 (TS 38.211 §6.3.2.7). UCI: π/2-BPSK or QPSK; DMRS: low-PAPR sequence.

Intra-slot frequency hopping: When enabled, the first half of the symbols use one PRB and the second half “hop” to another PRB for diversity. Applicable to all formats (Format 0 requires nrofSymbols=2).

Constellation
25
0
2
12
2
0
1
UCI DMRS Active PRB Dashed border = intra-slot 2nd hop Inter-slot: even slots → Start PRB, odd → 2nd Hop PRB
PUCCH Format 1: Time-domain OCC spreading. NSF from Table 6.3.2.4.1-1; wi(m)=ej2πφ(m)/NSF from Table 6.3.2.4.1-2.
38.211 Table 6.3.2.4.1-1: NSF (Spreading Factor)
PUCCH lengthNo intra-slot hopIntra-slot hop m'=0Intra-slot hop m'=1
4211
5211
6312
7312
8422
9422
10523
11523
12633
13633
14734
38.211 Table 6.3.2.4.1-2: φ(m) for wi(m)=ej2πφ(m)/NSF
NSFi=0i=1i=2i=3i=4i=5i=6
1[0]——————
2[0,0][0,1]—————
3[0,0,0][0,1,2][0,2,1]————
4[0,0,0,0][0,2,0,2][0,0,2,2][0,2,2,0]———
5[0,0,0,0,0][0,1,2,3,4][0,2,4,1,3][0,3,1,4,2][0,4,3,2,1]——
6[0,0,0,0,0,0][0,1,2,3,4,5][0,2,4,0,2,4][0,3,0,3,0,3][0,4,2,0,4,2][0,5,4,3,2,1]—
7[0,0,0,0,0,0,0][0,1,2,3,4,5,6][0,2,4,6,1,3,5][0,3,6,2,5,1,4][0,4,1,5,2,6,3][0,5,3,1,6,4,2][0,6,5,4,3,2,1]
PUCCH Format 4: Pre-DFT OCC. Orthogonal sequences wn(m) per 38.211 Tables 6.3.2.6.3-1/2. n = occ-Index (PUCCH-format4.occ-Index in RRC).
38.211 Table 6.3.2.6.3-1: wn(m) when NSFPUCCH,4=2
nwn
0[+1,+1,+1,+1,+1,+1,+1,+1,+1,+1,+1,+1]
1[+1,+1,+1,+1,+1,+1,-1,-1,-1,-1,-1,-1]
38.211 Table 6.3.2.6.3-2: wn(m) when NSFPUCCH,4=4
nwn
0[+1,+1,+1,+1,+1,+1,+1,+1,+1,+1,+1,+1]
1[+1,+1,+1,-1,-1,-1,-1,-1,-1,+j,+j,+j]
2[+1,+1,+1,-1,-1,-1,+1,+1,+1,-1,-1,-1]
3[+1,+1,+1,+j,+j,+j,-1,-1,-1,-j,-j,-j]
PUCCH Format 0: m0 = initialCyclicShift. Payload Size selects 1-bit or 2-bit table (independent of Nr Symbols). HARQ-ACK determines mCS per 38.213 Tables 9.2.3-3/4.
mCS = 0; Total = m0+mCS = 0
38.213 Table 9.2.3-3: Mapping for one HARQ-ACK information bit
HARQ-ACK ValueSequence cyclic shift
0mCS = 0
1mCS = 6
38.213 Table 9.2.3-4: Mapping for two HARQ-ACK information bits
HARQ-ACK ValueSequence cyclic shift
{0, 0}mCS = 0
{0, 1}mCS = 3
{1, 1}mCS = 6
{1, 0}mCS = 9

 

Usage

Format: Select PUCCH Format 0–4. The parameter panel shows only relevant inputs for that format.

Parameters: No of PRB for CBW sets the channel bandwidth (24–273 PRBs). Start PRB / 2nd Hop PRB set the PRB index for the first and second hop. Start Sym (0–13 for Format 0/2, 0–10 for Format 1/3/4), Nr Symbols (1–2 for short, 4–14 for long), Init Cyclic (Format 0/1), Nr PRBs (Format 2/3 only; Format 4 is fixed at 1 PRB), Time OCC 0–6 (Format 1), OCC Length/Index (Format 4). Intra-slot Freq Hop / Inter-slot Freq Hop, Add DMRS, π/2 BPSK, Simul HARQ+CSI, Nr Slots (2/4/8 for Format 1–4).

Grid: X-axis = OFDM symbols (0–13), Y-axis = subcarriers. Blue = UCI, Red = DMRS. When Nr Slots > 1, a Multi-Slot Timeline shows mini-grids side-by-side: same template per slot, but Inter-slot Freq Hop swaps the PRB (even slots = Start PRB, odd = 2nd Hop PRB). Dashed border = intra-slot 2nd hop.

Constellation: Format-specific I/Q plot. Format 0: 12 points on a circle (cyclic shifts). Payload Size (1 or 2 bits) selects which HARQ table applies, independent of Nr Symbols. Phase = α⋅n per TS 38.211 (subcarrier n multiplies cyclic shift). Hover over an RE to see its value as a yellow vector. For Formats 3/4 with π/2-BPSK, click a symbol in the grid to switch which symbol’s constellation (even/odd) is shown.

Key Concepts

  • FDM (Format 2): DMRS and UCI share the same symbol on different subcarriers (every 3rd subcarrier is DMRS). Both use QPSK. No additionalDMRS.
  • TDM alternating (Format 1): Even-indexed symbols within the allocation are DMRS; odd-indexed are UCI. additionalDMRS pairs consecutive DMRS symbols.
  • TDM lookup (Formats 3, 4): DMRS positions are fixed per nrofSymbols from TS 38.211 Table 6.3.2.6.1-1/2, not a simple alternating pattern.
  • Format 4 (1 PRB): Format 4 is strictly limited to 1 PRB. Pre-DFT OCC allows multiple users to share the same REs via orthogonal cover codes.
  • Intra-slot hopping: First half of symbols at one PRB, second half at another for frequency diversity.
  • Inter-slot hopping: With Nr Slots > 1, even slots use Start PRB, odd slots use 2nd Hop PRB. The side-by-side timeline shows the same "stamp" (shape) with frequency agility. Multi-slot repetition accumulates energy for cell-edge UEs.

Multi-Slot: Same vs. Different

FeatureSame across Slots?Notes
Num SymbolsYesDefined by nrofSymbols
Start SymbolYesDefined by startingSymbolIndex
PRB IndexNoSwaps between Start PRB and 2nd Hop PRB if Inter-slot Freq Hop is ON
DMRS PatternYesThe RS stays in the same relative REs