Web Simulation 

  

 

 

 

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.

Sections

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).

Simulation

The interactive simulator is below. Use the controls to explore the concepts described above.

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 length

No intra-slot hop

Intra-slot hop m'=0

Intra-slot hop m'=1

4

2

1

1

5

2

1

1

6

3

1

2

7

3

1

2

8

4

2

2

9

4

2

2

10

5

2

3

11

5

2

3

12

6

3

3

13

6

3

3

14

7

3

4

38.211 Table 6.3.2.4.1-2: φ(m) for wi(m)=ej2πφ(m)/NSF

NSF

i=0

i=1

i=2

i=3

i=4

i=5

i=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

n

wn

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

n

wn

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 Value

Sequence cyclic shift

0

mCS = 0

1

mCS = 6

38.213 Table 9.2.3-4: Mapping for two HARQ-ACK information bits

HARQ-ACK Value

Sequence 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

Feature

Same across Slots?

Notes

Num Symbols

Yes

Defined by nrofSymbols

Start Symbol

Yes

Defined by startingSymbolIndex

PRB Index

No

Swaps between Start PRB and 2nd Hop PRB if Inter-slot Freq Hop is ON

DMRS Pattern

Yes

The RS stays in the same relative REs

Limitations

  • Resource-mapping visualization, not a PHY chain. The tool shows which REs carry UCI vs DMRS per format and the modulation per RE; it does not encode real UCI bits, perform channel coding, IFFT/transmit, or decode at a receiver.
  • Ideal grid, no channel. No fading, noise, timing/frequency offset, or PAPR effects; the constellation shows nominal modulation points, not received samples.
  • Single UE, single antenna. Pre-DFT OCC (Format 4) is depicted as a code index but multi-user multiplexing, spatial multiplexing, and inter-cell interference are not simulated.
  • Subset of parameters. Common PUCCH parameters are exposed, but not every RRC configuration, hopping pattern, or capability combination from the spec is reproduced.
  • Spec snapshot. DMRS lookups and tables follow TS 38.211 (§6.3.2) at the implemented release; later corrections/optional features may differ.
  • No link adaptation. Payload size, repetition (Nr Slots), and format choice are set manually; the demo does not model the scheduler logic that selects them for a given UCI payload and coverage.