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What type of PUCCH are there in 5G ?

In 5G NR (New Radio), the Physical Uplink Control Channel (PUCCH) is responsible for carrying Uplink Control Information (UCI) such as HARQ-ACK, Scheduling Requests (SR), and Channel State Information (CSI) from the User Equipment (UE) to the network. To efficiently support different payload sizes, latency requirements, and multiplexing needs, 3GPP has defined five distinct PUCCH formats, each optimized for specific scenarios:

  • Format 0:
    • Type: Short PUCCH (1 or 2 symbols)
    • Payload: Up to 2 bits (typically HARQ-ACK or SR)
    • Multiplexing: Supports up to ~12 UEs per PRB using different sequence selections
    • Use Case: Efficient for sending small control information with minimal resource usage and low latency.
  • Format 1:
    • Type: Long PUCCH (4–14 symbols)
    • Payload: Up to 2 bits (HARQ-ACK or SR)
    • Multiplexing: Supports a higher number of UEs (up to ~36 or 84) per PRB by time-multiplexing UCI and DMRS
    • Use Case: Used when more robust transmission is needed (e.g., at cell edge or with higher interference), still for small payloads.
  • Format 2:
    • Type: Short PUCCH (1 or 2 symbols)
    • Payload: More than 2 bits (e.g., CSI, larger UCI)
    • Multiplexing: No multiplexing; dedicated to a single UE per PRB
    • Use Case: For short-duration, larger UCI payloads where multiplexing is not required.
  • Format 3:
    • Type: Long PUCCH (4–14 symbols)
    • Payload: More than 2 bits (large UCI payloads)
    • Multiplexing: No multiplexing; one UE per PRB
    • Use Case: For transmitting large UCI payloads over a longer duration, providing robustness and reliability.
  • Format 4:
    • Type: Long PUCCH (4–14 symbols)
    • Payload: More than 2 bits (large UCI payloads)
    • Multiplexing: Supports multiplexing of ~2 or 4 UEs per PRB
    • Use Case: Similar to Format 3 but allows limited multiplexing, balancing resource efficiency and payload size.

Summary Table:

Format

Duration (Symbols)

Payload

Multiplexing

Typical Use

Format 0

1–2

≤ 2 bits

~12 UEs/PRB

Small UCI, low latency

Format 1

4–14

≤ 2 bits

~36/84 UEs/PRB

Small UCI, robust, cell edge

Format 2

1–2

> 2 bits

1 UE/PRB

Larger UCI, short duration

Format 3

4–14

> 2 bits

1 UE/PRB

Large UCI, robust

Format 4

4–14

> 2 bits

2 or 4 UEs/PRB

Large UCI, some multiplexing

The selection of PUCCH format depends on the amount of control information to be sent, the required robustness, and the need for multiplexing multiple UEs. This flexibility allows 5G NR to efficiently support a wide range of use cases and deployment scenarios.

Further Readings