For now, there are 5 different types of PUCCHs defined in the specification. These formats provide different options for transmitting UCI, such as HARQ-ACK, Scheduling Requests (SR), and CSI, with varying lengths and capacities to support different numbers of multiplexed UEs. The choice of format can affect the resource efficiency and the amount of information that can be sent.
- Format 0: A short PUCCH format that can accommodate up to two bits of control information. It is suitable for use cases where a small amount of control data, such as HARQ-ACK, needs to be sent. It supports multiplexing of approximately 12 UEs in the same Physical Resource Block (PRB) by using different sequence selections.
- Format 1: This is a long PUCCH format sitting across 4~14 symbols. It still carries less than or equal to two bits of control information. It supports a higher number of multiplexed UEs (around 36 or 84) in the same PRB by time-multiplexing the Uplink Control Information (UCI) and Demodulation Reference Signals (DMRS).
- Format 2: Also a short PUCCH format, it is designed for cases where more than two bits of information are transmitted. It does not support multiplexing; hence, it is dedicated to a single UE in a PRB. It employs frequency multiplexing for UCI and DMRS.
- Format 3: A long PUCCH format for transmitting large UCI payloads without multiplexing, thus, one UE per PRB. This format is capable of sending more than two bits of information by time-multiplexing UCI and DMRS over a range of 4 to 14 OFDM symbols.
- Format 4: Similar to Format 3, this is a long PUCCH format designed for more than 2 bits of UCI payloads. It supports multiplexing of approximately 2 or 4 UEs in the same PRB. This format also covers a range of 4 to 14 OFDM symbols.