5G Uplink Control Information (UCI) multiplexing on PUSCH
Uplink Control Information, as the name suggests, carries control signals from UE-to-gNB in the uplink direction (it is the counterpart of Downlink Control Information or DCI from gNB-to-UE).
Generally, PUCCH (Physical Uplink Control Channel) is supposed to carry the UCI. On the other hand, the UL data is sent via PUSCH (Physical Uplink Shared Channel).
But in 5G NR, in certain instances, the PUSCH can also carry Control Information in the uplink (i.e. UCI) as well. This is called UCI multiplexing on PUSCH. (this feature was also available in LTE as well).
This so-called multiplexing is in complete contrast to Downlink Control Information (DCI) which is carried *always* over the PDCCH (Physical Downlink Control Channel) and never on PDSCH.
Uplink Control Information
Uplink Control Information (UCI) carry the following contents
- HARQ ACK/NACK
- Scheduling Request (SR)
- Channel State Information — Report.
Possible Contents of UCI
The UCI can be transmitted in any of the possible combinations from the contents named above:
- Only HARQ ACKNACK
