DCI stands for Downlink Control Information. It is used to carry downlink control information for one or more cells with one RNTI. It also provides the UE with necessary information such as physical layer resource allocation, power control commands, HARQ information for both uplink and downlink. DCI is transmitted on PDCCH with 24-bit CRC attachment.
In 4G LTE, 16-bit CRC was used and the increased CRC size reduces the risk of incorrect reception at the receiver end. Different DCI formats are defined to meet needs for 5G efficient working but the number of DCI formats are less as compared to LTE. Unlike LTE DCI formats, several of NR DCI formats can share same DCI size.
There are following three Category of DCIs shown below used for Uplink Allocation DCI Format 0_x , Downlink Allocation DCI Format 1_x and UE group Common Signaling DCI Format 2_x .
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