Downlink Control Information or DCI in LTE
- The PDCCH carries Downlink Control Information or DCI to indicate the resource assignment in UL or DL for one RNTI.
- A DCI can convey various pieces of information, but the useful content depends on the specific case of system deployment or operations.
- If the MIMO is not used during the transmission, there is no need to transmit the MIMO parameter in the DCI.
- There are several format of DCI defined by the 3GPP for each need.
- UE feed backs the network with CQI (Channel Quality Indication) giving an estimation of the channel quality
The network adapts downlink transmission accordingly by changing:
- The coding rate (amount of information bits over number of transmitted bits)
- The modulation (QPSK, 16QAM, 64QAM)
- Radio resources are shared among users: a trade-off is needed between maximizing the bitrates and using
- the smallest amount of resource blocks
- For MIMO configuration, the RI and PMI are also reported
The main DCI formats are:
- Format 0
For scheduling of the PUSCH (UL Grant) - Format 1A
Used during the Random Access Procedure - Format 1
For the scheduling of the PDSCH (DL Grant)
In case of TxDiv - Format 2A
For the scheduling of the PDSCH (DL Grant)
In case of Open Loop SU- MIMO - Format 2
For the scheduling of the PDSCH (DL Grant)
In case of Closed Loop SU- MIMO
Downlink Control Information (DCI) used to grant UL/DL traffic
- DCI0 for uplink grant of PUSCH
- DCI1 and DCI1A for downlink grant of PDSCH with one single codeword
- DCI2 for downlink grant of PDSCH with one or two codewords (closed-loop MIMO)
- DCI2A for downlink grant of PDSCH with one or two codewords (open-loop MIMO)
- DCI carried in PDCCH transport channel
