MIMO Single User for LTE
SU-MIMO = Single User MIMO
- It is the most common form of MIMO.
- Each user is served by only one BS and it occupies the resource exclusively, including
- It can be applied in the uplink or downlink. But it is generally applied only in DL. The UE can easily have 2 antennas in reception but only 1 antenna can transmit
The Single User MIMO is used in DL and means that the 2 TB send by the 2 antennas using the same radio resources are for the same UE.
In UL, it is not possible to use this MIMO.
There are two operation modes in SU-MIMO spatial multiplexing:
The closed-loop spatial multiplexing mode
- The UE reports the CQI, the RI (Rank Indicator) and the PMI (Precoding Matrix indicator)
The open-loop spatial multiplexing mode
- The reports only the CQI and the RI.
- The RI (Rank Indicator) indicates the number of spatial layers (data streams) that can be supported by the current channel experienced at the UE.
- The PMI (Precoding Matrix Indicator) is the UE feedback.
The required UE feedback for the MIMO are:
- RI, Rank Indicator. By this one the UE can indicate if it is able to separate 2 TB. If Yes the eNodeB can use the MIMO. If not it uses the TxDiv
- PMI, Precoding Matrix indicator. It is used only for the Closed Loop MIMO. The UE indicates the eNodeB how to map the data on the 2 antennas to optimize the reception.