LTE MIMO

Multiple-input, multiple-output (MIMO) techniques have been integrated as one
of the key approaches to provide the peak data rate, average throughput, and system
performance
The operation mode of multiple transmit antennas at the cell site

1. spatial division multiplexing (SDM)
2. precoding
3. transmit diversity (TD).

Base on the allocation of the multiple transmission streams in MIMO, the different types of MIMO mode are 

single user (SU)-MIMO 

multiuser (MU)-MIMO

Downlink MIMO
For the LTE downlink, a 2x2 configuration for MIMO is assumed as
baseline configuration, i.e. 2 transmit antennas at the base station and 2
receive antennas at the terminal side. Configurations with 4 antennas are
also being considered.

Uplink MIMO
Uplink MIMO schemes for LTE will differ from downlink MIMO schemes to
take into account terminal complexity issues. For the uplink, MU-MIMO can
be used. Multiple user terminals may transmit simultaneously on the same
resource block. This is also referred to as spatial domain multiple access
(SDMA). The scheme requires only one transmit antenna at UE side which
is a big advantage. The UEs sharing the same resource block have to apply
mutually orthogonal pilot patterns.