An easy approach to understand tech specs
Here is a diagram of downlink MIMO 2X2 scenario. The implementation is using two antennas to receive downlink signals. The detailed discussion on the format of Downlink Frame
LTE Downlink MIMO and frame format.
Control - PCFICH, PHICH, PDCCH
Reference signal - MIMO Antenna 1
Reference signal - MIMO Antenna 2
In above LTE frame format the sub-carriers are highlighted in frequency domain and symbols in times domain. Control information is passed as PCFICH, PHICH, PDCCH. The data is passed as PDSCH. The reference signals for each MIMO antenna is also highlighted.
Similar concept can be extended for 4x4 MIMO.
LTE downlink frame format with reference signal allocations for two MIMO antennas.
LTE downlink by default requires MIMO 2x2 antenna configuration (In WiMax its optional). By MIMO 2x2 we mean 2 transmit antennas at the base station and 2 receive antennas at the mobile. Antenna configurations with MIMO 4x4 are also discussed in the standard.