The eNodeB determines the downlink transmit energy per resource element (lte epre). Downlink cell-specific reference-signal (RS) lte epre is constant across the downlink system bandwidth and constant across all subframes until different cell-specific RS power information is received. The downlink RS lte epre is given by the parameter Reference-signal-power provided by higher layers.
In cases 16QAM, 64QAM, spatial multiplex TRI>1 or multi-user MIMO the DL power is given by ρA and ρB
A = + P power-offset ρ δ
10log (2) power-offset 10 = + + A A ρ δ P
(if precoding for transmit diversity with 4 cell-specific antenna ports is used.) Furthermore PA and PB are signalled values, also setting the ratio
δpower-offset is used for multi-user MIMO Depending on the number of antenna ports and CP configuration ρA and ρB are applied to the OFDM symbols 0..6.
thats simple idea behind lte epre downlink power control in lte