RACH Preamble Power

the PRACH Power (P_PRACH) is determined by the following equation.

P_PRACH = min{P_CMAX, PREAMBLE_RECEIVED_TARGET_POWER + PL}

PL stands for Path Loss between eNB Tx antenna and UE Rx Antenna. PREAMBLE_RECEIVED_TARGET_POWER is the PRACH power that eNB expect to recieve.

The meaning of this equation is as follows :

i) Calculate PREAMBLE_RECEIVED_TARGET_POWER + PL

ii) if the calculated value is less than P_CMAX(23 dBm), transmit the PRACH at the calculated value. If the calculated value is greater than P_CMAX(23 dBm), transmit the PRACH at P_CMAX

PREAMBLE_RECEIVED_TARGET_POWER = preambleInitialReceivedTargetPower(in SIB2) + DELTA_PREAMBLE

You would still find one unknown parameter called DELTA_PREAMBLE. It is determined by which Preamble Format is used as shown below.

PL = eNB Transmitter Power - UE Reciever Power

This eNB Tx power is notifed by a SIB2 parameter referenceSignalPower

PREAMBLE_RECEIVED_TARGET_POWER = preambleInitialReceivedTargetPower(inSIB2) + DELTA_PREAMBLE+ (PREAMBLE_TRANSMISSION_COUNTER – 1) * powerRampingStep(SIB 2)