Query about UMTS Open Loop Power Control Paramter: "PowerOffsetPpm"

[Osman Nayeem]

Dear Experts,

Following is the formula to calculate initial preamble power for UMTS outer loop power control:

P_RACH(Preamble_Initial_Power) = PCPICHPower - CPICH_RSCP + RTWP + constantValueCprach

For a particular moment, lets say, CPICH_RSCP= -67dBm, RTWP = -100dBm, PCPICHPower = 33dBm & Constantvalue = -27(e******* default), which gives, P_RACH = -27dBm

Lets say, last submitted preamble power is -20dBm when UE receives a positive acquisition indicator. Next we have to calculate RACH transmitting power, RACH Transmitting power = last submitted preamble power + "PowerOffsetPpm"

As per my understanding, RACH transmitting power should be equal to or greater than -20dBm(last submitted preamble power), which means "PowerOffsetPpm" should be equal to or greater than zero.

Question: My confusion is, E******* recommended value for PowerOffsetPpm is -4dBm (negative offset !!). Huawei is also used a negative offset for this parameter. Can anyone please explain why?


Thanks,
Osman Nayeem

[ninjafine]

Dear Experts,

Following is the formula to calculate initial preamble power for UMTS outer loop power control:

P_RACH(Preamble_Initial_Power) = PCPICHPower - CPICH_RSCP + RTWP + constantValueCprach

For a particular moment, lets say, CPICH_RSCP= -67dBm, RTWP = -100dBm, PCPICHPower = 33dBm & Constantvalue = -27(e******* default), which gives, P_RACH = -27dBm

Lets say, last submitted preamble power is -20dBm when UE receives a positive acquisition indicator. Next we have to calculate RACH transmitting power, RACH Transmitting power = last submitted preamble power + "PowerOffsetPpm"

As per my understanding, RACH transmitting power should be equal to or greater than -20dBm(last submitted preamble power), which means "PowerOffsetPpm" should be equal to or greater than zero.

Question: My confusion is, E******* recommended value for PowerOffsetPpm is -4dBm (negative offset !!). Huawei is also used a negative offset for this parameter. Can anyone please explain why?


Thanks,
Osman Nayeem

Hi! Check the thread below.

http://www.finetopix.com/showthread.php?13842-PRACH-power-control-question