The relation of LTE cell max transmit power with PA PB and RS power Basic conception/definition conception/definition 1) Cell specific RS EPRE (EPRE rs) :The downlink reference-signal transmit power is defined as the linear average over the power contributions (in [W]) of all resource elements that carry cell-specific reference signals within the o perating system bandwidth. 2)
ρa:PDSCH
EPRE(type A symbol (type A symbol, refers to symbol 1 ,2,3,5,6 in normal
frame type, where in the symbols only PDSCH is carried))/Cell specific RS EPRE 3)
ρb: PDSCH
EPRE(type B symbol sym bol (type B symbol refers to symbol 0 ,4 in normal frame type,
where in these symbols both PDSCH and RS are carried))/Cell specific RS EPRE 4) PB in configurable, it is a cell specific parameter, the value value can be 0,1,2,3, PB decides the relationship of ρa and ρb, table 5.2-1 5) PA is configurable, it i s a UE specific parameter, the value can be -3、-4.77、-6、—-1.77、 0、 1、2、3. Unit is Db。 In the protocal protocal the difination of PA is: is equal to Δ power-offset PA [dB] in most case Δ power-offset=0, (except in case of multi user MIMO) ρa =PA ρa
The cell Max transmit power calculation is based on the configured PA, but the PA is a user specific parameter, it could be dynamic changed for different users, but the system will guarantee the total transmit power of the cell not exceeding the maximum.
Discussion on LTE max transmit power
1) Definition of Cell max transmit power as blow: The formula below is applicable for ERAN3.0 and later version, in earlier version the max transmit power only take the type A symbol, the first part of the formula. Max. Output Cell Power (per antenna port) =
-
We can also express it in the following way: Max. Output Cell Power (per antenna port) =
In case two or more TX antenna ports: Max transmit power of one Type A symbol (in dBm) =10 * log [ EPRE rs (mw) * Pa (linear) * 12 * Nrb ] Max transmit power of one Type B symbol (in dBm) = 10 * log (linear) *
(linear) *
[ ( EPRE rs (mw) * Pa
8 * Nrb ) + ( EPRE rs (mw) * 2 * Nrb ) ]
In case one TX antenna port: Max transmit power of one Type A symbol (in dBm) =10 * log [ EPRE rs (mw) * Pa (linear) * 12 * Nrb ] Max transmit power of one Type B symbol (in dBm) = 10 * log (linear) *
(linear) *
[ ( EPRE rs (mw) * Pa
10 * Nrb ) + ( EPRE rs (mw) * 2 * Nrb ) ]
Let us see several calculation examples for 1T1R: Example 1: 20 Mhz, 100 RB, EPRErs = 15.2 dBm,Pb=1 Pa = 0,
Max. Ouput Cell Power (per antenna port) = MAX{ Max transmit power of one Type A symbol, Max transmit power of one Type B symbol } Where: Max transmit power of one Type A symbol (in dBm) =10 * log [EPRE rs (mw) * Pa (linear) * 12 * Nrb] = 10 * log (33,11 * 1 * 1200) = 46 dBm Max transmit power of one Type B symbol (in dBm) = 10 * log [(EPRE rs (mw) * Pa (linear) * (linear) * 10 * Nrb) + (EPRE rs (mw) * 2 * Nrb)] = 10 * log [(33,11 * 1 * 4/5 * 1000) + (33,11 * 200)] = 45.2 dBm
Max. Ouput Cell Power (per antenna port) = MAX{ 46 dBm, 45.2 dBm } = 46 dBm
Example 2: 20 Mhz, 100 RB, EPRErs = 18.2 dBm, Pb=1, Pa = -3 dB
Max. Ouput Cell Power (per antenna port) = MAX{ Max transmit power of one Type A symbol, Max transmit power of one Type B symbol } Where: Max transmit power of one Type A symbol (in dBm) =10 * log [EPRE rs (mw) * Pa (linear) * 12 * Nrb] = 10 * log (66,22 * 1/2 * 1200) = 46 dBm Max transmit power of one Type B symbol (in dBm) = 10 * log [(EPRE rs (mw) * Pa (linear) * (linear) * 10 * Nrb) + (EPRE rs (mw) * 2 * Nrb)] = 10 * log [(66,22 * 1/2 * 4/5 * 1000) + (66,22 * 200)] = 46 dBm
Max. Ouput Cell Power (per antenna port) = MAX{ 46 dBm, 46 dBm } = 46 dBm
Example 3: 20 Mhz, 100 RB, EPRErs = 15.2 dBm, Pb=0, Pa = 0 dB
Max. Ouput Cell Power (per antenna port) = MAX{ Max transmit power of one Type A symbol, Max transmit power of one Type B symbol } Where:
Max transmit power of one Type A symbol (in dBm) =10 * log [EPRE rs (mw) * Pa (linear) * 12 * Nrb] = 10 * log (33,11 * 1 * 1200) = 46 dBm Max transmit power of one Type B symbol (in dBm) = 10 * log [(EPRE rs (mw) * Pa (linear) * (linear) * 10 * Nrb) + (EPRE rs (mw) * 2 * Nrb)] = 10 * log [(33,11 * 1 * 1 * 1000) + (33,11 * 200)] = 46 dBm
Max. Ouput Cell Power (per antenna port) = MAX{ 46 dBm, 46 dBm } = 46 dBm
2) The Maximum. transmit power can be obtained by executing MML COMMAND DSP CELL the result is the same as Max. Output Cell Power (per antenna port) calculated in Step 1) in this email.
3) Maximum Output Cell Power of the cell is always calculated dynamically based on EPRE RS, Pa, Pb and Cell Bandwidth following formula provided in step 1)
With exceptions When RRU Power lock is set, the max power of the RRU will accordingly limited by the locked Max Power (the command is LOC RRUTC. 4) how it is done the RS Power Boosting in 1T1R cells and how it is provided the extra power used to boost the RS in symbol 0 and symbol 4 of the OFDMA frame in that scenario (1T1R)? In case of 1T1R Huawei do not recommend to have power boosting, PA-PB configure to 00