[Aso]

hi
I would like to know how the power leveling is perform in ALU when the cell is configured for both GMSK and 8 PSK and how it done.

[Bijoy]

Hi Aso
Nice question
There is no fixed relation as how much the 8-PSK power level will be lower than GMSK power level.It is assumed that The maximum average output power for 8-PSK is 4 dB lower compared to GMSK if the transceiver unit is configured with maximum output power.

In Nokia & Ericsson ,there is no parameter by which we can regulate the 8-PSK power level.In Huawei ,we have a separate attenuation parameter to do this,but it is recommended not to use it as it might lead to inaccurate MS meaurements.

[aso]

Hi Bijoy
Thanks for your help may one of our ALU colleague help .
BR

[pix]

aso,

Few days ago, i wrote a huge answer but it got f*** erased.
What bijoy said also applies for ALU. The 8PSK is levelled only if the GMSK is attenuated by parameters (BS TX PWR MAX). The goal is that the 8PSK never gets stronger than the GMSK.

In ALU, you cannot decrease the power of 8PSK only. The only parameter is BS TX PWR MAX, which acts on the GMSK power. And under condition explained above, it will act on the 8PSK.

Basically, the operator has nothing to do, it is all automatic.

The only thing is if you have a cell that contains only TRX for older generations (all TRX are TRAG/TRAD or older, without even 1 TRAGE or 1 TRADE). In this case, the 3GPP recommends to set the BS TXPWR MAX to -2dB.
(This is a matter of RxLev mesasurements from neighbour cells) (it is not critical, most operators don’t really care)

Pix

[aso]

Thanks PIX for explanation i saw in one of technical ALU doc and i copied exactly what wrriten below that make me some how not getting the idea

Example:

GSM 900, a mix BTS sector configuration is considered:

ANc combined with 4 TRA (TRAs = EGPRS capable TRE):

TRE 1 (BCCH): 60W GMSK (25W in 8-PSK)

TRE 2..4: 45W GMSK (15W in 8-PSK)

BS_TXPWR_MAX = 2 dB;

RESULTS:

1st step: Output power at BTS antenna connector (after combiner and
duplexer stage):

TRE 1 GMSK = 43.4 dBm; 8-PSK = 39.6 dBm

TRE 2..4 GMSK = 42.1 dBm; 8-PSK = 37.4 dBm

2nd step: LEVELING (BTS automatic GMSK power balancing):

TRE 1..4 GMSK = 42.1 dBm (Sector GMSK power)

[Pix]

What matters is the TRX power at BTS output.
Between the TRX and the BTS output, there are some combiners (ANCs, ANYs), as many as you need.

Each of them will drop the TX PWR by 4dB (approx).

In case of 4 TRX, only one ANC. So each TRX losses about 4dB.

At BTS output, the weakest TRXs are the TRX2, 3 and 4. So the TRX1 will be attenuated so it doesn’t exceed the output power of the 3 other TRXs.
That is for GMSK only.

IN 8PSK, the TRX1 will send the max power, and so does the other TRX2,3,4. But of course, Tx Pwr 8PSK in TRX1 is stronger than in the 3 others. But here, there is no levelling. The TRX1 is not attenuated in 8PSK.

I hope it is clear now. If not, I’ll just blow my own head off.

Cheers 🙂
Pix

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