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apo7
2009-06-28, 03:57 AM
For overshooting cells, we always downtilt that particular cell. Why we don't just change the transmit power parameter in the database to prevent the cell from overshooting. What are the cons of changing the transmit power?


Thank you.

NILCTG
2009-06-28, 04:14 AM
U may loose/reduce indoor coverage if u change Transmit power. Also u have to change a number of relevant parameters(such as power control parameters) in the database. :)

RF engineer
2009-06-28, 04:20 AM
Dear
Normally tilt is the first choice because any decrease in output power let say by 3 dB it means you reduced the radius coverage by around 45 to 50% and the area of coverage by 22 to 25 %. so you can see from the percentage the change of power is critical just it will as final solution.

apo7
2009-06-28, 02:52 PM
Dear
Normally tilt is the first choice because any decrease in output power let say by 3 dB it means you reduced the radius coverage by around 45 to 50% and the area of coverage by 22 to 25 %. so you can see from the percentage the change of power is critical just it will as final solution.

Do you have any documents that show the relation between the transmit power and the coverage radius/area?

Thank you.

ghassen
2009-06-28, 05:52 PM
Do you have any documents that show the relation between the transmit power and the coverage radius/area?

Thank you.

there is no doucument at now but this is a matter of experience in RF engeneering

ghassen
2009-06-29, 04:26 AM
there is no doucument at now but this is a matter of experience in RF engeneering

i will try to find some

RF engineer
2009-06-29, 04:50 AM
Dear
let assume your out put power is 46 dBm then convert to watt it gives around 40 watt if you reduced from 46 to 43 it give you around 20 watt so half power gone so it means half coverage radius gone the coverage is A=K*(R)^2
K is constant let say R is reduced to 1/2 it means 1/4 it gives around 25%.
BR
RF

dexterhaba
2009-06-29, 06:45 PM
will downtilting increase indoor coverage? Also there is a topic which says 1800 frequency can have better penetration than 900,, but to my experience 1800 sites have very low indoor coverage compared to 900 , but for IBS 1800 is better than 900?? , why is that?

torex
2009-06-29, 06:58 PM
The usage DCS 1800 for IBS mostly to prevent spillage in surrounding area of building which may cause another problem for example call drop if user in high speed car pass by.


will downtilting increase indoor coverage? Also there is a topic which says 1800 frequency can have better penetration than 900,, but to my experience 1800 sites have very low indoor coverage compared to 900 , but for IBS 1800 is better than 900?? , why is that?

newbielinz
2009-06-29, 10:35 PM
For overshooting cells, we always downtilt that particular cell. Why we don't just change the transmit power parameter in the database to prevent the cell from overshooting. What are the cons of changing the transmit power?


Thank you.

dear friend,

reduce transmit power is one of the solution to reduce the overshooting, but unfortunately it will reduce coverage and have big impact to indoor penetration loss.

so u must carefully if you wanna reduce any power because it will have big impact to the end user directly.:)


thx
Newbielinz

atese
2009-06-30, 01:54 AM
Hi my friend.
By reducing power transmission you can loss indoor coverage and unbalancing the traffic of cells around, Power ouput should be always the last choice.

Try first by downtilt.

regards

aircom_vn
2010-03-16, 04:02 AM
The usage DCS 1800 for IBS mostly to prevent spillage in surrounding area of building which may cause another problem for example call drop if user in high speed car pass by.

Quote:
Originally Posted by dexterhaba
will downtilting increase indoor coverage? Also there is a topic which says 1800 frequency can have better penetration than 900,, but to my experience 1800 sites have very low indoor coverage compared to 900 , but for IBS 1800 is better than 900?? , why is that?


@dexterhaba: You r correct.
as in my opinion, DCS1800 has better penetration than GSM900, but the pathloss in Air environment is higher. so that it is usually indoor signal of 1800 is less than indoor signal of 900 (for macro site). but for IBS, the distance from antenna to user is very short, that means path loss of Air environment is same same, so the 1800 signal is better the 900 one due to it could penetrate better.

Lesmana
2010-04-07, 07:50 PM
Quote:
Originally Posted by dexterhaba
will downtilting increase indoor coverage? Also there is a topic which says 1800 frequency can have better penetration than 900,, but to my experience 1800 sites have very low indoor coverage compared to 900 , but for IBS 1800 is better than 900?? , why is that?


@dexterhaba: You r correct.
as in my opinion, DCS1800 has better penetration than GSM900, but the pathloss in Air environment is higher. so that it is usually indoor signal of 1800 is less than indoor signal of 900 (for macro site). but for IBS, the distance from antenna to user is very short, that means path loss of Air environment is same same, so the 1800 signal is better the 900 one due to it could penetrate better.



Dear experts,

please explain a little more about building penetration loss for GSM 900 and 1800 band. for example :

Outdoor Rx_level is -70 dbm.And the Rx_level is -82dbm inside the building.
Measuring frequency is GSM 900 band.(There is only one brick wall which is penetrate by the signal)


WHAT WOULD BE THE Rx-Level inside the same building for GSM 1800 band?
Let say the outdoor Rx-Level is -70dbm in case of GSM 1800 as well.

aircom_vn
2010-04-09, 11:11 PM
Hi my friend.
By reducing power transmission you can loss indoor coverage and unbalancing the traffic of cells around, Power ouput should be always the last choice.

Try first by downtilt.

regards

Yep, u r correct. Be careful with Power output. Reducing PWR involves the coverage and Path Balance.

apollo13
2010-04-10, 02:02 AM
The usage DCS 1800 for IBS mostly to prevent spillage in surrounding area of building which may cause another problem for example call drop if user in high speed car pass by.

That is true. The 1800MHz IBS is mostly to prevent spillage due to higher propagation loss. This loss is directly associated to the Frequency. The higher the frequency the higher the loss. One can explain it by the Wave length formula: L = V/F

Where L= wave length (m)
V= Light Speed (m/s)
F= Frequency (Hz)

Therefore for 900MHz the wave length is L= 3x10^8 / 900x10^6 = 0.333m = 33.33cm. On the other hand for 1800MHz the wave length is L=3x10^8/1800x10^6 = 0.1667m = 16.67cm.

Everybody knows that a smaller wave length has more difficulties to overcome an obstacle (diffraction). So from that we can see that the 1800MHz will have bigger losses once it has a smaller wave length. The 1800Mhz signal will be better contained inside the building than the 900MHz, and so having less spillage.

Regarding to Power you have to be careful as you can read on other colleagues posts. But this not means you always have to use full power on the BTS side. We have to balance the UL and the DL path losses. This is known as Link-budget. Normally the transmition on the UL (mobile) is the limitation once the mobile has less output power (Up-Link limitted). Therefore you have to adjust the Max Output power on the BTS.

I hope I could help to clarify your doubts.

Best regards, :p

Ps.: If you find this info useful, please give reputation.

--------------
Apollo13

turkzon
2010-04-10, 05:05 PM
For overshooting cells, we always downtilt that particular cell. Why we don't just change the transmit power parameter in the database to prevent the cell from overshooting. What are the cons of changing the transmit power?


Thank you.

Hi Friend;

firstly i would like to say that ,as you know "power is money" ,its not logical decrease power if you have more one.so its not recommended and also i dont prefer this option as reduce transmit power of cell,you can optimise and reduce bad affects of overshooting cell maybe;
antenna type change (has low gain and VBeamw. from existing one)
reducing antenna height,
prefer electical downtilt if you can,
change locating parameters (TALIM,LAYERTHR,LAYER,LAYERHYT...)carefully..

thanks

punto
2010-04-10, 08:11 PM
Of course, reduction of power is always and ever - last option ...
You want to have highest % of coevering target area to have better quality of voice, it is not just you make sure that there is a signal, but you care for its voice quality as well ... and there is also the data transfer throughput which is higher as higher is the received signal strength at MS, meaning C/I higher directly influences triggering the higher coding scheme that assures you higher speed of data transfer. OK, 900 MHz penetrates better indoors, and 1800 has problems in penetration through building walls, so you will in this case, help amplifivation of signal , not just for rural distant MS from BS with TMA amplification in UL, to have balance DL and UL, but also in urban areas with lots of thick concrete walls. Dtilt , antenna height and change of azimuth, together with right choice of beamwidth of BS antenna, will help you to reach targeted coverage area, and keep the interference and overshooting to minimum. Try to form some thinking in this direction ... enjoy , P:)

kevin_h811
2010-04-13, 03:14 PM
Hi APO7,

They are all right...Power Reduction is the last resort...If u have already maximize the downtilt angle of your antenna, u can change the value of RXLEV ACCESS MIN gradually, that is if u have still overshooting...but take note, it will affect your neighbor sites and your KPI stats...this is only an additional suggestion that u can make a trial on it.Good Luck!

Regards\\