- This topic has 13 replies, 1 voice, and was last updated 14 years ago by Abhilash.
24th January 2008 at 04:30 #50586MKTGuest
Is reducing the BTS power
is one of the standard practice to counter in a multi-cell urban environment?
If choice is given then, what should be the priority order among TILT,HEIGHT,POWER.
If it is the vendor who initially plans the height and tilt of antenna for operator then,…..shouldn’t he(vendor) be held responsible for the overshooting(if any).
And last…if tilt can provide us a small cell and at the same time a good, strong signal(indoor coverage)..then for what purpose the option of attenuation of BTS power is there. I mean in which condition we have no way other then to attenuate the BTS power.
MKT24th January 2008 at 08:08 #50587pixGuest
you missed the most important 🙂
1. type of antenna (V aperture and H aperture, gain, backlobe)
The power is mostly used when it appears that you are covering the intended area with a very strong signal. There is no need to provide -60dBm in average in the cell, with -70dBm at the cell border.
By decrease the power by 10dB, you have -70dBm in average and -80dBm at cell border, which is acceptable. Of course, you must ensure the indoor coverage is not impacted (check TCH traffic after power reduction)
You can also decrease power of indoor sites, because you can’t play around with tilt or height. To avoid exposing surrounding people too much and to avoid overshooting outdoors.
Regards,24th January 2008 at 09:26 #50588MKTGuest
Is there any thing wrong in having -60dBm in a cell and -70dBm at the cell border?
Question still remains as it is….Why do one need to make the SIGNAL weak? OR the feature is there for Lazy ones…who think that playing with height at tilt consumes time as well as effort/money?24th January 2008 at 09:34 #50589MKTGuest
To be more clear….
the case being discussed here is of outdoor BTS sites. My vendor engineer(Nokia)has attenuated the power of BTS sites ranging from 4dB to 8dB. The cells(where power is attenuated) had poor indoor coverage.
The excuse given by Nokia is to prevent overshooting.
My theory is..if you are having overshooting then increase the tilt.And if the problem still persists then ask the vendor to reduce height. And this time he has no excuse as he is the one who has planned the height.
Prevention of overshooting at the cost of indoor coverage is NO.24th January 2008 at 09:38 #50590pixGuest
sorry, maybe i’m not very clear..
after having a perfect tilt, it can happen that the power emitted by the BTS is so strong that it “leaks” too much into other neighbours. not everybody is leaving in a flat country : with hills or mountains, the coverage can be very hard to control. A little help from the power reduction is always welcome.
there is nothing wrong within the cell, but it pollutes other cells.
and my second example with microcell, it’s a different situation. do you agree with it ?
however, you can see those are very specific case : power reduction is the last little tuning to make a cell perfect. It’s not the first tuning to perform !25th January 2008 at 11:37 #50591WirelessNetNutGuest
Another point of view to consider…
Depending on your antennas it can be difficult to perform antenna tilting. If you do not have remote tilting on your antenna (even just remoted to the base of your cell site tower or base station equipment room) and you need to get an elevated platform/crane/cherry picker to the site to make the change, it can be expensive to do so. Motorised remote tilt makes such optimisation manipulations much easier (very important in a WCDMA or CDMA based network). You may if a situation is bad enough consider down powering a site as a short term measure until the antenna tilt can be changed – but typically that is only for short term situations.
Having said that, I still would not advocate for power reduction as an optimisation technique unless it was last resort.
Indeed there are instances where overshoot may be acceptable, particularly if you have to tollerate it to achieve your coverage objectives – but it is a careful tradeoff between how much overshoot to tolerate verses overall network performance. A balance needs to be struck and only sites covering areas where no other coverage can really be achieved any other way should be considered for up-tilting and hence acceptance of overshoot situations. If you are running a GSM network, it may be possible to work around an overshooting cell through careful frequency planning – leaving the cell it overshoots as an embedded cell operating on a different frequency. If it is a CDMA based network then that option most likely doesnt exist.16th August 2009 at 08:49 #50592AyatGuest
what is the eefect of overshooting in mobile network ?????
cell with wide coverage16th August 2009 at 18:36 #50593RexGuest
Congestion, Interference …
Regards,17th August 2009 at 06:54 #50594ayatGuest
more expalition17th August 2009 at 10:32 #50595RexGuest
cell with wide coverage could lead to sdcch and tch congestion because of big coverage, then sdcch assignment failure, sdcch drop, they all could be the consequencies of that. To much area covered, possibility to interfer and to be interfered is high. To far MSs may camp to that cell, so, possibility for sdcch congestion for MSs near the site, assignment failure for MSs far from the site etc. This is only my assumption, it depends from number of subscribers in the area, number of sites, frequencies etc.
Regards,17th August 2009 at 15:31 #50596VanderleyGuest
In our network we use power reduction. But for only one case having nothing to do with overshooting.
Initialy we start the sites with 2 TRX configuration. Then due to traffic increase we have to go for more TRX. Then as it is said we go from coverage mode to capacity mode (3 to 3.5 dB less DL power due to combiner losses). In order to avoid this change we sometimes start the site with 4 dB less power. This way from the very begining we could measure the coverage we will provide in the future.17th August 2009 at 16:45 #50597HSHGuest
And some time you need to use power reduction to create a power balance of the TRXs at the same cell if dividing the cell TRXs between 2 combiners or duplexers when you have NO. of TRXs higher than the combiner capacity; 5, 6, 7 TRXs,
regards26th August 2009 at 11:52 #50598AyatGuest
to fix the accesblity of our network
i have to modify the TA and power level??????1st September 2009 at 12:10 #50599AbhilashGuest
Well definitely reducing power to avoid overshooting is not a preferable solution to the problem.
A step-wise approach need to be adapted to overcome this problem.
1. A slight tilt needs to be given to the RF antenna.
2. Thorough drives to be done at the cell coverage, especially at the border areas and check for interference.
3. If still problem exists and no further tilt can be given, then power optimization comes to picture.
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