GSM Downlink power control

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vine.palli@gmail.com - 24 Apr 2006 13:19 GMT

I have been wondering and trying to find information about power
control of downlink in GSM. I know that powercontrol for both uplink
and downlink are made in steps of 2 db, but is it also so that in
downlink speed is maximum 2 db / 60 ms like in uplink?

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krg - 24 Apr 2006 15:36 GMT

hi,
and don't know about downlink, but uplink in 60 ms?? as far as i
experienced, a
measurement report takes about 480 ms to get to the BTS, so any action,
as regards
power control, can happen only in intervals of 480 ms. but whatever,
definitely not 60
ms. but then again, depends, as to where you observed this timings.
would you please clarify??

Care & Take Care,

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vine.palli@gmail.com - 24 Apr 2006 15:46 GMT

krg kirjoitti:

> hi,
> and don't know about downlink, but uplink in 60 ms?? as far as i
[quoted text clipped - 7 lines]
>
> Care & Take Care,

True, measurement reports are sent in SACCH about once in 480 ms. But
with 60 ms I mean, if we think about situation where mobile phone hears
basestation very well, but suddenly the strength of signal goes lower
(user maybe goes inside building, which blocks quite good radio
signals). GSM standard says that mobilephone can change its' powerlevel
maximum 2 dB/ 60 ms, not faster than that.

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Saurabh - 25 Apr 2006 11:37 GMT

Hi,

Radio equipment in GSM is distinguished from each other by among other
things, the different transmitter power levels they can produce.
Each of power levels in the various classes are separated from each
other by something greater than 2 db.
Two consecutive power level values must have a difference of at least
0.5 db but no more than 3.5 db from each other.
For the MS:
5 power classes for GMSK (GSM, GPRS) and 3 power classes for EDGE which
range from maximum output power - (GSM900) 0.8W - 8W and (GSM1800)
0.25W - 4W
For the BTS:
8 power classes for GMSK which range from maximum output power (GSM900)
2.5W - 320W and (GSM1800) 2.5W - 20W

Power Levels in GSM System

Power Class        Max Power (MS)        Max Power (BS)
1            20 W (43 dbm)*        320 W (55 dbm)
2            8 W (39 dbm)        160 W (52 dbm)
3            5 W (37 dbm)        80 W (49 dbm)
4            2 W (33 dbm)        40 W (46 dbm)
5            0.8 W (29 dbm)        20 W (43 dbm)
6                        10 W (40 dbm)
7                        5 W (37 dbm)
8                        2.5 W (34 dbm)

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krg - 26 Apr 2006 10:15 GMT

hi,
true again, but if your original question meant how fast can an
MS change power level in Uplink direction?? then my answer would be
that it is a lot slower than 60 dB/ms. after a MEAS_REP is caught hold
of by the BTS it commands a power level
change to the MS on the SACCH. after having got the entire SACCH block,
the MS decodes it and now starts to implement the change. but, it can't
do this change in one
go, so now it does what you mentioned, changing the power level in
steps of 2 dB every 60 ms. so if the BTS commanded a very big level
change, its gonna be this long,
480 + T_DecodeSACCHMsg + 60*DesiredPowerLevel/2 milliseconds
Note that while changing the power level, the MS just neglects any
further power level change messages if received from the BTS, but i
fear, this is again implementation dependent.
clarified??? MS would never volunteer to change its power level without
the BSS knowing of it. Legal MS' don't do this.

Care & Take Care,

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vine.palli@gmail.com - 27 Apr 2006 16:33 GMT

Hello and thanks for the answers. But information what I need is that
if power control is applied on downlink (BTS to MS direction), then is
it also applied with same speed 2 dB/60 ms?

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