BS-11 power measurement results

[Dieter Spaar]

Hello Harald,

On Sun, 21 Jun 2009 01:05:27 +0200, "Harald Welte" <laforge at gnumonks.org> wrote:
> 
> mh. I see.  Seems like there is some more research required here.  With
> the recent "L1 Info" IE decoding that I committed, we should always see
> the actual RF power in dBm used by the MS during reception of measurement
> results.

The MS power can easily be observed with the Network Monitor of the
Nokia phones, the updated frequency of the display is fast enough.
I can for example see that the MS POWER of the ACTIVATE CHANNEL
command is set (as expected of course).

> No, this is actually the inverse test:  MAke sure the power does _not_ change
> if TCH and BCCH are on the same TRX and we send different BS POWER values
> for the TCH CHANNEL ACTIVATE.  Right now we send a value of 15 (!).

The BS power of the BCCH does not change. From my understanding, this
is the expected behaviour because the BCCH frequency is the reference
of the cell for all such things as cell re-selection or handover. I
think (without being 100% sure) that this even affects all other
timeslots of the BCCH TRX because if a phone measures the signal
strength of a neighbor cell, it does not neccessarily measure on TS0
(not sure how it is acually done, RSSI average over a certain amount
of time ?)

I cannot confirm with a measurement that the TCH power is not changed
because I cannot measure it if TCH and BCCH use the same frequency.

BTW, what does the MS measure and report in the measurment report if
there is an acctive connection, is it the strength of the TCH or the
BCCH ?

> CCCH is the channel that contains the BCCH.  So I'm actually asking for
> what you "don't think", i.e. an attempt to alter the BS POWRE on the TRX
> that carries the BCCH.

As I said, I don't see a change. But as long as it is not 100% sure what
I or the phone measures (BCCH or TCH) there is still a chance that the
TCH is adjusted, although I don't expect it (not that it isn't possible,
I have read that on a TRX which does not carry the BCCH, a different
power level on every timeslot is allowed).

One other observation: I tried to use a different ARFCN for the TCH
on the BS-11 using only one TRX. This does not seem to work, although
I can see with LMT the ARFCN set for all the TCH timeslots and can
also see that the phone switches to the other ARFCN, there is no RF
activity of the BS on this ARFCN. All the commands to activate the
channel are acknowledged and use the other ARFCN, no errors. The
only strange thing is the ARFCN list of the TRX, I have added the
other ARFCN but LMT displays "0" for all additional ARFCNs in the
list, only the first has a different value.

Maybe I am doing something wrong or this is just the expected
behaviour, a TRX which carries the BCCH cannot use a different
ARFCN for the TCH (but this would also mean that no hopping is
allowed).

Best regards,
  Dieter
-- 
Dieter Spaar, Germany                           spaar at mirider.augusta.de