We use the completion call-back from L1 to compare the instructed
TRX board output power with the actual value as reported back from
L1.
Right now we only print an error message in case the values disagree.
In the future we might want to either use that value as part of our
calculation or send an OML alarm report to the BSC.
In order to support transmit power reduction by thermal management
as well as the variety of new internal / external PA configurations
of BTSs, we need a slightly more complex system.
Also, as at high power a single dB can be quite a big difference,
we are now doing all computations in milli-dB(m), i.e. 1/10000 bel.
Ramping is now used both for up and down ramping, as that is useful in
cases where you want to gracefully shut down a cell by shrinking its
radius, gradually handing over subscribers to neighboring cells.
Furthermore, this code is becoming part of the 'common' codebase, as it
is not really specific to how sysmobts is working.
The user can specify a single aggregate value for external system
gain/attenuation. Let's say you have 1dB loss of antenna cable, so you
can put that as 'user-gain -1' into the config, which means that a
'transmit power of 20dBm' will be compensatet for that and the TRX is
instructed to output 21dBm to compensate the cable loss. Similarly,
external PAs can be described by a positive user-gain.
One of the next steps will be to communicate those values and the
nominal power capability of the specific BTS to the BSC, so the BSC will
automatically show correct signal levels in the VTY and log files.
The code includes provisions for future extensions regarding
* an external and an internal PA with calibration tables
* a thermal attenuation setting to be controlled by the site manager
Harald Welte
Holger Hans Peter Freyther