Change in osmo-bsc[master]: power_control: implement BCCH carrier power reduction operation

historical

Hello Jenkins Builder, neels, laforge, 

I'd like you to reexamine a change. Please visit

    https://gerrit.osmocom.org/c/osmo-bsc/+/24777

to look at the new patch set (#4).

Change subject: power_control: implement BCCH carrier power reduction operation
......................................................................

power_control: implement BCCH carrier power reduction operation

The BCCH carrier (sometimes called C0) of a BTS shall maintain
discontinuous Downlink transmission at full power in order to
stay 'visible' to the mobile stations.  Because of that, early
versions of 3GPP TS 45.008 prohibited BS power reduction on C0.

However, starting from version 13.0.0 (2015-11) there is a feature
called 'BCCH carrier power reduction operation'.  This is a special
mode of operation, where the variation of RF level for some
timeslots is relaxed for the purpose of energy saving.

In BCCH carrier power reduction operation, for timeslots on the
C0 carrier, except timeslots carrying BCCH/CCCH, the output power
may be lower than the output power used for timeslots carrying
BCCH/CCCH.  In this case the maximum allowed difference in output
power actually transmitted by the BTS is 6 dB.

Introduce a VTY command to turn on and off the BCCH carrier power
reduction operation.  Also introduce a CTRL command.  On the
A-bis/RSL, abuse the BS POWER CONTROL message by setting
the Channel Number IE to 0x80 (RSL_CHAN_BCCH).

Currently, only osmo-bts-trx is supported.  A value greater than
zero makes it reduce the power on *inactive* timeslots of the
BCCH carrier.  Sending zero disables the BCCH power reduction
mode completely.

For more details, see 3GPP TS 45.008, section 7.1, and 3GPP TR 45.926.

Change-Id: I047fce33d4d3e4c569dd006ba17858467a2f4783
Related: SYS#4919
---
M doc/manuals/chapters/power_control.adoc
M include/osmocom/bsc/bts.h
M src/osmo-bsc/bsc_ctrl_commands.c
M src/osmo-bsc/bsc_vty.c
M src/osmo-bsc/bts.c
M src/osmo-bsc/bts_osmobts.c
M tests/osmo-bsc.vty
7 files changed, 235 insertions(+), 1 deletion(-)

  git pull ssh://gerrit.osmocom.org:29418/osmo-bsc refs/changes/77/24777/4
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Gerrit-Project: osmo-bsc
Gerrit-Branch: master
Gerrit-Change-Id: I047fce33d4d3e4c569dd006ba17858467a2f4783
Gerrit-Change-Number: 24777
Gerrit-PatchSet: 4
Gerrit-Owner: fixeria <vyanitskiy at sysmocom.de>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: laforge <laforge at osmocom.org>
Gerrit-Reviewer: neels <nhofmeyr at sysmocom.de>
Gerrit-CC: pespin <pespin at sysmocom.de>
Gerrit-MessageType: newpatchset
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