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osmotrx: configuration: Add section to document multi-arfcn feature 

Change-Id: Id04c7f7c36d8a8be8145ef8009ece26ef1a7cdff
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Pau Espin 2018-09-19 17:43:09 +02:00 committed by Neels Hofmeyr
parent 6b50b62b12
commit 038ab45137
1 changed files with 49 additions and 0 deletions
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doc/manuals/chapters/configuration.adoc
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@ -34,3 +34,52 @@ trx
<7> Configure the first channel. As no other channels are specified, `osmo-trx` assumes it is using only one channel.
<8> Configure the device to use `BAND1` Tx antenna path from all the available ones (device specific).
<9> Configure the device to use `LNAW` Rx antenna path from all the available ones (device specific).
[[multiarfcn_mode]]
=== Multi-ARFCN mode
The Multi-ARFCN feature allows to have a multi-carrier approach multiplexed on a
single physical RF channel, which can introduce several benefits, such as lower
cost and higher capacity support.
Multi-ARFCN support is available since osmo-trx release `0.2.0`, and it was
added specifically in commit `76764278169d252980853251daeb9f1ba0c246e1`.
This feature is useful for instance if you want to run more than 1 TRX with an
Ettus B200 device, or 3 TRX with an Ettus B210 device, since they support only 1
and 2 physical RF channels respectively. No device from other providers or even
other devices than B200 and B210 from Ettus are known to support this feature.
With multi-ARFCN enabled, ARFCN spacing is fixed at 800 kHz or 4 GSM channels.
So if TRX-0 is set to ARFCN 51, TRX-1 _must_ be set to 55, and so on. Up to
three ARFCN's is supported for multi-TRX.
From BTS and BSC point of view, supporting multiple TRX through multi-ARFCN
feature in OsmoTRX doesn't make any difference from a regular multi-TRX setup,
leaving apart of course the mentioned ARFCN limitations explained above and as a
consequence physical installation and operational differences.
.Example: osmo-bts-trx.cfg using 2 TRX against an osmo-trx driven device
----
phy 0
osmotrx ip local 127.0.0.1
osmotrx ip remote 127.0.0.1
instance 0
instance 1
bts 0
...
band GSM-1800
trx 0
phy 0 instance 0
trx 1
phy 0 instance 1
----
.Example: osmo-trx.cfg using Multi-ARFCN mode to run 2 TRX
----
trx
...
multi-arfcn enable
chan 0
chan 1
----