multiple phy with osmo-trx

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Tom Tsou tom at tsou.cc
Wed Aug 10 17:35:02 UTC 2016


On Wed, Aug 10, 2016 at 7:17 AM, Max <msuraev at sysmocom.de> wrote:
> <0002> gsm_subscriber.c:309 Subscriber 1640000005666 ATTACHED LAC=1
> <001d> input/ipaccess.c:277 Bad signalling message,sign_link returned error
> <001d> input/ipaccess.c:277 Bad signalling message,sign_link returned error
> <0000> abis_rsl.c:1835 (bts=0,trx=1,ts=0,ss=0) ERROR INDICATION
> cause=Timer T200 expired (N200+1) times in state=RELEASE REQUESTED
>
> Could you share which versions/branches have you used in your tests?

I was using master branch at the time. I will test with more recent
master branch updates later today.

> Also could elaborate on '-m' - what's this option for and when it's
> necessary? How it's support to affect osmo-bts configuration?

There are two ways to implement multi-ARFCN with the B210 - using
independent, direct channels for each ARFCN and mutiplexing multiple
ARFCN's onto a single RF channel.

The direct approach uses separate physical channels of the B210 (one
ARFCN each for side A and side B). Note that channels are not 100%
independent on the B210 because they share a single local oscillator
(LO). For that reason ARFCN channel separation is limited to roughly
25 MHz. This is the configuration if '-m' is not specified.

The 'multi-carrier' approach multiplexes up to 3 ARFCN channels onto a
single physical RF channel (side A) on the B210. Channel spacing is
fixed at 800 kHz, or 4 ARFCN channels. ARFCN settings from OpenBSC
must match accordingly. The '-m' option enables this configuration.

Also note that the above configurations cannot be combined.

  -TT



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