SDR (Software Defined Radio) » gr-gsm » OsmocomBB SDR PHY

Well, I think e.g. this 'FCCH+SCH+CCCH+BCCH' combination clearly defines
which types of bursts we would expect on a given timeslot...

This is already implemented in OsmoTRX, have a look:

https://git.osmocom.org/osmo-trx/tree/Transceiver52M/Transceiver.h#n131
https://git.osmocom.org/osmo-trx/tree/Transceiver52M/Transceiver.cpp#n411

Also, trxcon is capable to send 'SETSLOT <TS> <TYPE>' command, which
AFAIR contains exactly a channel combination number...

For sure, we may also implement an advanced channel combination option, which
would allow to specify required burst types manually, e.g. 'sb,fb,nb'...

Initial work can be found in a separate branch: https://git.osmocom.org/gr-gsm/log/?h=fixeria/mf_config

As it turns out, indicating a channel combination alone is not enough, because unlike the BTS, we don't
need to detect and demodulate bursts on all logical channels of a given timeslot configuration.
So, I am not sure if the current API is exactly what we need, it's too low level...

A possible solution is to define the most useful channel combinations from GSM 05.02 in Receiver,
either as it's done in trxcon and osmo-bts, or as it's done in the firmware of OsmocomBB:

https://git.osmocom.org/osmocom-bb/tree/src/host/trxcon/sched_mframe.c
https://git.osmocom.org/osmocom-bb/tree/src/target/firmware/layer1/mframe_sched.c

and introduce a new TRXC command, that will be used to activate or deactivate particular
logical channels, e.g.:

SETLCHAN <TS> <LCHAN> <STATE>

SETLCHAN 0 FCCH 1
SETLCHAN 0 SCH 1
SETLCHAN 0 CCCH 1

SETLCHAN 1 TRXC_SACCH4_3 0
SETLCHAN 1 TRXC_SDCCH4_3 1

Ok, I am agree with you. There is no need to overload the Receiver with GSM 05.02 channel combinations, we can offload this to grgsm_trx or even to trxcon. Please see my initial (hackish and draft) attempt: https://git.osmocom.org/gr-gsm/log/?h=fixeria/mf_config.