RF power problems with current master of osmo-trx

Andreas Eversberg andreas at eversberg.eu
Sat Jan 25 06:22:56 UTC 2014


Alexander Chemeris wrote:
>
> Could you please provide more details about your setup and experiments 
> you did?
> E.g. what PC so you run it on, what is the CPU utilization, have you 
> tried to run it with real-time priority, what exactly you feed into 
> the osmo-trx and what do you see on your monitoring phone, how exactly 
> long is "longer", etc
>
> We noticed, that Linux kernel 3.3 had issues with 1GbE chips from 
> Intel, so we switched to the kernel version 3.8, which works stable. 
> We use kernels from the stock Ubuntu Server 12.04.
>
dear alexander,

sorry, but this was my fault. here is the reason why i have only RF 
power on two slots:

- i configured TS 0 with CCCH and TS1..TS7 with SDCCH8
- i set bts type at osmo-nitb to "nanobts", which rejects SDCCH8 on TS2..TS7
- no "Set Chan Attr" was sent from osmo-nitb to osmo-bts for TS2..TS7, 
so osmo-bts did not send SETTSC to osmo-trx.

the thing is that the transceiver will only send bursts to umtx, if 
SETTSC was given. (makes sense)

i found out that sending no butsts from osmo-trx to the transceiver will 
cause no RF output. this is why osmo-bts sends dummy bursts for the 
first TRX, so there is RF power on all TS all the time. on other TRX, 
osmo-bts send bursts, only if the logical channel (the bursts belong to) 
is activated. this is the way it is done to reduce noise on the 
spectrum. i can see it one the osmocombb-RSSI application. once a 
channel was activeated, there will be RF power on the specific TS, even 
when osmo-bts does not send bursts anymore. i guess that some filler 
table of osmo-trx causes it. i think it would be nice if osmo-trx would 
stop transmitting, when there are no more bursts comming from osmo-bts. 
(at least after a while.)

best regards,

andreas





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