[srslte-users] Trouble connecting commersial UE (and some basic questions..)

[Andre Puschmann]

Hi Gunnar,

On 18/4/20 12:17, Gunnar Kulbotten wrote:
> Hi!
> Using srsUE seems to work fine. Also connecting a Samsung S4 seems to
> work as it should, I can ping the phone from the PC running srsENB and
> srsEPC. Im̀ setting up this srsLTE network to do some testing of a
> Quectel EG25 commercial UE collocated with some other transmitting
> equipment.
> 
> The Quectel modem sometimes connect to to the LTE network, and I can
> ping it from the PC, as with the phone. But usually I get a lot of
> messages after a short while that suggest that the conenction is lost. A
> lot of these from srsENB, and some other messages from the srsEPC.

The phone usually PRACHs again if it loses sync with the eNB.

> 
> RACH:  tti=1341, preamble=3, offset=0, temp_crnti=0xeb
> Disconnecting rnti=0xeb
> 
> Is this a sync problem?

I think so, yes.

> 
> Im using the Ettus B210 SDR. I dont have a GPS.
> 
> A (maybe stupid..) question regarding the B210: For Transmission Modus
> 1, am I supposed to use one or two antennas? There are two LEDs lit on
> RF-A, the red is for TX/RX, and the green for RX2.
> The Quectel modem came with only one antenna, connected to a port named
> "Main" It also has a unused port named "D" It also has a port for GPS,
> which is connected to a GPS-antenna.

You are supposed to connect antennas to both, one for Rx and one for Tx.
The commercial modems usually just expose ports that combine Rx+Tx into
a single connector. The second connector is perhaps for an optional antenna.

LTE UEs are actually required to have at least two receive antennas.
With a B210 you can also add a second Rx antenna to the other ports if
you want.



> I`ve read a lot of threads from this mailing list, and it seems that
> many have trouble using commercial UEs with srsLTE. I find a few pieces
> of information here and there
> , but it is a very steep learning curve, and much of it is way over my
> head..
> Any advice on how to troubleshoot is appreciated :-)

UE reattaching to the eNB is usually performance issues. If you have a
few Lates on the eNB, the UE might not be able to sync and then reattaches.

Cheers
Andre


> 
> 
> 
> 
> 
> _______________________________________________
> srslte-users mailing list
> srslte-users at lists.softwareradiosystems.com
> http://www.softwareradiosystems.com/mailman/listinfo/srslte-users
>