[srslte-users] Srsue with USRP N310 for MIMO 2x2

[Andre Puschmann]

Hey François,


[1]
https://docs.srsran.com/en/latest/app_notes/source/5g_nsa/source/index.html#srsue

On 16/6/21 20:04, François Légal wrote:
> I’m trying to use srsue with a USRP N310 vs an LTE cell in conducted
> mode. Using RF port 0 and 1 on the same daughter board.
>  
> -When the cell is configured in SISO, the srsue can attach without any
> issue.
> -When the cell is configured in 2x2 MIMO, srsue cannot attach at all.
> Srsue is configured with 2 antennas in ue.conf.

that is likely an issue with UHD and how the streamers are configured.
You can circumvent that by configuring a fixed sample rate that is
configured at startup, see [1] for how to do that with the UE.

For the N310, use 15.36e6 as sample rate for 10 MHz cells. And make sure
to set the LTE sample rate option.

>  
> Based on the logs, srsue can decode the MIB on the small band of 1920.
> Then there is a switch to a wider band of 15360 (for 10 MHz chBW cell),
> the MIB is not decoded anymore. 
> It seems that there is no correlation peak found for PSS this time in
> this second stage for cell search / CAMPING
> Then we are stuck in this SYNC attempt loop.
>  
> With a USRP B210, the attach works fine in MIMO 2x2
>  
> The call to srsue is made without specific RF options in the command
> line. All other options are specified in the ue.conf file.

try:

[rf]
nof_antennas = 2
device_name = uhd
device_args = type=x300,clock=external,sampling_rate=15.36e6
srate = 15.36e6

[expert]
lte_sample_rates = true

>  
> 1-Is it a known issue and it there an easy workaround such a using
> specific RF parameters for USRP ?

See above.

> 2-To which extend srsue (srsran) has been validated in front of a USRP
> N310 in MIMO 2x2, 4x4 etc.

We don't use the N310 a lot and it also doesn't work well with UHD4. I
strongly recommend to use 3.15.

In general, we don't support 4x4 MIMO, "just" 2x2.


Cheers
Andre