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

[François Légal]

Hello
With your recommended settings it works like a charm.

By the way is there another way to avoid having to force the sampling rate like this ?
e.g if we want the UE to attach to a 20 MHz cell we would have to change the sampling rate and restart srs.
Thanks a lot

François


> Le 16 juin 2021 à 22:41, Andre Puschmann <andre at srs.io <mailto:andre at srs.io>> a écrit :
> 
> Hey François,
> 
> 
> [1]
> https://docs.srsran.com/en/latest/app_notes/source/5g_nsa/source/index.html#srsue <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

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