[srslte-users] Some commercial UEs can't detect the enb

[Yi Chu]

Hi Paul,

Many thanks for getting back!

>
> 2) Check that there are no interfering signals on the frequencies of use
>     - B1 and B7 are fully allocated in the UK (
> https://www.spectrummonitoring.com/frequencies/#UK) so use a Faraday cage
> or check for existing carriers
>

I used the USRP as a spectrum analyser and checked the LTE bands in my
area, the frequencies I picked are not occupied at the moment. I might be
able to run the tests in an anechoic chamber at some point.


> 3) use a GPSDO or external clock source, or make sure carrier frequency
> offset is small enough
>     - Are you using an external clock source or do you have access to
> equipment to check the frequency accuracy?
>

I have an external clock source with GPSDO but I don't have access to it
immediately, I will try that once I can.


> 4) Enable logs on the eNodeB and check if PRACH is detected
>

I enabled the debug level enb logs, but the last logs I can see is normally
the S1 setup response.


> 5) Try adjusting tx_gain, reducing it or increasing. If the UE sees low
> power (<pmax threshold), it won't PRACH
>

I have tried tx_gain from 80 to 120, the UE is within 2 meters from the
antenna. How is the gain mapped to the actual gain of the USRP? I can't
find it in the enb.log or the logs shown in the terminal.

For the iPhone 7 case, you could compare PRACH, SIB1 and SIB2
> configurations for differences between srsENB and OAI. You could also add
> SIB3 configuration in case the UEs require it.
>

I will try matching the SIB1 and SIB2 configurations and give the iPhone 7
another go.


> Are you using the default config files for everything except EARFCN? If
> not, could you share your config files?
>

I only modified the enb and rf sections, anyway here is the enb.conf.

The other minor thing to mention is that I'm using the 19_12 release which
is stable for VoLTE setup. I have tested the 20_04 release with the Huawei,
iPhone, Samsung S5 and MI Mix 2 but the results are the same.

Regards
Yi
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