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

[Paul Sutton]

Hi Yi,

Here are a few generic things to check:

1) Make sure the entire signal bw is inside the band of use
    - the DL/UL frequencies you're using should be fine
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
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?
4) Enable logs on the eNodeB and check if PRACH is detected
5) Try adjusting tx_gain, reducing it or increasing. If the UE sees low
power (<pmax threshold), it won't PRACH

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.

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

Best regards,
Paul

On 05/08/2020 17:08, Yi Chu wrote:
> Dear community,
>
> I have been testing srslte with a few different commercial UEs, some
> worked perfectly and some couldn't find the enb after network search.
> I found several similar issues such as this one
> http://www.softwareradiosystems.com/pipermail/srslte-users/2019-November/003153.html
> <http://www.softwareradiosystems.com/pipermail/srslte-users/2019-November/003153.html> 
> but none of these really reached a conclusion. Here is my setup:
>
> A Ubuntu 18.04 laptop, srsenb and srsepc on the physical machine. I
> have been testing VoLTE as well so I have Open5GS (nextepc) running on
> a virtual machine, and I switch between the two EPC frequently. I have
> tested Band 7 DL=2.65GHz and UL=2.53GHz, also Band 1 DL=2.16GHz and
> UL=1.97GHz. The radio is a USRP B205mini (main USRP) and a USRP X300.
> PRB is 25. The USIM is from opencells. One the same laptop I have a
> working OAI (enb+epc) as well so I also run this setup to test the UEs.
>
> I have tested 6 commercial smartphones and here are the results.
> 1. Huawei P30 with stock Android 10 (unroot): so far the most
> favourable UE. It works with srsenb+srsepc, srsenb+open5gs, and OAI
> enb+epc, both Bands 1 and 7, and two mcc/mnc combinations 00101 and 20892.
>
> 2. IPhone 7 with IOS 12: it starts to get odd from here. It works with
> OAI enb+epc on both LTE bands, with mcc/mnc 20892. Once I switch to
> srsenb+srsepc, the UE can't find the enb in network search.
>
> 3. Samsung S5: I first tested it when it had the stock Android 4
> (unroot and yes it's old), it worked fine with srsenb+srsepc and OAI
> enb+epc, mcc/mnc=20892, band 7. The I flashed Lineage 16 (Android 9,
> unroot) on it and updated the firmware, the UE stops seeing either
> srsenb or OAI enb.
>
> 4. There are three UEs that can't find either srsenb or OAI enb on
> either LTE bands in network search. MI Mix2 (Android 8, unroot),
> Samsung A10 (Android 9, unroot) and Samsung A20e (Android 10, root).
> The Samsung UEs don't seem to support mcc=001 so I have tested 20892
> and but no luck. I'm using the same USIM which just worked on the
> Huawei UE. I have also tested these with USRP X300 but the results are
> the same.
>
> I have no clue what could cause the inconsistency of the IPhone 7, the
> results of the Samsung S5 is very strange as well, it looks like
> updating the firmware has made some impact. 
>
> Anyone has any ideas of further tests/debug I can do, please let me
> know, many thanks!
>
> Best regards
> Yi
>
>
> _______________________________________________
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> srslte-users at lists.softwareradiosystems.com
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-- 
________________________________________________________________
Paul Sutton Ph.D.

Software Radio Systems (SRS)
http://www.softwareradiosystems.com
paul at softwareradiosystems.com

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