[srslte-users] srsenb disconnection problem

Sat Oct 28 22:21:34 UTC 2017

CFI is always set to 3 and I already tried with 50 rb, with the same
result: during high load the mobile performs a random access which succeeds
and cause the misalignment between epc and enb.
How can I get the cause of the "DCI can't be scheduled"?

Thanks,
Nicola

On Oct 28, 2017 18:17, "Ismael Gomez" <ismael.gomez at softwareradiosystems.com>
wrote:

Hi Nicola,

I see you are using 25 PRB, what value you have for nof_ctrl_symbols in
enb.conf? Can you try setting it to 3 if you haven't already? If you have,
can you try with 50 PRB?

In the logs it looks like the DCIs can't be scheduled. You can see log
messages like this:

13:54:15.964584 [MAC ] Warning [05901] SCHED: Could not schedule DL DCI for
rnti=0x46, pid=0

You can also see that the eNodeB receives no PUCCH in messages like this:

13:54:15.965262 [PHY0] Info    [05898] PUCCH: rnti=0x46, corr=0.02,
n_pucch=20, n_prb=1, ack=0

Look at corr value, it must be at least >0.8. This is because the UE didn't
receive the PDCCH grant and therefore is not sending the PUCCH ACK signal.

We use a quite conservative scheduler for PDCCH and it might try to use
highest aggregation level and it can't fit. I'll look into it, in the
meantime, can you try with 50 PRB and send me the log again if you see the
same issue?

thanks

On Fri, 27 Oct 2017 at 12:32 Nicola Bui <n.bui at northeastern.edu> wrote:

> Another thing I just noticed is that the sequence of operations in the
> phone is as follows:
> - the phone is connected
> unknown trigger
> - the phone attempts a new random access
> - the random access succeeds and the phone gets a new c-RNTI from the eNB
> together with a new IP address
> - the eNB disconnects the old c-RNTI
> It looks to me that at this point the mobile phone is connected to the eNB
> on a TEID that mismatch the one it is using in the EPC.
> Is there a way to understand if a new random access procedure is perfomed
> by a terminal considered already connected to the eNB?
> Maybe I am just wrong.
>
> Looking forward to your interpretation.
> Best,
>
>
> Nicola Bui
> Senior Research Scientist
> College of Computer and Information Science
> 655E Interdisciplinary Science and Engineering Complex
> Boston, MA 02115
>
> On Fri, Oct 27, 2017 at 2:08 PM, Nicola Bui <n.bui at northeastern.edu>
> wrote:
>
>> Hi Ismael,
>>
>> attached you can find the log. To get the error I did the following:
>> - start the epc (OAI - hss, mme, spgw)
>> - start srsenb
>> - turn on the off
>> - some pings to 172.16.0.1 to check the connectivity
>> - speedtest (in the middle of the download test) the C-RNTI got released
>> 13:54:16.034525 <0345%2025> [RRC ] Info    Disconnecting rnti=0x46.
>> Before this, in the log you can find that there is another RRC connection
>> request, which should not be there to the best of my knowledge.
>> After the disconnection the mobile phone continue using the new C-RNTI
>> obtained with the strange connection request, but, apparently, only the
>> uplink is working.
>>
>> Please, let me know should you need other tests and thank you for the
>> support.
>> Best regards,
>>
>>
>> Nicola Bui
>> Senior Research Scientist
>> College of Computer and Information Science
>> 655E Interdisciplinary Science and Engineering Complex
>> Boston, MA 02115
>>
>> On Fri, Oct 27, 2017 at 11:28 AM, Ismael Gomez <ismael.gomez@
>> softwareradiosystems.com> wrote:
>>
>>> Hi nicola, can you send the enb.log?
>>>
>>> El vie., 27 oct. 2017 3:52, Nicola Bui <n.bui at northeastern.edu>
>>> escribió:
>>>
>>>> Thanks Ishmael, Kewin,
>>>>
>>>> that's not my issue: the problem happens while the phone is active, in
>>>> particular when the last is high.
>>>> I already tried increasing the inactivity timer and the error count in
>>>> the configuration file.
>>>> The stranger thing is, as soon as the phone is disconnected (I believe
>>>> it is the enb starting the disconnection) it gets a new rnti and, from the
>>>> phone perspectives, the network is visible and connected. However, nothing
>>>> works anymore like the new rnti is not linked anymore to the proper device
>>>> in the epc.
>>>> Instead, if I toggle the network from the phone, everything is resumed
>>>> properly.
>>>> I cannot send a log right now but I'll try to generate one containing
>>>> the issue and send it to you.
>>>>
>>>> Best,
>>>>
>>>> Nicola
>>>>
>>>> On Oct 27, 2017 04:00, "Kewin Rausch" <krausch at fbk.eu> wrote:
>>>>
>>>>> Hi everyone,
>>>>>
>>>>> I had a similar issue (dunno if it's really the same), and I partially
>>>>> resolved it by following Ismael answer and increasing the inactivity
>>>>> timeout period (now I set it at 60 seconds).
>>>>> Basically If i leave the UE connected to 4G but I do not generate
>>>>> traffic (for about the time the inactivity timeout value), it get
>>>>> disconnected by the eNB.
>>>>>
>>>>> This is not happening while I'm connected to a commercial base
>>>>> station, which means that something nasty is happening, and maybe paging is
>>>>> not correctly handled.
>>>>>
>>>>> I've tried the configuration with a Nexus 5, and once it get
>>>>> disconnected I need to reset everything by switching on and off the
>>>>> Airplane mode.
>>>>>
>>>>> Cheers,
>>>>> Kewin
>>>>>
>>>>> On Fri, Oct 27, 2017 at 8:35 AM, Ismael Gomez <ismael.gomez@
>>>>> softwareradiosystems.com> wrote:
>>>>>
>>>>>> Hi nicola, can you send us the enb.log? It is normal behavior to
>>>>>> release the connection after inactivity. You can extend the timeout in the
>>>>>> enb.conf file, expert section.
>>>>>>
>>>>>> However the UE should reconnect when paging is received when you ping
>>>>>> it for instance. If you send me the log I can check it.
>>>>>>
>>>>>> Regards
>>>>>>
>>>>>> El jue., 26 oct. 2017 17:27, Nicola Bui <n.bui at northeastern.edu>
>>>>>> escribió:
>>>>>>
>>>>>>> Dear all,
>>>>>>>
>>>>>>> I am running srsenb using oai as EPC. My mobile phone (moto g5+)
>>>>>>> connects to the network and for a while behave normally (ping is ok,
>>>>>>> surfing is ok, speedtest is fine). However, after some time everything
>>>>>>> stops working even though the phone still has an IP address the enb says
>>>>>>> the UE is attached (c-RNTI assigned properly).
>>>>>>> Actually, in the enb log I can see the c-RNTI got released and a new
>>>>>>> one got assigned to the UE, but the new connection is not working anymore.
>>>>>>> The only way for recovering the connectivity is from the mobile toggling on
>>>>>>> and off the airplane mode.
>>>>>>> The only error message I can see is: Unhandled feature in RRC
>>>>>>> function: liblte_rrc_unpck_rrc_connection_setup_complete
>>>>>>> However this appears even when the connection has been properly
>>>>>>> setup.
>>>>>>>
>>>>>>> It will be great if I can get a more stable connection or if the
>>>>>>> connection can be automatically reestablished.
>>>>>>> Any suggestion on how to debug this?
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Nicola Bui
>>>>>>> Senior Research Scientist
>>>>>>> College of Computer and Information Science
>>>>>>> 655E Interdisciplinary Science and Engineering Complex
>>>>>>> Boston, MA 02115
>>>>>>> _______________________________________________
>>>>>>> srslte-users mailing list
>>>>>>> srslte-users at lists.softwareradiosystems.com
>>>>>>> http://www.softwareradiosystems.com/mailman/listinfo/srslte-users
>>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> srslte-users mailing list
>>>>>> srslte-users at lists.softwareradiosystems.com
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>>>>>>
>>>>>>
>>>>>
>>
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