[srslte-users] Request for information on handoff support in srsLTE

[Francisco Paisana]

Hey Soumyadeep,

I was wondering now whether a more direct way to do this would be to add
the cell PCIs that you are interested in measuring directly in the UE
"objects" variable of the rrc::rrc_meas class. Then you could force the UE
to do cell reselection once it finds a stronger cell. Would that work for
you?

Regards,
Francisco

On Sat, Jun 22, 2019 at 2:05 AM Soumyadeep Datta <dsoumyadeep97 at gmail.com>
wrote:

> Hi Francisco,
>
> Thank you so much for your insightful reply. However, I am really new to
> this, hence I could not fully understand what you are suggesting.
>
> I am working on the master branch, and as suggested by you, I checked the
> code in ./srsue/src/upper/rrc.cc and a header file
> ./lib/include/srslte/asn1/rrc_asn1.h to see how the
> RRCConnectionReconfiguration works in srsLTE. I could not find the exact
> parameter in the "meas_cfg" structure where I can add the neighbour cell
> index and recover its signal strength.
>
> I shall be highly obliged if you could direct me to the correct file(s) I
> may need to look at for this in case I am wrong with that, and the correct
> parameters I might need to modify to be able to monitor the signal strength
> to both the eNBs (I shall initially attempt to make the setup with 2 eNBs).
>
> Yours sincerely,
> Soumyadeep Datta.
>
> On Fri, 21 Jun 2019 at 04:25, Francisco Paisana <
> francisco.paisana at softwareradiosystems.com> wrote:
>
>> Our srsUE already supports handover. Its signal strength measurement
>> configuration is set by the RRCConnectionReconfiguration message. So, if
>> you need to extract neighbour cells' signal strength, you could add the
>> cells you need to the measCfg in the eNB
>> RRCConnectionReconfiguration message.
>>
>> Making the actual S1 handover is much more complicated though. If you
>> don't really mind extra latencies, you could just force the UE to establish
>> a new cell selection and RRC connection once it finds a stronger target
>> cell.
>>
>> Another issue you have to pay attention to is having the source and
>> target cells well aligned in frequency. The way UEs perform signal strength
>> measurement of neighbour cells assumes good inter-cell frequency
>> synchronization. This can be achieved with an external clock reference
>> (e.g. ettus octoclock).
>>
>> Regards,
>> Francisco
>>
>> On Thu, Jun 20, 2019 at 4:43 PM Soumyadeep Datta <dsoumyadeep97 at gmail.com>
>> wrote:
>>
>>> Hi Francisco,
>>>
>>> Thank you for your reply.
>>>
>>> I need to implement handoff dynamically, for example, in a mobility
>>> situation where a UE moves from one BS's coverage region to another.
>>>
>>> To be able to do that in real time, I need a way to retrieve the
>>> received signal strength or some other parameter which will help me decide
>>> in favour of one BS over the other and thereafter implement the handoff.
>>>
>>> Yours sincerely,
>>> Soumyadeep Datta.
>>>
>>>
>>> On Thu 20 Jun, 2019, 5:00 AM Francisco Paisana, <
>>> francisco.paisana at softwareradiosystems.com> wrote:
>>>
>>>> Hey Soumyadeep,
>>>>
>>>> Our eNB does not yet support S1 handover. Regarding your second
>>>> question, do you want to set the UE's cell dynamically or just at startup?
>>>>
>>>> Regards,
>>>> Francisco
>>>>
>>>> On Thu, Jun 20, 2019 at 9:04 AM Soumyadeep Datta <
>>>> dsoumyadeep97 at gmail.com> wrote:
>>>>
>>>>> Hello,
>>>>>
>>>>> I am a new user of srsLTE platform. I wanted to know if the srsLTE
>>>>> stack has support for handoff/mobility in the ePC/Core network. If not, is
>>>>> there a provision to manually control the eNB to which the UE attaches? (I
>>>>> was considering retrieving some suitable parameter, for instance, received
>>>>> signal strength, to achieve this.)
>>>>>
>>>>> Yours sincerely,
>>>>> Soumyadeep Datta
>>>>> Final year Dual Degree student,
>>>>> Department of Electrical Engineering,
>>>>> IIT Kanpur.
>>>>> _______________________________________________
>>>>> srslte-users mailing list
>>>>> srslte-users at lists.softwareradiosystems.com
>>>>> http://www.softwareradiosystems.com/mailman/listinfo/srslte-users
>>>>>
>>>>
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