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

[Soumyadeep Datta]

Hi Francisco,

Thanks again for patiently responding to me.

I could find the rrc:meas class, but I am still a little confused. I can
add a cell pci variable there in the meas_obj structure but that will
require me to change the way the meas class is used in the entire
repository, right? Or will a single change in the rrc.cc file of the srsue
directory suffice?

I also noticed implementation of section 5.5.4 of 3GPP TS 36.331 in the
code. I was wondering, can't the handover be implemented by somehow
redirecting the measurement reports there on a trigger to a file/database I
can access in real time? (I was hoping to get access to the RSSI/RSRP/RSRQ
at different neighbouring BSs) If yes, could you guide me as to how that
can be possible?

Yours sincerely,
Soumyadeep Datta.

On Mon 24 Jun, 2019, 6:11 AM Francisco Paisana, <
francisco.paisana at softwareradiosystems.com> wrote:

> 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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