[srslte-users] What is the "time_adv_nsamples" parameter for?

[Xavier Arteaga]

Hi Federico,
You need to set time_adv_nsamples to zero and then check the UE attaches.
Once the UE is attached, calculate from the ta_us from trace the number of
samples you need to put in advance according to the sampling rate.
time_adv_nsamples = fs * ta_us

If the ue does not attach with time_adv_nsamples=0, try a negative number
in steps of -100us. If the UE attaches, then add the required samples to
make the ta_us 0.

Regards,
Xavier

On Wed, 15 May 2019 at 11:27, Federico Quattrin <fede.quattrin at gmail.com>
wrote:

> Hi Xavier and Naz,
> I have a question too, how do I know the value of this variable for my
> specific SDR?
> I'm trying to make it work a N210 and maybe this could help me
> Greetings!
> Federico
>
> Xavier Arteaga <xavier at softwareradiosystems.com> schrieb am Mi., 15. Mai
> 2019, 11:15:
>
>> Hi Naz,
>> The srsue shall transmit at a given time relative to the eNb and the UE
>> uses the RF front end (B210, lime micro, ...) time stamps for indicating
>> the transmission time. However, the RF front ends are not perfect and it
>> normally takes them some extra samples to transmit. This is translated into
>> a delayed transmission which will be reflected into a non zero Time
>> Alignment while the UE is near the eNb.
>>
>> time_adv_nsamples is for calibrating the rf-front end, so the Time
>> Alignment is zero when the UE is near the eNb. However, if this parameter
>> is overset, it will cause a negative TA for which the eNb are not prepared
>> and the UE will fail to attach.
>>
>> I hope my explanation makes sense.
>>
>> Kind regards,
>> Xavier
>>
>> On Wed, 15 May 2019 at 06:59, zir ikh <nazirmik at gmail.com> wrote:
>>
>>> Hi, can someone tell me what the following parameter does? I'm not
>>> entirely clear on it.
>>>     *time_adv_nsamples*
>>>
>>> It is specified in the *ue.conf* file.
>>>
>>> regards
>>>
>>> Naz
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