[srsran-users] LTE Range-Finding Technique

[Justin Tallon]

Hey Dan,

In order to attach to a commercial cell with srsUE you would need a sim
card of that network and a sim card to usb reader, once you are attached,
initial TA is sent via RAR and then updates via MAC headers are sent by the
network as needed.

You don't even need to attach to the network though, a network will send an
RAR in response to a PRACH message from the UE so you can just send a PRACH
when you want to get a TA and then just never send the msg3 message to
continue the attach process, this way you don't need the SIM. You could do
this as frequently as you want.
It would disrupt the network somewhat however if you did it too often.


Regards,
Justin

On Mon, 6 Dec 2021, 22:56 Dan Dole-Muinos, <
daniel.dolemuinos at blackswifttech.com> wrote:

> Justin,
>
> Thanks again, as you can likely tell I'm new to LTE--I appreciate the
> insight.
>
> Another clarifying question that arose from your response, could I indeed
> attach the srsUE to any LTE tower, let's say one owned by some cellular
> service such as T-Mobile/AT&T/Verizon/etc? Or would I need to register with
> a particular network to access that network's eNodeBs?
>
> Lastly, how frequently is this TA value sent by the eNodeB?
>
> I'm building up my knowledge of LTE now, so if there are any resources you
> recommend that could help me answer these questions independently, I am
> amenable to that as well.
>
> If I could truly use the srsUE to assess the distance to any provider's
> eNodeBs, and the updates are relatively frequent, that would be quite a
> revelation for this project!
>
> Thanks again for your time,
> Dan
>
>
> On Mon, Dec 6, 2021 at 2:28 PM Justin Tallon <justin.tallon at srs.io> wrote:
>
>> Hey Dan,
>>
>> This is part of the LTE standard, every eNodeB and UE do this.
>>
>> If you attach to any eNodeB with srsUE, the eNodeB will send this TA
>> value in the RAR (random access response). if you have a look at the
>> reception of the RAR in the UE, you should be able to see where this TA
>> value is pulled out and just print it to screen or save it to a file, the
>> conversion from TA value to distance is trivial, you can find it online.
>>
>> Regards,
>> Justin
>>
>>
>>
>>
>>
>> Justin Tallon
>>
>> Senior Engineer
>>
>> Software Radio Systems Ltd.
>> +353860670753
>> justin at srs.io
>> www.srs.io
>> Barcelona, Spain
>> [image: twitter] <https://twitter.com/srssystems>
>> [image: linkedin] <https://www.linkedin.com/in/justin-tallon-71807136/>
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>>
>> On Mon, Dec 6, 2021 at 10:00 PM Dan Dole-Muinos <
>> daniel.dolemuinos at blackswifttech.com> wrote:
>>
>>> Hi Justin,
>>>
>>> Thank you for your quick response! Would this be the case for any
>>> eNodeB, or just the eNodeB included as part of srsRAN? In my project, we
>>> are hoping to find ranges to existing LTE towers.
>>>
>>> Best,
>>> Dan
>>>
>>> On Mon, Dec 6, 2021, 13:46 Justin Tallon <justin.tallon at srs.io> wrote:
>>>
>>>> Hey Dan,
>>>>
>>>> The distance from a UE to an eNodeb is calculated as part of the attach
>>>> procedure, it's called the timing advance or ta.
>>>>
>>>> It is printed in the terminal when our UE attaches to our eNodeB.
>>>>
>>>> Regards,
>>>> Justin
>>>>
>>>> On Mon, 6 Dec 2021, 21:37 Dan Dole-Muinos, <
>>>> daniel.dolemuinos at blackswifttech.com> wrote:
>>>>
>>>>> Hello all,
>>>>>
>>>>> I am working on a project involving finding the ranges from a UE to
>>>>> LTE towers--I was wondering if there was any previous work in this area?
>>>>> Otherwise, any advice on this be greatly appreciated!
>>>>>
>>>>> Thank you,
>>>>> Dan
>>>>> _______________________________________________
>>>>> srsran-users mailing list
>>>>> srsran-users at lists.srsran.com
>>>>> https://lists.srsran.com/mailman/listinfo/srsran-users
>>>>>
>>>>
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