[srslte-users] Multiple RAR messages + UE does not reply to RRC Connection setup msg

[Francisco Paisana]

Hey Michalis,

Can you send the logs of the eNB and UE?

Regards,
Francisco

On Fri, Sep 28, 2018 at 4:52 PM michalis13 <michalis13 at protonmail.com>
wrote:

> Hi all,
>
> I have created here in our lab a fully controlled NW using srsLTE, which
> is connected to a COTS UE though a channel Emulator.
> The test environment is fully controlled and all devices are connected
> together using RF cables.
> I am trying to extract different TA values in order to import them to a
> ray tracing software we have create in-house in order to perform accurate
> channel estimation. The UE contains a programmable SIM card from sysmocom,
> and the SIM info is registered to the HSS. It might be important to mention
> that we are using OpenAir-CN for our EPC.
>
> The problem is as follows:
> 1. I found difficulties calibrating the TA for my USRP B205mini. I am
> still not sure if the value I have chosen for time_adv_nsamples is the
> best, but still looks better than before were auto was used. Apparently I
> concluded that 140 is the best so far. It would be very helpful if there
> was some kind of calibration functionality for the transceiver of different
> USRP boards. I am very willing to dig into it a find a solution if someone
> can guide me. Unfortunately my coding skills are not the best.
> 2. Using 140 as time_adv_nsamples I started experimenting for the past few
> days playing with the parameters in sib and enb config files
> 3. The results were disappointing in some occasions
>     A) The pcap captured by the eNodeB revealed the eNB was sending
> multiple RAR responses (up to 10 sometimes) to the UE without receiving the
> appropriate             answer back.
>         This was not the case for all times however it was occurring very
> often
>     B) Other times, the UE was sending RRC Connection Request, with the
> enb replying with an RRC Connection Setup. After that no Attach Request
> from the UE            or any other response. This was happening multiple
> times, some of them there was a response from the UE sometimes nothing.
>
> I am not sure if this is problem with my CPU or with my RF path.
> These problems occur when I configure the emulator accordingly to emulate
> distances of TA more than 2.
> When the time delay profile of the channel is for TA 0 or 1 this problem
> is not very obvious.
>
> Anyone has a clue or can suggest how I can approach this issue?
> Thanks
> *Best Regards,*
> *Michalis*
>
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