[srslte-users] Prach UE in srsLTE

[Germán Corrales Madueño]

Hello,

I'm running OpenAirInterface LTE eNodeB at 2.66GHz with 25RBs and the
following PRACH Configuration:

        prach_root                                = 0;
>         prach_config_index                        = 0;
>         prach_high_speed                          = "DISABLE";
>         prach_zero_correlation                    = 1;
>         prach_freq_offset                         = 2;
>
> Meaning that preamble format used is 0 (0.9 ms). If I try to use prach_ue
example with:

$  sudo ./prach_ue -f 2660000000 -F 2540000000 -p 2 -v
>


the cell is detected and preamble is transmitted:

 Setting sampling rate 5.76 MHz
>  - Cell ID:         0     1.8, FrameCnt: 0, State: 1
>  - Nof ports:       1
>  - CP:              Normal
>  - PRB:             25
>  - PHICH Length:    Normal
>  - PHICH Resources: 1/6
>  - SFN:             84
> Decoded MIB. SFN: 84, offset: 1
> Send prach sfn: 85. Last frame time = 11.728130, send prach time =
> 11.738130
> Looking for RAR in sfn: 86 sf_idx: 4
>
>
However no RAR is received, which is to be expected since the eNB does not
detect preamble activity. When I looked into the output signal of the UE
(srsLTE) in the spectrum analyzer, I could see the envelope spanning for
almost 8ms (8x times longer than expected). Image below...

[image: Imágenes integradas 1]
Envelope View: http://pasteboard.co/14TY5GgX.png
Spectrum View: http://pasteboard.co/14TO4mot.png

Next week I will look into the code, but I would be nice to know if
prach_ue is operational.

Thanks,
Germán
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