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AIF2 SYNC reception

Naoki Takahashi
Prodigy 130 points

Hi,

I am having a trouble with AIF2 RM synchronization.

What I am trying to do now is to capture the CPRI SYNC symbol in between the window specified by pi_min and pi_max parameters.

I'm setting pi_min = 0x0 and pi_max = 0x3E66, which is about the same size as one CPRI hyperframe. Since there must be a SYNC symbol within this period, I'm expecting the pi_capt value (at_pivalue_lk[0]) would fall somewhere between pi_min and pi_max.

However when I do run the test the pi_capt value reports some very large value such as 0x255AE9 (close to the end of one 10ms radio frame).

Any idea?

Other things to note:

  • No LOS is detected
  • AIF2 is operating in CPRI mode
  • So far I was able to bring the receive statemachine to ST3 (which is equivalent to CPRI HFNSYNC state) so the external CPRI transmitter is surely transmitting SYNC once per hyperframe. This was further confirmed by applying a protocol decoder on the SerDes waveform.
  • The SYNC control symbol is {K28.5 + D16.2}(IDLE2 by CPRI Spec) but not {K28.5+D5.6} (IDLE1). I'm not sure if this is okay for AIF2.
  • The AT is configured for 10ms LTE mode. It is triggered by external radsync and physync pins.

BR,
Naoki

  • 0
    Prodigy 130 points

    Hi all,

    Problem self-solved.

    It seems that AIF2 not only checks SYNC symbol but HFN embedded in the CPRI stream (at Z.64.0).
    So even if the SYNC symbol is within the window, it's not recognized as the beginning of the CPRI frame unless the embedded HFN is #0.

    After modifying the HFN offset of the external CPRI transmitter, I was able to see pi_capt value become 0x1AEB, about 28 [usec] from the PhyT frame boundary.

    BR,
    Naoki