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Unknown Null insertion in BCP Rate dematcher output.

Naveen kumar2
Prodigy 130 points

Hi,

   I am running BCP example project on EVM 6670 . I am passing symbol Deinterleaved data as input to SSL and collecting output dumps of Rate Dematcher for PUSCH input data. In the output dump I am observing a null insertion of 0x00000000 after system,parity1 and parity2 blocks each. In 10 RB case the number of nulls is 3 after each of system,parity1 and parity2 block. Please clarify the behaviour.

Thanks & Regards

Naveen Kumar

  • 0
    TI__Mastermind 30405 points

    Hi Naveen,

    The zero words you see after Systematic, P1 and P2 blocks in the Rate Dematcher output is padding. This is shown in Figre 4-130 (RD Output format for CQI and TCP3D for LTE) in the BCP user guide. Padding is inserted at the end of each individual output block (Systematic, P1 and P2) to make the next output block start at the next 128-bit quad-word boundary.

    Regards

    -Nitin

  • 0 in reply to Nitin Sakhuja
    Prodigy 130 points

    Hi Nitn,

               Thanks for reply , that was my understanding as well, but for higher RB count say 10, after each block (Systematic,P1 and P2 ) three zore words are inserted, are these words going to increase with increase in RB count.

    Thanks & Regards

    Naveen Kumar

  • 0 in reply to Naveen kumar2
    TI__Mastermind 30405 points

    Hi Naveen,

    The BCP Rate Dematcher inserts zero bytes, if needed, at the end of Sys, P1 and P2 blocks so that the next output block starts on the "very next" 128 bit quad-word boundary. Since the RD outputs 8-bit soft values, there can be at max 16 soft-bits in a 128-bit quad-word. Thus the amount of zero-bytes/padding inserted after each individual stream (Sys, P1, P2) can be 15 bytes at max to make the next stream start at a 128 bit quad-word. Think of this padding as being used simply to justify the individual output blocks with no relation to the RB count.

    For eaxmple, if there are 146 bytes in the systematic stream, there will be 14 zero bytes (16 minus (146 Mod 16) = 14)  inserted at the end of systematic output so that the P1 stream starts at a 128-bit quad-word (or 16 byte) boundary, and so on for P1 and P2.

    Regards
    -Nitin