+ Post New Thread
Results 1 to 4 of 4
  1. #1
    Member level 2
    Points: 673, Level: 5

    Join Date
    Mar 2016
    Posts
    51
    Helped
    1 / 1
    Points
    673
    Level
    5

    how cross-correlation divided by auto-correlation is implemented ?or should I do it?

    I'm trying to detect the start of each OFDM symbol in a continuous OFDM data flow. Each OFDM is composed of a cyclic prefix part and the data part.
    One OFDM example: 6 7 8 1 2 3 4 5 6 7 8.
    The data part is [1 2 3 4 5 6 7 8], the cyclic prefix is [6 7 8]. As you can see, the first 3 samples are exactly the same as the last 3 samples.

    Because of the similarities between prefix and the tail of OFDM symbol, we could do the following operations, and there're periodic peaks which indicate the start of an OFDM.
    Click image for larger version. 

Name:	1.png 
Views:	2 
Size:	3.9 KB 
ID:	134751

    My question is,
    1. ALmost every paper I read mentions this method, but there's division involved. Is it common to do this cross-correlation / auto-correlation in FPGA?(NOT IN MATLAB).
    2. Any suggestions to how to implement this method? Or other algorithms that could help detection.

    Thanks.

    •   AltAdvertisement

        
       

  2. #2
    Advanced Member level 4
    Points: 6,208, Level: 18

    Join Date
    Feb 2015
    Posts
    1,020
    Helped
    287 / 287
    Points
    6,208
    Level
    18

    Re: how cross-correlation divided by auto-correlation is implemented ?or should I do

    Use

    A/b < c/d
    A d < c d

    For a b c d nonnegitive.

    You are comparing ratios.



    •   AltAdvertisement

        
       

  3. #3
    Advanced Member level 4
    Points: 6,208, Level: 18

    Join Date
    Feb 2015
    Posts
    1,020
    Helped
    287 / 287
    Points
    6,208
    Level
    18

    Re: how cross-correlation divided by auto-correlation is implemented ?or should I do

    Edit:

    A*d < c*b



    •   AltAdvertisement

        
       

  4. #4
    Member level 2
    Points: 673, Level: 5

    Join Date
    Mar 2016
    Posts
    51
    Helped
    1 / 1
    Points
    673
    Level
    5

    Re: how cross-correlation divided by auto-correlation is implemented ?or should I do

    thanks for ur suggestion.

    I've decided to use the sign bit of the input signals to do the correlation. By doing this tons of hardware resources could be saved. The downside is that the angle might not be so accurate.



--[[ ]]--