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QAM constellation

Discussion in 'Electronic Basics' started by M.Nasiriyan, Nov 24, 2003.

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  1. M.Nasiriyan

    M.Nasiriyan Guest

    Hi.
    Please consider an uniform and a nonuniform constellation of for
    example
    16-QAM. As the output we allocate 00, 01, 10 and 11 to the I axe
    respectively from the left and the same to the Q axe from the down.
    This allocation is the same for both systems. So what is the
    difference between two constellation?
     
  2. Huh ??
     
  3. Charles Jean

    Charles Jean Guest



    Would someone please let the Doctor know that it's time for Mr.
    Nasiriyan's daily Thorazine injection? Thank you.
     
  4. Ross Mac

    Ross Mac Guest

    Someone here swallowed the bong water!
     
  5. IMHO it not a stupid question - but not one for a newsgroup named BASICS ;-)
     
  6. MG

    MG Guest

    For each of the 4 points on the I axis (00,01,10,11) there are 4 points on
    the Q axes (00,01,10,11). This constellation is then composed of 16
    different points, called symbols.
    The receiver and decoder will spit out any one of the 16 symbols you can
    make out of 4 bits. Two bits are encoded onto the I axis and the other two
    are encoded onto the Q axes.

    00_00
    00_01
    00_10
    00_11
    01_00
    01_01
    01_10
    01_11
    fill in the blanks
    11_10
    11_11

    The underscore character is only for readability, 2 axes, 2 bit per axes,
    each symbol received contains 4 bits of information.

    Your question is not stupid, and is very basic.

    MG
     
  7. M.Nasiriyan

    M.Nasiriyan Guest

    Thank you for your paying attention. But I think I couldn't explain my
    question well. I know every symbol consists of 4 bits ( 2 bits as real
    part and 2 for imag.)myself , but this 4 bits is similar for two
    different constellations.what I don't know is that how does the
    channel differ between two constellations ?
     
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