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In 16 QAM, each channel \$I\$ and \$Q\$ carries bits of the information it wants to encode. For example: if the symbol is (0011) then \$I\$ and \$Q\$ channel carries two bits (00 and 11 respectively).

How about for 8 QAM, where only 3 bits represent a symbol, how are the bits shared between \$I\$ and \$Q\$ channels, does \$I\$ carry 2 bits and \$Q\$ carry 1 bit or vice versa?

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They can be split in any way you want, and don't even need to use 2 bits for one axis and 1 bit for the other, but it is possible.

As an example, you can have a sine wave with constant amplitude but 8 different phases representing 3 bits.

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  • \$\begingroup\$ Hi, thanks, but wouldnt this be similar to PSK(where the phase alone gets changed?). \$\endgroup\$ Feb 2 at 11:12
  • \$\begingroup\$ @AnanthTenappan Yes it would because PSK is a special case of QAM. You can also have 8 different amplitudes at some phase and you will now realize ASK is also a special case of QAM. And, both APSK and QAM modulate the phase and amplitude. Like I said, you can choose any 8 points how you like. \$\endgroup\$
    – Justme
    Feb 2 at 11:18

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