Neither qpsk nor 8psk transmit complex data. Both can, though, be represented using complex data, with qpsk being more natural to represent that way.

qpsk can be interpreted as two independent psk channels offset by 90 degrees, so if one wanted to describe the state of the system at any point, one could represent one of the channels as the real portion of a complex number, and represent the other channel as the imaginary portion of the complex number. But that does not mean that data is actually complex: it is just a notation. One could use a notation such as (1,0) or (1,-1) or 10 instead.

8psk can be interpreted as two independent qpsk channels offset by 45 degrees. That gives three components per state, and representation as complex becomes messier but is still possible.

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