The constellation order of a digitally modulated signal is the number of distinct symbols in its constellation, i.e. how many unique points exist in the IQ plane (complex plane where real = I, imaginary = Q). A higher order encodes more bits per symbol but requires a higher SNR to distinguish them reliably.
| Modulation | Order | Bits/symbol |
|---|---|---|
| BPSK | 2 | 1 |
| QPSK | 4 | 2 |
| 8-PSK | 8 | 3 |
| 16-QAM | 16 | 4 |
| 64-QAM | 64 | 6 |
| 256-QAM | 256 | 8 |