# QAM Constellations in Digital Communication Standards

Quadrature Amplitude Modulation (QAM) is one of the most spectrally efficient modulation schemes. This is why it is used in a wide range of digital and wireless communication systems.

Recently, Ref. [1] describes a list of QAM schemes used in the standards as below which I think can be useful for an interested reader.

From the above numbers, observe that the general trend is to push the limits of QAM size although transmission of each extra bit requires doubling the number of constellation points. The relation is not linear, it is logarithmic and this is why the law of diminishing returns sets in as we go higher up.

### References

[1] P. Singya et al., A Survey on Higher-Order QAM Constellations: Technical Challenges, Recent Advances, and Future Trends, IEEE Open Journal of the Communications Society, Vol. 2, March 2021.