Increasing the number of amplitude level and phase shift, we can gain higher level xQAM, such as 64QAM and 256QAM. It seems the transmission rate can be as high as we want by using this kind of modulation. Is it true? Explain briefly.
What will be an ideal response?
We cannot increase the number of points in a signal constellation without
increasing the transmitted power. As the number of points increase, the distance
between them goes on decreasing, and it is difficult for the receiver to
differentiate between them. To increase the distance between them, we must
increase the radius of the unit circle, that is, the transmitting power.
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