Why QAM is more bandwidth efficient?
The primary benefit of QAM variants is efficient usage of bandwidth. This is because QAM represents more bits per carrier. For example, 256-QAM maps 8 bits per carrier and 16-QAM maps 4 bits per carrier.
Is QAM digital or analog?
Fundamentally, QAM enables an analog signal to efficiently transmit digital information. It also provides the means by which an operator transmits more bits in the same time period, which effectively increases the bandwidth.