Maximum Throughput of QAM system

The maximum data rate that can be achieved using 256-QAM scheme is up to 38 Mbps (downstream).

1. How much bandwidth does a QAM occupy?
2. What is highest QAM modulation?
3. Why QAM is more bandwidth efficient?
4. Can we say that 256 QAM is better than 16-QAM in terms of bandwidth efficiency?

How much bandwidth does a QAM occupy?

The channel bandwidth is 6 megahertz, and the QAM signal's -3 dB bandwidth is equal to the symbol rate ( for more on this, see “Digital Transmission: Carrier-to-Noise, Signal-to-Noise, and Modulation Error Ratio,” by Broadcom's Bruce Currivan and yours truly, available here).

What is highest QAM modulation?

“The 802.11be standard increases the QAM modulation order to 4096 QAM to achieve the highest data rate.

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.

Can we say that 256 QAM is better than 16-QAM in terms of bandwidth efficiency?

As the level increases, QAM technique becomes more bandwidth efficient but it requires very robust algorithms in order to decode complex symbols to bits at receiver. For example 256-QAM is complex than 16-QAM. QAM is more bandwidth efficient compare to BPSK but it is less robust.