Thanks Iain - this was actually very insightful! While it's great to know that there are different modulations, understanding WHY there are different modulations is helpful - at least for how I think about things.

@iain_explains

3 жыл бұрын

Glad it was helpful!

Hi Ian. Good video :-). The other main advantage of APSK besides the decision regions is the PAPR. For the same constellation power, APSK has a smaller PAPR which means we don’t vary much around the amplification saturation point unlike the QAM. The best constellation regarding this saturation would be PSK ( constant power) but having 16 points on the same ring degrades the minimum distance. Looking forward your next video 👍.

@iain_explains

3 жыл бұрын

Well, it's not really another advantage, it's actually the same advantage. The only reason PAPR is a problem is because of the reasons I discussed in the video. As you say, the main issue is the effect of the amplifier saturation on the minimum distance between the outer constellation points - which is what I highlight in the video when I discuss the decision boundaries for the top-right QAM constellation point. I probably should have pointed the PAPR aspect out more explicitly, now that I think about it. And also the effect of the decision boundaries on the error rate (not just that the boundaries are hard to calculate). Thanks for your comment.

Great job, sir. Well explained!

@iain_explains

7 ай бұрын

Glad you liked it.

Great explanation. I really enjoy your channel. Greetings from Vietnam

@iain_explains

2 жыл бұрын

Glad you like the channel. I love Vietnam. I visited in 1998. That's a long time ago, now that I think about it!

Great explanation. I really enjoy your channel. Greetz from Germany

@iain_explains

3 жыл бұрын

That's great to hear. Glad you like them!

You did it! Thank you!!

@iain_explains

3 жыл бұрын

You're welcome.

Thank you for this… very useful.

@iain_explains

Жыл бұрын

Glad it was helpful!

Hi Ian, german viewer here, struggling with a question for my class: How does I/Q-Modulation of a random but band limited signal affect it's power spectral density?

@iain_explains

2 жыл бұрын

Sorry, but your question is a bit confusing / not very precise. What does it mean to have a "signal" that you then apply I/Q-Modulation to? Generally, we would say that there is a "data sequence" that gets "I/Q-Modulated" to generate the "signal" that is to be transmitted. ie. the "signal" is the output from the I/Q modulator, not the input. Also, generally, we only talk about the "band limited" nature of a "signal" when we are talking about the transmitted "signal" - not the data sequence that is going into the I/Q modulator. Hope these clarifications help. For more details on Power Spectral Density, see: "Autocorrelation and Power Spectral Density (PSD) Examples in Digital Communications" kzread.info/dash/bejne/iout1rWFir22YaQ.html

why did you do 3*x^2 ?

@iain_explains

2 жыл бұрын

I'm using x for the radius of the outer circle in APSK, and the quadrants each have 3 points in them that are on the outer circle. So therefore their contribution to the power is 3 times x^2

@ahmetkoraysonal5841

2 жыл бұрын

Sir . Thank you very much . I understand now

Hi Can you please explain the constellations for QPSK 4QAM 16 QAM , 64 QAM and QPSK... please

@iain_explains

3 жыл бұрын

Thanks for the suggestion, I've added it to my "to do" list.

@mjtechstar9992

3 жыл бұрын

@@iain_explains Thanks Iain