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 👍.
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.
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.
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?
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" ruclips.net/video/XWytSLZZP1A/видео.html
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
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 👍.
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.
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.
Glad it was helpful!
Great explanation. I really enjoy your channel. Greetings from Vietnam
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 job, sir. Well explained!
Glad you liked it.
Great explanation. I really enjoy your channel. Greetz from Germany
That's great to hear. Glad you like them!
Thank you for this… very useful.
Glad it was helpful!
You did it! Thank you!!
You're welcome.
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?
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" ruclips.net/video/XWytSLZZP1A/видео.html
why did you do 3*x^2 ?
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
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
Thanks for the suggestion, I've added it to my "to do" list.
@@iain_explains Thanks Iain