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" ua-cam.com/video/XWytSLZZP1A/v-deo.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 job, sir. Well explained!
Glad you liked it.
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!
Thank you for this… very useful.
Glad it was helpful!
Great explanation. I really enjoy your channel. Greetz from Germany
That's great to hear. Glad you like them!
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" ua-cam.com/video/XWytSLZZP1A/v-deo.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