Thank you for doing this! It provides a great explanation of the identification of impairments to QAM-based systems, and helps with the understanding of why these impairments affect, for example 256-QAM far more than 8-QAM. Great job!
Great to watch a video renewing my memory on a topic, i wrote an FPGA implementation years ago for (simulating hardware impairments in real-time). Great refresher! Thanks
@@pauldenisowski Thank you so much for this gold video regarding constellation diagram interpretation, Please, what about symbol rotations in the constellation diagram for QAM-OFDM? what is the reason? it is related to the channel? Thank you so much for your response and help :)
@@bstanis1237 Phase noise (unlike "normal" noise) is normally due to imperfections in the transmitter and/or receiver, not in the channel. Hope that helps!
Thanks, point well taken - I appreciate precision in language :) I assume you're referring to slide 3 ("Carrier shifted between discrete states "). Since the carrier always moves from one state to one another state, I used "between" in this case. I would absolutely agree with "among" when there is not a direct motion between states: e.g. "during demodulation, the receiver must choose from among these discrete states" Again, many thanks!
But most modern communication system uses OFDM in which the I/Q value are put on the subcarrier. Therefore, most of conclusions in this video are no more valid.
Constellation diagrams are also used in OFDM-based communications systems. In fact, in some of our other videos you can see constellation diagrams created from 5GNR and 802.11ac signals (both OFDM-based technologies) ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-_dZhxmgT1bE.html ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-su0orD9E7Nk.html You make a good point regarding OFDM in that each subcarrier is individually modulated, so the creation of constellations from the recovered, per-subcarrier IQ values is somewhat more complicated than in non-multicarrier systems. But constellation diagrams and the methods by which they are interpreted still apply in OFDM-based systems as well.
