Hi and thank you for an excellent explanation of OFDM.I am just beginning to try to understand OFDM and have one ( probably stupid ) question though: Let's say you use some QAM-modulation. In to the IDFT you then have complex numbers from a constellation diagram. Out from the IDFT you have some other complex numbers that are serialized and transmitted. In the receiver, these complex numbers are sampled and fed into the DFT that calculates the original complex numbers from the constellation diagram. The question: If you can send and then detect the complex numbers from the IDFT, why can't you send and detect the complex numbers from the constellation diagram directly ?
Yes, 64 Channel are inside 20Mhz (in reality if i do not mistake subcarriers are something like 10khz each other, the multiplexing of many users in the same Channel is done by assigning a SET of subcarriers to users)... 20Mhz is the intermediate frequency modulation (the output of IFFT converte to analogo, before the main modulation at 5GHz)
Hi and thank you for an excellent explanation of OFDM.I am just beginning to try to understand OFDM and have one ( probably stupid ) question though:
Let's say you use some QAM-modulation. In to the IDFT you then have complex numbers from a constellation diagram.
Out from the IDFT you have some other complex numbers that are serialized and transmitted.
In the receiver, these complex numbers are sampled and fed into the DFT that calculates the original complex numbers from the constellation diagram.
The question: If you can send and then detect the complex numbers from the IDFT, why can't you send and detect the complex numbers from the constellation diagram directly ?
Don't forget Collins radio in the 50's. Kineplex used coherent synchronous signaling techniques.
13:25 why 64 channels with a span of 20MHz occupy 5GHz bandwidht? How latge is every channel? I thought in OFDM each channel is 64KHz or less
Yes, 64 Channel are inside 20Mhz (in reality if i do not mistake subcarriers are something like 10khz each other, the multiplexing of many users in the same Channel is done by assigning a SET of subcarriers to users)... 20Mhz is the intermediate frequency modulation (the output of IFFT converte to analogo, before the main modulation at 5GHz)
@@albertosimeoni7215 grazie Alberto
thank you
intresting