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Both are orthogonal in your example, in different ways. The FDM example provides orthogonality by properly spacing the signals in the frequency domain (their dot product is 0). OFDM is far more spectrally efficient where you have overlapping carriers that are orthogonal. From an implementation standpoint OFDM can be achieved with a DFT. Each of the ...


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For OFDM we select the known gold sequence as the preamble or pilots. We can correctly estimate the channel(10 to 20taps). As you talked about channel delay spread, which is expressed in tap, I assume you want to track the frequency variation. This is equivalent to "correct" sampling channel frequency response. Denote $\tau_m$ the delay spread (the longest ...


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For eg. Using a length of 8 pilot samples can we detect a channel of 20 taps? If your OFDM system is sensibly designed, then, no, you need a pilot on every subcarrier. They don't necessarily have to be sent in the same OFDM symbol. "Sensible" OFDM design means that you choose your subcarrier spacing no smaller than you have to. The reason that you're doing ...


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