The addition of a cyclic prefix to each symbol solves both ISI and ICI. In our system, we assume the channel impulse response has a known length *L*. The prefix consists simply of copying the last *L*-1 values from each symbol and appending them in the same order to the front of the symbol. By having this buffer of essentially junk data in the front, the convolution of the impulse response with the signal at the end of a symbol does not affect any of the actual data at the beginning of the next symbol. In addition, by repeating the last elements at the beginning, the first real "data" elements of each symbol experience overlap with the "end" of the symbol, just as in cyclic convolution. This means the linear convolution of the channel impulse response with the concatenated symbols becomes concatenated cyclic convolutions of the impulse response with the individual symbols. Since cyclic convolution directly corresponds to multiplication in the frequency domain, this has great import with respect to equalization, as we will see later. After the time-domain signal passes through the channel, it is broken back into the parallel symbols and the prefix is simply discarded.

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