OFDMA_Part7 - cfw_x0, x1, xN-2, xN-1: xn = 1 N X e k=0 k N...

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7 { x 0 , x 1 ,…, x N-2 , x N-1 }: x n = 1 N X k e j 2 π nk / N k = 0 N 1 where 0 n ( N 1) …(E1) These N time-domain symbols can collectively be considered as one OFDM symbol/block. Each OFDM block has a duration of T s seconds and is passed through the cyclic prefix (CP) block. Assume that the CP consists of α time-domain symbols that have a total duration of T cp seconds. Then the CP x , x ( 1) ,..., x 2 , x 1 { } is prefixed to the N time-domain samples to give the combined symbol { x CP + OFDM }: x CP + OFDM { } = x , x ( 1) ,..., x 2 , x 1 , x 0 , x 1 ,..., x N 2 , x N 1 { } …(E2) where x = x N ; x ( 1) = x N ( 1) ;…; x 2 = x N 2 ; x 1 = x N 1 …(E3) and hence: x CP + OFDM { } = x N , x N ( 1) ,..., x N 2 , x N 1 , x 0 , x 1 ,..., x N 2 , x N 1 { } …(E4) { x CP + OFDM } has a time duration of T = T s + T cp seconds. Notice that the duration of the combined
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