Patent ID: 7450490

Claim:
A method of communication using Orthogonal Frequency Division Multiplexing (‘OFDM”), the method comprising the steps of: generating bit streams b n ε(0,1), n=0,1, . . . ,K−1 and the corresponding sets of frequency domain carrier amplitudes (X 0 (k) to X N (k)), where k is the OFDM symbol number, modulated as OFDM symbols to be transmitted from a transmitter, inserting prefixes as guard intervals in said sample streams, transmitting said OFDM symbols from said transmitter to a receiver, using information from said prefixes to estimate the Channel Impulse Response (H D (F) ) of the transmission channels at the receiver, where (H D (F) ) is the length D vector defined as the channel impulse response vector in the frequency domain, denoted by superscripted, F, and using the estimated Channel Impulse Response (Ĥ D (F) ) to demodulate said bit streams in the signals received at said receiver, wherein said prefixes (α k. c 0 to α k. c D−1 ) are deterministic and are known to said receiver as well as to said transmitter, where c is the set of vectors containing constant postfix samples, (α k ) is a weighting factor proportional to ⅇ j ⁢ 2 ⁢ π N + D ⁢ m , where J is the square root of −1, N is the useful OFDM symbol size, D is the size of the prefix vector, and m is an integer, and further performing the multiplication by a matrix proportional to R ( 1 ) ⁡ ( k ) = N + D · [ V ^ ] · r ⁢ ⁢ ( k ) , ⁢ where [ V ^ ] = ⁢ ( ∑ n = 0 N + D - 1 ⁢ ⁢  β k  - 2 ⁢ n N + D ) - 1 2 · ⁢ diag ⁢ ⁢ { 1 , β k ⁢ 1 N + D , … ⁢ , β k ⁢ N_D - 1 N + D } , where β k is the ratio of consecutive α k , β k = a k a k + 1 , calculating the frequency shifted CIR coefficients H ^ N + D Shifted , F = ( H ^ ⁢ ⁢ ( β k - 1 N + D ) ⁢ … ⁢ , H ^ ⁢ ⁢ ( β k - 1 N + D · ⅇ j ⁢ ⁢ 2 ⁢ π ⁢ N + D - 1 N + D ) ) , performing a component-by-component division R ( 2 ) ⁡ ( k ) = R ( 1 ) ⁡ ( k ) = ⊗ H ^ N + D Shifted , F , performing a multiplication by a matrix proportional to R ( 3 ) ⁡ ( k ) = [ V ^ ] - 1 · 1 N + D · R ( 2 ) ⁡ ( k ) , extracting the N equalized samples corresponding to the k th data symbol to the vector S EQ (k), and transforming the symbol ŝ^(k) into frequency domain by performing a Fourier Transform: S (F) EQ (k)=[F NXN ]·S EQ (k).