Patent ID: 8422570

Claim:
An OFDM transmitter comprising: an inverse discrete cosine transform (IDCT) functional unit configured to produce a set of time domain samples for each OFDM symbol interval in which data symbols are mapped to a set of N orthogonal sub-carriers of the form cos(2πnF Δ t) where n=0, 1, . . . , N−1 and 0≦t<T, where N≧2, F Δ is a frequency spacing between subcarriers, T is a time duration of each OFDM symbol interval, wherein the set of time domain symbols {right arrow over (Y)}(i) equal D T X (i) where X (i) are the data symbols, and wherein D T is the transpose of an N×N matrix with the element in the cth row and the rth column defined by D r , c = 2 N ⁢ β r ⁢ cos ⁡ ( π ⁢ ⁢ r ⁡ ( 2 ⁢ c + 1 ) 2 ⁢ N ) for 0≦r≦N−1, and 0≦c≦N−1, where β r = { 1 / 2 , r = 0 1 , r = 1 , 2 , … ⁢ , N - 1 ; and a zero padding functional unit that for each OFDM symbol interval is configured to insert a contiguous set of zeros in the time domain after the set of time domain samples; wherein the inverse discrete cosine transform functional unit is an N-point IDCT that produces N time domain samples; the zero padding functional unit is configured to insert G zeros in the time domain after each set of N time domain samples, where G is selected to substantially eliminate intersymbol interference (ISI) between consecutive OFDM symbols after transmission over a channel, to produce a zero-padded sequence equal to {right arrow over (Y)}′(i)=C zp {right arrow over (Y)}(i) where C zp =[I N 0 N×G ] T is an M× N zero-padding matrix, and I N is an N×N identity matrix, and O N×G is an N×G matrix containing all zeros.