Patent ID: 7103115

Claim:
An apparatus for communicating, comprising: a first transmit device that transmits a set of first training symbols; and a second transmit device that transmits a set of second training symbols; wherein a cross-correlation estimate between the set of first training symbols and the set of second training symbols is essentially zero, whereby a channel estimation is achieved without performing a matrix inversion; wherein the set of second training symbols is substantially identical to the set of first training symbols with a phase shift; wherein the set of second training symbols is related to the set of first training symbols according to: t 2 [n,k]=t 1 [n,k]W K −kl o , where t 1 [n, K] is the set of first training symbols, t 2 [n, k] is the set of second training symbols and W K - k ⁢ ⁢ l o = exp ⁢ ( - j ⁢ 2 ⁢ π ⁢ ⁢ k ⁢ ⁢ l 0 K ) , where n is an Orthogonal Frequency Division Multiplexing (OFDM) block, k is an OFDM sub-band, K is a total number of OFDM sub-bands and l o is a reference frequency.