A novel pilot sequences design for MIMO OFDM systems with virtual subcarriers

Conventional optimal pilot sequences designed for MIMO OFDM system are derived with an assumption of fully employed subcarriers, like the phase shift sequences proposed by Imad. However, virtual subcarriers exist in practical OFDM based systems and they will lead to the loss of orthogonality for conventional multiple antenna pilot sequences. So in this paper we design a set of short orthogonal sequences and the placement of pilot subcarriers is optimized with the existence of virtual subcarriers. By the proposed pilot design, the interference among transmit antennas could be minimized. Simulation shows that great performance gain can be achieved by the proposed method.