Abstract: A Space-Time Eigenbeam Coded scheme is discussed to improve the performance of Space-Time Coding for downlink wideband correlated fading channels. This novel transmission scheme combining Eigenbeam forming with OFDM is proposed. A group of eigenvectors of the Spatial-Correlated-Matrix (SCM) is introduced as the weights of the Space-Time code-matrix. The scheme can channel the transmit power in the directions with the biggest gains and convert correlated fading channels into an independent FIR channel with 2 transmitting antennas and N receiving antennas by Eigenbeam forming and reducing the dimensions. Then OFDM is utilized to convert this FIR channel into a group of independently paralIe1 subchannels to carry Space-Time Codes. The BER(Bit Error Rate) performance comparisons with the traditional Alamouti code under different multi-path and transmit antenna conditions, through extensive Monte-Carlo simulation. The simulation results show that the proposed scheme has a lower BER than the traditional Alamouti code and the Signal-to-Noise Rate (SNR) is higher meanwhile. The performance is 5dB higher than that of the traditional Alamouti code under 6 transmitting antennas and 16 paths. The proposed scheme leads to a better diversity gain and increases equivalent channel total power.

Key words: space-time coding, eigenbeam forming, eigen value decomposition, antenna arrays