一种用于下行传输的特征波束发射分集方案

Transmit diversity scheme based on eigenbeams for downlink transmission

发射分集要求不同发射天线的信道衰落是相互独立的,而作为智能天线核心技术之一的特征波束形成则需要利用发射天线之间的相关性来实现,它可以将衰落相关信道转换为相互独立的衰落信道。将发射分集技术和特征波束形成技术相结合,研究了一种用于下行传输衰落相关信道的发射分集实现方案。利用空域协方差矩阵的特征矢量作为空时码矩阵的加权因子,即利用相互正交的特征波束来承载空时码。载有空时码的特征波束可以选择空间能量最集中的方向发射信息,从而提高了发射分集在衰落相关信道中的传输性能,降低了系统实现的复杂度。

Transmit diversity technique requires that the channel fading of different transmitting antennas is independent. However, eigenbeamforming, as the core of smart antenna technique, relies on the correlation between different antenna elements. It can be used to convert correlated fading channels into independent ones. The transmit diversity and the eigenbeamforming are combined to study the realization and performance of transmit diversity over correlated fading channels for downlink transmission. Eigenvectors of the spatial correlation matrix serve as the weights of the space-time code matrix. The space-time codes are carried by orthogonal eigenbeams. The space-time coded eigenbeams can channel the transmit power in the directions with the biggest gains and point the signals to these directions, thus improving the performance of wireless transmission. Eigenbeamforming is a dimension-reducing process for the realization of the system.