MIMO Smart Antenna Technology with High Reliability in OFDM Wireless Communications

OFDM传输方案被认为是未来将无线通信和广播相结合的技术。这是因为该方案在宽带和抗多径传播方面具有优异的特性。本研究从2004年开始，对引入OFDM传输方式的MIMO（Multi-Input/Multi-Output，多输入/多输出）无线通信中的高功能、高性能的天线系统（自适应阵列或智能天线）进行了两年的研究。结果如下。(1)二元系统已被检查作为一个自适应阵列的便携式终端。在这种情况下，阵元间的互耦较大，严重影响了自适应阵的性能。研究表明，方向性分集效应改善了MMSE自适应阵列的性能。(2)本文讨论了合成接收和发射最佳方向图的技术 ...更多信息 iscussed。它使用递归DOA估计算法。研究了OFDM系统中最小均方误差（MMSE）自适应阵列保护间隔优化算法的初始值，提出了有效的初始化方法。(3)提出了一种NS（Noise Subspace）循环ESPRIT算法，该算法仅对期望信号的DOA进行估计。它是基于发射信号的循环平稳性。此外，还对NS循环ESPRIT算法进行了改进，减小了干扰波的残余分量。(4)研究了MIMO系统中控制信号间干扰的方法，将交叉极化引入MIMO系统的分支。研究发现，当传播路径的交叉极化幅度比较大时，干扰抑制效果较好，在此基础上，讨论了MIMO-OFDM系统的几种组成技术，为未来的高性能MIMO-OFDM系统提供了重要的理论依据。

The OFDM transmission scheme is considered promising as the technology that integrates the wireless communication and the broadcasting in the future. This is because that scheme has excellent characteristics in broadband and anti-multipath propagation. In this research, the antenna system (adaptive array or smart antenna) with high function and high performance in MIMO (Multi-Input/Multi-Output) wireless communications introducing the OFDM transmission scheme have been researched for two years from 2004. Some results are shown as follows.(1) Two-element system has been examined as an adaptive array for the portable terminal. In this case, the mutual coupling between elements is large, so yielding serious influence on the characteristic of the adaptive array. It is clarified that the characteristic of MMSE adaptive array is improved due to the effect of directivity diversity.(2) The technique for synthesizing the optimum directional patterns for the reception and transmission has been d … More iscussed. It uses the recursive DOA estimation algorithms. Moreover, the initial value of the optimization algorithm of guard interval MMSE adaptive array for OFDM has been investigated, and the effective initializing method is proposed.(3) NS (Noise Subspace) Cyclic ESPRIT is proposed which can estimate the DOA of the desired signal only. It is based on cyclostationarity of the transmitted signal. In addition, the improvement of NS Cyclic ESPRIT is carried out with the decrease of the interfering wave residual component.(4) The method to control the interference between signals in MIMO has been examined, which incorporates the cross polarization into the branch of MIMO. It is found that a sufficient effect of the interference rejection is achieved when the cross polarization amplitude ratio of the propagation path is high.In this way, several constituent technologies which are useful for MIMO-OFDM have been discussed, and the important findings are obtained for future MIMO-OFDM systems with high performance Less