摘要：This paper describes a Least Squares (LS) channel estimation scheme for mimo OFDM systems based on time-domain training sequence. We first compute the minimum mean square error (MSE) of the LS channel estimation, and then derive the optimal criteria of the training sequence with respect to the minimum MSE. It is shown that optimal time-domain training sequence should satisfy two criteria. First, the autocorrelation of the sequence transmitted from the same antenna is an impulse function in a region longer than the channel maximum delay. Second, the cross-correlation between sequences transmitted from different antennas is zero in this region. Simulation results show that the estimator using optimal time-domain training sequences has better performance than that using optimal frequency training sequence at low signal-to-noise ratio (SNR). To reduce the training overhead, a suboptimal training sequence is also proposed. Comparing with optimal training sequence, it has low computation complexity and high transmission efficiency at the expense of little performance degradation.

摘要：This paper proposes a joint nonlinear transceiver design scheme based on minimum mean square error （MMSE） criterion for non-regenerative multiple input multiple output （mimo） relay system. The proposed scheme decomposes the error covariance matrix, reformulates the original joint design problem as two separate optimization problems, and then provides a closed-form solution with only local channel state information （CSI） available at the source and destination. Performance evaluation shows that the proposed scheme significantly outperforms linear schemes, and has a competitive performance compared with existing global CSI based nonlinear schemes, both iterative and non-iterative.

摘要：This paper addresses the robust linear filter design issues for non-regenerative multiple input multiple output （mimo） relay systems with imperfect channel state information （CSI） in both or partial hops. By considering statistical Kronecker channel model involving channel mean and antenna correlation, the robust linear processing schemes in imperfect CSI scenario for both hops are first derived based on mean squared error （MSE） criterion. In addition to this, the result is also extended to two practical scenarios, i.e. imperfect CSI for relay link with perfect CSI for access link and imperfect CSI for access link with perfect CSI for relay link. Simulation results show that the proposed scheme is capable of mitigating the performance degradation caused by the imperfect CSI.

摘要：Single-symbol maximum-likelihood （ML） decodable space-time block codes （SSDCs） can achieve a maximal symbol rate of 6/7 for multiple-input multiple-output （mimo） communication system with five or six transmit antennas by using rate-efficient generalized coordinate interleaved orthogonal designs （RE-GCIODs）. Unfortunately, there are many zero entries in the eodeword matrix of RE-GCIODs. The zero entries result in high peak-to-average power ratio （PAPR） and also impose a severe constraint on hardware implementation. In this paper, for mimo communication systems with five or six transmit antennas and one receive antenna, a new SSDC is proposed. By combining Alamouti code and orthogonal space-time block code （OSTBC）, desirable properties like RE-GCIODs can be achieved and are derived, including maximal symbol rate up to 6/7, full diversity and single-symbol ML decodability. Moreover, by reducing the number of zero entries in the codeword matrix, the peak-to-average power ratio （PAPR） of our proposed code is lower than RE-GCIODs. Simulation results show that the proposed codes outperform RE-GCIODs under peak power constraint while performing almost same under average power constraint.

摘要：This article investigates transmitter design in Rayleigh fading multiple input multiple output （mimo） channels with spatial correlation when there are channel uncertainties caused by a combined effect of channel estimation error and limited feedback. To overcome the high computational complexity of the optimal transmit power allocation, a simple and suboptimal allocation is proposed by exploiting the transmission constraint and differentiating a bound based on Jensen inequality on the channel capacity. The simulation results show that the mutual information corresponding to the proposed power allocation closely approaches the channel capacity corresponding to the optimal one and meanwhile the computational complexity is greatly reduced.

摘要：In this article, the authors consider joint design of a linear precoder and power allocation for uplink multiuser multiple input multiple output （mimo） communication systems with limited feedback to improve the bit error rate （BER） performance for all users. Precoder selection from the codebook set is directly based on the exact BER performance, instead of other suboptimal criteria, to achieve the optimal precoder matrix, but closed-form expressions may not exist in the view of power allocation based directly on the BER criterion. From this perspective, the authors propose the joint transmitter optimization algorithm for the consideration of precoder design, with total power constraint for asymptotic MBER （AMBER） criterion. In this AMBER criterion, a closed-form solution has been derived for power allocation with an optimal precoder. The simulation results show that the proposed joint design algorithm can achieve a much better performance than precoding with uniform power allocation and only consideration of power allocation.

摘要：针对mimo有限拍无振荡数字控制器设计表述各异的情况 ,提出一种切实可行的设计方法 ,给出一个mimo系统设计实例 .仿真结果表明 ,所提出的设计方法是正确的 .

摘要：综述了多跳无线网络mimo(multiple-input multiple-output)技术的研究进展,分析了mimo技术的引入对多跳无线网络各层及整体设计的影响.以跨层协议设计为重点,详细介绍了当前典型的基于mimo的多跳无线网络协议算法的核心机制,并比较分析了这些算法的特点和性能差异与存在的缺陷.最后,结合本领域内的研究现状,指出了基于mimo的多跳无线网络走向实际工程应用环境所亟待解决的关键问题,指出了基于mimo技术设计自适应调整、高性能多跳无线网络跨层模型及协议的重要性.

摘要：针对mimo ARQ系统中使用的重发机制,采用跨层设计思想,提出非理想信道估计条件下基于系统容量准则的次最优序贯线性预编码器的设计方案。首先推导出mimo ARQ系统中存在信道估计误差时系统容量的上界和下界。理论分析和仿真结果表明,mimo ARQ系统的容量在高信噪比时取决于信道估计误差。为简化处理,利用系统容量的下界并根据序贯预编码的思想,设计出ARQ重发时的次最优预编码器。仿真结果表明该次最优序贯预编码器可以获得良好的系统性能。

摘要：机载线阵3维SAR成像技术在军事和民用方面都有着广泛应用,是当前雷达成像领域的研究热点。其切航迹向分辨率是利用机翼上的线阵所获取,阵列分布直接影响到成像性能。受机翼体积的限制,机载线阵3维SAR系统的阵元数有限,可以采用mimo技术来获取更多的目标信息,提高切航迹向的空间采样能力。该文研究了机载线阵3维SAR系统的阵列设计问题,即以空间卷积原理为基础,归纳出卷积逆运算的规律,从而通过卷积逆运算求解出多组mimo线阵设计方案,并从机载线阵3维SAR成像的需求出发,分析了各组设计方案的优缺点,为实际构建机载线阵3维SAR成像系统提供了技术支撑。