Generalized channel inversion methods for multiuser MIMO systems
Generalized channel inversion methods for multiuser MIMO systems
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DOI：
10.1109/tcomm.2009.11.070404
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发表时间：
2009-11
影响因子：
8.3
通讯作者：
Hakjea Sung;Sang-Rim Lee;Inkyu Lee
中科院分区：
文献类型：
--
作者：
Hakjea Sung;Sang-Rim Lee;Inkyu Lee
块对角化（BD）是多用户多输入多输出（MIMO）广播信道中众所周知的预编码方法。该方案可以被视为迫零（ZF）信道反转到每个接收器配备多个天线的情况的扩展。 BD的局限性之一是，在中低信噪比范围内，总速率不会随着用户和发射天线的数量线性增长，因为多用户干扰的完全抑制是以噪声增强为代价实现的。在不完善的信道状态信息下它的表现也很差。在本文中，我们提出了一种针对多天线用户的广义最小均方误差（MMSE）信道反演算法，以克服多用户 MIMO 系统中 BD 的缺点。我们首先介绍一种广义 ZF 通道反演算法作为传统 BD 的一种新方法。将这一思想应用于MMSE信道求逆以识别预编码器的正交基向量，并采用MMSE标准来寻找其组合矩阵，所提出的方案增加了每个用户接收器处的信号与干扰加噪声之比。仿真结果证实，与 BD 方案相反，所提出的方案表现出总速率的线性增长。对于具有四个发射天线的块衰落信道，所提出的方案在 1% 帧错误率下比传统 BD 方案提供了 3 dB 增益。此外，我们还针对具有信道估计误差的系统提出了一种改进的预编码方法，并表明所提出的算法对信道估计误差具有鲁棒性。
Block diagonalization (BD) is a well-known precoding method in multiuser multi-input multi-output (MIMO) broadcast channels. This scheme can be considered as a extension of the zero-forcing (ZF) channel inversion to the case where each receiver is equipped with multiple antennas. One of the limitation of the BD is that the sum rate does not grow linearly with the number of users and transmit antennas at low and medium signal-to-noise ratio regime, since the complete suppression of multi-user interference is achieved at the expense of noise enhancement. Also it performs poorly under imperfect channel state information. In this paper, we propose a generalized minimum mean-squared error (MMSE) channel inversion algorithm for users with multiple antennas to overcome the drawbacks of the BD for multiuser MIMO systems. We first introduce a generalized ZF channel inversion algorithm as a new approach of the conventional BD. Applying this idea to the MMSE channel inversion for identifying orthonormal basis vectors of the precoder, and employing the MMSE criterion for finding its combining matrix, the proposed scheme increases the signal-to-interference-plus-noise ratio at each user's receiver. Simulation results confirm that the proposed scheme exhibits a linear growth of the sum rate, as opposed to the BD scheme. For block fading channels with four transmit antennas, the proposed scheme provides a 3 dB gain over the conventional BD scheme at 1% frame error rate. Also, we present a modified precoding method for systems with channel estimation errors and show that the proposed algorithm is robust to channel estimation errors.