Joint optimization of source and relay precoding in non-regenerative MIMO relay systems
Joint optimization of source and relay precoding in non-regenerative MIMO relay systems
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DOI：
10.1002/wcm.2213
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发表时间：
2013-12
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通讯作者：
Yang Zhang;Jiandong Li;Lihua Pang;Z. Ding
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作者：
Yang Zhang;Jiandong Li;Lihua Pang;Z. Ding
研究了放大转发多输入多输出中继系统中的预编码优化问题。大多数关于这个问题的报道主要集中在中继预编码器的设计，而不同时优化的直接链路。在本文中，我们提出了一种联合源/中继预编码器的设计方法，同时考虑直接和中继链路。我们的设计是基于最大限度地提高互信息（MI）有限的传输功率约束下的源和中继，分别。我们首先制定一个约束优化问题，然后放松原来的成本函数的易处理性，并推导出MI下限。这个精心设计的界限可以渐近地接近MI的精确表达式在一个迭代的方式。与以前的策略相比，我们证明了源和中继预编码器的最佳结构共同将多输入多输出中继信道转换为一组单输入单输出中继信道，而不必假设波束成形结构以简化推导。具体而言，线性预编码设计问题退化为多个单输入单输出中继信道之间的功率负载。应用标准的拉格朗日技术的结果是一个标量凸优化，它可以很容易地解决迭代注水。数值例子表明，该方案，无论是利用部分或全部信道状态信息，显着优于现有的方法。版权所有© 2012约翰威利父子有限公司.
We investigate the problem of precoding optimization in an amplify-and-forward multiple-input-multiple-output relay system. Most reported works on this problem focus chiefly on the design of relay precoder without simultaneously optimizing the direct link. In this paper, we propose a method for joint source/relay precoder design, taking both direct and relay links into account. Our design is based on maximizing the mutual information (MI) under limited transmission power constraints at the source and relay, respectively. We first formulate a constrained optimization problem before relaxing the original cost function for tractability and derive a MI lower bound. This elaborate bound can asymptotically approach the exact expression of MI in an iterative fashion. In contrast to previous strategies, we then prove that the optimal structure of the source and relay precoders jointly convert the multiple-input-multiple-output relay channel into a bank of single-input-single-output relay channels without having to assume a beamforming structure to simplify the derivation. Specifically, the linear precoding design problem degenerates into power loading among multiple single-input-single-output relay channels. Applying standard Lagrange technique results in a scalar convex optimization, and it can be readily solved by iterative water filling. Numerical examples demonstrate that the proposed scheme, either exploiting partial or full channel state information, significantly outperforms the existing methods. Copyright © 2012 John Wiley & Sons, Ltd.