Joint Spatial Division and Multiplexing-The Large-Scale Array Regime
Joint Spatial Division and Multiplexing-The Large-Scale Array Regime
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DOI：
10.1109/tit.2013.2269476
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发表时间：
2013-10-01
影响因子：
2.5
通讯作者：
Caire, Giuseppe
中科院分区：
文献类型：
--
作者：
Adhikary, Ansuman;Nam, Junyoung;Caire, Giuseppe
我们提出联合空间分割和多路复用（JSDM），这是一种多用户MIMO下行链路的方法，它利用信道矢量的相关结构，以便在基站中允许大量天线，同时要求发射机（CSIT）的降维信道状态信息。JSDM在下行链路训练和CSIT上行反馈中都实现了显著的节省，因此在基站中使用大型天线阵列可能也适用于频分双工（FDD）系统，因为上行/下行信道互惠不能被利用。在该方案中，多用户MIMO下行预编码器是通过将仅依赖于信道二阶统计量的预波束形成矩阵与经典的多用户预编码器串联起来获得的，该预波束形成矩阵基于得到的降维“有效”信道矩阵的瞬时知识。我们证明了一个简单的条件，在这个条件下，JSDM相对于完整的CSIT情况不会导致最优性损失。对于线性等间距阵列，我们证明了在天线数量大的限制下，这种条件是接近的。对于这种情况，我们使用Szego的Toeplitz矩阵渐近理论来证明基于dft的预波束形成矩阵是接近最优的，只需要关于用户到达角和角扩展的粗略信息。最后，我们将这些思想扩展到二维基站天线阵列的情况下，具有三维波束形成，包括仰角方向的多个波束。我们为预波束形成优化提供了指导方针，并在比例公平和最大最小公平准则下计算了系统的频谱效率，显示出极具吸引力的性能。我们的数值结果是通过渐进随机矩阵理论获得的，避免了冗长的蒙特卡罗模拟，并为实际（有限）数量的天线和用户提供了准确的结果。
We propose joint spatial division and multiplexing (JSDM), an approach to multiuser MIMO downlink that exploits the structure of the correlation of the channel vectors in order to allow for a large number of antennas at the base station while requiring reduced-dimensional channel state information at the transmitter (CSIT). JSDM achieves significant savings both in the downlink training and in the CSIT uplink feedback, thus making the use of large antenna arrays at the base station potentially suitable also for frequency division duplexing (FDD) systems, for which uplink/downlink channel reciprocity cannot be exploited. In the proposed scheme, the multiuser MIMO downlink precoder is obtained by concatenating a prebeamforming matrix, which depends only on the channel second-order statistics, with a classical multiuser precoder, based on the instantaneous knowledge of the resulting reduced dimensional "effective" channel matrix. We prove a simple condition under which JSDM incurs no loss of optimality with respect to the full CSIT case. For linear uniformly spaced arrays, we show that such condition is approached in the large number of antennas limit. For this case, we use Szego's asymptotic theory of Toeplitz matrices to show that a DFT-based prebeamforming matrix is near-optimal, requiring only coarse information about the users angles of arrival and angular spread. Finally, we extend these ideas to the case of a 2-D base station antenna array, with 3-D beamforming, including multiple beams in the elevation angle direction. We provide guidelines for the prebeamforming optimization and calculate the system spectral efficiency under proportional fairness and max-min fairness criteria, showing extremely attractive performance. Our numerical results are obtained via asymptotic random matrix theory, avoiding lengthy Monte Carlo simulations and providing accurate results for realistic (finite) number of antennas and users.