论文标题

在MIMO-TDD中克服训练不对称的后代反馈方法

A Post-coder Feedback Approach to Overcome Training Asymmetry in MIMO-TDD

论文作者

Miryala, Arun Kumar, Baby, Irina Merin, Appaiah, Kumar, Pillai, Sibi Raj B.

论文摘要

时间鸿沟双工(TDD)无线通信系统本质上是双向的,它有助于利用基于上行链路和下行链路的基于试点的通道估计来利用通道互惠。但是,在上行链路和下行链路的通道估计复杂性中存在严重的不对称性,特别是对于多个输入多重输出(MIMO)TDD系统。通常,具有更多天线的基站(BS)需要估计每个天线的较少参数,而用户设备(UE)的估计要求较高。与UE不同,BS具有功能强大的硬件,计算资源和能源,可准确估算和跟踪频道配置文件。为了克服这种不对称性,我们为MIMO-TDD下行链路通信提出了一个解决方案,其中在BS处对通道基质的后代组成部分进行量化,并通过低速率通道传达给UE。在可实现的下行链路上使用渐近紧密的下限,我们量化了提出的方案的性能。模拟表明,中等数量的量化位足以在接近链路容量的情况下实现速率。我们进一步表明,当BS的天线比UE具有更多的天线时,可以通过适当的传输域预编码来补偿该通道,而无需在UE时编码后知识。

Time Divison Duplex (TDD) wireless communication systems are inherently bidirectional, which facilitates exploiting channel reciprocity for pilot based channel estimation of both uplink and downlink. However, there exists a gross asymmetry in channel estimation complexity for the uplink and downlink, particularly for Multiple Input Multiple Output (MIMO) TDD systems. Usually, Base Stations (BS) with more antennas need to estimate fewer parameters from each antenna, whereas the estimation requirement is disproportionately higher at the User Equipment (UE). Unlike the UE, the BS has powerful hardware, computational resources and energy to accurately estimate and track channel profiles. To overcome this asymmetry, we propose a solution for MIMO-TDD downlink communication, wherein the post-coder part of the channel matrix is quantized at the BS, and is communicated to the UE via a low-rate channel. Using asymptotically tight lower bounds on the downlink achievable rates, we quantify the performance of the proposed scheme. Simulations reveal that a moderate number of quantization bits are sufficient to achieve rates close to the the link capacity. We further show that, when the BS has many more antennas at than the UE, the channel can be compensated by appropriate transmit domain precoding without post-coder knowledge at the UE.

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