Massive MIMO and small cells: How to densify heterogeneous networks
Massive MIMO and small cells: How to densify heterogeneous networks
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DOI：
10.1109/icc.2013.6655455
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发表时间：
2013-06
期刊：
影响因子：
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通讯作者：
Kianoush Hosseini;J. Hoydis;S. Brink;M. Debbah
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文献类型：
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作者：
Kianoush Hosseini;J. Hoydis;S. Brink;M. Debbah
我们提出了一种基于时分双工（TDD）的网络架构，其中具有“大规模”多输入多输出（MIMO）基站（BS）的宏小区层与密集的小小区层（SCs）覆盖。在这种情况下，TDD协议和由此产生的信道互易性具有两个令人信服的优势。首先，可以部署大量的BS天线，而不会产生令人望而却步的信道训练开销。其次，BS可以从SC层估计干扰协方差矩阵，这可以用于下行预编码。特别是，BS设计了其预编码向量，在与最强干扰方向所张成的子空间正交的同时，向用户传输独立的数据流；从而最大限度地减少施加在sc上的总干扰。换句话说，BS“牺牲”了一些天线来消除干扰，而TDD协议允许两层之间的隐式协调。仿真结果表明，在给定足够大的BS天线数量的情况下，该方案可以以较小的宏观性能损失为代价显著提高SC层的和速率。
We propose a time division duplex (TDD) based network architecture where a macrocell tier with a “massive” multiple-input multiple-output (MIMO) base station (BS) is overlaid with a dense tier of small cells (SCs). In this context, the TDD protocol and the resulting channel reciprocity have two compelling advantages. First, a large number of BS antennas can be deployed without incurring a prohibitive overhead for channel training. Second, the BS can estimate the interference covariance matrix from the SC tier which can be leveraged for downlink precoding. In particular, the BS designs its precoding vectors to transmit independent data streams to its users while being orthogonal to the subspace spanned by the strongest interference directions; thereby minimizing the sum interference imposed on the SCs. In other words, the BS “sacrifices” some of its antennas for interference cancellation while the TDD protocol allows for an implicit coordination across both tiers. Simulation results suggest that, given a sufficiently large number of BS antennas, the proposed scheme can significantly improve the sum-rate of the SC tier at the price of a small macro performance loss.