Multiple-antenna channel hardening and its implications for rate feedback and scheduling
Multiple-antenna channel hardening and its implications for rate feedback and scheduling
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DOI：
10.1109/tit.2004.833345
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发表时间：
2004-09-01
影响因子：
2.5
通讯作者：
Tarokh, V
中科院分区：
文献类型：
--
作者：
Hochwald, BM;Marzetta, TL;Tarokh, V
无线数据流量预计将在未来几年内增长，将提供数据服务的技术仍在争论中。一种可能性是在基站和终端使用多个天线，以在丰富的散射环境中获得非常高的频谱效率。这样的多输入/多输出(MIMO)信道然后可以与调度和速率反馈算法结合使用，以进一步增加信道吞吐量。本文分析了调度带来的预期增益和速率反馈所需的比特数。我们的分析需要MIMO信道互信息分布的精确近似。由于瑞利衰落环境下互信息的精确分布很难分析，我们证明了具有大量天线的MIMO信道的中心极限定理。虽然MIMO信道的平均互信息(容量)随天线数量的增长是众所周知的，但事实证明，随着天线数量的增加，互信息的方差可以非常缓慢地增长，甚至缩小。我们讨论了这种“通道强化”结果对数据和语音服务、调度和速率反馈的影响。我们还简要讨论了包括阴影衰落效应时的影响。
Wireless data traffic is expected to grow over the next few years and the technologies that will provide data services are still being debated. One possibility is to use multiple antennas at base stations and terminals to get very high spectral efficiencies in rich scattering environments. Such multiple-input/multiple-output (MIMO) channels can then be used in conjunction with scheduling and rate-feedback algorithms to further increase channel throughput. This paper provides an analysis of the expected gains due to scheduling and bits needed for rate feedback. Our analysis requires an accurate approximation of the distribution of the MIMO channel mutual information. Because the exact distribution of the mutual information in a Rayleigh-fading environment is difficult to analyze, we prove a central limit theorem for MIMO channels with a large number of antennas. While the growth in average mutual information (capacity) of a MIMO channel with the number of antennas is well understood, it turns out that the variance of the mutual information can grow very slowly or even shrink as the number of antennas grows. We discuss implications of this "channel-hardening" result for data and voice services, scheduling, and rate feedback. We also briefly discuss the implications when shadow fading effects are included.