Mode Switching for the Multi-Antenna Broadcast Channel Based on Delay and Channel Quantization
Mode Switching for the Multi-Antenna Broadcast Channel Based on Delay and Channel Quantization
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DOI：
10.1155/2009/802548
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发表时间：
2008-12
影响因子：
1.9
通讯作者：
Jun Zhang;R. Heath;M. Kountouris;J. Andrews
中科院分区：
文献类型：
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作者：
Jun Zhang;R. Heath;M. Kountouris;J. Andrews
信道状态信息不完善会降低多输入多输出通信的性能；它对单用户（SU）和多用户（MU） MIMO传输的影响是完全不同的。特别是，MU-MIMO由于信道状态信息不完善而遭受剩余的用户间干扰，而SU-MIMO仅遭受功率损失。本文比较了SU - mimo和MU-MIMO在广播信道中由于时延和信道量化而造成的吞吐量损失。精确的闭式近似推导出SU和MU-MIMO的可实现速率。结果表明，SU-MIMO对延迟和量化信道信息具有较强的鲁棒性，而采用强制零预编码的MU-MIMO在固定延迟或固定码本大小的情况下会失去空间复用增益。在此基础上，提出了一种基于平均信噪比、归一化多普勒频率和信道量化码本大小在SU和MU-MIMO模式之间切换的模式切换算法，以提高频谱效率。确定了具有不同延迟和码本大小的SU和MU模式的工作区域，并利用它们来选择首选模式。结果表明，MU模式只有在归一化多普勒频率很小，码本尺寸较大时才有效。
Imperfect channel state information degrades the performance of multiple-input multiple-output (MIMO) communications; its effects on single-user (SU) and multiuser (MU) MIMO transmissions are quite different. In particular, MU-MIMO suffers from residual interuser interference due to imperfect channel state information while SU-MIMO only suffers from a power loss. This paper compares the throughput loss of both SU and MU-MIMO in the broadcast channel due to delay and channel quantization. Accurate closed-form approximations are derived for achievable rates for both SU and MU-MIMO. It is shown that SU-MIMO is relatively robust to delayed and quantized channel information, while MU-MIMO with zero-forcing precoding loses its spatial multiplexing gain with a fixed delay or fixed codebook size. Based on derived achievable rates, a mode switching algorithm is proposed, which switches between SU and MU-MIMO modes to improve the spectral efficiency based on average signal-to-noise ratio (SNR), normalized Doppler frequency, and the channel quantization codebook size. The operating regions for SU and MU modes with different delays and codebook sizes are determined, and they can be used to select the preferred mode. It is shown that the MU mode is active only when the normalized Doppler frequency is very small, and the codebook size is large.