标题： 有限反馈下SDMA正交波束成形的性能 显示英文标题

标题： Performance of Orthogonal Beamforming for SDMA with Limited Feedback

摘要： 在多天线广播信道中，空间自由度支持同时向多个用户传输。 最优的多用户传输，称为脏纸编码，无法直接实现。 此外，接近最优的解决方案，如Tomlinson-Harashima预编码，对CSI不准确性敏感。 本文考虑了一种更实际的设计，称为每个用户单位和速率控制（PU2RC），该设计已被提出用于新兴的蜂窝标准。 PU2RC支持多用户同时传输，允许有限反馈，并能够利用多用户分集。 其关键特性是正交波束成形（或预编码）约束，其中每个用户从包含多个正交基的代码本中选择一个波束成形器（或预编码器）。 在本文中，推导了在用户池较大时PU2RC在不同信噪比（SNR）范围内的渐近吞吐量扩展规律。 在多用户干扰受限的范围内，PU2RC的吞吐量被证明与用户数量呈对数增长。 在正常SNR和噪声受限的范围内，吞吐量被发现与用户数量呈双对数增长，并且与基站的天线数量呈线性增长。 此外，数值结果表明，如果用户数量足够大，PU2RC的吞吐量更高，并且比零 forcing 波束成形的流行替代方案更能抵抗CSI量化误差。 显示英文摘要

摘要： On the multi-antenna broadcast channel, the spatial degrees of freedom support simultaneous transmission to multiple users. The optimal multiuser transmission, known as dirty paper coding, is not directly realizable. Moreover, close-to-optimal solutions such as Tomlinson-Harashima precoding are sensitive to CSI inaccuracy. This paper considers a more practical design called per user unitary and rate control (PU2RC), which has been proposed for emerging cellular standards. PU2RC supports multiuser simultaneous transmission, enables limited feedback, and is capable of exploiting multiuser diversity. Its key feature is an orthogonal beamforming (or precoding) constraint, where each user selects a beamformer (or precoder) from a codebook of multiple orthonormal bases. In this paper, the asymptotic throughput scaling laws for PU2RC with a large user pool are derived for different regimes of the signal-to-noise ratio (SNR). In the multiuser-interference-limited regime, the throughput of PU2RC is shown to scale logarithmically with the number of users. In the normal SNR and noise-limited regimes, the throughput is found to scale double logarithmically with the number of users and also linearly with the number of antennas at the base station. In addition, numerical results show that PU2RC achieves higher throughput and is more robust against CSI quantization errors than the popular alternative of zero-forcing beamforming if the number of users is sufficiently large.