Frequency Selective Hybrid Precoding for Limited Feedback Millimeter Wave Systems
Frequency Selective Hybrid Precoding for Limited Feedback Millimeter Wave Systems
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DOI：
10.1109/tcomm.2016.2549517
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发表时间：
2016-05-01
影响因子：
8.3
通讯作者：
Heath, Robert W., Jr.
中科院分区：
文献类型：
--
作者：
Alkhateeb, Ahmed;Heath, Robert W., Jr.
混合模拟/数字预编码在毫米波 (mmWave) 系统中实现了硬件复杂性和系统性能之间的折衷。这种类型的预编码允许毫米波系统利用足够的链路余量所必需的大天线阵列增益，同时允许低成本和低功耗的硬件。大多数先前的工作都集中在窄带毫米波系统的混合预编码上，并在发射机处具有完美或估计的信道知识。然而，毫米波系统可能会在具有频率选择性的宽带信道上运行。因此，本文考虑了发射器和接收器之间反馈通道有限的宽带毫米波系统。首先，推导出给定射频码本的最佳混合预编码设计。这为任何其他启发式算法提供了基准，并为码本设计提供了有用的见解。其次，开发了高效的混合模拟/数字码本，用于宽带毫米波系统中的空间复用。最后，提出了一种基于Gram-Schmidt正交化的低复杂度但接近最优的贪婪频率选择性混合预编码算法。仿真结果表明，与无约束解决方案相比，所开发的混合码本和预编码器设计实现了非常好的性能，同时要求的复杂性要低得多。
Hybrid analog/digital precoding offers a compromise between hardware complexity and system performance in millimeter wave (mmWave) systems. This type of precoding allows mmWave systems to leverage large antenna array gains that are necessary for sufficient link margin, while permitting low cost and power consumption hardware. Most prior work has focused on hybrid precoding for narrow-band mmWave systems, with perfect or estimated channel knowledge at the transmitter. MmWave systems, however, will likely operate on wideband channels with frequency selectivity. Therefore, this paper considers wideband mmWave systems with a limited feedback channel between the transmitter and receiver. First, the optimal hybrid precoding design for a given RF codebook is derived. This provides a benchmark for any other heuristic algorithm and gives useful insights into codebook designs. Second, efficient hybrid analog/digital codebooks are developed for spatial multiplexing in wideband mmWave systems. Finally, a low-complexity yet near-optimal greedy frequency selective hybrid precoding algorithm is proposed based on Gram-Schmidt orthogonalization. Simulation results show that the developed hybrid codebooks and precoder designs achieve very-good performance compared with the unconstrained solutions while requiring much less complexity.