When a channel consists of a line-of-sight (LoS) path as well as non-LoS components, codebook design for channel state information (CSI) quantization is required to take account of both of them. However, the conventional codebook design requires infinitely many optimal codebooks corresponding to all possible Rician factors, which is impossible in practice. In this regard, we propose an effective codebook adaptive to any Rician factors, while guaranteeing comparable performance to the optimal codebook. Contrary to the conventional approaches, the adaptation to Rician factors suffices by sharing only a single common codebook between the transmitter and receiver. We first investigate the distribution of the angle between the channel vector and the LoS component, where the distribution depends on Rician factors that reflect the power ratio of LoS and non-LoS components. Driven by the analysis, we devise a band-structured non-homogeneous codebook and derive the upper bound of the quantization error of the proposed codebook. The design parameters of the proposed codebook are optimized to minimize the quantization error bound. Using an approximation, we also derive a tractable near-optimal solution of the parameters determining the proposed codebook. Numerical results exhibit that the proposed codebook substantially outperforms conventional methods and achieves near-optimal performance in terms of the average quantization distortion and average sum rate.

中文翻译：

---

有限反馈 MIMO 莱斯衰落信道中信道状态信息量化的新颖码本设计


当信道由视距 (LoS) 路径和非 LoS 组件组成时，信道状态信息 (CSI) 量化的码本设计需要考虑这两者。然而，传统的码本设计需要无限多个对应于所有可能的莱斯因子的最优码本，这在实践中是不可能的。在这方面，我们提出了一种适应任何莱斯因素的有效码本，同时保证与最佳码本相当的性能。与传统方法相反，通过在发射器和接收器之间仅共享单个公共码本来适应莱斯因子就足够了。我们首先研究信道矢量和视距分量之间的角度分布，其中该分布取决于反映视距和非视距分量功率比的莱斯因子。在分析的驱动下，我们设计了带结构非齐次码本，并推导出所提出的码本的量化误差的上限。所提出的码本的设计参数经过优化以最小化量化误差范围。使用近似值，我们还得出确定所建议的码本的参数的易于处理的近乎最优的解决方案。数值结果表明，所提出的码本大大优于传统方法，并且在平均量化失真和平均和率方面实现了接近最优的性能。