The rollout of millimeter-wave (mmWave) cellular network enables us to realize the full potential of 5G/6G with vastly improved throughput and ultra-low latency. MmWave communication relies on highly directional transmission, which significantly increase the training overhead for fine beam alignment. The concept of using out-of-band spatial information to aid mmWave beam search is developed when multi-band systems operating in parallel. The feasibility of leveraging low-band channel information for coarse estimation of high-band beam directions strongly depends on the spatial congruence between two frequency bands. In this paper, we try to provide insights into the answers of two important questions. First, how similar is the power angular spectra (PAS) of radio channels between two well-separated frequency bands? Then, what is the impact of practical system configurations on spatial channel similarity? Specifically, the beam direction-based metric is proposed to measure the power loss and number of false directions if out-of-band spatial information is used instead of in-band information. This metric is more practical and useful than comparing normalized PAS directly. Point cloud ray-tracing and measurement results across multiple frequency bands and environments show that the degree of spatial similarity of beamformed channels is related to antenna beamwidth, frequency gap, and radio link conditions.
翻译:毫米波(mmWave)蜂窝网络的推出使我们能够充分发挥5G/6G的潜力,大大改进了输送量和超低纬度。MWave通信依靠高度定向传输,这大大增加了微光线调整的培训间接费用。当多波段系统同时运行时,就开发了利用带外空间信息协助毫米Wave光束搜索的概念。利用低频频道信息对高频波方向进行粗略估计的可行性在很大程度上取决于两个频段之间的空间一致性。在本文中,我们试图提供对两个重要问题的答案的洞察。首先,两个清晰的频段之间无线电频道的三角光谱(PAS)的能量如何相似?然后,实际系统配置对空间频道相似性的影响是什么?具体地说,基于光谱方向的衡量标准是,如果使用带外空间信息而不是带信息,则测量断层空间信息断断面和断面天线的频率链路段,则直接显示多频谱频段和多频段的频段测量结果。