The performance of WiFi-based localization systems is affected by the spatial accuracy of WiFi AP. Compared with the imprecision of AP location and antenna separation, the imprecision of AP's or antenna's orientation is more important in real scenarios, including AP rotation and antenna irregular tilt. In this paper, we propose Anteumbler that non-invasively, accurately and efficiently measures the orientation of each antenna in physical space. Based on the fact that the received power is maximized when a Tx-Rx antenna pair is perfectly aligned, we construct a spatial angle model that can obtain the antennas' orientations without prior knowledge. However, the sampling points of traversing the spatial angle need to cover the entire space. We use the orthogonality of antenna directivity and polarization and adopt an iterative algorithm to reduce the sampling points by hundreds of times, which greatly improves the efficiency. To achieve the required antenna orientation accuracy, we eliminate the influence of propagation distance using a dual plane intersection model and filter out ambient noise. Our real-world experiments with six antenna types, two antenna layouts and two antenna separations show that Anteumbler achieves median errors below 6 degree for both elevation and azimuth angles, and is robust to NLoS and dynamic environments. Last but not least, for the reverse localization system, we deploy Anteumbler over LocAP and reduce the antenna separation error by 10 mm, while for the user localization system, we deploy Anteumbler over SpotFi and reduce the user localization error by more than 1 m.

翻译：基于WiFi的定位系统性能受WiFi接入点空间精度的影响。相较于接入点位置与天线间距的不精确性，接入点或天线朝向的不精确性在实际场景中更为关键，包括接入点旋转与天线不规则倾斜。本文提出Anteumbler，一种能够非侵入式、精确且高效地测量物理空间中各天线朝向的方法。基于发射-接收天线对完全对准时接收功率最大这一物理事实，我们构建了无需先验知识即可获取天线朝向的空间角度模型。然而，遍历空间角度的采样点需覆盖整个空间。利用天线方向性与极化特性的正交性，我们采用迭代算法将采样点数量降低数百倍，从而显著提升效率。为实现所需的天线朝向测量精度，我们通过双平面交会模型消除传播距离的影响，并滤除环境噪声。我们在真实环境中使用六种天线类型、两种天线布局及两种天线间距进行实验，结果表明Anteumbler在俯仰角与方位角上的中值误差均低于6度，且对非视距传播与动态环境具有鲁棒性。最后，对于反向定位系统，我们在LocAP上部署Anteumbler并将天线间距误差降低10毫米；对于用户定位系统，我们在SpotFi上部署Anteumbler并将用户定位误差降低超过1米。