This paper details the design of an autonomous alignment and tracking platform to mechanically steer directional horn antennas in a sliding correlator channel sounder setup for 28 GHz V2X propagation modeling. A pan-and-tilt subsystem facilitates uninhibited rotational mobility along the yaw and pitch axes, driven by open-loop servo units and orchestrated via inertial motion controllers. A geo-positioning subsystem augmented in accuracy by real-time kinematics enables navigation events to be shared between a transmitter and receiver over an Apache Kafka messaging middleware framework with fault tolerance. Herein, our system demonstrates a 3D geo-positioning accuracy of 17 cm, an average principal axes positioning accuracy of 1.1 degrees, and an average tracking response time of 27.8 ms. Crucially, fully autonomous antenna alignment and tracking facilitates continuous series of measurements, a unique yet critical necessity for millimeter wave channel modeling in vehicular networks. The power-delay profiles, collected along routes spanning urban and suburban neighborhoods on the NSF POWDER testbed, are used in pathloss evaluations involving the 3GPP TR38.901 and ITU-R M.2135 standards. Empirically, we demonstrate that these models fail to accurately capture the 28 GHz pathloss behavior in urban foliage and suburban radio environments. In addition to RMS direction-spread analyses for angles-of-arrival via the SAGE algorithm, we perform signal decoherence studies wherein we derive exponential models for the spatial/angular autocorrelation coefficient under distance and alignment effects.

翻译：本文详细介绍了用于28 GHz车联万物（V2X）传播建模的自主对准与跟踪平台设计，该平台在滑动相关器信道探测仪配置中机械操控方向性喇叭天线。其云台子系统通过开环伺服单元驱动，并由惯性运动控制器协调，实现沿偏航轴和俯仰轴的无限制旋转机动性。由实时运动学增强精度的地理定位子系统，借助具备容错能力的Apache Kafka消息中间件框架，在发射机和接收机之间共享导航事件。本系统展示了17 cm的三维地理定位精度、1.1度的平均主轴定位精度以及27.8 ms的平均跟踪响应时间。至关重要的是，全自主天线对准与跟踪实现了连续测量序列的获取，这是车载网络毫米波信道建模中独特且关键的需求。通过在NSF POWDER试验平台上沿城市和郊区路径采集的功率延迟分布，本文将其用于涉及3GPP TR38.901和ITU-R M.2135标准的路损评估。实验表明，这些模型未能准确捕捉城市植被和郊区无线电环境中的28 GHz路损行为。除通过SAGE算法进行到达角均方根方向扩展分析外，我们还进行了信号去相干研究，在其中推导了距离和对准效应下空间/角度自相关系数的指数模型。