Millimeter wave (mmWave) is a practical solution to provide high data rate for the vehicle-to-everything (V2X) communications. This enables the future autonomous vehicles to exchange big data with the base stations (BSs) such as the velocity and the location to improve the awareness of the advanced driving assistance system (ADAS). In this context, we consider a single-cell multiuser doubly-selective system wherein the BS simultaneously serves multiple vehicles. To accomplish this requirement, the BS is implemented in hybrid architecture to support multiple spatial streams while the vehicles have analog-only structures. In this work, we develop a low-complexity hybrid precoding algorithm wherein the design of the hybrid precoder at the BS and the analog combiner at the vehicles require small training and feedback overhead. We propose a two-stage hybrid precoding algorithm wherein the first stage designs the analog beamformers as in single user scenario while the second stage designs the multiuser digital precoder at the BS. In the second stage, we derive closed-form digital precoders such as Maximum Ratio Transmission (MRT), Zero-Forcing (ZF) and Minimum Mean Square Error (MMSE) as a first variant while we propose iterative digital precoder as a second variant. The design of the digital precoders for the two variants requires the limited feedback sent from the vehicles to BS. We refer to the random vector quantization (RVQ) and the beamsteering codebooks to quantize the feedbacks for variants I and II, respectively, since the perfect feedback requires long overhead and large training. We evaluate the rate loss incurred by the quantization of the digital and analog codebooks against the perfect channel state information at the transmitter (CSIT).
翻译:mmWave) 是一个实用的解决方案, 用于为车辆到全部设备( V2X) 通信提供高数据率。 这使得未来自主车辆能够与基站( BS) 交换大数据, 如速度和位置, 以提高高级驾驶协助系统( ADAS) 的认识。 在这方面, 我们考虑一个单细胞多用户选择系统, 由BS 同时为多车辆服务。 为了达到这一要求, 在混合结构中实施 BS, 以支持多空间流, 而车辆则有模拟专用结构。 在这项工作中, 我们开发了一种低兼容性混合的混合数据预编码预编码预编码, 使BS 和 车辆模拟组合的设计需要小型培训和反馈。 我们提出一个两阶段混合的混合预编码, 第一阶段设计模拟比方的模拟系统, 而第二阶段设计多用户数字预编码。 在第二个阶段, 我们从最高级的 IRC 传输( MRT ) 、 Zreareal develrial Serverial Serverial 中, 我们提出一个数字格式前的版本, 和Dreal-Dreal-BMDreal- Freal Develop 。