Bandwidth and Energy Efficient Compact Multi-Antenna Systems for Connected Autonomous Vehicles

自动驾驶是智能交通系统（ITS）的关键推动因素，预计将对环境、经济和社会等方面产生重大影响。智能交通系统承诺将司机从繁琐的工作中解脱出来，提高驾驶效率和安全性，减少交通堵塞、伤害和气体排放。在智能交通系统中，需要车辆之间的无缝通信，并且将出现车辆自组织网络（vanet）来支持自动驾驶。在VANETs中，车辆对车辆（V-V）和车辆对基础设施（V-I）的通信通过称为车载单元（OBUs）的无线设备进行。OBUs被指定在5.9 GHz专用短距离通信（DSRC）标准化技术下运行。天线系统作为OBUs的一部分，负责发射和接收携带有用信息的电磁波。天线系统是电磁设计，连接到专门的射频电路。这样的电路依次在天线接收信息之前和之后处理信息。完整的系统包括无线车载环境（或车载信道），其中电磁波沿着从发射天线到接收天线的路径传播。由于其物理传播机制，包括三维（3d）散射、视线（LOS）遮挡以及发射器、接收器和周围物体的快速移动（例如其他车辆的移动），这种环境本身就非常复杂且时变迅速。多天线系统包括许多天线一起工作，以提高在复杂无线环境中的通信性能。因此，能够在有限的OBU空间内实现最佳性能的紧凑多天线设计对于支持车辆通信至关重要。这种设计应考虑到天线所连接的射频电路和周围无线车辆环境所施加的一系列因素，而无线车辆环境是发送和接收信息消息的环境。我们必须挖掘车辆频道提供的每一个潜力，以最大限度地提高性能。终端射频电路的特性也会影响性能，必须在早期设计阶段就加以考虑和补偿。拟议的研究活动将结合车载信道和终端射频电路的特性，以获得最佳的紧凑多天线系统。因此，完整的“射频电路/印刷多天线/车载信道”优化端到端系统将出现。作为标准的关键性能指标（KPI），优化将首先通过最大化带宽效率来实现。随后将采用能源效率KPI进行优化。该KPI将首次用于评价实际的紧凑型多天线系统的性能。针对车辆环境的特定特征对操作概念（CONOPs）和kpi进行描述是第一步。采用通用车载信道模型，可适应任何无线环境和操作频率，将使优化的DSRC-5.9 GHz和毫米波-60 GHz多天线系统的设计成为可能。评估将毫米波频段用于车辆通信的可行性将是拟议研究活动的另一项成果。最后一步将是DSRC和毫米波最佳多天线系统的概念验证演示。虽然这里的目标是为车辆通信提供最佳的“射频电路/印刷多天线/车载信道”端到端系统，但该项目可能有利于未来5G毫米波和大规模MIMO系统的发展。

Autonomous driving is a key enabler for Intelligent Transportation Systems (ITS), which are expected to have major impacts on several environmental, economic and social aspects. ITS promise to relieve driver from tedious tasks, improve driving efficiency and safety and reduce traffic jams, injuries and gas emissions. In ITS, seamless communications between vehicles are required and vehicular ad hoc networks (VANETs) will emerge to support autonomous driving. In VANETs, vehicle-to-vehicle (V-V) and vehicle-to-infrastructure (V-I) communications take place via wireless devices called on-board units (OBUs). OBUs are designated to operate under the 5.9 GHz dedicated short range communication (DSRC) standardized technology. Antenna systems, as part of OBUs, are responsible for transmitting and receiving the electromagnetic wave which carries the useful information message. Antenna systems are electromagnetic designs which are connected to specialized RF circuitry. In turn, such circuitry processes the information message before the transmission and after the reception by the antennas. The complete system includes the wireless vehicular environment (or vehicular channel) in which the electromagnetic wave propagates along the way from the transmitting to the receiving antenna. Such environment is inherently very complex and rapidly time varying due to its physical propagation mechanisms including three-dimensional (3-D) scattering, obstructed line-of-sight (LOS) and fast mobility of transmitter, receiver and surrounding objects (e.g., mobility of other vehicles). Multi-antenna systems include many antennas operating together in order to increase communication performance in complex wireless environments. Accordingly, compact multi-antenna designs that perform optimally and can be packed in the limited OBU space become of paramount importance to support vehicular communications. Such designs should take into account a series of factors as imposed by the RF circuit, in which the antenna is connected and the surrounding wireless vehicular environment, in which the information message is transmitted and received. We have to exploit every potential the vehicular channel offers in order to maximize performance. The termination RF circuit characteristics affect performance as well and have to be taken into account and compensated at the early design stage. The proposed research activity will incorporate both the characteristics of the vehicular channel and termination RF circuit to derive optimal compact multi-antenna systems for OBUs. Thus, complete "RF circuit/printed multi-antenna/vehicular channel" optimized end-to-end systems will arise. Optimization will take place by maximizing the bandwidth efficiency first, as a standard key performance indicator (KPI). Optimization adopting the energy efficiency KPI will then follow. Such KPI will be employed for the first time to evaluate performance of realistic compact multi-antenna systems. The description of concepts of operation (CONOPs) and KPIs with respect to the particular features of vehicular environments constitutes the first step. The adoption of a generic vehicular channel model, adaptable to any wireless environment and frequency of operation, will enable the design of optimized DSRC-5.9 GHz and mm-wave-60 GHz multi-antenna systems. Assessing the feasibility of using mm-wave frequency bands for vehicular communications will be one more achievement of the proposed research activity. The last step will be proof-of-concept demonstrators for both DSRC and mm-wave optimal multi-antenna systems.While the objective here is to present optimal "RF circuit/printed multi-antenna/vehicular channel" end-to-end systems for vehicular communications, this project could benefit the development of future 5G mm-wave and massive MIMO systems.