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、经济和社会方面产生重大影响。它承诺将司机从繁琐的任务中解放出来，提高驾驶效率和安全性，并减少交通拥堵、伤害和气体排放。在ITS中，车辆之间需要无缝通信，将出现支持自动驾驶的车载自组织网络(VANET)。在VANET中，车辆到车辆(V-V)和车辆到基础设施(V-I)通信通过称为车载单元(OBus)的无线设备进行。OBU被指定在5.9 GHz专用短程通信(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信息的电磁波。天线系统是连接到专门的射频电路的电磁设计。接着，这样的电路在发送之前和天线接收之后处理信息消息。完整的系统包括无线车载环境(或车载信道)，在该环境中，电磁波沿着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(3-D)散射、视线受阻(LOS)和发射器、接收器和周围物体的快速移动性(例如，其他车辆的移动性)，这种环境本质上是非常复杂和快速时变的。多天线系统包括许多共同工作的天线，以提高复杂无线环境中的通信性能。因此，能够在有限的OBU空间中实现最佳性能并且可以封装的紧凑型多天线设计对于支持车载通信变得至关重要。这种设计应考虑到由连接天线的射频电路和发送和接收信息消息的周围无线车辆环境强加的一系列因素。我们必须开发车辆通道提供的每一种潜力，以实现性能最大化。终端射频电路特性也会影响性能，必须在早期设计阶段考虑和补偿。拟议的研究活动将结合车载信道和终端射频电路的特点，为Obus提供最佳的紧凑型多天线系统。这样，就产生了完整的“射频电路/印制多天线/车载通道”优化的端到端系统。优化将首先最大化带宽效率，作为标准的关键性能指标(KPI)。随后将采用能效KPI进行优化。这样的KPI将首次被用于评估现实紧凑型多天线系统的性能。第一步是针对车辆环境的特定特征描述操作概念(CONOPS)和关键绩效指标。采用适用于任何无线环境和操作频率的通用车载信道模型，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的研究活动的另一项成果。最后一步将是对短波通信和毫米波最优多天线系统的概念验证。虽然这里的目标是为车载通信提供最佳的端到端系统，但这个项目可能会对未来5G毫米波和大规模MIMO系统的发展有所帮助。

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.