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、经济和社会等多个方面产生重大影响。ITS承诺将驾驶员从繁琐的任务中解脱出来，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，车辆之间需要无缝通信，车辆自组织网络（VANELS）将出现以支持自动驾驶。在VAN中，车辆到车辆（V-V）和车辆到基础设施（V-I）通信经由称为车载单元（OBU）的无线设备进行。OBU被指定在5.9 GHz专用短程通信（DSRC）标准化技术下操作。天线系统作为车载单元的一部分，负责发射和接收携带有用信息的电磁波。天线系统是连接到专用RF电路的电磁设计。进而，这种电路在天线发送之前和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），其中电磁波沿沿着从发射天线传播到接收天线。这种环境由于其物理传播机制（包括三维（3-D）散射、视线受阻（LOS）以及发射机、接收机和周围物体（例如，其他交通工具）。多天线系统包括一起操作的许多天线，以便在复杂的无线环境中提高通信性能。因此，最佳地执行并且可以封装在有限的OBU空间中的紧凑的多天线设计对于支持车辆通信变得至关重要。这种设计应该考虑到由RF电路（其中连接天线）和周围无线车辆环境（其中发送和接收信息消息）所施加的一系列因素。我们必须充分利用车辆信道提供的每一个潜力，以最大限度地提高性能。端接RF电路特性也会影响性能，必须在早期设计阶段加以考虑和补偿。拟议的研究活动将结合车辆信道和终端RF电路的特性，以获得最佳的紧凑型多天线系统的OBU。因此，完整的“RF电路/印刷多天线/车载信道”优化的端到端系统将出现。优化将首先通过最大化带宽效率来进行，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将首次用于评估现实的紧凑型多天线系统的性能。关于车辆环境的特定特征的操作概念（CONOPs）和KPI的描述构成第一步。通用车载信道模型的采用，适用于任何无线环境和频率的操作，将使优化的DSRC-5.9 GHz和毫米波-60 GHz的多天线系统的设计。评估将毫米波频带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器。虽然这里的目标是为车辆通信提供最佳的“RF电路/印刷多天线/车辆信道”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系统的开发。

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.