  This paper is the first to provide a thorough system design overview along
with the fusion methods selection criteria of a real-world cooperative
autonomous driving system, named Infrastructure-Augmented Autonomous Driving or
IAAD. We present an in-depth introduction of the IAAD hardware and software on
both road-side and vehicle-side computing and communication platforms. We
extensively characterize the IAAD system in the context of real-world
deployment scenarios and observe that the network condition that fluctuates
along the road is currently the main technical roadblock for cooperative
autonomous driving. To address this challenge, we propose new fusion methods,
dubbed "inter-frame fusion" and "planning fusion" to complement the current
state-of-the-art "intra-frame fusion". We demonstrate that each fusion method
has its own benefit and constraint.
