Revisiting Message Generation Strategies for Collective Perception in Connected and Automated Driving

Collective perception enables vehicles to exchange preprocessed sensor data and is being standardized as a 2nd generation V2X communication service. The European standardization in ETSI foresees the exchange of detected objects and defined a dedicated message type (Collective Perception Message, CPM) with rules to decide when and with which objects the message should be generated, referred to as generation rules. The choice of these rules is not straightforward and influences both channel load and perception quality. For the object inclusion, ETSI currently follows a similar policy as for the generation of Cooperative Awareness Messages (CAM): The objects are filtered based on their dynamics. We regard this approach as conservative. The present paper revisits the generation rules for the CPM and applies two approaches for object inclusion to the CPM - the conservative strategy of ETSI and a more 'greedy' strategy. We assess the performance by discrete-event simulations in a scenario representing a city with realistic vehicle densities and mobility patterns. The simulations take into account the effects imposed by decentralized congestion control. Considering that ETSI currently follows the conservative strategy, we conclude that the application of a greedy strategy improves the perception quality in low-density scenarios.