Resolving Hidden-Node Problems in C-V2X

Hidden-node problems in C-V2X systems come in two forms. Firstly, in an urban “concrete jungle” city like Singapore, direct vehicle-to-vehicle (V2V) communication, vehicle-to-PMD or vehicle-to-pedestrian (V2PP) communication at 5.9GHz may be blocked by big buildings or large vehicles like trucks. Such non-or obstructed-line of sight scenarios severely hamper the periodic exchange of basic safety message (that contain vehicle’s location, speed and travelling direction information) between vehicles, making almost all safety-related V2X applications ineffective.  Secondly, in countries where some vehicles use DSRC on-board units (OBU) while other vehicles use C-V2X OBUs, the exchange of safety messages fail due to incompatible communication protocols, even if the vehicles have clear line of sight. These scenarios are illustrated in Figure 1.

This project aims to design a message relaying system that makes use of a dual-V2X-mode roadside units (RSU) or 5G base stations (gNodeB) to re-transmit the safety messages to the hidden nodes using 2-hop communication, as shown in Figure 2.

WP2 will conduct Cellular V2V and vehicle-to-infrastructure (V2I) link quality measurement to derive radio link models for the hidden nodes, design and build V2X relaying protocols for the various hidden node problems described above, apply 5G New Radio techniques to enhance the C-V2X system capacity, and develop a scalable V2X RSU with extended coverage for Singapore’s ERP2 (electronic road pricing) devices.

The project will develop software and hardware prototypes of the proposed relaying systems for industry or statutory collaborators to validate.