Rethinking Transmit Power Control for SAE J3161/1 Congestion Control Algorithm

The Society of Automotive Engineers (SAE) has specified wireless channel congestion control algorithm for vehicle-to-everything (V2X) communication: J2945/1 for Dedicated Short Range Communication (DSRC) and J3161/1 for cellular V2X (C-V2X) environment. Although J2945/1 utilizes both transmit (Tx) power control and message rate control, the more recently specified J3161/1 standard for C-V2X environment has opted to abandon the power control. It is understandable as previous studies have demonstrated the inefficacy of power control in J2945/1, resulting in the rate control solely fighting congestion. Consequently, channel congestion leads to a fast increase in packet inter-reception time (PIR) and potentially tracking error. This letter advocates for the reinstatement of Tx power control in J3161/1 as a means to minimize PIR, while proposing a distinct approach from J2945/1 to show the feasibility of an effective combined control. Based on vehicle traffic engineering principles, the approach switches control modes to use power control to cope with increased vehicle density and rate control with increased channel utilization. It leads to significant improvements in packet delivery characteristics while more effectively managing channel load.