Toward Safe and Energy-Efficient 5G NR V2X Communications in Rural Environments

Connected braking can reduce fatal collisions in connected and autonomous vehicles (CAVs) by using reliable, low-latency 5G New Radio (NR) links, especially NR Sidelink Vehicle-to-Everything (V2X). In rural areas, road side units are sparse and power-constrained, so energy efficiency must be considered alongside safety. This paper studies how three communication control factors including subcarrier spacing (SCS), modulation and coding scheme (MCS), and transmit power (<inline-formula> <tex-math notation="LaTeX">${\boldsymbol{P}}_{\text {t}}$ </tex-math></inline-formula>) should be configured to balance safety and energy consumption in rural scenarios in light and heavy traffic scenarios. Safety is quantified by the packet receive ratio (PRR) against the minimum communication distance <inline-formula> <tex-math notation="LaTeX">${\boldsymbol{D}}_{\text {comm}}$ </tex-math></inline-formula>, defined as the distance that the vehicle travels during the transmission of the safety message. Results show that, under heavy traffic, increasing <inline-formula> <tex-math notation="LaTeX">${\boldsymbol{P}}_{\text {t}}$ </tex-math></inline-formula> and selecting a low-rate MCS at SCS = 30 kHz sustains high PRR at <inline-formula> <tex-math notation="LaTeX">${\boldsymbol{D}}_{\text {comm}}$ </tex-math></inline-formula>, albeit with higher energy cost. In light traffic, maintaining lower <inline-formula> <tex-math notation="LaTeX">${\boldsymbol{P}}_{\text {t}}$ </tex-math></inline-formula> with low MCS levels achieves a favorable reliability-energy trade-off while preserving acceptable PRR at <inline-formula> <tex-math notation="LaTeX">${\boldsymbol{D}}_{\text {comm}}$ </tex-math></inline-formula>. These findings demonstrate the necessity of adaptive, energy-aware strategy to guarantee both safety and energy efficiency in rural V2X systems.