Optimising Communication Control Factors for Energy Consumption in Rural V2X

TL;DR

This work tackles energy-aware safety in rural 5G NR V2X by jointly analysing three communication control factors: transmit power $P_t$, subcarrier spacing (SCS), and modulation and coding scheme (MCS). It introduces the safety metric $D_{\mathrm{comm}}$ and derives analytical expressions for $D_{\mathrm{comm}}$, $PRR$, and energy, then validates findings with extensive simulations across light and heavy rural traffic. The results show that configuring $SCS=30$ kHz and $MCS=8$ provides robust safety performance at the risk threshold, while adaptive $P_t$—lower in light traffic and higher in dense traffic—significantly affects energy consumption and PRR. The study demonstrates the necessity of adaptive, energy-aware strategies to guarantee safety and efficiency in rural V2X systems, offering baseline formulations for future adaptive control solutions.

Abstract

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 or off-grid, so energy efficiency must be considered alongside safety. This paper studies how three communication control factors including subcarrier spacing ($\mathrm{SCS}$), modulation and coding scheme ($\mathrm{MCS}$), and transmit power ($P_{\mathrm{t}}$) 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 ($\mathrm{PRR}$) against the minimum communication distance $D_{\mathrm{comm}}$, defined as the distance that the vehicle travels during the transmission of the safety message. Results show that, under heavy traffic, increasing $P_{\mathrm{t}}$ and selecting a low-rate $\mathrm{MCS}$ at $\mathrm{SCS} = 30$ kHz sustains high $\mathrm{PRR}$ at $D_{\mathrm{comm}}$, albeit with higher energy cost. In light traffic, maintaining lower $P_\mathrm{t}$ with low $\mathrm{MCS}$ levels achieves a favorable reliability-energy trade-off while preserving acceptable $\mathrm{PRR}$ at $D_{\mathrm{comm}}$. These findings demonstrate the necessity of adaptive, energy-aware strategy to guarantee both safety and energy efficiency in rural V2X systems.

Figures (16)

• Figure 1: Traffic system model where $\texttt{RSU}$ sends a braking signal to $\texttt{Ego}$ to activate the brake. $D_\mathrm{comm}$ is shown as the distance that $\texttt{Ego}$ travels during the transmission.
• Figure 2: The process of sending and receiving safety signals between $\texttt{RSU}$ and $\texttt{Ego}$.
• Figure 3: Minimum $D_{\mathrm{comm}}$ under various values of ${P}_{\mathrm{t}}$ and $v$.
• Figure 4: $\mathrm{PRR}$ benchmark between $\mathrm{SCS}$ = $15$ kHz and $\mathrm{SCS}$ = $30$ kHz. In this simulation, traffic densities are from $30$ to $100$ vehicles/km, with $P_{\mathrm{t}} = 23$ and $\mathrm{MCS}$ = $8$.
• Figure 5: $\mathrm{PRR}$ tested with $\rho \in \{30, 50, 80, 100\}$ vehicles/km. In this simulation, $\mathrm{SCS}$ = $30$ kHz, $\mathrm{MCS}$ = $8$, and $P_{\mathrm{t}} = 24$.

Theorems & Definitions (5)

• Lemma 1: The Formulation of Critical Distance
• proof
• Lemma 2: Total energy spent on transmissions with truncated HARQ
• proof
• Remark 1