Securing OFDMA-Based Cooperative Vehicular IoT Systems From Untrusted Platooning Networks

As the Internet of Things (IoT) becomes more integrated with everyday life, Vehicle-to-Vehicle (V2V) communication is becoming increasingly crucial for Intelligent Transportation Systems (ITS). However, ensuring secure V2V communication is crucial to fully realise the potential and usefulness of IoT-enabled ITS. Therefore, this paper proposes a novel joint optimisation framework for securing Orthogonal Frequency Division Multiple Access (OFDMA) based V2V communications in untrusted vehicle platooning networks. To address this timely non-convex optimisation problem in cooperative vehicular IoT systems, we divide it into two sub-problems: power control and subcarrier allocation. For each sub-problem, we propose dual solution strategies, prioritising low computational cost and emphasising high accuracy, albeit at a higher computational expense. The low-complexity approach for subcarrier allocation utilises channel power gains within platoons. On the other hand, the high-accuracy strategy involves a branch-and-bound (BNB) algorithm to obtain the near-global optimal solution for this NP-hard problem. Similarly, we introduce a low-complexity strategy based on a high signal-to-interference-plus-noise ratio (SINR) transformation, enabling closed-form solutions through fractional programming (FP) for optimal power control, which is ideal for automated vehicles. The alternative approach adopts a direct FP transformation for precise power distribution, attaining the near-global optimum numerically but with increased computational demands. Numerical simulations are conducted to validate our theoretical assertions and to offer nontrivial vital design insights. Our policy of jointly allocating BNB subcarriers and directly controlling FP power significantly increases the sum secrecy rate by more than 58% compared to conventional schemes in typical intelligent vehicle settings for IoT environments.