Securing OFDMA in V2V Communication Among Untrusted Platoons

With the Internet of Things becoming an essential part of our lives, Vehicle-to-vehicle (V2V) communication is becoming very popular to meet the growing demands of having an Intelligent Transportation System (ITS). However, ensuring secure V2V communication is the key to realizing the full potential and utility of ITS. Therefore, this paper develops a secure framework for orthogonal frequency division multiple access (OFDMA) based V2V communication among the untrusted platoons. Specifically, we propose optimal subcarrier and power allocation policies to maximize the sum secrecy rate across the vehicles which share the subcarriers with the vehicles outside their platoons. We start with allocating sub-carriers to the vehicles inside each platoon based on their underlying channel power gains. After that, noting the non-convexity of the power allocation problem, we propose a high signal-to-interference-plus-noise ratio-based transformation to develop two optimal power control policies. While both are based on fractional programming (FP), one yield closed-form power allocation and the other provides the optimal global solution numerically at a higher computational complexity. Lastly, the numerical simulations verify the analytical claims, provide key design insights and demonstrate that our proposed power control policies can improve the sum secrecy rate of benchmark schemes by over 4dB for the eight vehicles setting.