Channel-Adaptive Robust Resource Allocation for Highly Reliable IRS-Assisted V2X Communications

This paper addresses the challenges of resource allocation in vehicular networks enhanced by Intelligent Reflecting Surfaces (IRS), considering the uncertain Channel State Information (CSI) typical of vehicular environments due to the Doppler shift. Leveraging the 3GPP's Mode 1 cellular V2X architecture, our system model facilitates efficient subcarrier usage and interference reduction through coordinated V2I and V2V communications. Each Cellular User Equipment (CUE) shares its spectrum with at most one Vehicular User Equipment (VUE) in a one-to-one reuse pattern. We formulate a joint optimization problem for vehicular transmit power, Multi-User Detection (MUD) matrices, V2V link spectrum reuse, and IRS reflection coefficients in IRS-aided V2X communication with imperfect CSI. To tackle this, a novel robust resource allocation algorithm is developed by first decomposing the problem into manageable sub-problems such as power allocation, MUD matrices optimization and IRS phase shifts, and then using the Block Coordinate Descent (BCD) method to alternately optimize these subproblems for optimal resource allocation. Our contributions include efficient approaches for self-learning based power allocation and phase shift optimization that adapt to CSI uncertainties, significantly enhancing the reliability and efficiency of vehicular communications. Simulation results validate the effectiveness of the proposed solutions in improving the Quality of Service (QoS) and managing the complex interference inherent in dense vehicular networks.

Joint Spectrum and Power Allocation for V2X Communications with Imperfect CSI

In Vehicle-to-Everything (V2X) communication, the high mobility of vehicles generates the Doppler shift which leads to channel uncertainties. Moreover, the reasons for channel uncertainties also include the finite channel feedback, channels state information (CSI) loss and latency. With this concern, we formulate a joint spectrum and power allocation problem for V2X communication with imperfect CSI. Specifically, the sum capacity of cellular user equipments (CUEs) is maximized subject to the minimum Signal-to-Interference-and-Noise Ratio (SINR) requirements of CUEs and the outage probability constraints of vehicular user equipments (VUEs). Then, two different robust resource allocation approaches are designed to solve the problem. One is Bernstein Approximation-based Robust Resource Allocation approach. More specifically, Bernstein approximations are employed to convert the chance constraint into a calculable constraint, and Bisection search method is proposed to obtain the optimal allocation solution with low complexity. Then, for further reducing the computational complexity, Self-learning Robust Resource Allocation approach, which includes a learning method and an analytical mapping method, is proposed as the second approach. The learning method is devised to learn the uncertainty set which transforms the chance constraint into calculable constraints, and the analytical mapping method is proposed to obtain closed-form solutions of the resource allocation problem. Finally, the simulation results prove that the proposed approaches can improve the capacity of all CUEs effectively whilst ensuring the reliability of the channel.