Joint Spectrum Sharing and V2V/V2I Task Offloading for Vehicular Edge Computing Networks Based on Coalition Formation Game

Vehicular edge computing (VEC) enables vehicles to perform computation-intensive and delay-sensitive tasks through task offloading. Previous works either focused on task offloading based on vehicle-to-infrastructure (V2I) mode or assumed the existence of sufficient spectrum resources. However, given the exponential increase in the number of vehicles, it is essential to explore the influence of both spectrum scarcity and inter-vehicle cooperation on VEC network performance. In this paper, we investigate a joint spectrum sharing and task offloading scheme to minimize the total completion delay of tasks. Differing from previous works, our scheme incorporates task offloading based on vehicle-to-vehicle (V2V) and V2I modes while enabling V2V links to share the uplink spectrum of V2I links. To solve the formulated non-convex mixed-integer nonlinear programming problem, we propose a distributed and iterative algorithm based on the coalition formation game (CFG). Specifically, we formulate spectrum sharing and task offloading problems as many-to-one matching games with externalities and obtain the sub-channel allocation and server selection policies using the CFG approach, whose stability and convergence are analyzed. On this basis, power control and offloading ratio policies are derived using dual decomposition and quadratically constrained quadratic programming, respectively. Numerical results show that the proposed scheme reduces the total completion delay by an average of $65.31\%$ , $51.22\%$ , and $29.97\%$ , respectively, compared to three baseline schemes under varying numbers of task vehicles.