  In this paper, a multi-vehicle multi-task nonorthogonal multiple access
(NOMA) assisted mobile edge computing (MEC) system with passive eavesdropping
vehicles is investigated. To heighten the performance of edge vehicles, we
propose a vehicle grouping pairing method, which utilizes vehicles near the MEC
as full-duplex relays to assist edge vehicles. For promoting transmission
security, we employ artificial noise to interrupt eavesdropping vehicles.
Furthermore, we derive the approximate expression of secrecy outage probability
of the system. The combined optimization of vehicle task division, power
allocation, and transmit beamforming is formulated to minimize the total delay
of task completion of edge vehicles. Then, we design a power allocation and
task scheduling algorithm based on genetic algorithm to solve the mixed-integer
nonlinear programming problem. Numerical results demonstrate the superiority of
our proposed scheme in terms of system security and transmission delay.
