Emergency message transmission method based on D2D communication in internet of vehicles

A method for transmitting an emergency message based on Device-to-Device (D2D) communication in Internet of Vehicles, comprising following steps of:

• 1) vehicle i collecting information wirelessly received from an adjacent vehicle about an adjacent vehicle j during driving, comprising a position (xj,yj) of the vehicle j, a speed vj of the vehicle j, and a lane R1 or R2 where the vehicle j is traveling;
• wherein xj represents a coordinate of the vehicle j along a driving direction which is a positive direction of x-axis, yj represents a coordinate of the vehicle j along a direction perpendicular to the driving direction, R1 represents a first lane, and R2 represents a second lane;
• 2) calculating a distance Dij between the vehicle i and a following vehicle j, wherein the following vehicle j meets xj<xi, xi represents a coordinate of the vehicle i along the driving direction;
• 3) comparing the distance Dij between the vehicle i and the following vehicle j with a preconfigured communication range R of the vehicle i;
• determining the vehicle j as a destination of the emergency message sent by the vehicle i and defining the vehicle j as a vehicle k when Dij<R;
• and establishing a set S containing all of the vehicle k, wherein, a total number of vehicles meeting the condition of Dij<R is TN,k′ k=1, 2, 3, . . . , TN,k;
• 4) comparing a distance Dik between the vehicle i and the vehicle k defined in the step 3) with a predetermined safety distance Ds between vehicles;
• calculating a priority index λik when Dik<Ds which represents that the vehicle k is within the safety distance of the vehicle i, wherein a smaller a value of the Dik is, the smaller the priority index λik becomes;
• establishing a D2D connection pair between the vehicle i and the vehicle k in order of the priority index from small to large to transmit the emergency message;
• 5) deleting vehicles to which the emergency message have been transmitted in the step 4) from the set S established in the step 3) to establish a new set S2, wherein the vehicle k in the set S2 outside the safety distance Ds of the vehicle i, within the preconfigured communication range R, in a direction following the vehicle i, and meeting a condition of xk<xi, wherein xk represents a coordinate of the vehicle k along the driving direction;
• 6) defining a prediction processing time interval, and predicting a distance Dik ′ between a vehicle k in the set S2 and the vehicle i according to the vehicle speed;
• and
• 7) calculating a priority index λik ′ for vehicles in the set S2, and establishing a D2D connection pair between the vehicle i and the vehicle kin order of the priority index λik ′ from small to large to transmit the emergency message.