Estimation and Reservation for Autonomous Resource Selection in C-V2X Mode 4

In this paper, the decentralized resource selection for Cellular Vehicle to Everything (C-V2X) communication is investigated. The immunity against packet collisions and selection of resource allocation are examined. It is found that the improvement of collision ratio and packet reception ratio (PRR) with the estimation and reservation of resource allocation, is the best way to improve the message broadcasting reliability. However, Sensing-based Semi-Persistent Scheduling (S-SPS), has been proposed for C-V2X Mode 4. The S-SPS faces several serious problems, like half duplex errors, hidden terminal errors, and packet collision errors. We propose an algorithm to enhance the performance aimed at decreasing the collision ratio and increasing PRR. The idea is that each vehicle lists all resource locations of the received packets that have the same random counter. This allows each terminal to estimate which resource location will be free in the next resource selection. Also, the announced next location in the list will be the current location when the random counter reaches zero. This way the vehicle does not need to depend on the sensing process, and resources utilization is improved. Our simulations show a significant improvement in the performance of our proposed algorithm as compared to S-SPS.