Mathematical Representation for Reliability of Sensing-Based Semi-Persistent Scheduling in LTE-V2X

Since 3GPP has introduced sensing-based semi-persistent scheduling (SPS) into the MAC layer of LTE-V2X Mode 4 in release 14, various studies have been carried out to evaluate its performance. However, until now, there is still no clear mathematical expression for the reliability of this scheduling. To this end, we try to provide a theoretical representation of the scheduling reliability. Firstly, we present a description of the physical layer and MAC layer of sensing-based SPS, and then we abstract the scheduling mathematically and give the definition of the scheduling reliability and channel busy rate. Secondly, according to the characteristics of semi-persistent of scheduling, we formulate the reliability equation through the principle of iteration, thereby obtaining the closed-form expression of the scheduling reliability. Finally, we compare the theoretical representation of reliability with system simulations, and results show that the theoretical curve can represent the reliability of scheduling excellently.