# On the Impact of Multiple Access Interference in LTE-V2X and NR-V2X Sidelink Communications +
## 1 Introduction
Supporting enhancements to V2X (eV2X) use cases associated with connected and autonomous driving is the aim of the NR-V2X sideline. The counterparts in NR-V2X of LTE-V2X Mode 3 and Mode 4 are NR-V2X Mode 1, which utilizes an altered version of the sensing-based SPS (SB-SPS) algorithm, for planned resource selection, and NR-V2X Mode 2, which employs autonomous resource selection. [PERSON] et al. [16] discussed the main differences, challenges, potential technical developments, and open issues related to resource allocation in C-V2X technologies. The performance of C-V2X systems has been predominantly examined in the literature via simulations [17; 18]. Most analytical models consider IEEE 802.11-based V2X [19] or LTE-V2X Mode 3 [20] with infrastructure support. For LTE-V2X communications, Mode 3 and Mode 4 were developed to satisfy latency requirements while accommodating significant Doppler spreads and vehicle density. The research in [21] proposed a model that measures the four different types of packet errors that affect the performance of LTE-V2X sidelink: errors caused by half-duplex transmissions, errors caused by received signal power below the sensing power threshold, errors caused by propagation effects, and errors caused by packet collisions. The multiple access interference scenario is modeled using simplified assumptions, even though the model is quite accurate in its depiction of the SPS scheme. As an example, a random traffic generation pattern is the way to define the presence of automobiles statistically. In our previous work in [22], we developed an analytical framework for the LTE-V2X sidelink communication protocol in terms of packet success probability by simulating the intricate relationship between the SB-SPS and the propagation environment. In this paper, we extend the analysis to include the relevant characteristics of NR-V2X communications. Since this distribution fits in more measurement campaigns than the other distributions, the Nakagami-lognormal distribution is often employed for model fading. This distribution was first published in [23] to evaluate the outage probability in scenarios with several co-channel interferers. The difficulty in differentiating between small-scale fading and shadowing processes in compact stationary contexts such as automotive environments and vehicular communication has recently increased interest in this distribution [24]. We first derive an approximation of the probability density function (PDF) for the signal-to-interference-and-noise ratio (SINR) by using the Nakagami-lognormal propagation model and multiple-access interference. To achieve this, the SINR is approximated via a lognormal random variable, the statistics of which are acquired by moment matching [25; 26; 27]. This approach is more convenient than stochastic geometry (e.g., as in [28]) since the performance needs to be derived for the specific relative distance between vehicles and it is important to be able to distinguish the SINR for a specific vehicle in transmission with interferers at a relatively fixed position, as in platooning scenarios. Finally, using the Look-Up Table (LUT) reasoning outlined in [29], the packet success probability is determined numerically. The SB-SPS technique is explicitly accounted for to characterize the interference patterns, and the resulting channel schedule is used to derive the SINR statistics. Our model, which is specifically tailored to the platooning scenario, allows us to describe the packet success probability as a function of the number of interfering vehicles, the number of available resources, and the distance between the transmitter and the receiver. This contrasts with earlier works in the literature (e.g., [21]). The proposed approach also captures the intricate interplay between the channel access strategy and the propagation environment.