# Interference Analysis for Vehicle-to-Vehicle Communications at 28 GHz
## 1 Introduction
### Related Work  
Experimental research platforms for using the mmWave band in the automotive industry have been developed since 1980. Lately, some studies have focused on the analysis of interference in mmWave vehicle communications [22; 23; 24; 25]. In [22], a base station (BS) to vehicle communication at 60 GHz is modeled and outage probability is analyzed by taking into account the Rice channel model. The result shows that due to the movement of vehicles, the reflected signal from road infrastructure can be neglected as it has no impact. Furthermore, it is shown that high atmospheric absorption at 60 GHz leads to small cell sizes which, on one hand, increase the reuse factor, but on the other hand, enable frequent handovers. Nevertheless, it has been shown that communication can be established up to 100-200 m with a suitable value of outage probabilities. The authors of [23] have considered interference from a nearby base-station during vehicle-to-infrastructure communication. It is shown that the dominating line-of-sight (LOS) interference, which determines the outage probability, is from BSs on the same street as the serving station, while the BSs on the cross street have insignificant effects in most cases. Furthermore, the results provided by the authors show that with the large intensity of BSs, the interference level rises and the network becomes interference-limited. Also, the coverage probability scales linearly with the street intensity. Therefore, the deployment of more BSs in an already dense Urban environment does not improve the coverage. Interference from the sideline during mmWave V2V communication was measured by the authors of [24] for both highway and urban scenarios. Using these measurements, the authors estimated the signal-to-noise ratio (SNR) and performed capacity analysis for 79 and 300 GHz. The results indicate that the interference from the sidelines can be well approximated by 2D stochastic models. Besides, the interference level greatly depends on the radiation pattern and angle of arrival. The study presents a notable impact of interference from the sidelines on the link-layer performance of V2V communication systems. A detailed framework to characterize the coverage and connectivity of a mmWave vehicular network deployed along a multi-lane highway is presented in [25]. The results show that stable connectivity requires both accurate alignments between vehicles and satisfactory signal quality. In sparse networks, it is observed that performance can be improved by considering narrower beams due to the beamforming gain. However, in dense networks, larger beams should be produced to generate large connectivity regions that ensure robust alignment between vehicles. Overall, better connectivity and throughput performance are achieved by considering frequent beam alignments that enable endpoints to reduce the outage time. Many investigations are carried out for V2X communication in 6 GHz bands such as [26; 27; 28; 29]. These studies provide closed-form expressions for the achievable throughput and analyze coverage for V2V communication in various scenarios. However, the propagation characteristics at 5.9 GHz are completely different from those of mmWave communication. Also, communication in a conventional vehicular system is omnidirectional although beamforming is possible after the link has been established. Therefore, these solutions cannot be applied to mmWave scenarios, where highly directional transmission schemes are required. Most of the above studies consider frequencies above a 60 GHz band. However, significant signal attenuation can be experienced at these frequency ranges. A more suitable approach is to use a 28 GHz frequency range where the atmospheric attenuation is identical to the cellular band [30].