# Coverage, Rate, and Last Hop Selection in Multi-Hop Communications in Highway Scenarios
## 1 Introduction
### Related Studies  
Signal propagation in the Vehicle to Everything (V2X) environment has been well investigated in the context of LTE and mmWave systems. For example, in [12], the influence of the location of the antenna on the car on the fading during data transmission was characterized. Six types of antenna locations were analyzed. As a result, it is shown that the closer the receiver and transmitter are located, the more likely the signal is blocked by the car body, and the best location for the transceiver is on the side pillars. For our scenario, three locations turned out to be the most suitable: (i) bumper, (ii) engine, and (iii) windshield. In addition, we have considered various cases of distances between the receiver and transmitter, although only 10 m and 100 m are suggested. The authors in [13] investigated the dependence of the coverage area on the signal attenuation. Multiple cases of data transmission in the line-of-sight (LoS) zone and in the blocked zones by other cars are considered. The result showed that it is necessary to forcibly limit the connection to the nearest car in order to maintain reliable connectivity. In our work, we consider three communication scenarios: LoS, non-LoS (NLoS), as well as reflection from cars in the adjacent lane. The study [14] investigated the effect of interference in the simultaneous transmission of data from several vehicles. A two-lane road with cars and a data transfer scenario from the BS to a car in the far lane are considered. The probability of packet loss was studied, as well as the average throughput when the signal is blocked by a neighboring car. The results show that the packet loss probability depends on the number of antenna clusters installed on the BS, as well as on the channel nonlinearity. In our study, we also take into account blockage by other vehicles. However, we explore the possibility of relaying through other vehicles using directional antennas to improve the reliability of communications. An equally important problem in V2X communications in mmWave/sub-THz bands is beamforming and interference. In [15], the authors investigated the signal quality polling rate to recalculate beam direction and improve the quality of data transmission. The considered average speed of cars is set at 10.5 miles per hour, which is typical for suburban and dense urban conditions. The authors reported an optimal channel state polling time of 300 ms for the indicated initial data. The applied approach also allows us to study the polling frequency for other vehicle speeds. In our work, we studied the movement of a traffic flow at a speed of 25 m/s, which is a more complex scenario in terms of polling the channel state. Addressing the problem of interference the authors in [16] demonstrated that, for directions communications in the mmWave/sub-THz bands, its effect is negligible. In addition to the main quality indicators and different ways to establish single-hop communications, an important issue is the position of cars in the lane. The scenario involving different offsets of vehicle locations with respect to the lane width is considered in [17]. The aim of the study was to propose an efficient beamforming method for predicting the directions to the communicating entity based on past information. In our work, this aspect is not taken into account as we assume that the vehicles are positioned in the middle of the lanes. An interesting study was performed in [18], where the authors considered an intersection scenario with multiple concurrent transmissions from two BS. Their results showed that the use of Non-Orthogonal Multiple Access (NOMA) access technology reduces the probability of blockage by approximately two times, depending on the channel parameters. At the same time, blockage of propagation paths by both external and other vehicles is provided. The authors of the study compared the NOMA and OMA methods using an analytical model, and also validated their studies using the Monte Carlo simulations.