Hybrid of Angular and Distance Protection for Coexistence of 5G Base Stations and Satellite Earth Stations  
[PERSON]  
1 Division of Electronics and Electrical Engineering, Dongguk University, Seoul 04620, Korea; [EMAIL_ADDRESS] (S.  
wireless services while accommodating incumbents. In addition, the FCC sought comments on proposals, in order to promote a more spectrum-efficient, intensive, and fixed use of the band on a shared basis. Several GSM studies have addressed the access to the current utilization of the C-band (3.5-4.2 GHz). These studies defined a strategy and roadmap to release this band to support the deployment of 5G services [5]. Interference is the primary problem of the coexistence of two communication systems on one frequency band. Four types of interference exist between 5G and FSS systems: from the 5G base station (BS) to the FSS earth station (ES), from 5G users to the FSS ES, from FSS devices to the 5G BS, and from FSS devices to 5G users. In this study, we followed previous research [6] and focused on minimizing the interference of BS to ES and achieving the coexistence of FSS and 5G BS. In previous studies, refs. [7; 8] confirmed that distance protection schemes can effectively solve the problems caused by interference. As part of the Citizens Broadband Radio Service (CBRS) development, we suggested a distance protection strategy for FSS ESs and 5G BSs [6]. The suggested method was evaluated against three real scenarios of rural macrocells (RMa), urban macrocells (UMa), and urban microcells (UMi), the size of the exclusion zone is different for various scenarios (RMa > UMa > UMi), where higher elevation angles imply larger off-boresight angles. Antenna arrays offer a wider confined area on the ES's north side than omnidirectional antennas. Increasing the number of antenna components also solves the problem of reducing the restricted region caused by directional attenuation. When the antenna array is employed in the urban scenario (UMa and UMi), the average Tx power reduction is minimal since many cells can only cut their Tx power by 1 dB. If the Tx power is lowered by 1 dB, and most BSs must further reduce Tx power when using an omnidirectional antenna. When using antenna arrays in UMa and UMi, the proposed power control strategy is more effective. It was found that the influence of ES/BS-related angles on frequency band coexistence was not studied in prior studies. In the study of [9], the distance protection scheme was incorporated into the analysis of the protection band and the angle of arrival to achieve the coexistence of LTE-Advanced and FSS services. Therefore, we propose an angular protection scheme to solve the influence of the ES antenna elevation angle on the protection mode. The angle protection was integrated into the exclusion and restricted zones proposed by the distance protection scheme for simulation analysis. Finally, in restricted areas, some interactive power control schemes inspired by the power control scheme used in CBRS were proposed and evaluated. The contributions of this article are summarized as follows:  
* The fixed BS-ES relative location, BS-ES relative distance, and angle changes illustrate the principle of angular protection from the easier to the more advanced cases;
* Shutting off the harmful beam was performed to decrease the exclusion and restriction zones, and to reduce the BS TX power in the restriction zone for angular protection. Three types of beam shut-off were investigated to demonstrate the tradeoff between the BS coverage and the coexistence of ES protection;  
Figure 1: Korea’s 5G frequency allocations and adjacent bands [1]. * The distance protection approach of the literature was used, and the combination of angular protection and distance protection was evaluated. In addition, the efficiency of the angular protection and the combination of angular protection and distance protection, were evaluated and compared.