# Inter-Beam Co-Channel Downlink and Uplink Interference for 5G New Radio in mm-Wave Bands +
###### Abstract  
This paper presents a methodology for assessing co-channel interference that arises in multi-beam transmitting and receiving antennas used in fifth-generation (5G) systems. This evaluation is essential for minimizing spectral resources, which allows for using the same frequency bands in angularly separated antenna beams of a 5G-based station (gNodeB). In the developed methodology, a multi-ellipsoidal propagation model (MPM) provides a mapping of the multipath propagation phenomenon and considers the directivity of antenna beams. To demonstrate the designation procedure of interference level we use simulation tests. For exemplary scenarios in downlink and uplink, we showed changes in a signal-to-interference ratio versus a separation angle between the serving (useful) and interfering beams and the distance between the gNodeB and user equipment. This evaluation is the basis for determining the minimum separation angle for which an acceptable interference level is ensured. The analysis was carried out for the lower millimeter-wave band, which is planned to use in 5G micro-cells base stations. a 2021 221 22 22  
ommidirectional and sectoral antennas and homogeneous environments, e.g., [5; 6; 7]. From the viewpoint of 5G systems that use mmWaves, massive-MIMO, and beamforming, such analysis should consider narrow beams of antenna systems. Examples of such studies are presented in [8; 9; 10; 11]. On the other hand, the analysis of co-channel interference is essential to assessing the coexistence and compatible functioning of different radio systems. The importance of this problem is presented in [9]. Besides, many new procedures in massive-MIMO and beamforming systems that increase the efficiency of 5G require assessing the level of interference between the antenna beams to and from individual users. The partial-nulling based statistical beamforming is an example of such a procedure, the use of which is based on the division of all users into two groups with a significantly different degree of spatial correlation [12]. The solution presented in [13] is another example that increases the spectral efficiency in massive-MIMO systems. These selected examples show the importance of assessing the level of interference between the beams of the antenna system from other users in developing and implementing new solutions. The utilization of narrow beams and the dominance of the multipath propagation phenomenon in urban areas significantly change interference analysis methods. In this case, the practical used method of the interference assessment is based on simulation tests. Parameters of transmitted and received signals as well as their statistical properties for various types of propagation environments are input for these studies. The 3 rd Generation Partnership Project (3 GPP) standard [14] is commonly used for this aim. This approach recommends using deterministic cluster delay lines (CDLs) for link-level simulations, where average angles of departure (AODs) and arrival (AOAs), in addition to tapped delay line (TDL), are defined. For system-level simulations, where a statistical approach is more appropriate, the 3 GPP standard [14] recommends the full three-dimensional (3D) modeling of a radio channel. The interference topic is widely represented in the literature. On the one hand, there are works on counteracting interference in the emerging and future systems. Examples include software algorithms and hardware solutions aimed at interference cancellation [15], mitigation [16], or awareness [17; 18]. In this case, the currently proposed solutions are mainly dedicated to multi-antenna systems. On the other hand, papers focusing on the interference evaluation and measurement [19] methodologies are presented. In general, the interference analysis can be performed at any distance from the signal source antenna. In the case of a near-field, the influence between the individual elements of the multi-antenna system can be investigated [20; 21; 22; 23; 24].