# Inter-Beam Co-Channel Downlink and Uplink Interference for 5G New Radio in mm-Wave Bands +
###### Abstract
In the case of a far-field, inter-beam [25; 26], inter-cell [18; 26; 27], or inter-system interferences, i.e., the coexistence of different systems and networks [9; 11; 28], might be studied. In the literature, the vast majority of scientific works concern coexistence topic and the inter-cell interference assessment, rather than inter-beam interference. In this paper, we present a methodology for assessing co-channel interference that is resulting from the utilization of the same frequency channels in different beams of the gNodeB antenna system. To evaluate the signal-to-interference ratio (SIR), we use simulation tests that are based on a 3D multi-ellipsoidal propagation model (MPM) [29; 30; 31]. However, the proposed methodology differs from the simulation approach recommended by the 3 GPP standard for link-level evaluations. In our methodology, using the MPM as a geometry-based model (GBM) provides a statistical SIR metric in contrast to the 3 GPP approach with the pre-determined AODs and AOAs. In our solution, the knowledge of spatial parameters such as the average AODs and AOAs of propagation paths is not required to obtain results and the use of any power delay profile (PDP) or the TDL makes it possible to adapt this model to any propagation scenarios. The use of the MPM and antenna radiation patterns allow determining a power angular spectrum (PAS) of the received signals. The obtained PASs are the basis for the SIR assessment in the multi-beam antenna system. The MPM geometry is constructed based on the PDP or TDL, which describe the transmission properties of a propagation environment. This original way of mapping the effects of propagation phenomena enables obtaining a fully statistical SIR evaluation. It ensures a relationship of simulation results with the analyzed type of propagation environment. The presented analysis is an extension of the paper [32], which focused only on the downlink (DL) interference in multi-beam 5G macro-cell for 3.5 GHz band and under non-line-of-sight (NLOS) conditions. In that case, we used a two-dimensional multi-elliptical model [31]. In this study, based on the 3D MPM, we discuss the inter-beam co-channel interference in DL and additionally uplink (UL) for 28 GHz band, under line-of-sight (LOS) and NLOS conditions. Using the 3D MPM to modeling the inter-beam interference level testifies to the novelty of the presented approach. In this case, an original approach to the UL interference assessment was proposed, taking path loss corrections into account, compared to the DL scenario [32] shown previously. The mutual configuration of the transmitting and receiving antenna beams is not only the factor considered in our methodology. The presented solution of the SIR determination also provides a mapping of the propagation environment influence on the PAS of the received signals. The 3 GPP methodology also takes this impact into account. However, it is limited to well-defined types of environments that are defined based on the determined channel characteristics and distributions of channel parameters. In the case of the MPM methodology presented in this paper, we have the option to assess the SIR for any type of propagation environment, whose transmission properties are defined by an appropriate PDP. This fact significantly distinguishes the developed method and proves its originality. The remainder of the paper is organized as follows: Section 2 shows the construction way of the MPM geometry based on the transmission properties of the propagation environment, i.e., the TDL. The essence of the PAS determination procedure and then the SIR assessment is presented in Section 3. In Sections 4 and 5, the description of the analyzed scenarios for the DL and UL transmissions and the results of simulation studies are drawn. Section 6 contains conclusions.