# Inter-Beam Co-Channel Downlink and Uplink Interference for 5G New Radio in mm-Wave Bands +
## 4 Assumptions and Scenarios of Simulation Studies  
The aim of the simulation tests is to present a method of modeling and assessing the co-channel interference that arises in the radio link with a multi-beam antenna system. The studies focused on determining the SIR relationship on the separation angle \(\Delta\alpha\) and changes in the distance \(D\) (or distances \(D_{S}\) and \(D_{I}\)) between the UEs and gNodeB. The simulations were carried out for carrier frequency of 28 GHz, typical for the 5G micro- and pico-cells, where multiple sub-arrays and beamforming technologies are planned for implementation. Besides, we considered two scenarios for the DL and UL, which are illustrated in Figures 2 and 3, respectively. In the DL scenario, we assumed that the gNodeB was generating two beams (serving and interfering) in the selected sector that were operating in the same sub-band (frequency channel). Thus, the SIR assessment came down to determining \(P_{S}\) and \(P_{I}\) powers induced in the UE antenna that come from the signals generated by the serving and interfering beams of the gNodeB, respectively. The distances between the gNodeB (Tx) and UE (Rx) was equal to \(D\). Besides, the serving (reference) gNodeB and UE beams were aligned, i.e.,  
Figure 3: UL spatial scenario of simulation studies. Figure 2: DL spatial scenario of simulation studies [32]. directed to each other (\(\alpha_{TS}=0\) and \(\alpha_{R}=0\), see Figure 1). In relation to the direction of the cell sector center, the reference and interfering gNodeB beams are oriented in \(\Phi_{S}\) and \(\Phi_{I}\) directions, respectively (see Figure 2). Thus, the separation angle of the beams is defined as:  
\[\Delta\alpha=\Phi_{S}-\Phi_{I}, \tag{15}\]  
Then the interfering beam orientation in relation to the Tx-Rx direction was equal to \(\alpha_{TI}=\Delta\alpha\). A similar scenario was taken into account for the UL transmission depicted in Figure 3. In this case, the analyzed gNodeB beam served one subscriber (UE-S) in its area, while another subscriber (UE-I) generated interferences towards this gNodeB beam. The UE-S and UE-I beams (Tx) were oriented to the gNodeB (Rx), i.e., \(\alpha_{TS}=\alpha_{TI}=0\) (see Figure 1). Whereas the gNodeB beam directions to the UE-S and UE-I were equal to \(\alpha_{RS}=0\) and \(\alpha_{RI}=\Delta\alpha\), respectively. So, in both scenarios, the separation angle, \(\Delta\alpha\), was always related with the direction of the gNodeB beam for the interfering link. In relation to the direction of the cell sector center, the gNodeB beam direction was equal to \(\Phi_{0}\) (see Figure 3). The distances between the gNodeB (Rx) and UE-S or UE-I (Tx) were equal to \(D_{S}\) or \(D_{I}\), respectively. In our tests, the direction of the reference gNodeB beam overlapped with the cell sector center, i.e., \(\Phi_{0}=\Phi_{S}=0\). Hence, we considered the change in separation angle in the ranges of \(0^{\circ}\div 60^{\circ}\). When analyzing the SIR changes in relation to the beam separation angle, we considered discrete distance values between the gNodeB and UE (or UE-I in the UL scenario), i.e., \(D_{S}=100\) m and \(D=D_{I}\in\{50,100,150\}\) (m). In this case, \(\Delta\alpha\) was changed from 0 to \(60^{\circ}\), which corresponds to half of a \(120^{\circ}\) sector. Analyzing the SIR versus \(D\) or \(D_{I}\) (for the DL or UL scenarios, respectively), we considered a continuous change of the distance in the ranges of \(10\div 250\) m, whereas the separation angle has discrete values \(15^{\circ}\), \(20^{\circ}\), and \(30^{\circ}\). For the UL scenario, we additionally used the close-in free space reference distance propagation models with path loss exponents equal to 1.9 and 4.5 for LOS and NLOS conditions, respectively [37]. To model the antenna power radiation patterns, we adopted 3 GPP recommendations [42]. Half-power beamwidths of main-lobes of the antenna beams were \(90^{\circ}\) for the UE and about \(12^{\circ}\) for the gNodeB, respectively.