## 2 System Architecture, Spectrum Sharing Technique, and Interference Management  
### System Architecture  
We consider evaluating the performance of the spectrum sharing techniques by employing them in an MNO termed MNO 1. Figure 3 shows the system architecture of the MNO 1. A part of the macro user equipment (UE) is assumed inside the buildings as well as offloaded to a number of picocells. A set of SBSs are considered deployed within a building, and a number of such buildings are deployed over the coverage of a macrocell of MNO 1. SBSs are located within buildings at the center of the ceiling of each apartment. For simplicity, only one building is shown in Figure 3. In the following, we briefly describe how each of the well-known spectrum sharing techniques is realized using ABS based eICIC in 3D in-building small cells. We contextualize the general concept of each technique to in-building small cells using eICIC. Numerous new approaches are proposed to realize a number of aforementioned spectrum sharing techniques and manage relevant co-channel interference.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Notation** & **Definition** \\ \hline \(\sigma_{t,i}\) & Link throughput at RB = \(i\) in TTI = \(t\) \\ \(M_{\text{MNO},1}\) & Number of RBs in the MNO 1 spectrum \\ \(M_{\text{MNO},2}\) & Number of RBs in the MNO 2 spectrum \\ \(M_{\text{MNO},\text{T}}\) & Total spectrum due to the spectrum pooling at CoRS \\ \(M_{\text{SGR}}\) & Number of RBs of MNO 2 that is rented to MNO 1 \\ \(M_{\text{ULS}}\) & Number of RBs in the 60 GHz unlicensed spectrum \\ \(M_{\text{SPS}}\) & Number of RBs in SPS spectrum \\ \(S_{\text{F}}\) & Number of small cells per building \\ \(S_{\text{P}}\) & Number of picocells per macrocell \\ \(S_{\text{M}}\) & Number of macrocells in the system \\ \(P_{\text{PC}}\) & Transmit power of a picocell \\ \(P_{\text{MC}}\) & Transmit power of a macrocell \\ \(P_{\text{SC},1}\) & Transmit power of transceiver 1 of an SBS \\ \(P_{\text{SC},2}\) & Transmit power of transceiver 2 of an SBS \\ \(T_{\text{ABS}}^{\text{SPS}}\) & A set of ABSs in the satellite spectrum \\ \(T_{\text{MNO},1}^{\text{MNO},1}\) & A set of ABSs in the MNO 1 spectrum \\ \(T_{\text{non-ABS}}^{\text{MNO},2}\) & A set of non-ABSs in the MNO 2 spectrum \\ \(T_{\text{ABS}}^{\text{SPS}}\) & A set of non-ABSs in the satellite spectrum \\ \(T_{\text{non-ABS}}^{\text{MNO},\text{SPS}}\) & A set of non-ABSs in the satellite spectrum \\ \(L\) & Total number of buildings per macrocell \\ \(\lambda_{\text{MNO},1,\text{SU}}\) & The average rate of arrival of small cell UEs of MNO 1 into a building \\ \(\lambda_{\text{MNO},2}\) & The average rate of arrival of tiles of MNO 2 into a building \\ \(\lambda_{\text{SPS}}\) & The average rate of arrival of satellite UEs of SPS into a building \\ \(\lambda_{\text{MNO},1,\text{iMU}}\) & The average rate of arrival of indoor macro UEs of MNO 1 into a building \\ \(T_{\text{APP},\text{DedA}}\) & The value of \(T_{\text{APP}}\) for the dedicated access technique \\ \(T_{\text{APP},\text{DySP}}\) & The value of \(T_{\text{APP}}\) for the DySP technique \\ \(T_{\text{APP},\text{ISA}}\) & The value of \(T_{\text{APP}}\) for the ISA technique \\ \(L_{\text{ow}}\) & External wall penetration loss \\ \(\sigma_{\text{E}}^{\text{SE}}\) & Spectral efficiency for any value of \(L\in_{>0}\) \\ \(\sigma_{\text{E}}^{\text{EE}}\) & Energy efficiency for any value of \(L\in_{>0}\) \\ \(\sigma_{\text{SC}}^{\text{SE}}\) & The minimum spectral efficiency requirement for 5G mobile systems \\ \(\sigma_{\text{SC}}^{\text{SE}}\) & The minimum energy efficiency requirement for 5G mobile systems \\ \(L^{*}\) & An optimal value of \(L\) \\ \hline \hline \end{tabular}
\end{table}
Table 2: \(Cont.\)