# On the Fidelity of NS-3 Simulations of Wireless Multipath TCP Connections
## 5 Simulation Model
### Simulator Parameters and Configuration  
Every node in the simulator has two network devices (same as network interface cards in real nodes). The simulator is configured to use a constant-position mobility model. Thus, the nodes remain stationary during the data transfer. We simulate the LTE network used in the testbed by utilizing LENA, an LTE/EPC simulation platform of ns-3. The core network of LTE is simulated using the ns-3 EPC model, which includes one MME and one more entity that assumes the SGW and PGW's responsibilities. The interfaces between these entities are implemented as high-speed point-to-point links to mimic the hardware implementation. The LTE model of ns-3 implements the LTE radio protocol stack at the eNodeB and the communicating nodes (UEs). The simulator's LTE stack includes all the layers of the real LTE stack, such as Radio Resource Control (RRC), Packet Data Convergence Protocol (PDCP), Radio Link Control (RLC), Medium Access Control (MAC), and Physical (PHY). The LTE stack parameters are configured, as listed in Table 1, to replicate the LTE settings of the testbed. Thus, the essential parameters such as the MAC scheduler, sounding reference signal (SRS) periodicity, maximum modulation coding scheme (MCS), and maximum transmission unit are set to the same value as in the configuration of the LTE network of the hardware testbed. The number of resource blocks is set to 100 to achieve a bandwidth of 20 MHz as in the testbed. The eNodeBs use the FDD mode in band 7 with a downlink frequency of 2660 MHz and an uplink frequency of 2540 MHz. \begin{table}
\begin{tabular}{c c} \hline \hline
**LTE Parameter** & **Value** \\ \hline LTE Access Mode & FDD \\ Number of Resource Blocks & 100 \\ DL-EARFCN & 3150 \\ LTE Scheduler & PFFMascheduler \\ SRS Periodicity & 320 ms \\ eNodeB Tx-Power & 30 dBm \\ eNodeB Noise Figure & 5 dB \\ Maximum Uplink MCS & 23 \\ Maximum Downlink MCS & 28 \\ UE MTU & 1500 bytes \\ UE Tx-Power & 10 dBm \\ UE Max-Power & 17 dBm \\ UE Noise Figure & 9 dB \\ LTE Loss Model & HybridBuildingsPropagation \\ \hline \hline \end{tabular}
\end{table} 
Table 1: LTE simulation parameters. Figure 4: Simulation Setup 2. The path loss model, transmission power, and eNodeB/UEs' positions are adjusted so that the average MCS value reported by the UEs in the simulator matches the one reported by the LTE hardware. As revealed in Figures 3 and 4, the LTE UEs (sender nodes) are located in an indoor environment (inside a building), whereas the eNodeB is located outside this building. This setting allows applying the HybridBuildingPropagation loss model of ns-3, which provides suitable flexibility to adjust its parameters to obtain similar path loss to the testbed's LTE network since it includes a path loss model with distance-dependent slope and path loss elements (external/internal wall loss and height loss). The indoor-outdoor scenario for the UEs and the eNodeB in the HybridBuildingPropagation model is based on the ItuR1411 path loss model [41]. In this model, the coordinates of the UEs and eNodeB determine whether the path is Line of Sight (LOS) or Non-LOS so the loss can be calculated accordingly. The considered simulation setup only involves LOS paths. According to the ItuR1411 path loss model, the path loss for LOS paths is characterized by two slopes and a single breakpoint. The path loss at the breakpoint is given by  
\[L_{bp}=20\times log_{10}(\lambda^{2}/(8\times\pi\times h1\times h2)) \tag{11}\]  
where \(\lambda\) is the wavelength, \(h1\) is height of the node, and \(h2\) is the height of the eNodeB.