# Method for Handling Massive IoT Traffic in 5G Networks
## 9 Simulation Model  
The analytical results of the derived model for resource block utilization are compared with simulation results for resource block usage. The simulation results in this paper are generated under simulation parameters given in Table 3. The evaluation underlines the case of relaying without multiplexing and the impact of relaying with multiplexing as well as timer mechanism. The two cases are compared to determine the multiplexing gain achieved both in analytical and simulation models. The OPNET simulation environment (Figure 5) is used for determination of resource block usage and multiplexing gain. The OPNET model developed in this work emulates the impact of fast fading, slow fading, path loss, and noise on transmitted signal. It also models the interference from neighboring BSs. Channel models and interference models are developed according to [34]. The frequency reuse factor is 1. Therefore, devices transmitting uplink signals over certain resource blocks would cause interference in the transmission of devices of the neighboring BSs using the same resource blocks. Figure 5: OPNET project model of hexagonal grid [35]. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value/Setting** \\ \hline Cell layout & 7 BSs, 1 RN connected to central BS \\ System bandwidth & 5 MHz \\ Adjacent BS distance & 500 m \\ Max IoT device power & 23 dBm \\ Path loss & \(128.1+37.6\log_{10}(R)\) \\ Slow fading & Log-normal shadowing, mean 0 dB, standard deviation 10 dB, correlation 1 \\ Fast Fading & Jakes’ model \\ Noise per resource block & \(-120.447\) dBm \\ Noise floor & 9 dB \\ Power Control & Fractional, \(\alpha=0.6\), \(P_{0}=-58\) dBm \\ Timer expiry \(T_{max}\) & 9 ms \\ IoT message size & Constant (29) bytes including upper layers overhead \\ Message inter-transmission time & 1 s (exponential) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Simulation parameters. European Telecommunications Standards Institute (ETSI) based path loss models for different environments are used for research purposes. ETSI vehicular test environment model has been used in this work for modelling of path loss. \[L=128.1+37.6\log_{10}(R) \tag{11}\]  
where \(L\) is path loss in dB and \(R\) is the distance between receiver and transmitter in km. For slow fading, the log-normal model with standard deviation of 10 dB, mean 0 and correlation of 1 over distance is used. For fast fading, a time-dependent random function known as Jakes' model is used. Thus, maps for coverage areas (cells) are generated using models in [34] and traces of these maps are fed into our OPNET simulation model. Noise and noise figure are modelled as per 3 GPP specifications. Interference is modelled with in such a way that signals arriving from neighboring cells after reduction of power due to path loss, slow fading, and fast fading cause interference. The RN OPNET model for relaying node is implemented to feature two radio interfaces, the Uu and the Un interfaces (Figure 6). The corresponding protocol stacks are implemented as per 3 GPP end-user protocols. The relaying scheduler is implemented in the MAC layer of RN Uu interface. The proposed packet aggregation and multiplexing scheme is implemented at the Packet Data Convergence Protocol (PDCP) layer of RN Uu interface. The GPRS (General Packet Radio Services) Tunneling Protocol (GTP) is also implemented where packet are tunneled at the RN and detunneling is performed at BS. In the simulation model, the multiplexing transition probabilities are figured out by using a method of packet counting where \(a_{x}\) is the likelihood of \((x+1)\) th packet arrival prior to the start  
Figure 6: OPNET RN model. of packet multiplexing such that \(x\) packets are already present in the buffer and \(1\leq x<r\). In the simulation model, for determining the values of \(a_{x}\), \(r\) is considered as the maximum number of small data packets in the buffer multiplexed to form a large packet. So \(x\) could get a value in the range \(1\leq x<r\).