## 4 Low-Cost Experimental Implementation Using on-Premises LTE/4G Network  
To implement an on-premises LTE/4G network, we used the Open Air Interface (OAI) software [39]. It is an open-source software program that runs on the Ubuntu Linux environment and is provided by University Eurecom. Its purpose is not only experimental. It actively participates in the research and development of 5G and other communication  
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Payload Size (kb)** & **0–200** & **200–400** & **400–600** & **600–800** & **800–1000** & **1000–1200** \\ \hline QoS 0 PT (ms) & 1.9575 & 3.3773 & 4.4756 & 5.9152 & 7.1644 & 7.6543 \\ QoS 0 TLS (ms) & 1.9738 & 3.8433 & 5.3904 & 7.5574 & 9.9594 & 11.8360 \\ QoS 0 TLSMA (ms) & 1.9233 & 3.5789 & 5.4169 & 7.0627 & 9.7204 & 11.7716 \\ \hline QoS 1 PT (ms) & 1.8276 & 2.8415 & 3.6975 & 5.1162 & 6.8120 & 7.8951 \\ QoS 1 TLS (ms) & 1.9451 & 3.5139 & 5.55778 & 7.9114 & 10.187 & 11.8742 \\ QoS 1 TLSMA (ms) & 1.7534 & 3.0070 & 4.4488 & 6.8328 & 9.9884 & 11.7456 \\ \hline QoS 2 PT (ms) & 2.8024 & 3.8195 & 4.5763 & 6.1935 & 7.6070 & 8.2785 \\ QoS 2 TLS (ms) & 2.5047 & 3.7768 & 5.3041 & 7.9585 & 11.425 & 12.8641 \\ QoS 2 TLSMA (ms) & 2.4494 & 3.7117 & 5.2145 & 7.7037 & 10.6853 & 12.0606 \\ \hline \end{tabular}
\end{table}
Table 2: Latency for TLS and non-TLs enhanced MQQT.  
products, also used on IP Multimedia System (IMS) platforms. Figure 6 describes the implementation of the isolated LTE/4G network. Applications include the operation of E-UTRAN (OAI eNB and UE) and OAI EPC (MME, S-GW, P-GW) and the HSS database for user management. The eNB application is running on an Ubuntu Linux low-latency kernel PC (eNB PC), and the MME, HSS, and SPGW applications are running on an Ubuntu Linux generic Kernel PC (EPC PC). The program can work in real-time with Software-Defined Radio (SDR) platforms and commercial User Equipment (UE).  
In Table 3, we describe the LTE/4G abbreviations.  
LTE networks are covered with several standard security procedures, where all components in the system, such as UE, eNB, MME, and HSS, are involved [40]. Our 4G/LTE network is an isolated on-premises network, and therefore, external users and passengers do not have access. We should also take into consideration that the radio channel characterization is subject to an investigation because of the propagation (reflection, scattering, and diffraction). Furthermore, many obstacles whose dimensions are similar to the wavelength of the transmitted electromagnetic wave are responsible for loss due to multipath fading, electromagnetic absorption, etc. In [41], the authors reported the LTE penetration losses measurement inside a building. They observed the penetration of the radio channel at 2.6 GHz through the exterior, interior, and plasterboard walls in a building. Their result shows that penetration loss reduces the radio frequency (RF) energy inside a building. Their statistical report is very useful, and therefore, we should carefully examine the number of base stations that we should install on the ship.  
\begin{table}
\begin{tabular}{l l} \hline
**ACRONYM** & **ABbreviation** \\ \hline eNB & Evolved Node B \\ EPC & Evolved Packet Core \\ EUTRAN & Evolved Terrestrial Radio Access Network \\ HSS & Home Subscriber Server \\ MME & Mobility Management Entity \\ OAI & Open Air Interface \\ PGW & Packet Data Network Gateway \\ SGW & Serving Gateway \\ UE & User Equipment \\ S1-C,S1-U,S11,S6a,SGi & Communication Protocols \\ \hline \end{tabular}
\end{table}
Table 3: 4G/LTE abbreviations.  
Figure 6: LTE/4G on-premises implementation—high level architecture.  
Below, we describe the experimental procedure that we followed to simulate the digital signage system of the cruise ship. Our experimental setup includes a digital LED strip installed on an LTE/4G module, placed on deck number 8 on the cruise ship.