## 4 Low-Cost Experimental Implementation Using on-Premises LTE/4G Network
### Experimental Implementation
Each change in the state of the \"SWITCH\" will automatically generate a message on the output with the specified digital LED strip color value (green or red). On the output is the \"MQTT OUT\" node, which is connected to the MQTT Broker and publishes the message. MQTT is one of the most commonly used communication protocols for IoT platforms. Whether it is from the perspective of device compatibility or resource consumption, and overall security, the MQTT protocol has certain advantages and is one of the most competitive communication protocols in the Industrial IoT [45]. \begin{table}
\begin{tabular}{l l} \hline
**PRODUCT** & **SIM7000G** \\ \hline Form Factor & \multicolumn{2}{l}{LCC, 68 PIN} \\ Dimensions (mm) & \multicolumn{2}{l}{24X24X2.6} \\  & Cat-M & B1/B2/B3/B4/B5/B6/B8/B12/B13/B17/B18/B19/B20/B25/B26/B28/B39 \\ Frequency Bands & Cat-NB & B1/B2/B3/B4/B5/B6/B8/B12/B13/B17/B18/B19/B20/B25/B26/B28 \\  & GSM & 850/900/1800/1900 MHz \\ Temperature GNSS & \(-40\,^{\circ}\)C\(\rightarrow\)+85\(\,{}^{\circ}\)C optional \\ ELECTRICAL FEATURES & \multicolumn{2}{l}{3.0\(-\)4.3} \\ Supply Voltage Range (V) & Power Off (uA) & 7 \\  & PSM (uA) & 9 \\ Power Consumption & Sleep (mA) & 1 \\  & Idle (mA) & 11 \\ DATA TRANSFER & \multicolumn{2}{l}{300(DL)/375(UL)} \\ Cat-M (Kbps) & \multicolumn{2}{l}{34(DL)/66(UL)} \\  & EGPRS (Kbps) & 85.6(DL)/85.6(UL) \\ SOFTWARE FEATURES & \multicolumn{2}{l}{TCP/UDP/LWM2M/COAP/MQTT/FTP/HTPP/TLS/DTLS/NTP} \\ Protocol & \multicolumn{2}{l}{TCP/UDP/LWM2M/COAP/MQTT/FTP/HTPP/TLS/DTLS/NTP} \\ FOTA & \multicolumn{2}{l}{\(\bullet\)} \\ Embedded AT & \multicolumn{2}{l}{\(\bullet\)} \\ Firmware Upgrade & USB/FOTA \\ INTERFACES & \multicolumn{2}{l}{USB/FOTA} \\ SIM Card & \multicolumn{2}{l}{1.8 V/3.0 V} \\ UART & \multicolumn{2}{l}{\(\bullet\)} \\ USB & \multicolumn{2}{l}{\(\bullet\)} \\ PCM & \multicolumn{2}{l}{\(\bullet\)} \\ ADC & \multicolumn{2}{l}{\(\bullet\)} \\ I2C & \multicolumn{2}{l}{\(\bullet\)} \\ CERTIFICATION & \multicolumn{2}{l}{RoHS/REACH/CCC/CE(RED)/GCF/Deutsche} \\ Regulatory & \multicolumn{2}{l}{Telekom/FCC/IC/OCD(Anatel)} \\ Carrier & \multicolumn{2}{l}{Deutsche Telekom/ORANGE/PTCRB} \\ \hline \end{tabular}
\end{table} 
Table 4: SIMCOM 7000G modem details. Figure 10 shows the two possible conditions for digital signage in \"Deck 8/Way 1\" that a user can control from the Node-RED dashboard. When the \"SWITCH\" remains in the \"SECURE\" direction (Figure 10a), the digital LED strip remains GREEN (Figure 11a),  
Figure 8: Experimental network architecture. Figure 10: Experimental dashboard for controlling digital signage (**a**) SECURE; (**b**) NOT SECURE. Figure 9: “Deck 8” experimental flow. and when the \"SWITCH\" goes to \"NOT SECURE\" direction (Figure 10b), the digital LED strip changes to a RED color (Figure 11b). For the experiment, we used one digital LED \"WS2813B, while we can connect any size (number of LEDs on the strip) we want, without permissions. WS2813B is an improved version of WS2812B, a popular LED strip for industrial projects given its low driving voltage, high brightness, and great color consistency. Each addressable LED has an integrated driver, and therefore the color and the brightness of each LED can be controlled individually. Thus, we can create any complex digital signage. The most significant advantage of WS2813B strips is their LED bypass property. If any LED in the middle of the chain burns out, then the circuit remains closed, and the remaining LEDs will still light up. Following this methodology, we can cover all ship's MVZs with low-cost open-source digital signage modules and control them centrally through a real-time IoT dashboard. Moreover, we can easily add low-cost, reliable sensors to increase the security of the evacuation procedure. For example, we can add smoke, gas, fire, or water sensors to automatically give signal alarms in emergency cases, change the digital signage, and inform the IoT dashboard at the same time. Below, we analyze an example of the digital signage system's scalability.