# An Emergency Alert Broadcast Based on the Convergence of 5G and ATSC 3.0
## 3 The Novel Emergency Alert Broadcast Approach Based on the Convergence  
### The Convergence Architecture and the Scenario  
Figure 6 illustrates the proposed overall architecture of the 5G and ATSC 3.0 convergence network for emergency alert broadcast. The alerting authority simultaneously sends an emergency alert message to the 5G and the ATSC 3.0 systems. In the convergence architecture, the N3 IWF is used for the convergence of the 5G and the ATSC 3.0 core networks. In Figure 6, the AEA message application produces the AEAT and the corresponding multimedia files, which belong to the NRT components. For an association with the CBS message, we propose a modified AEAT, which includes the additional CBS-related elements. Table 3 exhibits the additional elements. In Table 3, Header<CBS flag> indicates a Boolean value for whether the AEAT \begin{table}
\begin{tabular}{c c} \hline \hline
**Value** & **Meaning** \\ \hline
00 & No emergency to wake up devices is currently signaled \\
01 & Emergency to wake up devices—setting 1 \\
10 & Emergency to wake up devices—setting 2 \\
11 & Emergency to wake up devices—setting 3 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The meaning of the AEA wake-up field. Figure 6: The overall architecture of the 5G and ATSC 3.0 convergence network for emergency alert broadcast. is associated with a CBS message for emergency alert broadcast on the convergence network of Figure 6. In Table 3, Header<CBS ID> includes the identifier of the associated CBS message. In the convergence architecture of Figure 6, the scenario of the emergency alert broadcast includes the following steps:  
1. When an emergency occurs, the alerting authority simultaneously sends an emergency alert message to the CBE/CBCF of the 5G and the AEA application of the ATSC 3.0. 2. The CBCF converts the emergency alert message to the CBS message according to the CBS protocol [12]. Then, the CBCF sends the CBS message to the AMF in the 5G core network. Based on the received emergency alert message, the AEA application generates the modified AEAAT and the corresponding multimedia files (NRT components) according to the AEA protocol [24]. Then, the modified AEAAT and the NRT components are transmitted to the ATSC 3.0 core network using the UDP/IP protocol. 3. The AMF simultaneously sends the CBS message to the N3 IWF and the selected base stations of the RAN. 4. The N3 IWF extracts the CBS ID (as a trigger information) from the CBS message, and sends it to the ATSC 3.0 core network. 5. The selected base stations broadcast the CBS paging signals to the mobile phones in the corresponding cells. As soon as the paging signals are received, the mobile phones become ready for the CBS message and the AEA message (which includes the modified AEAAT and the NRT components) from the 5G base stations and the ATSC 3.0 broadcast stations, respectively. 6. In the ATSC 3.0 core network, the received trigger information causes the modified AEAAT and the NRT components to be transmitted to the ATSC 3.0 broadcast stations. 7. The 5G base stations and the ATSC 3.0 stations broadcast the CBS message and the AEA message, respectively, to the mobile phones in the corresponding cells. The steps 4, 5, and 6 reveal that the trigger information is used for a synchronization between the CBS paging signals and the AEA message. The trigger information causes the AEA message to be broadcast after the CBS paging signals are asserted. Figure 7 illustrates the presented specific framework for the interface between AMF and ATSC 3.0 core network using the N3 IWF. The ATSC 3.0 core network includes multiplexer, ATSC 3.0 gateway, and ATSC 3.0 modulator. In Figure 7, the novel procedure for simultaneous delivery of 5G CBS message and AEA message includes the following steps:  
1. The AMF sends the CBS message to the N3 IWF as well as the selected base stations. For the transmission of the CBS message, the AMF adopts the N2 protocol stack [34], which consists of 5G application protocol (5G-AP), SCTP, IP, layer 2 (L2), and layer 1 (L1).