# An Emergency Alert Broadcast Based on the Convergence of 5G and ATSC 3.0
## 2 Conventional Works
### AEA Protocol  
ATSC 3.0 systems support the UHD TV services for better audio/video quality, and adopt the IP-based protocol for various broadcast and broadband services. Figure 4 illustrates the stack of the IP-based protocol for ATSC 3.0 [23]. Figure 3: The radio protocol of the base station for 5G CBS. Figure 2: The network protocols for the CBS message transfer from CBCF to base station (RAN). In the ATSC 3.0, the real-time media components use the format of media processing unit (MPU) or the format of dynamic adaptive streaming over HTTP (DASH). As shown in Figure 4, the MPU components are transmitted on broadcast networks using MPEG media transport protocol (MMTP)/UDP/IP. The DASH components can be transmitted on broadcast networks or broadband networks using real-time object delivery over unidirectional transport (ROUTE)/UDP/IP or HTTP/TCP/IP, respectively. In the ATSC 3.0, the non-real time (NRT) components can be transmitted on broadcast networks or broadband networks using ROUTE/UDP/IP or HTTP/TCP/IP, respectively. The protocol stack of Figure 4 reveals that the real-time MPU components are transmitted on only broadcast networks, whereas the real-time DASH components and the NRT components can be transmitted on both broadcast and broadband networks. In Figure 4, the low level signaling (LLS) includes advanced emergency information table (AEAT), service list table (SLT), rate region table (RRT), system time, common alerting protocol (CAP), version information table (VIT), and content protection table (CPT). The LLS is transmitted on broadcast networks using UDP/IP. Since the AEAT consists of one or more AEA messages in the LLS, LLS/UDP/IP is used as the protocol for AEA message delivery in Figure 4.  
Table 1 includes the description of the AEAT elements for one AEA message [24]. In Table 1, the emergency text and the multimedia information are associated with the elements of AEAText and Media, respectively. Furthermore, the AEAT includes the associated information for a live broadcast stream in the element of LiveMedia. Therefore, the ATSC 3.0 can provide a rich information (text, multimedia, and live broadcast stream) for emergency alert. This indicates that the ATSC 3.0 can provide much more abundant information for emergency alert than the 5G. In addition to the rich information, the ATSC 3.0 can deliver an emergency area information using the AEAT element of Header<Location>. Using the area information, the receiver can discard the AEA message if the receiver user does not belong to the emergency area. However, the receiver is required to employ a location estimator such as GPS. A delicate location estimator usually causes high cost and high power consumption, which is not suitable for mobile terminals such as smart phones. A low-cost location estimator may give a poor estimation performance, which has a high potential to make a false discard of the AEA message. Note that the 5G CBS is very suitable for location-based emergency alert services, since the 5G AMF can select the appropriate base stations, which encompass emergency areas. Figure 4: The stack of the IP-based protocol for ATSC 3.0. In Table 1, the element of AEA<wakeup> is associated with the wake-up service of ATSC 3.0. The wake-up service is used in order to activate an idle-state receiver for emergency alert service. For the wake-up service, the ATSC 3.0 transmits the wake-up field. The wake-up field is embedded in the bootstrap of the physical layer frame. Figure 5 illustrates the structure of the physical layer frame in ATSC 3.0 [22]. The bootstrap is used for wake-up information, synchronization, channel estimation, and preamble information. The wake-up field consists of two bits, each of which is located in bootstrap symbol 1 and bootstrap symbol 2, respectively. Table 2 exhibits the meaning of the AEA wake-up field [22]. Table 2 reveals that an idle-state receiver can be activated if the received wake-up filed is decoded into '01', '10', or '11'. After the activation, the receiver finds an AEA message corresponding to the wake-up field.