'No Communication Blackout' - Disaster Roaming Methods of the Three Major Telecom Operators Revealed

[Asia Economy Reporter Seolgina Jo] In the future, even if a disaster such as a fire occurs and there is a problem with the network of the mobile carrier you are subscribed to, text messages and calls will not be cut off. This is thanks to the disaster roaming system of the three major carriers.

◆ "How does it work?" Demonstration = On the afternoon of the 25th, the Ministry of Science and ICT and the three major carriers held a 'Disaster Roaming Demonstration Event' where they showcased this system by assuming a disaster situation at the base stations of KT and LG Uplus among the three carriers.

First, when the phones of KT and LG Uplus subscribers were artificially switched to out-of-service areas, the devices showed no antenna signal and displayed messages saying "Restricted Area Service" and "Emergency Calls Only," respectively.

Immediately after, the SK Telecom Bundang office base station began broadcasting the Public Land Mobile Network (PLMN) identifier of the disaster communication carrier. Within less than a minute, the phones of KT and LG Uplus subscribers, which had been out of service, displayed the name "SK Telecom" at the bottom of the device. Without any action from the user, the device automatically connected to SK Telecom's network. The LTE icon appeared on the top status bar, and the signal strength bars rose to the maximum.

At the demonstration event, Jang Seok-young, the 2nd Vice Minister of the Ministry of Science and ICT, made a direct call from a KT subscriber's test device to the KT control center. When Vice Minister Jang asked, "Can you hear me well?" the KT control center replied, "We hear you clearly." Vice Minister Jang smiled and said, "It's amazing. It doesn't seem like we're connected to the KT network right now." He added, "The three carriers have competed a lot until now, but seeing them conduct a roaming test together today seems to have created an opportunity for collaboration." He also urged, "Disasters should not happen, but please pay special attention to ensuring that citizens' communication is not disrupted in case of a disaster."

On that day, KT and LG Uplus subscribers were able to make phone calls, place pizza delivery orders with card payments, and chat on KakaoTalk smoothly while connected to another carrier's base station.

◆ 3G requires USIM activation and call forwarding = The three major carriers have built dedicated disaster roaming networks capable of accommodating about one million lines each. When a crisis alert of "Warning" or higher is issued due to a communication disaster, the affected carrier requests roaming permission from the Ministry of Science and ICT.

4G (LTE) and 5G users can use another carrier's 4G network like international roaming without any special action. However, 3G requires separate procedures. The USIM must be activated at a store of a carrier not affected by the disaster, and call forwarding service must be applied to receive calls forwarded to the existing number. Afterwards, the user can apply for compensation for the USIM cost and usage fees during the disaster period from the affected carrier. According to the Ministry of Science and ICT, as of the end of April, the number of 3G subscribers in Korea was 6,897,167.

Even when connected to another carrier's network via disaster roaming, calls, texts, and data usage are possible. Data speed is controlled at about 100 kilobits per second (Kbps) through quality of service (QoS) management, but this is sufficient for conversations on KakaoTalk and similar apps. A Ministry of Science and ICT official explained, "During disasters, call volume and traffic can surge, so speed control is applied. Providing unlimited service could actually cause more load."