I don't really know. You'd have to look into the background and the creators' statements to get a clear idea. But often, these things are not straightforward and can be open to interpretation.
Signal is not based on a true story. It's a creation of the writers' imagination, although it might draw inspiration from various real-life elements to add depth and relatability.
It's not based on a true story. The Signal is a work of fiction that takes viewers into an invented world with fictional characters and events to tell an engaging tale.