How will the US detect China's Pacific attack? [ANALYSIS]

There are respective ways to build an early informing strategy against low-flying rockets and aircraft. The simplest is the usage of radiolocation and electronic surveillance aircraft (AWACS class), thus moving the radiolocation horizon (from Earth's curve). However, this method of action is besides very costly, as it forces the full fleet of aircraft to patrol continuously. And that for a long time and a large watershed is not just possible.