Urban rail transit not only relieves the pressure of urban traffic, but also facilitates the travel of the urban population. In many urban rail transit systems, the signal system is called the brain of urban rail transit, which is an important guarantee to ensure the safety of train operation and realize driving command. The signal system requires real-time and accurate information transmission between vehicle-ground systems, so the construction of a safe and reliable large bandwidth and low-latency vehicle-ground communication network has become the consensus of the subway industry. With the maturity of LTE private network, LTE-M private network has become an indispensable subsystem in the urban rail transit signal system.