Data downlink method compatible with CLASSA and CLASSB

The invention discloses a data downlink method compatible with CLASS A and CLASS B. The method comprises: when a server receives downlink data targeted at a terminal, determining whether the terminal is in a class A working mode or a class B working mode according to a terminal state stored by the server; and if the terminal is in the class A working mode, storing the downlink data in a queue, and delivering the downlink data to a base station to send when the terminal sends next uplink data; or if the terminal is in the class B working mode, calculating a next to-be-opened downlink window of the terminal according to a parameter of the class B working mode, and immediately delivering the data and the downlink window to a base station to send. The technical scheme of the invention can ensure randomness and security thereof. According to the method of the invention, downlink of the two modes, the class A mode and the class B modes, is realized by exposing only one interface to the outside, thereby simplifying