A data transmission method receiving a group identifier, a configuration information window length, and an offset between a start point of the configuration information window length and a paging occasion that are sent by a mobility management entity; establishing a public data radio bearer to a terminal corresponding to the group identifier; scrambling configuration information of the public data radio bearer by using a radio network temporary identifier; sending a paging message carrying the group identifier and the radio network temporary identifier to the terminal; sending the scrambled configuration information of the public data radio bearer to the terminal in the configuration information window length; and receiving uplink data transmitted by the terminal on the public data radio bearer.