Embodiments of this application provide a communication method, apparatus, and system. The communication method may be applied to a user equipment-to-network relay U2N relay scenario. In the communication method, relay UE receives a first MAC PDU sent by a base station. The first MAC PDU includes identity information and control information of remote UE. The relay UE sends a second MAC PDU to the remote UE through a sidelink. The second MAC PDU includes second information, and the second information indicates that the second MAC PDU includes the control information. Therefore, the method can resolve a technical problem that control information (for example, information about bit rate recommendation) cannot be exchanged between the base station and the remote UE through a MAC layer because there is no MAC entity for end-to-end communication between the remote UE and the base station in the U2N relay communication scenario.