A data transmission method, apparatus, and system are disclosed. The method includes: determining, by a first HCD, a target communication resource in a first time period; determining, by the first HCD, a third target communication sub-resource used to transmit data between a first LCD and the first HCD, and sending third indication information to the first LCD by using a fourth target communication sub-resource, where the third indication information is used to indicate the third target communication sub-resource; and receiving, by the first HCD, first target data that is sent by the first LCD by using the third target communication sub-resource, and transmitting the first target data to the access network device; and/or acquiring, by the first HCD, second target data from the access network device, and sending the second target data to the first LCD by using the third target communication sub-resource.