This application discloses a communications method, apparatus, and system, and a computer storage medium. A target device determines a first time-frequency sub-resource, and the first time-frequency sub-resource belongs to a first time-frequency resource. The target device sends a first request on the first time-frequency sub-resource, and the first request is used to request access or request scheduling. The first time-frequency resource is a predefined or preconfigured resource used to carry the request of the target device.