A first machine learning model is deployed in a first communication apparatus, and a second machine learning model is deployed in a second communication apparatus. First information is obtained that carries indication information of both a first transmission resource and a second transmission resource, wherein the first transmission resource is for the first communication apparatus to transmit a first output of the first machine learning model to the second communication apparatus, and wherein the second transmission resource is for the first communication apparatus to receive first feedback data that is from the second communication apparatus. The first feedback data includes a first gradient, wherein the first gradient is for updating the first machine learning model. The first communication apparatus transmits the first output to the second communication apparatus on the first transmission resource.