With the development of mobile communications technologies, a future mobile communications system provides higher-rate data transmission and wider service coverage. Carrier aggregation (CA) is a frequently used transmission manner and is increasingly widely applied in the field of mobile communications. A concept of CA is that an access network device configures and provides multiple carriers for UE that supports carrier aggregation, to perform uplink and downlink communication, so that higher-rate data transmission is supported. The carriers include a primary carrier and a secondary carrier.
In an existing Long Term Evolution (LTE) CA system, periodic CSI may be independently configured for each aggregation carrier, and the periodic CSI is carried on a physical uplink control channel (PUCCH) and fed back to an access network device. However, because a capacity of the PUCCH is restricted, in each subframe, only one piece of CSI on one carrier can be reported to the access network device. If multiple pieces of periodic CSI are simultaneously configured in a same subframe, UE discards periodic CSI according to a preconfigured priority, and eventually feeds back a piece of CSI with a highest priority to the access network device. In this way, CSI of some carriers is kept from being fed back to the access network device, or a feedback period is prolonged, eventually causing lowered performance of downlink data scheduling. When CA of more carriers is introduced to the CA system, because more acknowledgment (ACK) or negative acknowledgment (NACK) information needs to be fed back, the capacity of the PUCCH is further restricted. Consequently, the foregoing situation becomes severer.
Therefore, how to simultaneously transmit multiple pieces of CSI is currently a problem to be resolved urgently.