A Channel Quality Indicator (CQI) expression and feedback method prevents an excessive increase in the CQI feedback overhead while supporting both Single-User MIMO and Multi-User MIMO operations. When a default MIMO operation is set to Single-User MIMO or Multi-User MIMO, an access network can receive MIMO CQI feedback optimized for the corresponding MIMO operation. However, when a scheduler has selected an alternative MIMO operation other than the default MIMO operation, the access network calculates a CQI necessary for the alternative MIMO operation based on the default MIMO CQI feedback for the default MIMO operation and the DELTA CQI feedback for the alternative MIMO operation. In this manner, the invention enables the best operation in the default MIMO operation by providing a correct CQI, and enables the second best operation in the alternative MIMO operation. With use of the invention, the access network can dynamically select the Single-User MIMO and Multi-User MIMO operations, contributing to an increase in the resource management efficiency.