Radio base station and mobile communication method

A mobile communication method, comprising:

• a step A of determining a time direction resource, a frequency direction resource, and a code direction resource which are to be assigned as a reception quality notification resource that should be used for notifying each mobile station of a reception quality in a downlink;
• and
• a step B of notifying each mobile station of the time direction resource, the frequency direction resource, and the code direction resource which are assigned as the reception quality notification resource,
• wherein in the step A, the time direction resource and the frequency direction resource to be assigned as the reception quality notification resource are determined, and then the code direction resource to be assigned as the reception quality notification resource is determined, and
• wherein in the step A, each time direction resource are assigned as the reception quality notification resource, in order from a frequency direction resource with a lower usage rate of the code direction resource.