Cell reselection control method, base station, and radio terminal

A cell reselection control method used in a mobile communication system, the cell reselection control method comprising:

• transmitting from a base station configured to manage a cell belonging to a first frequency, to a radio terminal selecting the cell as a serving cell while being in an idle mode, an intra-frequency redistribution parameter for redistributing the radio terminal to another cell belonging to the first frequency, and an inter-frequency redistribution parameter for redistributing the radio terminal to at least one second frequency of multiple second frequencies different from the first frequency;
• receiving, by the radio terminal, the intra-frequency redistribution parameter and the inter-frequency redistribution parameter;
• and
• selecting, by the radio terminal, a redistribution target by using an identifier of the radio terminal and at least one of the intra-frequency redistribution parameter and the inter-frequency redistribution parameter, the redistribution target being a frequency or a cell provided with highest priority for cell reselection, wherein
• the selecting the redistribution target includes selecting the redistribution target by using the inter-frequency redistribution parameter with priority over the intra-frequency redistribution parameter,
• the intra-frequency redistribution parameter includes a parameter indicating a probability for each cell in the first frequency being selected as the redistribution target, and
• the inter-frequency redistribution parameter includes a parameter indicating a probability for each cell in the second frequency being selected as the redistribution target or a parameter indicating a probability for each second frequency being selected as the redistribution target.