Control apparatus, base station apparatus, radio terminal, and method for updating neighbour relation table

A control apparatus comprising:

• at least one memory configured to store a set of instructions and a neighbour relation table including a plurality of entries indicating neighbour-cell relations from a source cell to respective neighbour cells;
• and
• at least one processor configured to execute the set of instructions to automatically update the neighbour relation table,
• wherein the set of instructions further causes the at least one processor to add, to the neighbour relation table, a new entry indicating a neighbour-cell relation from the source cell to another cell different from both the source cell and a target cell of a handover from the source cell, in response to receiving by a base station controlling the source cell, from a base station controlling the another cell, from a base station controlling the target cell, or from a core network, a first message that is issued when a radio terminal that has experienced a failure involving disconnection of a radio link connection in the source cell or in the target cell attempts to re-establish the radio link connection to the another cell, and
• wherein the first message contains at least a Physical Cell Identifier (PCI) of the another cell.