Mobile communication system

A mobile communication system comprising:

• a base station device;
• a user equipment device configured to perform radio communication with said base station device;
• a relay device relaying the radio communication between said base station device and said user equipment device;
• said relay device performs radio communication with said user equipment device using a carrier having a different frequency from a frequency of a carrier used by the relay device in radio communication with said base station device;
• and said base station device notifies said user equipment device of information related to a radio communication link in the mobile communication system, and said user equipment searches for the relay station based on the notified information when the user equipment makes a determination about whether to communicate with the base station device or the relay device, the notified information including (a) information indicating that the radio communication link selected by said user equipment device is a backhaul link, (b) information of a frequency band, carrier, or component carrier used in a direct link between the base station device and the user equipment, and (c) information of a frequency band, carrier, or component carrier used in an access link between the relay device and the user equipment.

A mobile communication system comprising:

• a plurality of base station devices;
• first and second user equipment devices configured to perform radio communication with said base station devices;
• each of said base station devices performs, in a downlink of radio communication to said second user equipment device, radio communication using a carrier having the same frequency as that of a carrier used in a downlink of radio communication from another base station device to said second user equipment device;
• each of said base station devices performs, in an uplink of radio communication from said second user equipment device, radio communication using a carrier having a different frequency from that of a carrier used in an uplink of radio communication from said second user equipment device to said another base station device;
• and
• a first base station device, in said base station devices, includes a direct communication link to a second base station device in said base station devices, and the first base station device selects the second base station device in said base station devices based on a location of the first base station device, a location of the selected second base station device, and measurement result of a surrounding radio environment of the first base station device, and notifies the second base station device, via the direct communication link, of frequency information of the first base station device.