Mobile communication system

A mobile communication system comprising plural user equipments, a first base station and a second base station, the user equipments performing data transmission/reception using an orthogonal frequency division multiplexing (OFDM) system as a downlink access system and a single career frequency division multiple access (SC-FDMA) system as an uplink access system, the first base station being provided to a first cell made open only to specific ones of said user equipments and being configured to transmit, to said user equipments, control signals including a downlink synchronization signal using a radio frame including a predetermined number of subframes, the second base station being provided to a second cell made available for non-specific ones of said user equipments and being configured to transmit, to said user equipments, control signals including a downlink synchronization signal using a radio frame including the same number of subframes as those of said radio frame used in transmission by said first base station, wherein:

• said first base station assigns said control signals to a first subframe and a second subframe among a plurality of subframes constituting said radio frame;
• said second base station assigns said control signals to a third subframe and a fourth subframe among the plurality of subframes constituting said radio frame, the third subframe and the fourth subframe being disposed in frame slots that are shifted in time from frame slots in which said first subframe and said second subframe are disposed, frame slots of the first base station aligning with frame slots of the second base station;
• and
• said first base station and said second base station transmit said control signals in synchronization.