Mobile communication system
There is a problem that when a closed subscriber group (CSG) cell available to subscribers is installed in a macro cell area, communication cannot be performed due to the interference between a macro cell and the CSG cell in an area thereof. The CSG cell that is provided in the CSG cell area and transmits a downlink synchronization signal using a radio frame assigns control signals to a first subframe and a second subframe among a plurality of subframes constituting the radio frame, and the macro cell that is provided in the macro cell area and transmits a downlink synchronization signal using the radio frame assigns control signals to a third subframe and a fourth subframe, which are shifted from the first subframe and the second subframe by a predetermined number of subframes, respectively, among the plurality of subframes constituting the radio wave, the CSG cell and the macro cell being configured to perform transmission in synchronization with each other.
1. A mobile communication system comprising user equipments, a first base station, and a second base station, the user equipments performing data transmission and reception using an orthogonal frequency division multiplexing (OFDM) system as a downlink access system and a single carrier frequency division multiple access (SC-FDMA) system as an uplink access system, the first base station provided to a first cell made open only to specific ones of said user equipments or subscribers and transmitting, 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 provided to a second cell made available for non-specific ones of said user equipments or users and transmitting, 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 and said second base station each support a plurality of component carriers;
said radio frame used in said first base station and said radio frame used in said second base station have the same frame configuration for each of said component carriers, and
for each of said component carriers, said first base station and said second base station transmit said control signals by shifting said transmissions by a predetermined time interval such that transmission timings of at least signals of said control signals do not overlap each other, said signals being allocated over an entire frequency band of said subframes including all corresponding component carriers.
2. The mobile communication system according to claim 1 , wherein
said radio frame used in said first base station and said radio frame used in said second base station have the same configuration for each of aggregation carriers including said component carriers aggregated, and
for each of said aggregation carriers, said first base station and said second base station transmit said control signals by shifting the transmissions by a predetermined time interval such that transmission timings of at least signals of said control signals do not overlap each other, said signals being allocated over an entire frequency band of said subframes including all corresponding component carriers.
3. The mobile communication system according to claim 1 , wherein one of said first cell and said second cell
allocates said control signals using a frequency band of a physical resource to which said control signals of the other cell are not allocated, or
uses, as a frequency band of a physical resource to which said control signals are not allocated, a frequency band of a physical resource to which said control signals of the other cell are allocated.
4. The mobile communication system according to claim 1 , wherein said first base station and said second base station transmit said control signals in both of a time domain in which said predetermined time interval is provided and a time domain in which said predetermined time interval is not provided.