PURPOSE: A cognitive radio communication system using a MIMO(Multi Input Multi Output) communication system is provided to remove necessity of separate sensing time and quiet time and to increase capacity of the system. CONSTITUTION: A CR(Cognitive Radio) BS(Base Station)(910) includes a plurality of antennas, a group setting unit(911) and a signal generator(913). The group setting unit establishes one or more sensing terminal groups. One or more sensing terminal group includes one or more sensing terminals(920) among a plurality of terminals(930). In order that one or more sensing terminal secures the sensing time through channels formed between a plurality of antennas and plurality of terminals, the signal generator generates a transmission signal.
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