Base station, terminal, and wireless communication system

A terminal that is used in a wireless communication system in which a base station and the terminal perform a wireless communication by using a band after detecting a vacancy in the band at a predetermined frequency, the terminal comprising:

• a receiving unit that receives data that is transmitted from the base station in the band;
• a determining unit that determines whether data received by the receiving unit is collision data, which is data transmitted from the base station at same time as a signal transmitted from a different communication device in the band, or non-collision data, which is not the collision data;
• and
• a transmitting unit that transmits, to the base station, information that indicates whether each piece of data received by the receiving unit is any one of the collision data and the non-collision data.

A wireless communication system comprising a base station and a terminal, the base station and the terminal performing a wireless communication by using a band after detecting a vacancy in the band at a predetermined frequency, wherein

• the base station includes
• a first transmitting unit that transmits data to the terminal in the band;
• a first receiving unit that receives, from the terminal, information that indicates whether each piece of data transmitted by the first transmitting unit is collision data, which is data transmitted from the first transmitting unit at same time as a signal transmitted from a different communication device in the band, or non-collision data, which is not the collision data;
• a calculating unit that calculates an error rate of data, received by the terminal, based on information about the non-collision data that is received by the first receiving unit;
• and
• a correcting unit that corrects an index, which is used to select a modulation method and a coding rate when the first transmitting unit transmits data, based on the error rate, and
• the terminal includes
• a second receiving unit that receives data that is transmitted from the base station in the band;
• a determining unit that determines whether data received by the second receiving unit is any one of the collision data and the non-collision data;
• and
• a second transmitting unit that transmits, to the base station, information that indicates whether each piece of data received by the second receiving unit is any one of the collision data and the non-collision data.