after performing the band selection and the gain adjustment the relay system again converts the signal into a signal of the time domain by the ifft and then performs relay transmission fig7 is a diagram illustrating an example of the band selection gain adjustment by a first band selection gain control part of the first relay system the first band selection gain control part 161 of the first relay system selects as bands to relay both the band of the lte that performs the mimo transmission and the band of the 3g system that does not perform the mimo transmission furthermore the first band selection gain control part 161 of the first relay system may have a larger gain with respect to the band of the 3g system than the gain with respect to the band of the lte the second relay system does not select the band of the 3g system as a band to relay thus in the first relay system if the gain with respect to the band of the lte is the same as the gain with respect to the 3g system the gain with respect to the band of the 3g system is smaller than the gain with respect to the band of the lte in the whole radio relay device in the first relay system the gain with respect.