Radio communication apparatus and system

A radio communication system comprising a first radio communication apparatus connected to a first device including a first digital signal processing unit generating a first clock signal and a second radio communication apparatus connected to a second device including a second digital signal processing unit generating a second clock signal,

• the first radio communication apparatus comprising:
• an acquisition unit configured to acquire first frequency information on the first clock signal;
• a first measurement unit configured to measure a first signal power in a first frequency band;
• a first comparison unit configured to compare the first signal power with a first threshold;
• a first determination unit configured to determine that data communication be started when a bandwidth of a second frequency band whose first signal power is lower than the first threshold is more than a bandwidth of a frequency band necessary for the data communication;
• and
• a first transmission unit configured to transmit a communication request signal to the second radio communication apparatus to start the data communication,
• the second radio communication apparatus comprising:
• a first receiving unit configured to receive the communication request signal;
• and
• a second transmission unit configured to transmit a response signal corresponding to the communication request signal,
• the first radio communication apparatus further comprising:
• a first selection unit configured to select, from the second frequency band, a third frequency band necessary for data communication;
• a second selection unit configured to select an optimum communication scheme from a plurality of communication schemes of the data communication according to the first frequency information;
• and
• a third transmission unit configured to transmit first information including the third frequency band and the optimum communication scheme to the second radio communication apparatus,
• the second radio communication apparatus further comprising:
• a second receiving unit configured to receive the first information;
• a second measurement configured to measure a second signal power in the third frequency band;
• a second comparison unit configured to compare the second signal power with a second threshold;
• a second determination unit configured to determine that the data communication is performed while the third frequency band and the optimum communication scheme are set to a determined frequency band and a determined communication scheme respectively, when the second signal power is lower than the second threshold in the third frequency band;
• and
• a fourth transmission unit configured to transmit second information including the determined frequency band and the determined communication scheme to the first radio communication apparatus,
• the first radio communication apparatus further comprising:
• a third receiving unit configured to receive the second information;
• and
• a first start unit configured to start communication with the second radio communication apparatus by the determined frequency band and the determined communication scheme, and
• the second radio communication apparatus further comprising a second start unit configured to start communication with the first radio communication apparatus by the determined frequency band and the determined communication scheme.