Radio communication apparatus and radio communication method in communication system

A radio communication apparatus for use in an area where a plurality of communication systems coexist, comprising:

• a receiving unit configured to receive a cognitive signal including system information of each of the systems;
• a metric unit configured to prepare metric information indicating relationship degree between the radio communication apparatus and a communication system to which the radio communication apparatus does not belong;
• a condition determination unit configured to determine whether a restriction should be imposed on transmission by the radio communication apparatus based on the system information and the metric information;
• and
• a transmission unit configured to transmit a signal using predetermined radio resources when transmission by the radio communication apparatus is not prohibited,
• wherein each communication apparatus belonging to each of the plurality of communication systems transmits an existence notification signal indicating presence or absence of the own communication apparatus, and
• wherein the metric information is represented as receive quality of the existence notification signal received from a radio communication system to which the radio communication apparatus does not belong.

A radio communication method in a radio communication apparatus for use in an area where a plurality of communication systems coexist, comprising the steps of:

• receiving a cognitive signal including system information of each of the systems;
• preparing metric information indicating relationship degree between the radio communication apparatus and a communication system to which the radio communication apparatus does not belong;
• determining whether a restriction should be imposed on transmission by the radio communication apparatus based on the system information and the metric information;
• and
• transmitting a signal using predetermined radio resources when transmission by the radio communication apparatus is not prohibited,
• wherein the metric information is represented as a distance between a boundary and the radio communication apparatus, the boundary being between an area of a radio communication system to which the radio communication apparatus belongs and an area of a radio communication system to which the radio communication apparatus does not belong.

A radio communication method in a radio communication apparatus for use in an area where a plurality of communication systems coexist, comprising the steps of:

• receiving a cognitive signal including system information of each of the systems;
• preparing metric information indicating relationship degree between the radio communication apparatus and a communication system to which the radio communication apparatus does not belong;
• determining whether a restriction should be imposed on transmission by the radio communication apparatus based on the system information and the metric information;
• and
• transmitting a signal using predetermined radio resources when transmission by the radio communication apparatus is not prohibited,
• wherein each communication apparatus belonging to each of the plurality of communication systems transmits an existence notification signal indicating presence or absence of the own communication apparatus, and
• wherein the metric information is represented as receive quality of the existence notification signal received from a radio communication system to which the radio communication apparatus does not belong.