A radio communication system comprising a first terminal, a second terminal, a contact destination terminal, and a relay station, wherein
- the first terminal comprises:
- a first detection configuration comprising hardware or a combination of hardware and software configured to detect a specific sound;
- and
- a first transmission configuration comprising transmission hardware or a combination of hardware and software configured to transmit, in response to detection of a first sound,
- provided in the first terminal;
- (i) first sound information which is sound type information of the first sound,
- (ii) identification information of the contact destination terminal associated with the first terminal,
- (iii) position information of the first terminal, and
- (iv) detection time information of the first sound to the relay station as a first transmission request message,
- the second terminal comprises:
- a second detection configuration comprising hardware or a combination of hardware and software configured to detect a specific sound;
- and
- a second transmission configuration comprising transmission hardware or a combination of hardware and software configured to transmit, in response to detection of a second sound,
- provided in the second terminal;
- (i) second sound information which is sound type information of the second sound,
- (ii) identification information of the contact destination terminal associated with the second terminal,
- (iii) position information of the second terminal, and
- (iv) detection time information of the second sound to the relay station as a second transmission request message,
- the relay station comprises:
- a reception configuration configured to receive the first and second transmission request messages;
- and
- a determination configuration configured to determine whether or not the first and second sounds are caused by a same event based on at least one of conditions including:
- (a) sound type information of the first sound matches sound type information of the second sound;
- (b) a difference between the position information of the first terminal and position information of the second terminal is equal to or smaller than a predetermined position threshold;
- and
- (e) a detection time difference between the first and second sounds is equal to or smaller than a predetermined time threshold, and
- a creation configuration configured to, in response to the determination that the first and second sounds are caused by a same event, create a communication group obtained by combining:
- (i) respective detection terminals of the first and second terminals;
- and
- (ii) respective contact destination terminals identified by identification information contained in respective transmission request messages of the first transmission request message and the second transmission request message.