Derivation method, communication system and accommodation station apparatus

A communication system, comprising:

• an access point including an accommodation station device and an extension station device connected to each other through an optical fiber transmitting an optical signal;
• and
• a wireless terminal that communicates with the extension station device by using a radio-wave signal,
• wherein the accommodation station device includes
• a transmitter that, when a time in the accommodation station device and a time in the wireless terminal are synchronized with each other, transmits a first radio-wave signal according to an optical signal with a first wavelength, and a second radio-wave signal according to an optical signal with a second wavelength,
• a communication start time information acquisitor that acquires information on a first communication start time that is a time at which communication using the optical signal with the first wavelength is started, and information on a second communication start time that is a time at which communication using the optical signal with the second wavelength is started,
• a reception time information acquisitor that acquires information on a first reception time that is a reception time related to the first radio-wave signal, and information on a second reception time that is a reception time related to the second radio-wave signal, and
• an optical fiber length derivator that derives a length of the optical fiber, based on the first communication start time, the first reception time, the second communication start time, the second reception time, a group velocity or a group delay time of the optical signal with the first wavelength, and a group velocity or a group delay time of the optical signal with the second wavelength,
• wherein each of the transmitter, the communication start time information acquisitor, the reception time information acquisitor, and the optical fiber length derivator is implemented by:
• i) computer executable instructions executed by at least one processor,
• ii) at least one circuitry or
• iii) a combination of computer executable instructions executed by at least one processor and at least one circuitry.

An accommodation station device in a communication system including an access point and a wireless terminal, the access point including the accommodation station device and an extension station device connected to each other through an optical fiber transmitting an optical signal, and the wireless terminal communicating with the extension station device by using a radio-wave signal, the accommodation station device comprising:

• a transmitter that, when a time in the accommodation station device and a time in the wireless terminal are synchronized with each other, transmits a first radio-wave signal according to an optical signal with a first wavelength, and a second radio-wave signal according to an optical signal with a second wavelength;
• a communication start time information acquisitor that acquires information on a first communication start time that is a time at which communication using the optical signal with the first wavelength is started, and information on a second communication start time that is a time at which communication using the optical signal with the second wavelength is started;
• a reception time information acquisitor that acquires information on a first reception time that is a reception time related to the first radio-wave signal, and information on a second reception time that is a reception time related to the second radio-wave signal;
• and
• an optical fiber length derivator that derives a length of the optical fiber, based on the first communication start time, the first reception time, the second communication start time, the second reception time, a group velocity or a group delay time of the optical signal with the first wavelength, and a group velocity or a group delay time of the optical signal with the second wavelength,
• wherein each of the transmitter, the communication start time information acquisitor, the reception time information acquisitor, and the optical fiber length derivator is implemented by:
• i) computer executable instructions executed by at least one processor,
• ii) at least one circuitry or
• iii) a combination of computer executable instructions executed by at least one processor and at least one circuitry.