Calibration method, communication system, frequency control method, and communication device

A calibration method used with first and second communication devices that carry out communications in a TDD system to perform calibration on antennas included in the devices, the calibration method comprising:

• a step of first pilot signal transmitting in which the first communication device transmits a pilot signal;
• a step of first channel estimating in which the second communication device receives the pilot signal transmitted from the first communication device and calculates a first channel estimation value;
• a step of second pilot signal transmitting in which the second communication device transmits a pilot signal;
• a step of second channel estimating in which the first communication device receives the pilot signal transmitted from the second communication device and calculates a second channel estimation value;
• and
• a step of correction coefficient calculating in which the first communication device calculates a correction coefficient to adjust a signal transmitted and received to and from the second communication device, based on the second channel estimation value and the first channel estimation value obtained from the second communication device.

A frequency control method used with a first communication device and a second communication device that carry out communications to compensate a frequency difference of signals transmitted from both devices, the frequency control method comprising:

• a step of first pilot signal transmitting in which the first communication device transmits a pilot signal;
• a step of first channel estimating in which the second communication device receives the pilot signal transmitted from the first communication device and calculates a first channel estimation value;
• a step of second pilot signal transmitting in which the second communication device transmits a pilot signal whose phase is adjusted based on the first channel estimation value;
• a step of second channel estimating in which the first communication device receives the pilot signal transmitted from the second communication device and calculates a second channel estimation value;
• and
• a step of adjusting in which the first communication device adjusts a frequency of a transmitted signal based on the second channel estimation value.

A frequency control method used with a first communication device and a second communication device that carry out communications to compensate a frequency difference of signals transmitted from both devices, the frequency control method comprising:

• a step of first pilot signal transmitting in which the first communication device transmits a pilot signal;
• a step of first channel estimating in which the second communication device receives the pilot signal transmitted from the first communication device and calculates a first channel estimation value;
• a step of second pilot signal transmitting in which the second communication device transmits a pilot signal whose phase is adjusted based on the first channel estimation value;
• a step of second channel estimating in which the first communication device receives the pilot signal transmitted from the second communication device, calculates a second channel estimation value, and notifies the second channel estimation value to the second communication device;
• and
• a step of adjusting in which the second communication device adjusts a frequency of a transmitted signal based on the first channel estimation value and the second channel estimation value.