A communication method in a system where wireless communication is carried out between a base station and a communication terminal apparatus, the communication terminal apparatus comprising a plurality of antennas (201-1, 201-2) and the base station comprising a plurality of transmission antennas (105-1, 105-2, 105-3), the method comprising the steps of: at the communication terminal apparatus: receiving signals transmitted from the base station using the antennas (201-1, 201-2) at the communication terminal apparatus; estimating the reception electric field strength of each reception baseband signal downconverted from the received signals and obtaining the reception electric field strength of the entire system; calculating an effective reception electric field strength by multiplying each reception electric field strength by the minimum power of the eigenvalue and obtaining the mean effective reception electric field strength; andthe method characterized by comprising the steps of transmitting signals to the base station indicative of the reception electric field strength of the entire system, and the mean effective reception electric field strength; at the base station: receiving signals transmitted from the communication terminal apparatus; calculating a difference between the reception electric field strength of the entire system and the mean effective reception electric field strength; and determining that the transmission antennas (105-1, 105-2, 105-3) are not switchedwhen the difference is less than a predetermined threshold at the communication terminal apparatus: receiving signals transmitted from the base station using the antennas (201-1, 201-2) at the communication terminal apparatus; estimating the reception electric field strength of each reception baseband signal downconverted from the received signals and obtaining the reception electric field strength of the entire system; calculating an effective reception electric field strength by multiplying each reception electric field strength by the minimum power of the eigenvalue and obtaining the mean effective reception electric field strength; andthe method characterized by comprising the steps of transmitting signals to the base station indicative of the reception electric field strength of the entire system, and the mean effective reception electric field strength; at the base station: receiving signals transmitted from the communication terminal apparatus; calculating a difference between the reception electric field strength of the entire system and the mean effective reception electric field strength; and determining that the transmission antennas (105-1, 105-2, 105-3) are not switchedwhen the difference is less than a predetermined threshold receiving signals transmitted from the base station using the antennas (201-1, 201-2) at the communication terminal apparatus; estimating the reception electric field strength of each reception baseband signal downconverted from the received signals and obtaining the reception electric field strength of the entire system; calculating an effective reception electric field strength by multiplying each reception electric field strength by the minimum power of the eigenvalue and obtaining the mean effective reception electric field strength; andthe method characterized by comprising the steps of transmitting signals to the base station indicative of the reception electric field strength of the entire system, and the mean effective reception electric field strength; at the base station: receiving signals transmitted from the communication terminal apparatus; calculating a difference between the reception electric field strength of the entire system and the mean effective reception electric field strength; and determining that the transmission antennas (105-1, 105-2, 105-3) are not switchedwhen the difference is less than a predetermined threshold receiving signals transmitted from the communication terminal apparatus; calculating a difference between the reception electric field strength of the entire system and the mean effective reception electric field strength; and determining that the transmission antennas (105-1, 105-2, 105-3) are not switchedwhen the difference is less than a predetermined threshold