two power control loops for antenna switching transmit diversity are realized by a user terminal including two antennas , one power amplifier for amplifying the signals to be transmitted from each of the antennas , and a switch switching the transmission power of the power amplifier from one antenna to the other antenna . accordingly , the user terminal is enabled to alternately transmit data packets , with its two antennas . a closed loop power control mechanism in the user terminal is adapted to update , on receipt of a transmission power control command from a base station , the transmission power relative to the level of two slots previously .