A user equipment, UE, for performing communication in a wireless communication system supporting a circuit switched fallback, CSFB, service, comprising: a transceiver configured to transmit and receive a signal over a communication system switched from among a first communication system and a second communication system; a measuring receiver configured to receive a signal for measuring a channel status from the second communication system upon initiation of a CSFB process as a voice call occurs and measure the channel status from the second communication system; and a controller configured to control the transceiver to transmit , to the first communication system , a radio resource control, RRC, connection request message including information indicating that measurement on the channel status of the second communication system is being performed, to receive , from the first communication system , an RRC connection setup message including information for instructing to report a measurement result on the channel status of the second communication system , to transmit , to the first communication system , an RRC connection setup complete message comprising the measurement result on the channel status of the second communication system , to receive , from a base station of the first communication system , a command to switch to the second communication system , and to connect the voice call over the second communication system , wherein the command to switch to the second communication system is generated based on the measurement result on the channel status of the second communication system . a transceiver configured to transmit and receive a signal over a communication system switched from among a first communication system and a second communication system; a measuring receiver configured to receive a signal for measuring a channel status from the second communication system upon initiation of a CSFB process as a voice call occurs and measure the channel status from the second communication system; and a controller configured to control the transceiver to transmit , to the first communication system , a radio resource control, RRC, connection request message including information indicating that measurement on the channel status of the second communication system is being performed, to receive , from the first communication system , an RRC connection setup message including information for instructing to report a measurement result on the channel status of the second communication system , to transmit , to the first communication system , an RRC connection setup complete message comprising the measurement result on the channel status of the second communication system , to receive , from a base station of the first communication system , a command to switch to the second communication system , and to connect the voice call over the second communication system , to transmit , to the first communication system , a radio resource control, RRC, connection request message including information indicating that measurement on the channel status of the second communication system is being performed, to receive , from the first communication system , an RRC connection setup message including information for instructing to report a measurement result on the channel status of the second communication system , to transmit , to the first communication system , an RRC connection setup complete message comprising the measurement result on the channel status of the second communication system , to receive , from a base station of the first communication system , a command to switch to the second communication system , and to connect the voice call over the second communication system , wherein the command to switch to the second communication system is generated based on the measurement result on the channel status of the second communication system . <EOS>