A wireless power transmitter, a wireless power receiver and methods associated therewith are discussed. The wireless power transmitter includes a power converter configured to transfer wireless power to an external receiver; and at least one processor configured to communicate with the receiver to control transmission of the wireless power and to perform transmission or reception of data, wherein the processor is configured to receive, from the receiver, a received power packet (RPP) which informs a value of received power; transmit, to the wireless power receiver, a bit pattern for requesting communication in response to the RPP; and receive a polling packet from the receiver in response to the bit pattern.