A method for transmitting wireless power, the method performed by a wireless power transmitter and comprising: transmitting, to a wireless power receiver, a digital ping; receiving, from the wireless power receiver, a response for the digital ping; further comprising: receiving, from the wireless power receiver, a packet related to a control error, CE, or a packet related to a received power, RP; transmitting, to the wireless power receiver, a bit pattern requesting a communication based on receiving the packet related to the CE or the packet related to the RP; receiving, from the wireless power receiver, a response packet for granting the communication; transmitting, to the wireless power receiver, a capability data packet providing information for a capability of the wireless power transmitter after receiving the response packet; receiving, from the wireless power receiver, a renegotiation data packet requesting the wireless power transmitter to proceed to a renegotiation phase; transmitting, to the wireless power receiver, an acknowledgement, ACK, response related to the wireless power transmitter having switched to the renegotiation phase based on receiving the renegotiation data packet; receiving, from the wireless power receiver in the renegotiation phase, a first specific request data packet including information for a requested guaranteed power level; transmitting, to the wireless power receiver in the renegotiation phase, an ACK response to accept the requested guaranteed power level based on receiving the first specific request data packet; receiving, from the wireless power receiver in the renegotiation phase, a second specific request data packet to end the renegotiation phase; and transmitting, to the wireless power receiver, an ACK response related to the wireless power transmitter having concluded the renegotiation phase successfully and having switched to a power transfer phase. transmitting, to a wireless power receiver, a digital ping; receiving, from the wireless power receiver, a response for the digital ping; further comprising: receiving, from the wireless power receiver, a packet related to a control error, CE, or a packet related to a received power, RP; transmitting, to the wireless power receiver, a bit pattern requesting a communication based on receiving the packet related to the CE or the packet related to the RP; receiving, from the wireless power receiver, a response packet for granting the communication; transmitting, to the wireless power receiver, a capability data packet providing information for a capability of the wireless power transmitter after receiving the response packet; receiving, from the wireless power receiver, a renegotiation data packet requesting the wireless power transmitter to proceed to a renegotiation phase; transmitting, to the wireless power receiver, an acknowledgement, ACK, response related to the wireless power transmitter having switched to the renegotiation phase based on receiving the renegotiation data packet; receiving, from the wireless power receiver in the renegotiation phase, a first specific request data packet including information for a requested guaranteed power level; transmitting, to the wireless power receiver in the renegotiation phase, an ACK response to accept the requested guaranteed power level based on receiving the first specific request data packet; receiving, from the wireless power receiver in the renegotiation phase, a second specific request data packet to end the renegotiation phase; and transmitting, to the wireless power receiver, an ACK response related to the wireless power transmitter having concluded the renegotiation phase successfully and having switched to a power transfer phase. receiving, from the wireless power receiver, a packet related to a control error, CE, or a packet related to a received power, RP; transmitting, to the wireless power receiver, a bit pattern requesting a communication based on receiving the packet related to the CE or the packet related to the RP; receiving, from the wireless power receiver, a response packet for granting the communication; transmitting, to the wireless power receiver, a capability data packet providing information for a capability of the wireless power transmitter after receiving the response packet; receiving, from the wireless power receiver, a renegotiation data packet requesting the wireless power transmitter to proceed to a renegotiation phase; transmitting, to the wireless power receiver, an acknowledgement, ACK, response related to the wireless power transmitter having switched to the renegotiation phase based on receiving the renegotiation data packet; receiving, from the wireless power receiver in the renegotiation phase, a first specific request data packet including information for a requested guaranteed power level; transmitting, to the wireless power receiver in the renegotiation phase, an ACK response to accept the requested guaranteed power level based on receiving the first specific request data packet; receiving, from the wireless power receiver in the renegotiation phase, a second specific request data packet to end the renegotiation phase; and transmitting, to the wireless power receiver, an ACK response related to the wireless power transmitter having concluded the renegotiation phase successfully and having switched to a power transfer phase.