Data transmission device, method, and system

A method of data transmission comprising:

• determining, by an access network device, a downlink frequency shift according to a received uplink signal sent by a terminal device;
• determining, by the access network device, a second transmit frequency according to the downlink frequency shift and a first transmit frequency;
• sending, by the access network device, a downlink signal to the terminal device according to the second transmit frequency, wherein the downlink signal comprises downlink data;
• and
• sending indication information to the terminal device, and the indication information instructs the terminal device not to perform frequency compensation.

A method of data transmission, comprising:

• receiving, by a terminal device, a downlink signal according to a receive frequency, wherein the receive frequency is corresponding to a first transmit frequency, the downlink signal is sent by an access network device to the terminal device according to a second transmit frequency, the second transmit frequency is determined according to a downlink frequency shift and the first transmit frequency, and the downlink signal comprises downlink data;
• demodulating, by the terminal device, the downlink signal according to the receive frequency;
• and
• receiving indication information from the access network device, wherein the indication information instructs the terminal device not to perform frequency compensation.