A first communication device, comprising: a transceiver module, configured to: send a transmission frame to a second communication device, wherein the transmission frame comprises a first part and a second part, wherein the first part of the transmission frame comprises a preamble part of the transmission frame, the second part of the transmission frame comprises a data part of the transmission frame; and wherein the preamble part of the transmission frame carries information required for the second communication device to demodulate the second part of the transmission frame, wherein the preamble part of the transmission frame comprises a legacy short training field, L-STF, a legacy long training field, L-LTF, legacy signaling, L-SIG, and a high efficiency wireless local area network signaling, HEW-SIG, wherein the HEW-SIG carries the information required for the second communication device to demodulate the second part of the transmission frame; and wherein sending the first part of the transmission frame using a first quantity of subcarriers, sending the second part of the transmission frame using a second quantity of subcarriers, the first quantity is not equal to the second quantity; and wherein a transmission bandwidth used by the first part and a transmission bandwidth used by the second part are equal, a spacing of the first quantity of subcarriers is not equal to a spacing of the second quantity of subcarriers, the spacing of the first quantity of subcarriers is 312.5kHz, wherein the spacing of the first quantity of subcarriers is greater than the spacing of the second quantity of subcarriers; wherein sending the first part of the transmission frame using a first quantity of subcarriers comprises: sending the first part of the transmission frame using 64 subcarriers per 20MHz. send a transmission frame to a second communication device, wherein the transmission frame comprises a first part and a second part, wherein the first part of the transmission frame comprises a preamble part of the transmission frame, the second part of the transmission frame comprises a data part of the transmission frame; and wherein the preamble part of the transmission frame carries information required for the second communication device to demodulate the second part of the transmission frame, wherein the preamble part of the transmission frame comprises a legacy short training field, L-STF, a legacy long training field, L-LTF, legacy signaling, L-SIG, and a high efficiency wireless local area network signaling, HEW-SIG, wherein the HEW-SIG carries the information required for the second communication device to demodulate the second part of the transmission frame; and wherein sending the first part of the transmission frame using a first quantity of subcarriers, sending the second part of the transmission frame using a second quantity of subcarriers, the first quantity is not equal to the second quantity; and wherein a transmission bandwidth used by the first part and a transmission bandwidth used by the second part are equal, a spacing of the first quantity of subcarriers is not equal to a spacing of the second quantity of subcarriers, the spacing of the first quantity of subcarriers is 312.5kHz, wherein the spacing of the first quantity of subcarriers is greater than the spacing of the second quantity of subcarriers; wherein sending the first part of the transmission frame using a first quantity of subcarriers comprises: sending the first part of the transmission frame using 64 subcarriers per 20MHz. <EOS>