A method for transmitting data within an operating bandwidth in a wireless local area network, the method comprising: generating a physical layer protocol data unit, PPDU, including a first part and a second part, the first part comprising a legacy-short training field, L-STF, a legacy-long training field, L-LTF, a legacy-signal, L-SIG, and a signal-A field, the second part comprising a STF field, a LTF field, a signal-B field, and a data portion; transmitting the PPDU over the operating bandwidth, wherein the operating bandwidth is divided into a plurality of first sub-channels for transmission of the first part; wherein the operating bandwidth is divided into a plurality of second sub-channels for transmission of the signal-B field of the second part; wherein the signal-A field of the first part comprises bandwidth information indicating the operating bandwidth, wherein the signal-B field of the second part comprises user-specific information including a bandwidth for the data portion; in case the operating bandwidth is 40 MHz, phase-rotating, to transmit the PPDU, the signal-A field by multiplying one of +1 and +j to each sub-channel of the plurality of the first sub-channels; and phase-rotating, to transmit the PPDU, the signal-B field by multiplying one of +1 and -1 to each sub-channel of the plurality of the second sub-channels. generating a physical layer protocol data unit, PPDU, including a first part and a second part, the first part comprising a legacy-short training field, L-STF, a legacy-long training field, L-LTF, a legacy-signal, L-SIG, and a signal-A field, the second part comprising a STF field, a LTF field, a signal-B field, and a data portion; the first part comprising a legacy-short training field, L-STF, a legacy-long training field, L-LTF, a legacy-signal, L-SIG, and a signal-A field, the second part comprising a STF field, a LTF field, a signal-B field, and a data portion; transmitting the PPDU over the operating bandwidth, wherein the operating bandwidth is divided into a plurality of first sub-channels for transmission of the first part; wherein the operating bandwidth is divided into a plurality of second sub-channels for transmission of the signal-B field of the second part; wherein the signal-A field of the first part comprises bandwidth information indicating the operating bandwidth, wherein the signal-B field of the second part comprises user-specific information including a bandwidth for the data portion; wherein the operating bandwidth is divided into a plurality of first sub-channels for transmission of the first part; wherein the operating bandwidth is divided into a plurality of second sub-channels for transmission of the signal-B field of the second part; wherein the signal-A field of the first part comprises bandwidth information indicating the operating bandwidth, wherein the signal-B field of the second part comprises user-specific information including a bandwidth for the data portion; in case the operating bandwidth is 40 MHz, phase-rotating, to transmit the PPDU, the signal-A field by multiplying one of +1 and +j to each sub-channel of the plurality of the first sub-channels; and phase-rotating, to transmit the PPDU, the signal-B field by multiplying one of +1 and -1 to each sub-channel of the plurality of the second sub-channels.