Method and device for transmitting data unit

A device configured for communicating over an operating bandwidth in a wireless local area network, the device comprising:

• a radio frequency module configured to transmit and receive radio signals;
• and
• a processor operatively coupled with the radio frequency module;
• memory disposed to said processor, said memory including instructions, when executed by said processor causing the device to:
• receive a first part of a physical layer protocol data unit (PPDU)
• wherein the first part comprises a legacy-short training field (L-STF), a legacy-long training field (L-LTF), a first signal field, the first signal field having a first phase rotation,
• wherein the first signal field is received over the operating bandwidth that is divided into a plurality of first sub-channels for communication of the first signal field, and
• wherein the first phase rotation was realized by multiplying a first multiplication value to at least one sub-channel of the plurality of the first sub-channels, the first multiplication value selected from +1, −1 and +j based on a sub-carrier index value range of a corresponding first sub-channel;
• and
• receive a second part of the PPDU
• wherein the second part comprises an STF, an LTF, a second signal field, and a data portion, the second signal field having a second phase rotation,
• wherein the second signal field is received over the operating bandwidth that is divided into a plurality of second sub-channels for communication of the second signal field, and
• wherein the second phase rotation was realized by multiplying a second multiplication value to at least one sub-channel of the plurality of the second sub-channels, the second multiplication value selected from +1 and −1, and
• wherein the data portion is received over the operating bandwidth that is divided into a plurality of third sub-channels for communication of the data portion.