A method, comprising: generating a first signal field of a preamble of a physical layer data unit; generating a plurality of training fields of the preamble of the physical layer data unit; generating a second signal field of the preamble of the physical layer data unit, wherein the plurality of training fields are between the first signal field and the second signal field; mapping the second signal field to a first subset in a first plurality of data subcarriers corresponding to a first frequency portion of a first orthogonal frequency division multiplex, OFDM, symbol; setting a second subset of data subcarriers in the first plurality of data subcarriers to one or more predetermined values; mapping the second signal field to a first subset in a second plurality of data subcarriers corresponding to a second frequency portion of the first OFDM symbol; setting a second subset of data subcarriers in the second plurality of data subcarriers to one or more predetermined values; setting guard tones, direct current, DC, tones, and pilot tones in the first frequency portion and the second frequency portion; generating a data portion of the physical layer data unit, including generating one or more second OFDM symbols for the data portion, wherein the number of guard tones, DC tones, and pilot tones in the one or more second OFDM symbols is equal to the number of guard tones, DC tones, and pilot tones in the first OFDM symbol corresponding to the second signal field; and transmitting the physical layer data unit that includes the first OFDM symbol and the one or more second OFDM symbols in the preamble of the physical layer data unit. generating a first signal field of a preamble of a physical layer data unit; generating a plurality of training fields of the preamble of the physical layer data unit; generating a second signal field of the preamble of the physical layer data unit, wherein the plurality of training fields are between the first signal field and the second signal field; mapping the second signal field to a first subset in a first plurality of data subcarriers corresponding to a first frequency portion of a first orthogonal frequency division multiplex, OFDM, symbol; setting a second subset of data subcarriers in the first plurality of data subcarriers to one or more predetermined values; mapping the second signal field to a first subset in a second plurality of data subcarriers corresponding to a second frequency portion of the first OFDM symbol; setting a second subset of data subcarriers in the second plurality of data subcarriers to one or more predetermined values; setting guard tones, direct current, DC, tones, and pilot tones in the first frequency portion and the second frequency portion; generating a data portion of the physical layer data unit, including generating one or more second OFDM symbols for the data portion, wherein the number of guard tones, DC tones, and pilot tones in the one or more second OFDM symbols is equal to the number of guard tones, DC tones, and pilot tones in the first OFDM symbol corresponding to the second signal field; and transmitting the physical layer data unit that includes the first OFDM symbol and the one or more second OFDM symbols in the preamble of the physical layer data unit.