In a method for generating a physical layer (PHY) data unit, pilot tone contribution sequence values for a first set of orthogonal frequency division multiplexing (OFDM) symbols and for a second set of OFDM symbols are determined using a pilot mapping function. The first set is to be included in a signal field of the data unit, and the second set is to be included in a data portion of the data unit. The first set and the second set are generated to include pilot tones modulated based on the pilot tone contribution sequence values determined, respectively, for the first set of OFDM symbols and for the second set of OFDM symbols. The signal field is generated to include the first set, and the data portion is generated to include the second set. The data unit is generated to include at least the signal field and the data portion.