A communication device generates a first portion of a physical layer (PHY) preamble of a PHY data unit to include a first plurality of orthogonal frequency division multiplexing (OFDM) symbols. Each OFDM symbol of the first plurality of OFDM symbols is generated with a first OFDM tone spacing. The communication device generate a second portion of the PHY preamble to include a second plurality of OFDM symbols. Each OFDM symbol of the second plurality of OFDM symbols is generated with a second OFDM tone spacing that is a fraction 1/N of the first OFDM tone spacing, where N is a positive integer greater than one. The communication device generates a PHY data portion of the PHY data unit to include one or more third OFDM symbols. Each third OFDM symbol is generated with the second OFDM tone spacing.