High efficiency orthogonal frequency division multiplexing (OFDM) physical layer (PHY)

An apparatus, comprising:

• a network interface device having one or more integrated circuits, the network interface device including:
• a medium access control (MAC) processing unit implemented on the one or more integrated circuits, and
• a physical layer (PHY) processing unit coupled to the MAC processing unit, the PHY processing unit implemented on the one or more integrated circuits;
• wherein the one or more integrated circuits are configured to determine that an extension field is to be included in a PHY data unit to provide a receiver with more processing time to process data included in the PHY data unit, wherein the extension field is not required to be processed by the receiver;
• and
• wherein the PHY processing unit is configured to:
• generate a PHY preamble of the PHY data unit,
• generate a PHY data portion of the PHY data unit, including generating one or more orthogonal frequency division multiplexing (OFDM) symbols, wherein each OFDM symbol of the one or more OFDM symbols is generated with a first tone spacing, wherein the first tone spacing is a fraction 1/N of a second tone spacing, the second tone spacing defined by a second communication protocol, wherein N is a positive integer greater than one, and
• generate the extension field of the PHY data unit to include arbitrary data such that a power of the extension field equals a power of the data portion of the PHY data unit, the extension field being appended to an end of the data portion of the PHY data unit.