Physical layer preamble for wireless local area networks

A communication device generates a legacy portion of a physical layer (PHY) preamble of a PHY data unit. The legacy portion includes a plurality of legacy training fields and a legacy signal field that indicates a duration of the PHY data unit. The communication device generates a non-legacy portion of the PHY preamble to include a multi-bit signal field header to indicate at least one of i) a particular wireless communication protocol from among the multiple wireless communication protocols, and ii) a particular version of the particular wireless communication protocol. The communication device generates the non-legacy portion of the PHY preamble to also include a non-legacy signal field having a field format that conforms to the at least one of the i) particular wireless communication protocol and ii) the particular version of the particular wireless communication protocol.