A first network device detects at least a first orthogonal code included in a preamble of a network packet received at the first network device from a second network device in an orthogonal frequency division multiplexing (OFDM) communication network. The first network device determines whether the first orthogonal code included in the preamble is associated with an assigned orthogonal code for the first network device. The assigned orthogonal code for the first network device is orthogonal to other assigned orthogonal codes for other network devices in the OFDM communication network. An operational mode of the first network device is changed from a sleep mode to an awake mode in response to determining the first orthogonal code is associated with the assigned orthogonal code for the first network device.