Physical layer frame format for wlan

21:

• A method for generating and transmitting a physical layer (PHY) data unit for transmission via a communication channel, the PHY data unit conforming to a first communication protocol, the method comprising:
• generating, at a communication device, the PHY data unit, including generating a preamble of the PHY data unit, wherein
• the preamble is generated to include a first legacy portion and a first non-legacy portion that follows the first legacy portion,
• the first non-legacy portion is generated to include i) a first symbol that immediately follows the first legacy portion and that is modulated using a first-type modulation, and ii) a second symbol that immediately follows the first symbol and that is modulated using a second-type modulation that is different from the first-type modulation,
• the first symbol being modulated using the first-type modulation and the second symbol being modulated using the second-type modulation indicate to a receiver device that conforms to the first communication protocol that the data unit conforms to the first communication protocol,
• the first non-legacy portion is generated to further include fields that follow the second symbol and that conform to the first communication protocol,
• a second communication protocol defines a preamble format that includes i) a second legacy portion corresponding to the first legacy portion, and ii) a second non-legacy portion that follows the second legacy portion, the second communication protocol specifying that a third symbol that immediately follows the second legacy portion is modulated using the second-type modulation, and
• the first symbol is modulated using the first-type modulation to cause a receiver device that conforms to the second communication protocol to determine that the PHY data unit conforms to a third communication protocol that is different from the first communication protocol and the second communication protocol;
• and
• transmitting, with the communication device, the PHY data unit via the communication channel.

26:

• The method of claim 21, wherein:
• the second communication protocol is a protocol defined by the IEEE 802.11n standard;
• and
• the third communication protocol is a protocol defined by the IEEE 802.11a standard.

27:

• The method of claim 21, wherein:
• the first symbol and the second symbol correspond to a first signal field;
• the fields that follow the second symbol and that conform to the first communication protocol include:
• a plurality of training fields, and
• a second signal field that follows the plurality of training fields.

28:

• The method of claim 27,
• wherein transmitting the PHY data unit includes:
• transmitting, with the communication device, a first portion of the PHY data unit without beamsteering, wherein the first portion includes the legacy portion and the first signal field;
• and
• transmitting, with the communication device, a second portion of the PHY data unit with beamsteering, wherein the second portion includes the second signal field.

30:

• An apparatus, comprising:
• a wireless network interface device implemented at least partially on one or more integrated circuit (IC) devices, where the one or more IC devices are configured to generate a physical layer (PHY) data unit, including generating a preamble of the PHY data unit, and wherein:
• the preamble is generated to include a first legacy portion and a first non-legacy portion that follows the first legacy portion,
• the first non-legacy portion is generated to include i) a first symbol that immediately follows the first legacy portion and that is modulated using a first-type modulation, and ii) a second symbol that immediately follows the first symbol and that is modulated using a second-type modulation that is different from the first-type modulation,
• the first symbol being modulated using the first-type modulation and the second symbol being modulated using the second-type modulation indicate to a receiver device that conforms to the first communication protocol that the data unit conforms to the first communication protocol,
• the first non-legacy portion is generated to further include fields that follow the second symbol and that conform to the first communication protocol,
• a second communication protocol defines a preamble format that includes i) a second legacy portion corresponding to the first legacy portion, and ii) a second non-legacy portion that follows the second legacy portion, the second communication protocol specifying that a third symbol that immediately follows the second legacy portion is modulated using the second-type modulation, and
• the first symbol is modulated using the first-type modulation to cause a receiver device that conforms to the second communication protocol to determine that the PHY data unit conforms to a third communication protocol that is different from the first communication protocol and the second communication protocol;
• wherein the one or more IC devices are further configured to control the wireless network interface device to transmit the PHY data unit via a communication channel.

35:

• The apparatus of claim 30, wherein:
• the second communication protocol is a protocol defined by the IEEE 802.11n standard;
• and
• the third communication protocol is a protocol defined by the IEEE 802.11a standard.

36:

• The apparatus of claim 30, wherein:
• the first symbol and the second symbol correspond to a first signal field;
• the fields that follow the second symbol and that conform to the first communication protocol include:
• a plurality of training fields, and
• a second signal field that follows the plurality of training fields.

37:

• The apparatus of claim 36, wherein the one or more IC devices are configured to:
• control the wireless network interface device to transmit a first portion of the PHY data unit without beamsteering, wherein the first portion includes the legacy portion and the first signal field;
• and
• control the wireless network interface device to transmit a second portion of the PHY data unit with beamsteering, wherein the second portion includes the second signal field.