Physical layer frame format for WLAN
A first communication device generates a physical layer (PHY) preamble for a PHY data unit to be transmitted via a communication channel, the PHY data unit conforming to a first communication protocol. Generating the PHY preamble includes generating a legacy portion of the PHY preamble to include a legacy signal field, which is decodable by one or more second communication devices that conform to a second communication protocol to determine a duration of the PHY data unit. The PHY preamble is generated to also include a duplicate of the legacy signal field in the PHY preamble, wherein presence of the duplicate of the legacy signal field indicates to one or more third communication devices that conform to the first communication protocol that the PHY data unit conforms to the first communication protocol. The first communication device generates the PHY data unit to include the PHY preamble and a PHY payload.
1. A method for generating a physical layer (PHY) data unit that conforms to a first communication protocol, the method comprising:
generating, at a first communication device, a PHY preamble for the PHY data unit, including:
generating a legacy portion of the PHY preamble to include a legacy signal field, wherein the legacy portion of the PHY preamble is decodable by one or more second communication devices that conform to a second communication protocol, but do not conform to the first communication protocol, to determine a duration of the PHY data unit based on the legacy portion of the PHY preamble, and
including a duplicate of the legacy signal field in the PHY preamble, wherein presence of the duplicate of the legacy signal field indicates to one or more third communication devices that conform to the first communication protocol that the PHY data unit conforms to the first communication protocol; and
generating, at the first communication device, the PHY data unit to include the PHY preamble and a PHY payload, the PHY data unit for transmission via a communication channel.
2. The method of claim 1 , wherein generating the PHY preamble for the PHY data unit further includes:
generating a further signal field that conforms to the first communication protocol; and
including the further signal field in a non-legacy portion of the PHY preamble.
3. The method of claim 2 , wherein generating the PHY preamble for the PHY data unit further includes generating the PHY preamble such that:
the duplicate of the legacy signal field immediately follows the legacy signal field, and
the further signal field immediately follows the duplicate of the legacy signal field.
4. The method of claim 2 , wherein the non-legacy portion of the PHY preamble is not decodable by the one or more second communication devices that conform to the second communication protocol but do not conform to the first communication protocol.
5. The method of claim 2 , wherein generating the PHY preamble for the PHY data unit further includes:
including a duplicate of information from the further signal field in the non-legacy portion of the PHY preamble, wherein the duplicate information from the further signal field increases decoding reliability in a range extension mode of the first communication protocol.
6. The method of claim 1 , wherein generating the legacy portion of the PHY preamble comprises:
generating the legacy signal field to include a length subfield that indicates the duration of the PHY data unit.
7. The method of claim 6 , wherein:
generating the legacy portion of the PHY preamble comprises setting the length subfield of the legacy signal field to a value that is not a multiple of three; and
the second communication protocol specifies that the length subfield of the legacy signal field must be a multiple of three.
8. An apparatus, comprising:
a network interface device associated with a first communication device, the network interface device comprising one or more integrated circuits (ICs) configured to:
generate a PHY preamble for the PHY data unit, including:
generating a legacy portion of the PHY preamble to include a legacy signal field, wherein the legacy portion of the PHY preamble is decodable by one or more second communication devices that conform to a second communication protocol, but do not conform to the first communication protocol, to determine a duration of the PHY data unit based on the legacy portion of the PHY preamble, and
including a duplicate of the legacy signal field in the PHY preamble, wherein presence of the duplicate of the legacy signal field indicates to one or more third communication devices that conform to the first communication protocol that the PHY data unit conforms to the first communication protocol; and
wherein the one or more ICs are further configured to generate the PHY data unit to include the PHY preamble and a PHY payload, the PHY data unit for transmission via a communication channel.
9. The apparatus of claim 8 , wherein the one or more ICs are further configured to:
generate a further signal field that conforms to the first communication protocol; and
include the further signal field in a non-legacy portion of the PHY preamble.
10. The apparatus of claim 9 , wherein the one or more ICs are further configured to generate the PHY preamble such that:
the duplicate of the legacy signal field immediately follows the legacy signal field, and
the further signal field immediately follows the duplicate of the legacy signal field.
11. The apparatus of claim 9 , wherein the non-legacy portion of the PHY preamble is not decodable by the one or more second communication devices that conform to the second communication protocol but do not conform to the first communication protocol.
12. The apparatus of claim 9 , wherein the one or more ICs are further configured to:
include a duplicate of information from the further signal field in the non-legacy portion of the PHY preamble, wherein the duplicate information from the further signal field increases decoding reliability in a range extension mode of the first communication protocol.
13. The apparatus of claim 8 , wherein the one or more ICs are further configured to:
generate the legacy signal field to include a length subfield that indicates the duration of the PHY data unit.
14. The apparatus of claim 13 , wherein:
the one or more ICs are further configured to set the length subfield of the legacy signal field to a value that is not a multiple of three; and
the second communication protocol specifies that the length subfield of the legacy signal field must be a multiple of three.
15. The apparatus of claim 8 , further comprising a PHY processor implemented on the one or more integrated circuits, wherein the PHY processor is configured to:
generate the PHY preamble for the PHY data unit; and
generate the PHY data unit to include the PHY preamble and the PHY payload.
16. The apparatus of claim 15 , wherein the network interface device further comprises a media access control layer (MAC) processor implemented on the one or more integrated circuits, wherein the MAC processor is coupled to the PHY processor.
17. The apparatus of claim 16 , wherein the PHY processor includes one or more transceivers.
18. The apparatus of claim 17 , further comprising:
one or more antennas coupled to the one or more transceivers.
19. The apparatus of claim 17 , further comprising:
a host processor coupled to the network interface device.
20. The apparatus of claim 19 , further comprising:
one or more antennas coupled to the one or more transceivers.