Physical layer frame format for WLAN
A first communication device generates a PHY preamble of a PHY data unit to include a first orthogonal frequency division multiplexing (OFDM) symbol corresponding to a legacy signal field. The legacy signal field includes i) a length subfield, and ii) a rate subfield. The length subfield and the rate subfield indicate a duration of the PHY data unit, and the legacy signal field is formatted according to a legacy second communication protocol. The first communication device generates the PHY preamble of a PHY data unit to include a second OFDM symbol corresponding to a duplicate of the legacy signal field, and a plurality of additional OFDM symbols corresponding to a non-legacy signal field. The first communication device sets the length subfield of the legacy signal field to a length value such that a remainder value resulting from dividing the length value by three, indicates that the PHY data unit conforms to the first communication protocol.
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 of the PHY data unit to include:
a first orthogonal frequency division multiplexing (OFDM) symbol corresponding to a legacy signal field, the legacy signal field including i) a length subfield, and ii) a rate subfield, wherein the length subfield and the rate subfield indicate a duration of the PHY data unit, and wherein the legacy signal field is formatted according to a legacy second communication protocol,
a second OFDM symbol corresponding to a duplicate of the legacy signal field, the second OFDM symbol following the first OFDM symbol in time, and
a plurality of additional OFDM symbols corresponding to a non-legacy signal field;
in response to determining that the PHY data unit is to be generated according to a non-range extension PHY mode defined by the first communication protocol, generating, at the first communication device, the plurality of additional OFDM symbols to use a first modulation pattern; and
in response to determining that the PHY data unit is to be generated according to a range extension PHY mode define by the first communication protocol, generating, at the first communication device, the plurality of additional OFDM symbols to use a second modulation pattern to signal that the PHY data unit is generated according to the range extension PHY mode;
generating, at the communication device, a PHY data portion of the PHY data unit; and
transmitting, by the communication device, the PHY data unit via a wireless communication channel.
2. The method of claim 1 , wherein:
generating the PHY preamble to include the plurality of additional OFDM symbols corresponding to the non-legacy signal field comprises:
generating the PHY preamble to include a third OFDM symbol corresponding to the non-legacy signal field, and
generating the PHY preamble to include a fourth OFDM symbol corresponding to the non-legacy signal field; and
generating the plurality of additional OFDM symbols to use the second modulation pattern comprises:
generating the third OFDM symbol using binary phase shift keying (BPSK) modulation, and
generating the fourth OFDM symbol using quadrature binary phase shift keying (Q-BPSK) modulation to signal that the PHY data unit is generated according to the range extension PHY mode.
3. The method of claim 1 , wherein generating the PHY preamble further comprises generating the plurality of additional OFDM symbols to include:
information corresponding to the non-legacy signal field; and
a repetition of the information corresponding to the non-legacy signal field.
4. The method of claim 1 , wherein generating the PHY preamble further includes:
generating at least a portion of the PHY preamble with a transmission power boost as compared to the PHY data portion to increase a decoding range of the at least the portion of the PHY preamble.
5. The method of claim 1 , wherein:
generating the PHY preamble comprises generating OFDM symbols for a portion of the PHY preamble using a first tone spacing; and
generating the PHY data portion comprises generating OFDM symbols for the PHY data portion using a second tone spacing that is different than the first tone spacing.
6. A communication device, comprising:
a wireless network interface device having one or more integrated circuit (IC) devices configured to:
generate a PHY preamble of the PHY data unit to include:
a first orthogonal frequency division multiplexing (OFDM) symbol corresponding to a legacy signal field, the legacy signal field including i) a length subfield, and ii) a rate subfield, wherein the length subfield and the rate subfield indicate a duration of the PHY data unit, and wherein the legacy signal field is formatted according to a legacy second communication protocol,
a second OFDM symbol corresponding to a duplicate of the legacy signal field, the second OFDM symbol following the first OFDM symbol in time, and
a plurality of additional OFDM symbols corresponding to a non-legacy signal field;
wherein the one or more IC devices are further configured to:
in response to determining that the PHY data unit is to be generated according to a non-range extension PHY mode defined by the first communication protocol, generate the plurality of additional OFDM symbols to use a first modulation pattern, and
in response to determining that the PHY data unit is to be generated according to a range extension PHY mode defined by the first communication protocol, generate the plurality of additional OFDM symbols to use a second modulation pattern to signal that the PHY data unit is generated according to the range extension PHY mode,
generate a PHY data portion of the PHY data unit, and
control the wireless network interface device to transmit the PHY data unit via a wireless communication channel.
7. The communication device of claim 6 , wherein the one or more IC devices are further configured to:
as part of generating the PHY preamble to include the plurality of additional OFDM symbols corresponding to the non-legacy signal field:
generate the PHY preamble to include a third OFDM symbol corresponding to the non-legacy signal field as part of, and
generate the PHY preamble to include a fourth OFDM symbol corresponding to the non-legacy signal field; and
as part of generating the plurality of additional OFDM symbols to use the second modulation pattern:
generate the third OFDM symbol using binary phase shift keying (BPSK) modulation, and
generate the fourth OFDM symbol using quadrature binary phase shift keying (Q-BPSK) modulation to signal that the PHY data unit is generated according to the range extension PHY mode.
8. The communication device of claim 6 , wherein the one or more IC devices are further configured to generate the plurality of additional OFDM symbols to include:
information corresponding to the non-legacy signal field; and
a repetition of the information corresponding to the non-legacy signal field.
9. The communication device of claim 6 , wherein the one or more IC devices are further configured to:
generate at least a portion of the PHY preamble with a transmission power boost as compared to the PHY data portion to increase a decoding range of the at least the portion of the PHY preamble.
10. The communication device of claim 6 , wherein the one or more IC devices are further configured to:
generate OFDM symbols for a portion of the PHY preamble using a first tone spacing; and
generate OFDM symbols for the PHY data portion using a second tone spacing that is different than the first tone spacing.
11. The communication device of claim 6 , wherein the wireless network interface device comprises one or more transceivers implemented on the one or more IC devices.
12. The communication device of claim 11 , further comprising: one or more antennas coupled to the one or more transceivers.