Range extension mode for WiFi
A communication device generates a transmission signal for transmission via a wireless communication channel, wherein the transmission signal corresponds to a physical layer (PHY) data unit that conforms to a range extension mode of a first communication protocol. Generating the PHY data unit includes generating a preamble of a PHY data unit, wherein the preamble is generated to include: a legacy signal field that includes information indicating a duration of the PHY data unit, a duplicate of the legacy signal field, a plurality of subfields of a non-legacy signal field, and a plurality of additional subfields with the same data as the plurality of subfields of the non-legacy signal field. The plurality of subfields of the non-legacy signal field and the plurality of additional subfields are modulated to signal to a receiving device that the PHY data unit conforms to the range extension mode of a first communication protocol.
1. A method for generating and transmitting a physical layer (PHY) data unit, the method comprising:
generating, at a 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 information indicating a duration of the PHY data unit, wherein the legacy signal field is formatted according to a second, legacy 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, generating the plurality of additional OFDM symbols to use a first modulation pattern;
in response to determining that the PHY data unit is to be generated according to a range extension PHY mode, generating 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;
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 data portion comprises:
generating OFDM symbols for the PHY data portion to include a plurality of constellation symbols in a first bandwidth portion of a channel bandwidth and a copy of the plurality of constellation symbols in a second bandwidth portion of the channel bandwidth, wherein the first bandwidth portion and the second bandwidth portion have a same bandwidth.
5. The method of claim 4 , wherein generating the OFDM symbols for the PHY data portion comprises generating the copy of the plurality of constellation symbols to include a predetermined phase rotation.
6. 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.
7. 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.
8. The method of claim 7 , wherein:
the first tone spacing is i) a legacy tone spacing that conforms to the second, legacy communication protocol, and ii) an integer multiple of the second tone spacing.
9. The method of claim 8 , wherein:
the legacy tone spacing is four times the second tone spacing.
10. 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 information indicating a duration of the PHY data unit, wherein the legacy signal field is formatted according to a second, legacy 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, generate the plurality of additional OFDM symbols to use a first modulation pattern,
in response to determining that the PHY data unit is to be generated according to a range extension PHY mode, 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.
11. The communication device of claim 10 , wherein the one or more IC devices are further configured to:
generate the PHY preamble to include a third OFDM symbol corresponding to the non-legacy signal field;
generate the PHY preamble to include a fourth OFDM symbol corresponding to the non-legacy signal field;
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.
12. The communication device of claim 10 , 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.
13. The communication device of claim 10 , wherein the one or more IC devices are further configured to:
generate OFDM symbols for the PHY data portion to include a plurality of constellation symbols in a first bandwidth portion of a channel bandwidth and a copy of the plurality of constellation symbols in a second bandwidth portion of the channel bandwidth, wherein the first bandwidth portion and the second bandwidth portion have a same bandwidth.
14. The communication device of claim 13 , wherein the one or more IC devices are further configured to generate the copy of the plurality of constellation symbols to include a predetermined phase rotation.
15. The communication device of claim 10 , 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.
16. The communication device of claim 10 , 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.
17. The communication device of claim 16 , wherein:
the first tone spacing is i) a legacy tone spacing that conforms to the second, legacy communication protocol, and ii) an integer multiple of the second tone spacing.
18. The communication device of claim 17 , wherein:
the legacy tone spacing is four times the second tone spacing.
19. The communication device of claim 10 , wherein the wireless network interface device comprises one or more transceivers implemented on the one or more IC devices.
20. The communication device of claim 19 , further comprising:
one or more antennas coupled to the one or more transceivers.