Generating packets having orthogonal frequency division multiplexing (OFDM) symbols

1. A method for generating a physical layer (PHY) data unit for transmission via a wireless communication channel, method comprising:

generating, at a communication device, a first portion of a PHY preamble of the PHY data unit to include a first plurality of orthogonal frequency division multiplexing (OFDM) symbols, wherein each OFDM symbol of the first plurality of OFDM symbols is modulated on at most X OFDM subcarriers, wherein X is a positive integer greater than one;

generating, at the communication device, a second portion of the PHY preamble to include a second plurality of OFDM symbols, wherein each OFDM symbol of the second plurality of OFDM symbols is modulated on at most N*X OFDM subcarriers, wherein N is a positive integer greater than one;

generating, at the communication device, a PHY data portion of the PHY data unit to include one or more third OFDM symbols, wherein each third OFDM symbol is modulated on at most N*X OFDM subcarriers; and

transmitting, by the communication device, the PHY data unit via the wireless communication channel.

2. The method of claim 1 , wherein:

generating the first portion of the PHY preamble of the PHY data unit includes generating said each OFDM symbol among the first plurality of OFDM symbols to have a first duration; and

generating the PHY data portion includes generating each of the third OFDM symbols to have a third duration that is at least double the first duration.

3. The method of claim 1 , wherein:

the first portion of the PHY preamble includes a PHY signal field; and

the second portion of the PHY preamble includes one or more training fields.

4. The method of claim 1 , wherein:

X is 64;

N is 4;

generating the first portion of the PHY preamble comprises generating the first portion of the PHY preamble to span 20 MHz;

generating the second portion of the PHY preamble comprises generating the second portion of the PHY preamble to span 20 MHz; and

generating the PHY data portion comprises generating the PHY data portion to span 20 MHz.

5. The method of claim 1 , wherein:

X is 128;

N is 4;

generating the first portion of the PHY preamble comprises generating the first portion of the PHY preamble to span 40 MHz;

generating the second portion of the PHY preamble comprises generating the second portion of the PHY preamble to span 40 MHz; and

generating the PHY data portion comprises generating the PHY data portion to span 40 MHz.

6. The method of claim 1 , wherein:

X is 256;

N is 4;

generating the first portion of the PHY preamble comprises generating the first portion of the PHY preamble to span 80 MHz;

generating the second portion of the PHY preamble comprises generating the second portion of the PHY preamble to span 80 MHz; and

generating the PHY data portion comprises generating the PHY data portion to span 80 MHz.

7. The method of claim 1 , wherein:

X is 512;

N is 4;

generating the first portion of the PHY preamble comprises generating the first portion of the PHY preamble to span 160 MHz;

generating the second portion of the PHY preamble comprises generating the second portion of the PHY preamble to span 160 MHz; and

generating the PHY data portion comprises generating the PHY data portion to span 160 MHz.

8. The method of claim 7 , wherein:

generating the PHY data portion includes: i) generating a first 80 MHz segment using a first 1024-point inverse discrete Fourier transform (IDFT) calculator, and ii) generating a second 80 MHz segment using a second 1024-point IDFT calculator.

9. The method of claim 1 , wherein:

X is one of 64, 128, 256, and 512; and

N is two.

10. The method of claim 1 , wherein:

generating the first portion of the PHY preamble comprises using a first number of OFDM subcarriers as direct current (DC) subcarriers;

generating the second portion of the PHY preamble comprises using a second number of OFDM subcarriers as DC subcarriers, wherein the second number of OFDM subcarriers is larger than the first number of OFDM subcarriers; and

generating the PHY data portion comprises using the second number of OFDM subcarriers as DC subcarriers.

11. A wireless communication device, comprising:

a wireless network interface device implemented on one or more integrated circuits (ICs), wherein the wireless network interface device is configured to:

generate a first portion of a PHY preamble of the PHY data unit to include a first plurality of orthogonal frequency division multiplexing (OFDM) symbols, wherein each OFDM symbol of the first plurality of OFDM symbols is modulated on at most X OFDM subcarriers, wherein X is a positive integer greater than one,

generate a second portion of the PHY preamble to include a second plurality of OFDM symbols, wherein each OFDM symbol of the second plurality of OFDM symbols is modulated on at most N*X OFDM subcarriers, wherein N is a positive integer greater than one,

generate a PHY data portion of the PHY data unit to include one or more third OFDM symbols, wherein each third OFDM symbol is modulated on at most N*X OFDM subcarriers, and

transmit the PHY data unit via a wireless communication channel.

12. The wireless communication device of claim 11 , wherein the wireless network interface device is configured to:

generate said each OFDM symbol among the first plurality of OFDM symbols to have a first duration; and

generate each of the third OFDM symbols to have a third duration that is at least double the first duration.

13. The wireless communication device of claim 11 , wherein:

the first portion of the PHY preamble includes a PHY signal field; and

the second portion of the PHY preamble includes one or more training fields.

14. The wireless communication device of claim 11 , wherein:

X is 64;

N is 4; and

the wireless network interface device is configured to:

generate the first portion of the PHY preamble to span 20 MHz,

generate the second portion of the PHY preamble to span 20 MHz, and

generate the PHY data portion to span 20 MHz.

15. The wireless communication device of claim 11 , wherein:

X is 128;

N is 4; and

the wireless network interface device is configured to:

generate the first portion of the PHY preamble to span 40 MHz,

generate the second portion of the PHY preamble to span 40 MHz, and

generate the PHY data portion to span 40 MHz.

16. The wireless communication device of claim 11 , wherein:

X is 256;

N is 4;

the wireless network interface device is configured to:

generate the first portion of the PHY preamble to span 80 MHz,

generate the second portion of the PHY preamble to span 80 MHz, and

generate the PHY data portion to span 80 MHz.

17. The wireless communication device of claim 11 , wherein:

X is 512;

N is 4;

the wireless network interface device is configured to:

generate the first portion of the PHY preamble to span 160 MHz,

generate the second portion of the PHY preamble to span 160 MHz, and

generate the PHY data portion to span 160 MHz.

18. The wireless communication device of claim 17 , wherein the wireless network interface device is configured to:

generate a first 80 MHz segment of the PHY data portion using a first 1024-point inverse discrete Fourier transform (IDFT) calculator, and ii) generating a second 80 MHz segment of the PHY data portion using a second 1024-point IDFT calculator.

19. The wireless communication device of claim 11 , wherein:

X is one of 64, 128, 256, and 512; and

N is two.

20. The wireless communication device of claim 11 , wherein the wireless network interface device is configured to:

in the first portion of the PHY preamble, use a first number of OFDM subcarriers as direct current (DC) subcarriers;

in the second portion of the PHY preamble, use a second number of OFDM subcarriers as DC subcarriers, wherein the second number of OFDM subcarriers is larger than the first number of OFDM subcarriers; and

in the PHY data portion, use the second number of OFDM subcarriers as DC subcarriers.

21. The wireless communication device of claim 11 , wherein the wireless network interface device comprises:

a medium access control (MAC) processing unit implemented on the one or more ICs; and

a physical layer (PHY) processing unit coupled to the MAC processing unit, the PHY processing unit implemented on the one or more ICs;

wherein the PHY processing unit is configured to:

generate the first portion of the PHY preamble to include the first plurality of OFDM symbols,

generate the second portion of the PHY preamble to include the second plurality of OFDM symbols, and

generate the PHY data portion of the PHY data unit to include the one or more third OFDM symbols.