Orthogonal frequency division multiplexing (OFDM) symbol formats for a wireless local area network (WLAN)

1. A method of generating a multi-user physical layer (PHY) data unit for transmission via a communication channel, the method comprising:

generating, at a communication device, a first preamble portion of the multi-user PHY data unit;

generating, at the communication device, a plurality of training fields of the multi-user PHY data unit for transmission after the first preamble portion;

generating, at the communication device, a second preamble portion of the multi-user PHY data unit for transmission after the plurality of training fields, including:

encoding a plurality of information bits to generate a plurality of coded bits to be included in an orthogonal frequency division multiplexing (OFDM) symbol of the second preamble portion, wherein the plurality of information bits corresponds to a first bandwidth, and wherein the OFDM symbol includes a number of data tones corresponding to a second bandwidth, the second bandwidth larger than the first bandwidth,

mapping the plurality of coded bits to a plurality constellation symbols,

mapping the plurality of constellation symbols to a first plurality of data subcarriers corresponding to a first portion of the OFDM symbol,

mapping the plurality of constellation symbols to a second plurality of data subcarriers corresponding to a second portion of the OFDM symbol, and

generating the OFDM symbol to include at least the first plurality of data subcarriers and the second plurality of data subcarriers;

generating, at the communication device, a data portion of the multi-user PHY data unit for transmission after the second preamble portion, wherein a number of guard tones, direct current (DC) tones, and pilot tones in the second preamble portion is equal to a number of guard tones, DC tones, and pilot tones in the data portion of the multi-user PHY data unit; and

transmitting, by the communication device, the multi-user PHY data unit.

2. The method of claim 1 , wherein generating the second preamble portion further includes:

setting a subset of data subcarriers in the first plurality of data subcarriers to one or more predetermined values; and

setting a subset of data subcarriers in the second plurality of data subcarriers to one or more predetermined values.

3. The method of claim 2 , wherein setting the subset of data subcarriers in the first plurality of data subcarriers to one or more predetermined values comprises setting at least one data subcarrier in the subset of data subcarriers in the first plurality of data subcarriers to a null value; and

wherein setting the subset of data subcarriers in the second plurality of data subcarriers to one or more predetermined values comprises setting at least one data subcarrier in the subset of data subcarriers in the second plurality of data subcarriers to the null value.

4. The method of claim 2 , wherein setting the subset of data subcarriers in the first plurality of data subcarriers to one or more predetermined values comprises setting at least one data subcarrier in the subset of data subcarriers in the first plurality of data subcarriers to a non-zero value; and

wherein setting the subset of data subcarriers in the second plurality of data subcarriers to one or more predetermined values comprises setting at least one data subcarrier in the subset of data subcarriers in the second plurality of data subcarriers to the non-zero value.

5. The method of claim 1 , further comprising:

mapping the plurality of constellation symbols to a third plurality of data subcarriers corresponding to a third portion of the OFDM symbol; and

wherein generating the OFDM symbol further comprises including the third plurality of data subcarriers in the OFDM symbol.

6. The method of claim 1 , further comprising (i) inserting one or more additional bits into the plurality of information bits and (ii) duplicating the plurality of information bits and the additional bits, prior to encoding the information bits, to generate a plurality of duplicated bits; and

wherein encoding the information bits comprises encoding the plurality of duplicated bits.

7. The method of claim 1 , wherein the first bandwidth corresponds to a bandwidth B and the second bandwidth corresponds to a bandwidth mB, wherein m is a positive integer.

8. The method of claim 7 , wherein the bandwidth B is 20 MHz.

9. The method of claim 7 , wherein the bandwidth B is less than 20 MHz.

10. The method of claim 9 , wherein the bandwidth B is one of: 1 MHz, 2 MHz, and 4 MHz.

11. An apparatus, comprising:

a network interface device implemented on one or more integrated circuit (IC) devices, the network interface device including:

a media access control layer (MAC) processor implemented on the one or more IC devices, and

a physical layer (PHY) processor implemented on the one or more IC devices;

wherein the PHY processor is configured to:

generate a first preamble portion of a multi-user physical layer (PHY) data unit, the multi-user PHY data unit for transmission via a communication channel,

generate a plurality of training fields of the multi-user PHY data unit for transmission after the first preamble portion, and

generate a second preamble portion of the multi-user PHY data unit for transmission after the plurality of training fields, including:

encoding a plurality of information bits to generate a plurality of coded bits to be included in an orthogonal frequency division multiplexing (OFDM) symbol of the second preamble portion, wherein the plurality of information bits corresponds to a first bandwidth, and wherein the OFDM symbol includes a number of data tones corresponding to a second bandwidth, the second bandwidth larger than the first bandwidth,

mapping the plurality of coded bits to a plurality constellation symbols,

mapping the plurality of constellation symbols to a first plurality of data subcarriers corresponding to a first portion of the OFDM symbol,

mapping the plurality of constellation symbols to a second plurality of data subcarriers corresponding to a second portion of the OFDM symbol, and

generating the OFDM symbol to include at least the first plurality of data subcarriers and the second plurality of data subcarriers;

wherein the PHY processor is further configured to generate a data portion of the multi-user PHY data unit for transmission after the second preamble portion, wherein a number of guard tones, direct current (DC) tones, and pilot tones in the second preamble portion is equal to a number of guard tones, DC tones, and pilot tones in the data portion of the multi-user PHY data unit.

12. The apparatus of claim 11 , wherein the PHY processor is further configured to:

set a subset of data subcarriers in the first plurality of data subcarriers to one or more predetermined values; and

set a subset of data subcarriers in the second plurality of data subcarriers to one or more predetermined values.

13. The apparatus of claim 12 , wherein the PHY processor is configured to:

set at least one data subcarrier in the subset of data subcarriers in the first plurality of data subcarriers to a null value; and

set at least one data subcarrier in the subset of data subcarriers in the second plurality of data subcarriers to the null value.

14. The apparatus of claim 12 , wherein the PHY processor is configured to:

set at least one data subcarrier in the subset of data subcarriers in the first plurality of data subcarriers to a non-zero value; and

set at least one data subcarrier in the subset of data subcarriers in the second plurality of data subcarriers to the non-zero value.

15. The apparatus of claim 11 , wherein the PHY processor is further configured to:

map the plurality of constellation symbols to a third plurality of data subcarriers corresponding to a third portion of the OFDM symbol; and

include the third plurality of data subcarriers in the OFDM symbol.

16. The apparatus of claim 11 , wherein the PHY processor is further configured to:

insert one or more additional bits into the plurality of information bits; and

duplicate the plurality of information bits and the additional bits, prior to encoding the information bits, to generate a plurality of duplicated bits; and

wherein encoding the information bits comprises encoding the plurality of duplicated bits.

17. The apparatus of claim 11 , wherein the first bandwidth corresponds to a bandwidth B and the second bandwidth corresponds to a bandwidth mB, wherein m is a positive integer.

18. The apparatus of claim 17 , wherein the bandwidth B is 20 MHz.

19. The apparatus of claim 17 , wherein PHY processor includes:

a plurality of transceivers.

20. The apparatus of claim 19 , further comprising:

a plurality of antennas coupled to the plurality of transceivers.