Methods and apparatus for transmission of data at different modulation and/or coding rates

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

receiving first data and second data that correspond to a unit of audio, video, and/or image information;

encoding and modulating the first data and the second data so that a resulting data rate of the first data is less than a resulting data rate of the second data, wherein encoding and modulating the first data and the second data includes

modulating the first data according to a first constellation having a first number of constellation points, and

modulating the second data according to a second constellation that differs from the first constellation at least by having a second number of constellation points higher than the first number of constellation points;

parsing the first data and the second data to a plurality of spatial streams such that each spatial stream of the plurality of spatial streams includes only first data or only second data; and

generating a single PHY data unit that includes the plurality of spatial streams.

2. A method according to claim 1 , wherein encoding and modulating the first data and the second data so that the resulting data rate of the first data is less than the resulting data rate of the second data comprises:

encoding the first data at a first coding rate; and

encoding the second data at a second coding rate higher than the first coding rate.

3. A method according to claim 1 , wherein at least one spatial stream includes first data and second data.

4. A physical layer (PHY) processing unit for generating a PHY data unit for transmission via a communication channel, the PHY processing unit comprising:

a first encoder to encode first data that corresponds to a unit of audio, video, and/or image information;

a second encoder to encode second data that corresponds to the unit of audio, video, and/or image information;

a first modulator to modulate the first data according to a first constellation having a first number of constellation points;

a second modulator to modulate the second data according to a second constellation that differs from the first constellation at least by having a second number of constellation points higher than the first number of constellation points; and

a stream parser to parse the first data and the second data to a plurality of spatial streams such that each spatial stream of the plurality of spatial streams includes only first data or only second data,

wherein the PHY processing unit is configured to

encode and modulate the first data and the second data so that a resulting data rate of the first data is less than a resulting data rate of the second data, and

generate a single PHY data unit that includes the plurality of spatial streams.

5. A PHY processing unit according to claim 4 , further comprising a data parser to parse the first data to the first encoder and to parse the second data to the second encoder.

6. A PHY processing unit according to claim 4 , further comprising a first encoder parser to parse the second data to a first plurality of encoders including the second encoder.

7. A PHY processing unit according to claim 6 , further comprising a second encoder parser to parse the first data to a second plurality of encoders including the first encoder.

8. A PHY processing unit according to claim 4 , wherein the stream parser comprises:

a first stream parser to parse the first data to a first set of spatial streams; and

a second stream parser to parse the second data to a second set of spatial streams.

9. A PHY processing unit according to claim 8 , wherein the padding system includes a second padding unit to add second padding bits after parsing the information bits to the plurality of encoders.