Signal fields in a high efficiency wireless local area network (WLAN) data unit

1. A method for generating an orthogonal frequency division multiple access (OFDMA) physical layer (PHY) data unit that includes data for multiple receiving devices, the OFDMA PHY data unit for transmission via a communication channel, the method comprising:

generating a first signal field to be included in a preamble of the OFDMA PHY data unit, wherein the first signal field includes formatting information for a second signal field to be included in the OFDMA PHY data unit, wherein the generating the first signal field includes setting one or more bits in a subfield of the first signal field to a value that indicates a number of orthogonal frequency division multiplexing (OFDM) symbols in the second signal field;

generating the second signal field according to the formatting information in the first signal field, wherein the second signal field includes:

a first subfield that includes a value, selected from a codebook, that indicates resource allocation for the multiple devices, wherein each value in the codebook corresponds to a particular mapping between (i) a plurality of basic resource units and (ii) the multiple receiving devices, wherein each basic resource unit in the plurality of basic resource units includes a respective block of consecutive OFDM tones, and

a plurality of second subfields that respectively include formatting information, corresponding to a data portion of the OFDMA PHY data unit, for different ones of the multiple receiving devices;

generating the data portion according to the formatting information in the second signal field; and

generating the preamble to include at least the first signal field and the second signal field; and

generating the OFDMA PHY data unit to include the preamble and the data portion.

2. The method of claim 1 , wherein generating the first signal field includes generating the first signal field to include an indication of a modulation and coding scheme (MCS) used for generating the second signal field.

3. The method of claim 2 , wherein the MCS used for generating the second signal field is a first MCS, and wherein generating the first signal field includes using a second MCS for the first signal field, wherein the second MCS is different from the first MCS.

4. The method of claim 1 , wherein generating the first signal field includes generating the first signal field to include an identifier of a network in which the PHY data unit is to be transmitted.

5. The method of claim 4 , wherein generating the first signal field to include the identifier of the network comprises generating the first signal field to include an identifier of a basic service set (BSS).

6. The method of claim 1 , wherein:

the PHY data unit is a multi-user (MU) data unit directed to multiple receiving device, and

generating the second signal field includes generating (i) a common subfield that includes common formatting information for the multiple receiving devices and (ii) a plurality of user-specific subfields that respectively include formatting information for ones of the multiple receiving devices.

7. The method of claim 6 , wherein generating the second signal field includes generating the second signal field such that different ones of the user-specific subfields will be transmitted in parallel in different frequency sub-bands of the PHY data unit.

8. The method of claim 1 , wherein the first subfield includes fewer bits than a number of basic resource units in the plurality of resource units.

9. An apparatus, comprising:

a network interface device having one or more integrated circuits configured to

generate a first signal field to be included in a preamble of an orthogonal frequency division multiple access (OFDMA) physical layer (PHY) data unit that includes data for multiple receiving devices, wherein the first signal field includes formatting information for a second signal field to be included in the OFDMA PHY data unit, wherein the generating the first signal field includes setting one or more bits in a subfield of the first signal field to a value that indicates a number of orthogonal frequency division multiplexing (OFDM) symbols in the second signal field;

generate the second signal field according to the formatting information in the first signal field, wherein the second signal field includes:

a first subfield that includes a value, selected from a codebook, that indicates resource allocation for the multiple devices, wherein each value in the codebook corresponds to a particular mapping between (i) a plurality of basic resource units and (ii) the multiple receiving devices, wherein each basic resource unit in the plurality of basic resource units includes a block of consecutive OFDM tones, and

a plurality of second subfields that respectively include formatting information corresponding to a data portion of the OFDMA PHY data unit, for different ones of the multiple receiving devices;

generate the data portion according to the formatting information in the second signal field; and

generate the preamble to include at least the first signal field and the second signal field; and

generate the PHY data unit to include the preamble and the data portion.

10. The apparatus of claim 9 , wherein the one or more integrated circuits are configured to generate the first signal field to include an indication of a modulation and coding scheme (MCS) used for generating the second signal field.

11. The apparatus of claim 9 , wherein the MCS used for generating the second signal field is a first MCS, and wherein the one or more integrated circuits are configured to generate the first signal field using a second MCS, wherein the second MCS is different from the first MCS.

12. The apparatus of claim 9 , wherein the one or more integrated circuits are configured to generate the first signal field to include an identifier of a network in which the PHY data unit is to be transmitted.

13. The apparatus of claim 12 , wherein the one or more integrated circuits are configured to generate the first signal field to include the identifier of the network at least by generating the first signal field to include an identifier of a basic service set (BSS).

14. The apparatus of claim 12 , wherein:

the PHY data unit is a multi-user (MU) data unit directed to multiple receiving device, and

the one or more integrated circuits are configured to

generate (i) a common subfield that includes common formatting information for the multiple receiving devices and (ii) a plurality of user-specific subfields that respectively include formatting information for ones of the multiple receiving devices, and

generate the second signal field to include the common subfield and the plurality of user-specific subfields.

15. The apparatus of 16 , wherein the one or more integrated circuits are configured to generate the second signal field such that different ones of the user-specific subfields will be transmitted in parallel in different frequency sub-bands of the PHY data unit.

16. The apparatus of claim 9 , wherein the first subfield includes fewer bits than a number of basic resource units in the plurality of resource units.