Padding for orthogonal frequency division multiplexing (OFDM) symbols in a wireless communication system

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

generating, at a communication device, the PHY data unit to include i) a PHY preamble, ii) a PHY data portion that follows the PHY preamble, and iii) an extension field that follows the PHY data portion, including:

generating, at the communication device, the PHY preamble,

generating, at the communication device, a plurality of orthogonal frequency division multiplexing (OFDM) symbols corresponding to the PHY data portion of the PHY data unit,

wherein a last occurring OFDM symbol in the plurality of OFDM symbols includes padding bits starting from a boundary within the last occurring OFDM symbol,

determining, at the communication device, a duration of the extension field using a position of the boundary within the last occurring OFDM symbol, and

generating, at the communication device, the extension field to have the determined duration.

2. The method of claim 1 ,

wherein: generating the PHY preamble includes generating the PHY preamble to include a signal field, the signal field including a subfield that indicates the position of the boundary within the last occurring OFDM symbol.

3. The method of claim 2 ,

wherein: generating the PHY preamble includes setting a value of the subfield that indicates the position of the boundary to an integer selected from a set of four different integer values.

4. The method of claim 2 ,

wherein: the subfield also indicates the duration of the extension field.

5. The method of claim 2 ,

wherein: the signal field is a high efficiency signal field A (HE-SIGA).

6. The method of claim 1 , wherein:

generating the PHY preamble includes generating the PHY preamble to include a signal field, the signal field including a subfield that indicates a duration of the extension field.

7. The method of claim 1 , further comprising:

generating coded bits from information bits using a forward error correction code (FEC) encoder; and

adding the padding bits in the last occurring OFDM symbol to the coded bits after generating the coded bits using the FEC encoder.

8. The method of claim 7 , further comprising:

generating, at the communication device, the padding bits, including repeating a subset of the coded bits multiple times.

9. The method of claim 1 , further comprising:

wirelessly transmitting, by the communication device, the PHY data unit.

10. An apparatus, comprising:

a wireless local area network (WLAN) network interface device having one or more integrated circuit (IC) devices configured to:

generate a physical layer (PHY) data unit to include i) a PHY preamble, ii) a PHY data portion that follows the PHY preamble, and iii) an extension field that follows the PHY data portion, including:

generating the PHY preamble,

generating a plurality of orthogonal frequency division multiplexing (OFDM) symbols corresponding to the PHY data portion of the PHY data unit,

wherein a last occurring OFDM symbol in the plurality of OFDM symbols includes padding bits starting from a boundary within the last occurring OFDM symbol,

determining a duration of the extension field using a position of the boundary within the last occurring OFDM symbol,

generating the extension field to have the determined duration, and

control the WLAN network interface device to wirelessly transmit the PHY data unit.

11. The apparatus of claim 10 , wherein the one or more IC devices are further configured to:

generate the PHY preamble to include a signal field, the signal field including a subfield that indicates the position of the boundary within the last occurring OFDM symbol.

12. The apparatus of claim 11 ,

wherein the one or more IC devices are further configured to: set a value of the subfield that indicates the position of the boundary to an integer selected from a set of four different integer values.

13. The apparatus of claim 11 ,

wherein: the subfield also indicates the duration of the extension field.

14. The apparatus of claim 11 ,

wherein: the signal field is a high efficiency signal field A (HE-SIGA).

15. The apparatus of claim 10 ,

wherein the one or more IC devices are further configured to: generate the PHY preamble to include a signal field, the signal field including a subfield that indicates a duration of the extension field.

16. The apparatus of claim 10 ,

wherein the WLAN network interface device comprises:

a forward error correction code (FEC) encoder implemented on the one or more IC devices, the FEC encoder configured to generate coded bits from information bits; and

a post-encoder padding unit implemented on the one or more IC devices, the postencoder padding unit configured to generate the padding bits, and to append the padding bits to a set of coded bits generated by the FEC encoder.

17. The apparatus of claim 16 ,

wherein the post-encoder padding unit is configured to: generate the padding bits at least by repeating a subset of the coded bits multiple times.

18. The apparatus of claim 10 ,

wherein the WLAN network interface device comprises: one or more transceivers.

19. The apparatus of claim 18 ,

further comprising: one or more antennas coupled to the one or more transceivers.