Hybrid automatic repeat request for wireless local area network

1. A method for communicating in a wireless local area network (WLAN) that includes a first communication device and a second communication device, the method comprising:

generating, at the first communication device, a first physical layer (PHY) data unit as part of a hybrid automatic repeat request (HARQ) session, the first PHY data unit having a first plurality of media access control (MAC) protocol data units (MPDUs) including a first MPDU, wherein generating the first PHY data unit includes: for each MPDU in the first plurality of MPDU,

modulating and packing data of the MPDU into orthogonal frequency division multiplexing (OFDM) symbols such that each MPDU of the first plurality of MPDUs corresponds to a separate group of OFDM symbols in the first PHY data unit, each group of OFDM symbols in the first PHY data unit being formed with data from only a single respective MPDU of the first plurality of MPDUs wherein a constellation mapper is configured to map an interleaved sequence of bits in the single respective MPDU to constellation points corresponding to different subcarriers of an OFDM symbol;

transmitting, by the first communication device, the first PHY data unit;

determining, at the first communication device, that the second communication device did not acknowledge successfully receiving a set of one or more MPDUs among the first plurality of MPDUs, the set of one or more MPDUs including the first MPDU;

generating, at the first communication device, a second PHY data unit as part of the HARQ session, the second PHY data unit having a second plurality of MPDUs, including:

including at least the first MPDU in the second plurality of MPDUs in response to determining that the second communication device did not acknowledge successfully receiving the set of one or more MPDUs, and for each MPDU in the second plurality of MPDUs,

modulating and packing data of the MPDU into OFDM symbols such that each MPDU of the second plurality of MPDUs corresponds to a separate group of OFDM symbols in the second PHY data unit, each group of OFDM symbols in the second PHY data unit being formed with data from only a single respective MPDU of the second plurality of MPDUs; and

transmitting, by the first communication device, the second PHY data unit.

2. The method of claim 1 , wherein: generating the second PHY data unit includes generating the second PHY data unit to include

i) at least one MPDU, in the second plurality of MPDUs, that is an initial transmission in the HARQ session, and

ii) a PHY signal field that includes a subfield set to indicate a number of MPDUs, among the second plurality of MPDUs, that correspond to HARQ retransmissions.

3. The method of claim 2 , wherein: the first plurality of MPDUs includes a first MPDU and a second MPDU; the method further comprises

receiving from the second communication device a block acknowledgment to the first PHY data unit that includes

i) a negative acknowledgment for the first MPDU, and

ii) a positive acknowledgment for the second MPDU; and

determining that the second communication device did not acknowledge successfully receiving the set of one or more MPDUs among the first plurality of MPDUs includes

determining that the second communication device did not successfully receive the first MPDU based on the negative acknowledgment for the first MPDU.

4. The method of claim 1 , wherein: the method further comprises

establishing, with the first communication device, a transmit opportunity (TXOP) period corresponding to the HARQ session;

transmitting the first PHY data unit comprises transmitting the first PHY data unit during the TXOP period; and

transmitting the second PHY data unit comprises transmitting the second PHY data unit during the TXOP period.

5. The method of claim 4 , wherein establishing the TXOP period includes:

transmitting, by the first communication device, a request-to-send frame; and

receiving, at the first communication device, a clear-to-send frame in response to the request-to-send frame.

6. The method of claim 4 , wherein establishing the TXOP period includes:

transmitting, by the first communication device, a HARQ control frame; and

receiving, at the first communication device, a response frame that acknowledges HARQ control frame.

7. The method of claim 1 , wherein: generating the first PHY data unit includes

generating the first PHY data unit to include a first PHY signal field with a first subfield set to indicate that the first PHY data unit corresponds to the HARQ session; and

generating the second PHY data unit includes

generating the second PHY data unit to include a second PHY signal field with a second subfield set to indicate that the second PHY data unit corresponds to the HARQ session.

8. The method of claim 1 , wherein: generating the first PHY data unit includes

disabling a scrambler of the first communication device while generating the first PHY data unit; and generating the second PHY data unit includes

disabling the scrambler while generating the second PHY data unit.

9. The method of claim 1 , wherein: generating the first PHY data unit includes, separately for each MPDU of the first plurality of MPDUs:

encoding a bit stream for the MPDU into a coded bit stream, and

modulating and packing the coded bit stream for the MPDU into OFDM symbols such that each MPDU of the first plurality of MPDUs corresponds to a separate group of OFDM symbols in the first PHY data unit; and generating the second PHY data unit includes, separately for each MPDU of the second plurality of MPDUs:

encoding a bit stream for the MPDU into a coded bit stream, and

modulating and packing the coded bit stream for the MPDU into OFDM symbols such that each MPDU of the second plurality of MPDUs corresponds to a separate group of OFDM symbols in the second PHY data unit.

10. The method of claim 9 , wherein: generating the first PHY data unit includes, separately for each MPDU of the first plurality of MPDUs:

generating a service field for the MPDU, and

adding the service field to the coded bit stream for the MPDU; and generating the second PHY data unit includes, separately for each MPDU of the second plurality of MPDUs:

generating a service field for the MPDU, and

adding the service field to the coded bit stream for the MPDU.

11. An apparatus, comprising:

a wireless local area network (WLAN) interface device associated with a first communication device, the network interface device having one or more integrated circuits (ICs) configured to:

generate a first physical layer (PHY) data unit as part of a hybrid automatic repeat request (HARQ) session, the first PHY data unit having a first plurality of media access control (MAC) protocol data units (MPDUs) including a first MPDU, including: for each MPDU in the first plurality of MPDU,

modulate and pack data of the MPDU into orthogonal frequency division multiplexing (OFDM) symbols such that each MPDU of the first plurality of MPDUs corresponds to a separate group of OFDM symbols in the first PHY data unit, each group of OFDM symbols in the first PHY data unit being formed with data from only a single respective MPDU of the first plurality of MPDUs wherein a constellation mapper is configured to map an interleaved sequence of bits in the single respective MPDU to constellation points corresponding to different subcarriers of an OFDM symbol; and the one or more ICs are further configured to:

control the WLAN interface device to transmit the first PHY data unit,

determine that a second communication device did not acknowledge successfully receiving a set of one or more MPDUs among the first plurality of MPDUs, the set of one or more MPDUs including the first MPDU, and

generate a second PHY data unit as part of the HARQ session, the second PHY data unit having a second plurality of MPDUs, wherein generating the second PHY data unit comprises: including at least the first MPDU in the second plurality of MPDUs in response to determining that the second communication device did not acknowledge successfully receiving the set of one or more MPDUs, and for each MPDU in the second plurality of MPDUs,

modulate and pack data of the MPDU into OFDM symbols such that each MPDU of the second plurality of MPDUs corresponds to a separate group of OFDM symbols in the second PHY data unit, each group of OFDM symbols in the second PHY data unit being formed with data from only a single respective MPDU of the second plurality of MPDUs; and wherein the one or more ICs are further configured to

control the WLAN interface device to transmit the second PHY data unit.

12. The apparatus of claim 11 , wherein the one or more ICs are further configured to: generate the second PHY data unit to include

i) at least one MPDU, in the second plurality of MPDUs, that is an initial transmission in the HARQ session, and

ii) a PHY signal field that includes a subfield set to indicate a number of MPDUs, among the second plurality of MPDUs, that correspond to HARQ retransmissions.

13. The apparatus of claim 12 , wherein: the first plurality of MPDUs includes a first MPDU and a second MPDU; and the one or more ICs are further configured to

determine that the second communication device did not successfully receive the first MPDU based on a negative acknowledgment for the first MPDU in a block acknowledgment from the second communication device, the block acknowledgment corresponding to the first PHY data unit, wherein the block acknowledgment includes

i) the negative acknowledgment for the first MPDU, and

ii) a positive acknowledgment for the second MPDU.

14. The apparatus of claim 11 , wherein the one or more ICs are further configured to:

establish a transmit opportunity (TXOP) period corresponding to the HARQ session;

control the WLAN interface device to transmit the first PHY data unit during the TXOP period; and

control the WLAN interface device to transmit the second PHY data unit during the TXOP period.

15. The apparatus of claim 14 , wherein the one or more ICs are further configured to:

control the WLAN interface device to transmit a request-to-send frame for establishing the TXOP period; and

receive a clear-to-send frame transmitted by the second communication device in response to the request-to-send frame, the clear-to-send frame for establishing the TXOP period.

16. The apparatus of claim 14 , wherein the one or more ICs are further configured to:

control the WLAN interface device to transmit a HARQ control frame for establishing the TXOP period; and

receive a response frame transmitted by the second communication device that acknowledges HARQ control frame, the response frame for establishing the TXOP period.

17. The apparatus of claim 11 , wherein the one or more ICs are further configured to:

generate the first PHY data unit to include a first PHY signal field with a first subfield set to indicate that the first PHY data unit corresponds to the HARQ session; and

generate the second PHY data unit to include a second PHY signal field with a second subfield set to indicate that the second PHY data unit corresponds to the HARQ session.

18. The apparatus of claim 11 , wherein: the WLAN network interface device includes

a scrambler implemented on the one or more ICs; and the one or more ICs are further configured to:

disable the scrambler while generating the first PHY data unit, and

disable the scrambler while generating the second PHY data unit.

19. The apparatus of claim 11 , wherein: the WLAN network interface device includes

a PHY processing unit implemented on the one or more ICs; the PHY processing unit is configured to

generate the first PHY data unit and the second PHY data unit; the PHY processing unit is configured to, separately for each MPDU of the first plurality of MPDUs:

encode a bit stream for the MPDU into a coded bit stream, and

modulate and pack the coded bit stream for the MPDU into OFDM symbols such that each MPDU of the first plurality of MPDUs corresponds to a separate group of OFDM symbols in the first PHY data unit; and the PHY processing unit is further configured to, separately for each MPDU of the second plurality of MPDUs:

encode a bit stream for the MPDU into a coded bit stream, and

modulate and pack the coded bit stream for the MPDU into OFDM symbols such that each MPDU of the second plurality of MPDUs corresponds to a separate group of OFDM symbols in the second PHY data unit.

20. The apparatus of claim 19 , wherein the one or more ICs are further configured to: separately for each MPDU of the first plurality of MPDUs:

generate a service field for the MPDU, and

add the service field to the coded bit stream for the MPDU; and separately for each MPDU of the second plurality of MPDUs:

generate a service field for the MPDU, and

add the service field to the coded bit stream for the MPDU.

21. The apparatus of claim 11 , wherein the WLAN network interface device comprises:

a plurality of transceivers implemented using the one or more ICs.

22. The apparatus of claim 21 , further comprising:

a plurality of antennas coupled to the plurality of transceivers.