Data unit format for single user beamforming in long-range wireless local area networks (WLANs)

1. A method comprising:

receiving a plurality of data units each having a preamble, wherein the preamble of each data unit of the plurality of data units includes (i) a first preamble portion, and (ii) a second preamble portion following the first preamble portion;

detecting a symbol constellation rotation of one or more orthogonal frequency division multiplexing (OFDM) symbols in the first preamble portion of each data unit;

determining, based on each detected symbol constellation rotation, whether the preamble of the respective data unit conforms to a first format;

when it is determined that the preamble of the respective data unit conforms to the first format, processing the second preamble portion of the respective data unit according to the first format; and

when it is determined that the preamble of the respective data unit does not conform to the first format,

(i) determining whether one or more information bits in the first preamble portion of the respective data unit indicate a single-user data unit or a multi-user data unit,

(ii) when it is determined that the one or more information bits in the first preamble portion of the respective data unit indicate a single-user data unit, processing the second preamble portion of the respective data unit according to a second format different than the first format, and

(iii) when it is determined that the one or more information bits in the first preamble portion of the respective data unit indicate a multi-user data unit, processing the second preamble portion of the respective data unit according to a third format different than the first format and the second format.

2. A method according to claim 1 , wherein determining, based on each detected symbol constellation rotation, whether the preamble of the respective data unit conforms to a first format includes:

determining that the preamble of the respective data unit conforms to the first format when the detected symbol constellation rotation corresponds to one of (i) binary phase shift key (BPSK) modulation or (ii) quaternary binary phase shift key (QBPSK) modulation; and

determining that the preamble of the respective data unit does not conform to the first format when the detected symbol constellation rotation corresponds to the other one of (i) BPSK modulation or (ii) QBPSK modulation.

3. A method according to claim 1 , wherein:

detecting a symbol constellation rotation of one or more OFDM symbols in the first preamble portion of each data unit includes detecting a symbol constellation rotation of one or more OFDM symbols in a signal (SIG) field of the first preamble portion of each data unit; and

the SIG field of the first preamble portion of each data unit indicates a plurality of physical layer (PHY) parameters associated with the respective data unit.

4. A method according to claim 3 , wherein determining whether one or more information bits in the first preamble portion of the respective data unit indicates a single-user data unit or a multi-user data unit includes:

determining whether one or more information bits in the SIG field of the first preamble portion of the respective data unit indicates a single-user data unit or a multi-user data unit.

5. A method according to claim 1 , wherein processing the second preamble portion of the respective data unit according to the first format includes:

utilizing a long training field (LTF) at a beginning of the second preamble portion of the respective data unit to estimate a channel response.

6. A method according to claim 1 , wherein processing the second preamble portion of the respective data unit according to the second format includes:

utilizing a short training field (STF) at a beginning of the second preamble portion of the respective data unit to set an automatic gain control level of a receiver; and

utilizing one or more long training fields (LTFs) of the second preamble portion of the respective data unit to estimate one or more channel responses corresponding to one or more respective spatial streams associated with a single user.

7. A method according to claim 6 , wherein processing the second preamble portion of the respective data unit according to the second format further includes:

utilizing an additional LTF of the second preamble portion of the respective data unit to estimate a channel response of a first spatial stream of the one or more respective spatial streams, wherein

the additional LTF of the second preamble portion is identical to an initial LTF of the one or more LTFs of the second preamble portion, and

the additional LTF of the second preamble portion follows the one or more LTFs of the second preamble portion.

8. A method according to claim 1 , wherein processing the second preamble portion of the respective data unit according to the third format includes:

utilizing a short training field (STF) at a beginning of the second preamble portion of the respective data unit to set an automatic gain control level of a receiver; and

utilizing one or more long training fields (LTFs) of a plurality of LTFs in the second preamble portion of the respective data unit to estimate one or more channel responses, wherein

the one or more channel responses correspond to one or more respective spatial streams associated with a single user, and

the plurality of LTFs in the second preamble portion includes LTFs associated with a plurality of users.

9. A method according to claim 8 , wherein processing the second preamble portion of the respective data unit according to the third format further includes:

decoding information bits in a signal (SIG) field of the second preamble portion, wherein

the SIG field of the second preamble portion follows the plurality of LTFs of the second preamble portion, and

the information bits in the SIG field of the second preamble portion indicate one or more physical layer (PHY) parameters associated with (i) the respective data unit and (ii) the plurality of users.

10. A method according to claim 1 , further comprising:

detecting a symbol constellation rotation of one or more additional OFDM symbols in the first preamble portion of each data unit; and

determining, based on each detected symbol constellation rotation of the one or more additional OFDM symbols, whether the respective data unit corresponds to a first channel bandwidth.

11. A method according to claim 10 , wherein:

detecting a symbol constellation rotation of one or more OFDM symbols in the first preamble portion of each data unit includes detecting a symbol constellation rotation of a first OFDM symbol in a signal (SIG) field of the first preamble portion of each data unit;

detecting a symbol constellation rotation of one or more additional OFDM symbols in the first preamble portion of each data unit includes detecting a symbol constellation rotation of a second OFDM symbol in the SIG field of the first preamble portion of each data unit; and

the SIG field of the first preamble portion of each data unit indicates a plurality of physical layer (PHY) parameters associated with the respective data unit.

12. A method according to claim 11 , wherein the first OFDM symbol in the SIG field of the first preamble portion follows the second OFDM symbol in the SIG field of the first preamble portion.

13. An apparatus comprising:

a network interface configured to

receive a plurality of data units each having a preamble, wherein the preamble of each data unit of the plurality of data units includes (i) a first preamble portion, and (ii) a second preamble portion following the first preamble portion,

detect a symbol constellation rotation of one or more orthogonal frequency division multiplexing (OFDM) symbols in the first preamble portion of each data unit,

determine, based on each detected symbol constellation rotation, whether the preamble of the respective data unit conforms to a first format,

when it is determined that the preamble of the respective data unit conforms to the first format, process the second preamble portion of the respective data unit according to the first format, and

when it is determined that the preamble of the respective data unit does not conform to the first format,

(i) determine whether one or more information bits in the first preamble portion of the respective data unit indicate a single-user data unit or a multi-user data unit,

(ii) when it is determined that the one or more information bits in the first preamble portion of the respective data unit indicate a single-user data unit, process the second preamble portion of the respective data unit according to a second format different than the first format, and

(iii) when it is determined that the one or more information bits in the first preamble portion of the respective data unit indicate a multi-user data unit, process the second preamble portion of the respective data unit according to a third format different than the first format and the second format.

14. An apparatus according to claim 13 , wherein the network interface is configured to determine, based on each detected symbol constellation rotation, whether the preamble of the respective data unit conforms to a first format at least in part by:

determining that the preamble of the respective data unit conforms to the first format when the detected symbol constellation rotation corresponds to one of (i) binary phase shift key (BPSK) modulation or (ii) quaternary binary phase shift key (QBPSK) modulation; and

determining that the preamble of the respective data unit does not conform to the first format when the detected symbol constellation rotation corresponds to the other one of (i) BPSK modulation or (ii) QBPSK modulation.

15. An apparatus according to claim 13 , wherein:

the network interface is configured to detect a symbol constellation rotation of one or more OFDM symbols in the first preamble portion of each data unit at least in part by detecting a symbol constellation rotation of one or more OFDM symbols in a signal (SIG) field of the first preamble portion of each data unit; and

the SIG field of the first preamble portion of each data unit indicates a plurality of physical layer (PHY) parameters associated with the respective data unit.

16. An apparatus according to claim 15 , wherein the network interface is configured to determine whether one or more information bits in the first preamble portion of the respective data unit indicate a single-user data unit or a multi-user data unit at least in part by:

determining whether one or more information bits in the SIG field of the first preamble portion of the respective data unit indicate a single-user data unit or a multi-user data unit.

17. An apparatus according to claim 13 , wherein the network interface is configured to process the second preamble portion of the respective data unit according to the first format at least in part by:

utilizing a long training field (LTF) at a beginning of the second preamble portion of the respective data unit to estimate a channel response.

18. An apparatus according to claim 13 , wherein the network interface is configured to process the second preamble portion of the respective data unit according to the second format at least in part by:

utilizing a short training field (STF) at a beginning of the second preamble portion of the respective data unit to set an automatic gain control level of a receiver; and

utilizing one or more long training fields (LTFs) of the second preamble portion of the respective data unit to estimate one or more channel responses corresponding to one or more respective spatial streams associated with a single user.

19. An apparatus according to claim 18 , wherein the network interface is further configured to process the second preamble portion of the respective data unit according to the second format by:

utilizing an additional LTF of the second preamble portion of the respective data unit to estimate a channel response of a first spatial stream of the one or more respective spatial streams, wherein

the additional LTF of the second preamble portion is identical to an initial LTF of the one or more LTFs of the second preamble portion, and

the additional LTF of the second preamble portion follows the one or more LTFs of the second preamble portion.

20. An apparatus according to claim 13 , wherein the network interface is configured to process the second preamble portion of the respective data unit according to the third format at least in part by:

utilizing a short training field (STF) at a beginning of the second preamble portion of the respective data unit to set an automatic gain control level of a receiver; and

utilizing one or more long training fields (LTFs) of a plurality of LTFs in the second preamble portion of the respective data unit to estimate one or more channel responses, wherein

the one or more channel responses correspond to one or more respective spatial streams associated with a single user, and

the plurality of LTFs in the second preamble portion includes LTFs associated with a plurality of users.

21. An apparatus according to claim 20 , wherein the network interface is further configured to process the second preamble portion of the respective data unit according to the third format by:

decoding information bits in a signal (SIG) field of the second preamble portion, wherein

the SIG field of the second preamble portion follows the plurality of LTFs of the second preamble portion, and

the information bits in the SIG field of the second preamble portion indicate one or more physical layer (PHY) parameters associated with (i) the respective data unit and (ii) the plurality of users.