Data unit format for single user beamforming in long-range wireless local area networks (WLANs)
A method includes receiving data units each having a preamble with first and second preamble portions, detecting symbol constellation rotations of OFDM symbols in the first preamble portions, and determining, based on the detected rotations, whether the preambles conform to a first format. The method also includes, when it is determined that a preamble conforms to the first format, processing the second preamble portion according to the first format, and, when it is determined that a preamble does not conform to the first format, (i) determining whether information bits in the first preamble portion indicate a single- or multi-user data unit, (ii) when it is determined that the information bits indicate a single-user data unit, processing the second preamble portion according to a second format, and (iii) when it is determined that the information bits indicate a multi-user data unit, processing the second preamble portion according to a third format.
1. A method comprising:
receiving, at a communication device, a physical layer (PHY) data unit having a preamble, wherein the preamble includes (i) a first preamble portion, and (ii) a second preamble portion following the first preamble portion;
determining, at the communication device, whether a modulation of a first orthogonal frequency division multiplexing (OFDM) symbol in the first preamble portion is rotated with respect to an expected modulation of the first OFDM symbol of a first PHY format defined by a communication protocol;
when it is determined that the modulation of the first OFDM symbol is not rotated with respect to the expected modulation of the first OFDM symbol of the first PHY format, determining, at the communication device, that the preamble of the PHY data unit conforms to the first PHY format;
when it is determined that the preamble of the PHY data unit conforms to the first PHY format, processing, at the communication device, the second preamble portion of the PHY data unit according to the first PHY format; and
when it is determined that the modulation of the first OFDM symbol is rotated with respect to the expected modulation of the first OFDM symbol of the first PHY format,
(i) determining, at the communication device, whether a modulation of a second OFDM symbol in the first preamble portion is rotated with respect to an expected modulation of the second OFDM symbol of a second PHY format defined by the communication protocol, the second PHY format different than the first PHY format,
(ii) when it is determined that the modulation of the second OFDM symbol is not rotated with respect to the expected modulation of the second OFDM symbol of the second PHY format, determining, at the communication device, that the preamble of the PHY data unit conforms to the second PHY format, and processing, at the communication device, the second preamble portion of the PHY data unit according to the second PHY format, and
(iii) when it is determined that the modulation of the second OFDM symbol is rotated with respect to the expected modulation of the second OFDM symbol of the second PHY format, determining, at the communication device, that the preamble of the PHY data unit conforms to a third PHY format different than the first PHY format and the second PHY format, and processing, at the communication device, the second preamble portion of the PHY data unit according to the third PHY format.
2. The method of claim 1 , wherein:
when the PHY data unit conforms to the first PHY format:
the first OFDM symbol is modulated using binary phase shift keying (BPSK);
when the PHY data unit conforms to the second PHY format:
the first OFDM symbol is modulated using quaternary binary phase shift keying (QBPSK); and
when the PHY data unit conforms to the third PHY format:
the first OFDM symbol is modulated using QBPSK.
3. The method of claim 2 , wherein:
when the PHY data unit conforms to the second PHY format:
the second OFDM symbol is modulated using QBPSK; and
when the PHY data unit conforms to the third PHY format:
the second OFDM symbol is modulated using BPSK.
4. The method of claim 1 , wherein:
when the PHY data unit conforms to the first PHY format:
the first OFDM symbol and the second OFDM symbol correspond to a field that includes training signals, wherein the field that includes training signals precedes a signal field that conforms to the first PHY format;
when the PHY data unit conforms to the second PHY format:
the first OFDM symbol and the second OFDM symbol correspond to a signal field that conforms to the second PHY format; and
when the PHY data unit conforms to the third PHY format:
the first OFDM symbol and the second OFDM symbol correspond to a signal field that conforms to the third PHY format.
5. The method of claim 1 , wherein the second PHY format corresponds to single-user, non-beamformed communications.
6. The method of claim 1 , wherein the first PHY format corresponds to communications at a bandwidth smaller than bandwidths used with the second PHY format and the third PHY format.
7. The method of claim 1 , wherein the second preamble portion of the third PHY format includes an additional signal field not included in the first PHY format and the second PHY format.
8. The method of claim 1 , wherein the first preamble portion includes:
a short training field; and
a long training field with a double guard interval adjacent the short training field.
9. The method of claim 1 , wherein receiving the PHY data unit includes:
receiving the PHY data unit via a communication channel below 1 GHz.
10. The method of claim 1 , wherein receiving the PHY data unit includes:
when the PHY data unit corresponds to the first PHY format, receiving the PHY data unit via a communication channel having a bandwidth of 1 MHz.
11. An apparatus comprising:
a wireless network interface device having one or more integrated circuits configured to:
receive a physical layer (PHY) data unit having a preamble, wherein the preamble includes (i) a first preamble portion, and (ii) a second preamble portion following the first preamble portion,
determine whether a modulation of a first orthogonal frequency division multiplexing (OFDM) symbol in the first preamble portion is rotated with respect to an expected modulation of the first OFDM symbol of a first PHY format defined by a communication protocol,
when it is determined that the modulation of the first OFDM symbol is not rotated with respect to the expected modulation of the first OFDM symbol of the first PHY format, determine that the preamble of the PHY data unit conforms to the first PHY format, and
when it is determined that the preamble of the PHY data unit conforms to the first PHY format, process the second preamble portion of the PHY data unit according to the first PHY format; and
wherein the one or more integrated circuits are further configured to: when it is determined that the modulation of the first OFDM symbol is rotated with respect to the expected modulation of the first OFDM symbol of the first PHY format,
(i) determine whether a modulation of a second OFDM symbol in the first preamble portion is rotated with respect to an expected modulation of the second OFDM symbol of a second PHY format defined by the communication protocol, the second PHY format different than the first PHY format,
(ii) when it is determined that the modulation of the second OFDM symbol is not rotated with respect to the expected modulation of the second OFDM symbol of the second PHY format, determine that the preamble of the PHY data unit conforms to the second PHY format, and process the second preamble portion of the PHY data unit according to the second PHY format, and
(iii) when it is determined that the modulation of the second OFDM symbol is rotated with respect to the expected modulation of the second OFDM symbol of the second PHY format, determine that the preamble of the PHY data unit conforms to a third PHY format different than the first PHY format and the second PHY format, and process the second preamble portion of the PHY data unit according to the third PHY format.
12. The apparatus of claim 11 , wherein:
when the PHY data unit conforms to the first PHY format:
the first OFDM symbol is modulated using binary phase shift keying (BPSK);
when the PHY data unit conforms to the second PHY format:
the first OFDM symbol is modulated using quaternary binary phase shift keying (QBPSK); and
when the PHY data unit conforms to the third PHY format:
the first OFDM symbol is modulated using QBPSK.
13. The apparatus of claim 12 , wherein:
when the PHY data unit conforms to the second PHY format:
the second OFDM symbol is modulated using QBPSK; and
when the PHY data unit conforms to the third PHY format:
the second OFDM symbol is modulated using BPSK.
14. The apparatus of claim 12 , wherein the first PHY format corresponds to communications at a bandwidth smaller than bandwidths used with the second PHY format and the third PHY format.
15. The apparatus of claim 11 , wherein:
when the PHY data unit conforms to the first PHY format:
the first OFDM symbol and the second OFDM symbol correspond to a field that includes training signals, wherein the field that includes training signals precedes a signal field that conforms to the first PHY format;
when the PHY data unit conforms to the second PHY format:
the first OFDM symbol and the second OFDM symbol correspond to a signal field that conforms to the second PHY format; and
when the PHY data unit conforms to the third PHY format:
the first OFDM symbol and the second OFDM symbol correspond to a signal field that conforms to the third PHY format.
16. The apparatus of claim 11 , wherein the second PHY format corresponds to single-user, non-beamformed communications.
17. The apparatus of claim 11 , wherein the second preamble portion of the third PHY format includes an additional signal field not included in the first PHY format and the second PHY format.
18. The apparatus of claim 11 , wherein the first preamble portion includes:
a short training field; and
a long training field with a double guard interval adjacent the short training field.
19. The apparatus of claim 11 , wherein the wireless network interface device is configured to:
receive the PHY data unit via a communication channel below 1 GHz.
20. The apparatus of claim 11 , wherein the wireless network interface device is configured to:
when the PHY data unit corresponds to the first PHY format, receive the PHY data unit via a communication channel having a bandwidth of 1 MHz.
21. The apparatus of claim 11 , wherein the wireless network interface device comprises:
one or more wireless transceivers implemented on the one or more integrated circuit devices.
22. The apparatus of claim 21 , further comprising:
one or more antennas coupled to the one or more wireless transceivers.