Explicit beamforming in a high efficiency wireless local area network
A first communication device receives a sounding packet from a second communication device and develops beamforming information based on the sounding packet. The first communication device transmits beamforming feedback to the second communication device, the beamforming feedback including beamforming information for use by the second communication device to beamsteer a data packet to the first communication device, the data packet having a data portion that includes a second number of OFDM tones greater than a first number of OFDM tones in the sounding packet. After transmitting the beamforming feedback, the first communication device receives the data packet from the second communication device, the data packet including one or more data OFDM symbols, each of the one or more data OFDM symbols having the second number of OFDM tones.
1. A method for communication in a wireless communication network, the method comprising:
receiving, at a first communication device, a sounding packet from a second communication device, the sounding packet including a first plurality of training orthogonal frequency division multiplexing (OFDM) symbols, the first plurality of training OFDM symbols corresponding to OFDM tones of respective training OFDM symbols, among the first plurality of training OFDM symbols, having been modulated with training signals, wherein each of the respective training OFDM symbols, among the first plurality of training OFDM symbols, has a first time duration, and wherein each training OFDM symbol among the first plurality of training OFDM symbols includes a first number of OFDM tones on which a training signal is modulated;
developing, at the first communication device, beamforming information using the first plurality of training OFDM symbols, the beamforming information for the first number of OFDM tones;
transmitting, by the first communication device, beamforming feedback to the second communication device, the beamforming feedback including the beamforming information for the first number of OFDM tones, the beamforming information for use by the second communication device to beamsteer a data packet to the first communication device, the data packet having a data portion that includes a second number of OFDM tones greater than the first number of OFDM tones, wherein the beamforming feedback i) includes beamforming information for a first subset of OFDM tones in the data portion of the data packet and ii) omits beamforming information for a second subset of OFDM tones in the data portion of the data packet; and
after transmitting the beamforming feedback, receiving, at the first communication device, the data packet from the second communication device, the data packet including one or more data OFDM symbols in the data portion, each of the one or more data OFDM symbols having i) a second time duration that is longer than the first time duration, and ii) the second number of OFDM tones, wherein OFDM tones of the one or more data OFDM symbols include i) the first subset of OFDM tones beamsteered based on the beamforming feedback that incudes beamforming information for the first subset of OFDM tones and ii) the second subset of OFDM tones beamsteered based on the beamforming feedback that omits beamforming information for the second subset of OFDM tones.
2. The method of claim 1 , wherein the first time duration is shorter than the second time duration by a factor of at least 2.
3. The method of claim 1 , wherein the first time duration is 6.4 μs.
4. The method of claim 3 , wherein the second time duration is 12.8 μs.
5. The method of claim 1 , wherein:
the data packet includes a second plurality of training OFDM symbols, the second plurality of training OFDM symbols corresponding to OFDM tones of respective training OFDM symbols, among the second plurality of training OFDM symbols, having been modulated with training signals, wherein the respective training OFDM symbols, among the second plurality of training OFDM symbols, have a third time duration, and wherein the first time duration of the respective training OFDM symbols among the first plurality of training OFDM symbols is longer than the third time duration of the respective training OFDM symbols among the second plurality of training OFDM symbols; and
the method further comprises:
determining, at the first communication device, channel information using the second plurality of training OFDM symbols, and
processing, at the first communication device, the one or more data OFDM symbols of the data packet using the channel information.
6. The method of claim 5 , wherein:
the first time duration is 6.4 μs; and
the third time duration is 3.2 μs.
7. The method of claim 1 , further comprising:
the data packet includes a second plurality of training OFDM symbols, the second plurality of training OFDM symbols corresponding to OFDM tones of respective training OFDM symbols, among the second plurality of training OFDM symbols, having been modulated with training signals, wherein the respective training OFDM symbols, among the second plurality of training OFDM symbols, have a third time duration, and wherein the first time duration of the respective training OFDM symbols among the first plurality of training OFDM symbols is shorter than the third time duration of the respective training OFDM symbols among the second plurality of training OFDM symbols; and
the method further comprises:
determining, at the first communication device, channel information using the second plurality of training OFDM symbols, and
processing, at the first communication device, the one or more data OFDM symbols of the data packet using the channel information.
8. The method of claim 7 , wherein:
the first time duration is 6.4 μs; and
the third time duration is 12.8 μs.
9. The method of claim 1 , wherein receiving the sounding packet comprises receiving a null data packet (NDP) that omits a data portion.
10. The method of claim 1 , wherein:
the first plurality of training OFDM symbols of the sounding packet corresponds to a plurality of long training field (LTFs); and
the sounding packet further comprises one or more short training fields (STFs).
11. A first communication device, comprising:
a wireless network interface device implemented on one or more integrated circuits (ICs) that are configured to:
receive a sounding packet from a second communication device, the sounding packet including a first plurality of training orthogonal frequency division multiplexing (OFDM) symbols, the first plurality of training OFDM symbols corresponding to OFDM tones of respective training OFDM symbols, among the first plurality of training OFDM symbols, having been modulated with training signals, wherein each of the respective training OFDM symbols, among the first plurality of training OFDM symbols, has a first time duration, and wherein each training OFDM symbol among the first plurality of training OFDM symbols includes a first number of OFDM tones on which a training signal is modulated,
develop beamforming information using the first plurality of training OFDM symbols, the beamforming information for the first number of OFDM tones,
control the wireless network interface device to transmit beamforming feedback to the second communication device, the beamforming feedback including the beamforming information for the first number of OFDM tones, the beamforming information for use by the second communication device to beamsteer a data packet to the first communication device, the data packet having a data portion that includes a second number of OFDM tones greater than the first number of OFDM tones, wherein the beamforming feedback i) includes beamforming information for a first subset of OFDM tones in the data portion of the data packet and ii) omits beamforming information for a second subset of OFDM tones in the data portion of the data packet, and
after the wireless network interface device transmits the beamforming feedback, receive the data packet from the second communication device, the data packet including one or more data OFDM symbols in the data portion, each of the one or more data OFDM symbols having i) a second time duration that is longer than the first time duration, and ii) the second number of OFDM tones, wherein OFDM tones of the one or more data OFDM symbols include i) the first subset of OFDM tones beamsteered based on the beamforming feedback that incudes beamforming information for the first subset of OFDM tones and ii) the second subset of OFDM tones beamsteered based on the beamforming feedback that omits beamforming information for the second subset of OFDM tones.
12. The first communication device of claim 11 , wherein the first time duration is shorter than the second time duration by a factor of at least 2.
13. The first communication device of claim 11 , wherein the first time duration is 6.4 μs.
14. The first communication device of claim 13 , wherein the second time duration is 12.8 μs.
15. The first communication device of claim 11 , wherein:
the data packet includes a second plurality of training OFDM symbols, the second plurality of training OFDM symbols corresponding to OFDM tones of respective training OFDM symbols, among the second plurality of training OFDM symbols, having been modulated with training signals, wherein the respective training OFDM symbols, among the second plurality of training OFDM symbols, have a third time duration, and wherein the first time duration of the respective training OFDM symbols among the first plurality of training OFDM symbols is longer than the third time duration of the respective training OFDM symbols among the second plurality of training OFDM symbols; and
the one or more ICs are further configured to:
determine channel information using the second plurality of training OFDM symbols, and
process the one or more data OFDM symbols of the data packet using the channel information.
16. The first communication device of claim 15 , wherein:
the first time duration is 6.4 μs; and
the third time duration is 3.2 μs.
17. The first communication device of claim 11 , further comprising:
the data packet includes a second plurality of training OFDM symbols, the second plurality of training OFDM symbols corresponding to OFDM tones of respective training OFDM symbols, among the second plurality of training OFDM symbols, having been modulated with training signals, wherein the respective training OFDM symbols, among the second plurality of training OFDM symbols, have a third time duration, and wherein the first time duration of the respective training OFDM symbols among the first plurality of training OFDM symbols is shorter than the third time duration of the respective training OFDM symbols among the second plurality of training OFDM symbols; and
the one or more ICs are further configured to:
determine channel information using the second plurality of training OFDM symbols, and
process the one or more data OFDM symbols of the data packet using the channel information.
18. The first communication device of claim 17 , wherein:
the first time duration is 6.4 μs; and
the third time duration is 12.8 μs.
19. The first communication device of claim 11 , wherein the sounding packet comprises a null data packet (NDP) that omits a data portion.
20. The first communication device of claim 11 , wherein:
the first plurality of training OFDM symbols of the sounding packet corresponds to a plurality of long training field (LTFs); and
the sounding packet further comprises one or more short training fields (STFs).
21. The first communication device of claim 11 , wherein the wireless network interface device comprises one or more transceivers implemented at least partially on the one or more ICs.
22. The first communication device of claim 21 , further comprising:
a host processor coupled to the wireless network interface device.
23. The first communication device of claim 22 , further comprising:
one or more antennas coupled to the one or more transceivers.
24. The first communication device of claim 21 , further comprising:
one or more antennas coupled to the one or more transceivers.