Apparatus, computer readable medium, and method for alignment of long training fields in a high efficiency wireless local-area network

1. An apparatus of a high-efficiency (HE) wireless device, the apparatus comprising memory: and, circuitry configured to:

determine if a HE long training field (HE-LTF) portion of a HE physical layer convergence procedure (PLCP) protocol data unit (HE-PPDU) is to be extended;

if the HE-LTF portion is to be extended, configure the HE-LTF portion to use a longer symbol duration than a symbol duration of one or more other HE-LTF portions of one or more other HE-PPDUs that are to be concurrently transmitted, wherein the HE-LTF portion is to start at a same start time and end at a same end time as the one or more other HE-LTF portions, wherein the longer symbol duration is 6.4 μs or 12.8 μs; and

simultaneously transmit the HE-PPDU and the one or more other HE-PPDUs in accordance with orthogonal frequency division multiple access (OFDMA).

2. The apparatus of claim 1 , wherein the HE-LTF portion is to be extended if a HE-LTF portion of the one or more other HE-PPDUs has a longer duration than the HE-LTF portion of the HE-PPDU.

3. The apparatus of claim 2 , wherein the HE-LTF portion is to be extended to have a same duration as a longest duration of the HE-LTF portion of the one or more other HE-PPDUs.

4. The apparatus of claim 1 , wherein the circuitry is configured to determine the start time and the end time based on a received trigger frame.

5. The apparatus of claim 1 , wherein the circuitry is configured to determine a number of long training symbols to generate for the HE-LTF portion based on the longer symbol duration and a number of space time streams allocated to a HE wireless device to which the HE-PPDU is to be transmitted.

6. The apparatus of claim 1 , wherein the circuitry is further configured to transmit the HE-PPDU in accordance with multiple-user multiple-input multi-output (MU-MIMO).

7. The apparatus of claim 1 , wherein the circuitry is further configured to:

generate a resource allocation comprising a channel allocation, a duration, and a number of space-time-streams; and

determine to extend the HE-LTF portion based on the number of space-time-streams allocated to a HE wireless device to which the HE-PPDU is to be transmitted.

8. The apparatus of claim 1 , wherein the longer symbol duration is at least one from the following group: 12.8 μs, 2 times a symbol duration of another HE-LTF portion of one or more other HE-PPDUs, and 4 times a symbol duration of a legacy standard.

9. The apparatus of claim 1 , wherein the circuitry is further configured to:

determine to use the longer symbol duration based on a performance of a second HE wireless device; and

transmit the HE-PPDU in accordance with OFDMA to the second HE wireless device.

10. The apparatus of claim 1 , wherein the HE wireless device is one from the following group: a master station, an access point, a station, and a HE station.

11. The apparatus of claim 1 , wherein the circuitry is further configured to: repeat one or more additional HE-LTF, and wherein the one or more additional HE-LTFs are one from the following group: duplicates of other HE-LTFs of the HE-LTF portion, duplicates of other HE-LTF fields of the HE-LTF portion with a different overlay, and different sequences from other HE-LTF fields of the HE-LTF portion.

12. The apparatus of claim 1 , further comprising transceiver circuitry coupled to the memory; and one or more antennas coupled to the transceiver circuitry.

13. An apparatus of claim 1 , wherein the memory is configured to store the HE-PPDU.

14. A method performed by a high-efficiency (HE) wireless device, the method comprising:

determining if a HE long training field (HE-LTF) portion of a HE physical layer convergence procedure (PLCP) protocol data unit (HE-PPDU) is to be extended;

if the HE-LTF portion is to be extended, configure the HE-LTF portion to use a longer symbol duration than a symbol duration of one or more other HE-LTF portions of one or more other HE-PPDUs that are to be concurrently transmitted, wherein the HE-LTF portion is to start at a same start time and end at a same end time as the one or more other HE-LTF portions, wherein the longer symbol duration is 6.4 μs or 12.8 μs; and

simultaneously transmitting the HE-PPDU and the one or more other HE-PPDUs in accordance with orthogonal frequency division multiple access (OFDMA).

15. The method of claim 14 , wherein the HE-LTF portion is to be extended if a HE-LTF portion of the one or more other HE-PPDUs has a longer duration than the HE-LTF portion of the HE-PPDU.

16. The method of claim 14 , wherein the HE-LTF portion is to be extended to have a same duration as a longest duration of the HE-LTF portion of the one or more other HE-PPDUs.

17. A non-transitory computer-readable storage medium that stores instructions for execution by one or more processors, the instructions to configure the one or more processors to cause a high-efficiency (HE) wireless device to:

determine if a HE long training field (HE-LTF) portion of a HE physical layer convergence procedure (PLCP) protocol data unit (HE-PPDU) is to be extended;

if the HE-LTF portion is to be extended, configure the HE-LTF portion to use a longer symbol duration than a symbol duration of one or more other HE-LTF portions of one or more other HE-PPDUs that are to be concurrently transmitted, wherein the HE-LTF portion is to start at a same start time and end at a same end time as the one or more other HE-LTF portions, wherein the longer symbol duration is 6.4 μs or 12.8 μs; and

simultaneously transmit the HE-PPDU and the one or more other HE-PPDUs in accordance with orthogonal frequency division multiple access (OFDMA).

18. The non-transitory computer-readable storage medium of claim 17 , wherein the HE-LTF portion is to start at a same start time and end at a same end time as the one or more other HE-LTF portions of the one or more other HE-PPDUs, and wherein the HE-LTF portion is to be extended if a HE-LTF portion of the one or more other HE-PPDUs has a longer duration than the HE-LTF portion of the HE-PPDU.