Apparatus and method for channel sounding based on aggregated physical protocol data unit

1. A method for wireless communication between a first apparatus and at least one second apparatus in a wireless local area network (WLAN), the method comprising:

generating an aggregated physical layer protocol data unit (PPDU) comprising a first null data packet (NDP) based on a first protocol standard and a second NDP based on a second protocol standard, wherein the first NDP comprises a first set of fields based on the first protocol standard and the second NDP comprises a second set of fields different from the first set of fields based on the second protocol standard, wherein the first set of fields includes a merged field in which a plurality of fields of the first protocol standard are merged, and wherein the first NDP and the second NDP have a same duration based on the merged field; and

transmitting the aggregated PPDU to the at least one second apparatus, wherein the first NDP and the second NDP are transmitted in different frequency bands.

2. The method of claim 1 , wherein fields included in the first NDP and fields included in the second NDP are at least partially different.

3. The method of claim 1 , wherein a non-NDP of the first protocol standard comprises a first SIG field and a second SIG field, and wherein the merged field of the first NDP corresponds to the first SIG field of the non-NDP and comprises at least one subfield of the second SIG field of the non-NDP.

4. The method of claim 3 , wherein the merged field of the first NDP comprises at least one subfield with a value indicating that a PPDU is an NDP.

5. The method of claim 3 , wherein the merged field of the first NDP comprises at least one symbol modulated based on a first modulation scheme and at least one symbol modulated based on a second modulation scheme.

6. The method of claim 3 , wherein the first NDP comprises a packet extension field and the merged field of the first NDP comprises a subfield indicating a duration of the packet extension field.

7. The method of claim 1 , further comprising:

generating a null data packet announcement (NDPA) frame; and

transmitting a PPDU comprising the NDPA frame to the at least one second apparatus, wherein the NDPA frame comprises a field with a value indicating the first protocol standard and the second protocol standard.

8. A first apparatus for communicating with at least one second apparatus in a wireless local area network (WLAN) system, the first apparatus comprising:

a transceiver; and

processing circuitry configured to:

generate an aggregated physical layer protocol data unit (PPDU) comprising a first null data packet (NDP) based on a first protocol standard and a second NDP based on a second protocol standard, wherein the first NDP comprises a first set of fields based on the first protocol standard and the second NDP comprises a second set of fields different from the first set of fields based on the second protocol standard, wherein the first set of fields includes a merged field in which a plurality of fields of the first protocol standard are merged, and wherein the first NDP and the second NDP have a same duration based on the merged field; and

transmit the aggregated PPDU to the at least one second apparatus through the transceiver, wherein the first NDP and the second NDP are transmitted in different frequency bands.

9. The first apparatus of claim 8 , wherein the first NDP corresponds to a first SIG field among the first SIG field and a second SIG field included in a non-NDP, and comprises at least one subfield of the second SIG field of the non-NDP.

10. The first apparatus of claim 9 , wherein the processing circuitry is configured to set at least one subfield included in the merged field of the first NDP to a value indicating that a PPDU is an NDP.

11. The first apparatus of claim 9 , wherein the merged field of the first NDP comprises a first symbol and a second symbol, and wherein the processing circuitry is configured to generate the first symbol based on a first modulation scheme and generate the second symbol based on a second modulation scheme.

12. The first apparatus of claim 9 , wherein the first NDP comprises a packet extension field and the processing circuitry is configured to set a subfield included in the merged field of the first NDP to a value indicating a duration of the packet extension field.

13. The first apparatus of claim 8 , wherein the processing circuitry is configured to:

set a field included in a null data packet announcement (NDPA) frame to a value indicating the first protocol standard and the second protocol standard; and

transmit a PPDU comprising the NDPA frame to the at least one second apparatus through the transceiver.

14. A second apparatus for communicating with at least one first apparatus in a wireless local area network (WLAN) system, the second apparatus comprising:

a transceiver; and

processing circuitry configured to:

receive, from the first apparatus through the transceiver, an aggregated physical layer protocol data unit (PPDU) including a first null data packet (NDP) based on a first protocol standard and a second NDP based on a second protocol standard, wherein the first NDP comprises a first set of fields based on the first protocol standard and the second NDP comprises a second set of fields different from the first set of fields based on the second protocol standard, wherein the first set of fields includes a merged field in which a plurality of fields of the first protocol standard are merged, and wherein the first NDP and the second NDP have a same duration based on the merged field; and

estimate a channel based on the first NDP, wherein the first NDP and the second NDP are transmitted in different frequency bands.

15. The second apparatus of claim 14 , wherein the first NDP corresponds to a first SIG field among the first SIG field and a second SIG field included in a non-NDP, and comprises at least one subfield of the second SIG field of the non-NDP.

16. The second apparatus of claim 15 , wherein the processing circuitry is configured to identify a value indicating that a PPDU is an NDP, and wherein the value is in a subfield included in the merged field of the first NDP.

17. The second apparatus of claim 15 , wherein the merged field of the first NDP comprises a first symbol and a second symbol, and wherein the processing circuitry is configured to:

demodulate the first symbol and the second symbol based on a first modulation scheme; and

identify whether the second symbol is modulated based on a second symbol modulation scheme.

18. The second apparatus of claim 17 , wherein, when the second symbol is identified as being modulated based on the second symbol modulation scheme, the processing circuitry is configured to perform automatic gain control based on a third field of the first NDP subsequent to the first field of the first NDP.

19. The second apparatus of claim 15 , wherein the first NDP comprises a packet extension field, and the processing circuitry is configured to identify a duration of the packet extension field based on a value of a subfield included in the merged field of the first NDP.

20. The second apparatus of claim 14 , wherein the processing circuitry is configured to:

generate a feedback frame comprising information about the estimated channel; and

transmit a PPDU comprising the feedback frame to the first apparatus through the transceiver.