Communication apparatus and communication method for long training field for distributed tone resource unit

Abstract

Communication apparatuses and methods for determining long training field (LTF) for distributed tone resource unit (DRU) are provided. One exemplary embodiment provides a first communication apparatus comprising: circuitry, which in operation, generates a trigger-based physical layer protocol data unit (TB PPDU) comprising a long training field (LTF) and a data field, the data field comprising a distributed tone resource unit (DRU) subcarrier of a DRU and the LTF comprising an even-indexed LTF subcarrier that is based on the DRU subcarrier; and a transmitter, which in operation, transmits the TB PPDU in the DRU.

Description

DescriptionTitle of Invention: COMMUNICATION APPARATUS AND COMMUNICATION METHOD FOR LONG TRAINING FIELD FOR DISTRIBUTED TONE RESOURCE UNITTECHNICAL FIELD

[0001] The present disclosure relates to communication methods and apparatuses, and more particularly relates to methods and apparatuses for determining long training field (LTF) for distributed tone resource unit (DRU).BACKGROUND

[0002] Distributed tone resource unit (DRU) consisting of subcarriers spreading across a certain bandwidth for a transmission signal such as trigger-based physical layer protocol data unit (TB PPDU) has been considered as one of the features for wireless local area network (WLAN) system, such as IEEE 802.11 .

[0003] The DRU may also be incorporated in future WLAN generations or communication standards such as IEEE802.11, IEEE802.15, 3GPP. Long training field (LTF) schemes, which is used for channel estimation at receivers, for DRU have also been discussed in IEEE 802.11- 24 / 1097r0 (Thoughts on UHR-LTF design for DRU) and IEEE 802.11-24 / 1114r0 (UHR-LTF Design for DRU).

[0004] However, there has not been adequate discussion on the implementation of LTF for DRU.

[0005] There is thus a need for communication apparatuses and methods that can solve the above-mentioned issue. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the disclosure.SUMMARY

[0006] Non-limiting and exemplary embodiments facilitate providing communication apparatuses and communication methods for determining LTF for DRU.

[0007] According to an aspect of the present disclosure, there is provided a first communication apparatus comprising: circuitry, which in operation, generates a trigger-basedphysical layer protocol data unit (TB PPDU) comprising a long training field (LTF) and a data field, the data field comprising a distributed tone resource unit (DRU) subcarrier of a DRU and the LTF comprising an even-indexed LTF subcarrier that is based on the DRU subcarrier; and a transmitter, which in operation, transmits the TB PPDU in the DRU.

[0008] According to another aspect of the present disclosure, there is provided a second communication apparatus comprising: circuitry, which in operation, generates a trigger frame indicating an allocation of a distributed tone resource unit (DRU) subcarrier and a number of long training field (LTF) symbols associated with an even-indexed LTF subcarrier for a first communication apparatus, the first communication apparatus configured to generate a triggerbased physical layer protocol data unit (TB PPDU) comprising a LTF and a data field, the data field comprising the DRU subcarrier and the LTF comprising the even-indexed LTF subcarrier ; and a transmitter, which in operation, transmits the trigger frame to the first communication apparatus.

[0009] According to another aspect of the present disclosure, there is provided a communication method implemented by a first communication apparatus comprising: generating a trigger-based physical layer protocol data unit (TB PPDU) comprising a long training field (LTF) and a data field, the data field comprising a distributed tone resource unit (DRU) subcarrier of a DRU and the LTF comprising an even-indexed LTF subcarrier that is based on the DRU subcarrier; and transmitting the TB PPDU in the DRU.

[0010] According to another aspect of the present disclosure, there is provided a communication method comprising: generating a trigger frame indicating an allocation of a distributed tone resource unit (DRU) subcarrier and a number of long training field (LTF) symbols associated with an even-indexed LTF subcarrier for a first communication apparatus, the first communication apparatus configured to modulate the even-indexed LTF subcarrier based on an index of the DRU subcarrier for a trigger-based physical layer protocol data unit (TB PPDU); and transmitting the trigger frame to the first communication apparatus.

[0011] It should be noted that general or specific embodiments may be implemented as a system, a method, an integrated circuit, a computer program, a storage medium, or any selective combination thereof. Additional benefits and advantages of the disclosed embodiments will become apparent from the specification and drawings. The benefits and / or advantages may be individually obtained by the various embodiments and features of thespecification and drawings, which need not all be provided in order to obtain one or more of such benefits and / or advantages.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying figures where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to illustrate various embodiments and to explain various principles and advantages in accordance with present embodiments.

[0013] FIG. 1 depicts an illustration for long training field (LTF) subcarrier allocation according to various embodiments of the present disclosure.

[0014] FIG. 2 depicts a table for LTF subcarriers for 26-tone distributed tone resource units (DRUs) with only even-indexed subcarriers in a 40 MHz trigger-based physical layer protocol data unit (TB PPDU) according to various embodiments of the present disclosure.

[0015] FIG. 3 depicts an illustration of a DRU and its corresponding LTF subcarriers for 26- tone DRUs with only even-indexed subcarriers in a 40 MHz TB PPDU according to various embodiments of the present disclosure.

[0016] FIG. 4 depicts a table for LTF subcarriers for 26-tone DRUs with only odd-indexed subcarriers in a 40 MHz TB PPDU according to various embodiments of the present disclosure.

[0017] FIG. 5 depicts an illustration of a DRU and its corresponding LTF subcarriers for 26- tone DRUs with only odd-indexed subcarriers in a 40 MHz TB PPDU according to various embodiments of the present disclosure.

[0018] FIG. 6 depicts a table for LTF subcarriers for 52-tone DRUs in a 40 MHz TB PPDU according to various embodiments of the present disclosure.

[0019] FIG. 7 depicts an illustration of a DRU and its corresponding LTF subcarriers for 52- tone DRUs in a 40 MHz TB PPDU according to various embodiments of the present disclosure.

[0020] FIG. 8 depicts a flowchart for LTF symbol generation according to various embodiments of the present disclosure.

[0021] FIG. 9 depicts an illustration of an exemplary uplink (UL) multi-user (MU) transmission according to various embodiments of the present disclosure.

[0022] FIG. 10 depicts an illustration of an exemplary TB PPDU according to various embodiments of the present disclosure.

[0023] FIG. 11 depicts a table illustrating how an initial number of LTF symbols is calculated according to various embodiments of the present disclosure.

[0024] FIG. 12 depicts a table illustrating an example DRU allocation in a 40 MHz TB PPDU for an UL MU transmission according to various embodiments of the present disclosure.

[0025] FIG. 13 depicts a table illustrating another example DRU allocation in a 40 MHz TB PPDU for an UL MU transmission according to various embodiments of the present disclosure.

[0026] FIG. 14 depicts a flowchart illustrating a process by which an access point (AP) calculates a number of LTF symbols present in a TB PPDU according to various embodiments of the present disclosure.

[0027] FIG. 15 depicts an exemplary spatial stream (SS) allocation subfield format according to various embodiments of the present disclosure.

[0028] FIG. 16 depicts a table illustrating a matrix PLTFassignment for two DRUs that have overlapped LTF subcarriers according to various embodiments of the present disclosure.

[0029] FIG. 17 depicts an exemplary transmitter block diagram for LTF according to various embodiments of the present disclosure.

[0030] FIG. 18 depicts an exemplary PPDU with DRUs and regular RUs (RRUs) according to various embodiments of the present disclosure.

[0031] FIG. 19 depicts a table illustrating an exemplary LTF scheme indication for a DRU according to various embodiments of the present disclosure.

[0032] Fig. 20 shows an exemplary flowchart Illustrating a communication method according to various embodiments of the present disclosure.

[0033] FIG. 21 shows an exemplary flowchart illustrating another communication method according to various embodiments of the present disclosure.

[0034] FIG. 22 shows an exemplary schematic view of a communication apparatus that can be implemented for specifying LTF for DRU according to various embodiments of the present disclosure.

[0035] Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been depicted to scale.DETAILED DESCRIPTION

[0036] The following detailed description is merely exemplary in nature and is not intended to limit the embodiments or the application and uses of the embodiments. There is no intention to be bound by any theory presented in the preceding background or this detailed description. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the disclosure.

[0037] Some embodiments of the present disclosure will be described, by way of example only, with reference to the drawings. Like reference numerals and characters in the drawings refer to like elements or equivalents.

[0038] In the following paragraphs, certain exemplifying embodiments are explained with reference to one or more mobile terminals (also referred to herein as devices, peer devices, communication apparatuses, STAs (stations) or other similar terms) which may operate as an access point (AP) or a non-AP STA.

[0039] In the context of IEEE 802.11 (Wi-Fi) technologies, a mobile terminal is a communication apparatus that has the capability to use the IEEE 802.11 protocol. Based on the IEEE 802.11-2020 definition, a mobile terminal can be any device that contains an IEEE 802.11 -conformant media access control (MAC) and physical layer (PHY) interface to the wireless medium (WM).

[0040] For example, a mobile terminal may be any device such as a laptop, a desktop personal computer (PC), a personal digital assistant (PDA), an access point ora mobile phone in a wireless local area network (WLAN) environment. The mobile terminal here may be fixed or mobile.

[0041] Likewise, an AP, which may be interchangeably referred to as a wireless access point (WAP) or AP multi-link device (AP MLD) in the context of IEEE 802.11 (Wi-Fi) technologies, is a communication apparatus that allows mobile terminals in a WLAN to connect to a wired or another wireless network. The AP may be connected to a router (e.g., via a wired network) as a standalone device, but it can also be integrated with or employed in the router. A potential AP is used herein to describe a device (e.g., a mobile terminal) that can function both as an AP and as a non-AP depending on the circumstances, and can start, or in some embodiments restore, the operation of a wireless network.

[0042] A mobile terminal in a WLAN may operate as an AP at different occasions, and vice versa. This is because communication apparatuses in the context of IEEE 802.11 (Wi-Fi) technologies may include both non-AP hardware components and AP hardware components. In this manner, the communication apparatuses may switch between a non-AP mode and an AP mode, based on actual WLAN conditions and / or requirements.

[0043] Unless explicitly indicated otherwise, it will be appreciated that, the disclosure should be applicable to various generations of IEEE802.11 protocols and other standards and / or technologies in wireless communication involving similar features.

[0044] As mentioned above, the LTF for DRU in a TB PPDU has not been specified. In the present disclosure, an LTF scheme for DRU is thus proposed to address this issue and advantageously enable efficient transmission of TB PPDU and other PPDUs.

[0045] For example, a STA transmitting a TB PPDU in a DRU (e.g., comprising one or more even-indexed and / or odd-indexed DRU subcarriers) may modulate an even-indexed subcarrier set (e.g., comprising one or more even-indexed LTF subcarriers) in an OFDM symbol for LTF generation. The even-indexed LTF subcarrier(s) may be overlapped with the even-indexed DRU subcarrier(s) and / or even-indexed subcarrier(s) (which are not DRU subcarriers) adjacent to the odd-indexed DRU subcarrier(s). Advantageously, the resultingOFDM symbol has two identical periods in the time domain. Thus, it can be truncated by half, leading to a shorter LTF symbol duration.

[0046] In an implementation, a STA may be configured to generate a TB PPDU comprising a long training field (LTF) and a data field, the data field comprising a DRU subcarrier of a DRU and the LTF comprising an even-indexed LTF subcarrier that is based on the DRU subcarrier. The TB PPDU may then be transmitted in the DRU. Further, an AP may be configured to generate a trigger frame indicating an allocation of the DRU subcarrier and a number of LTF symbols associated with the even-indexed LTF subcarrier for the STA, and transmit the trigger frame to the STA prior to the transmission of the TB PPDU. The LTF field may be positioned in a preamble of the TB PPDU, while the DRU may be utilized for the subcarriers within the data field of the TB PPDU. The purpose of the LTF is to enable a receiver (in this case, an AP that receives the TB PPDU) to estimate the channels for the DRU subcarriers. In the present disclosure, even-indexed subcarriers are used for the LTF, resulting in time domain symbols for the LTF that consist of two identical halves (e.g., a first half and a second half of the time-domain symbol for the LTF are the same). Thus, only half of the symbol needs to be transmitted, which advantageously reduces overhead. It will be appreciated that although TB PPDUs are used as examples in the present disclosure, it is also possible to utilize the methods proposed herein for other PPDUs as well.

[0047] FIG. 1 depicts an illustration 100 for LTF subcarrier allocation according to various embodiments of the present disclosure, in which LTF subcarriers are overlapped with even- indexed DRU subcarriers and / or even-indexed subcarriers (which are not DRU subcarriers) adjacent to odd-indexed DRU subcarriers. In a case A, for a DRU 104 with only even-indexed subcarriers, LTF subcarriers 102 are the same as the DRU subcarriers. In a case B, for a DRU 108 with only odd-indexed subcarriers, LTF subcarriers 106 are the DRU subcarriers shifted by one subcarrier. In a case C, for a DRU 112 with both even and odd-indexed subcarriers, LTF subcarriers 110 consist of the even-indexed DRU subcarriers and the odd-indexed DRU subcarriers shifted by one subcarrier. It will be appreciated that the cases depicted in FIG. 1 are for illustrative purposes only. The LTF subcarrier patterns depend on the specific DRU tone plan and are not limited to the patterns shown in the figures. Advantageously, channel interpolation for odd-indexed DRU subcarriers may have limited performance loss thanks to the adjacent LTF subcarriers.

[0048] FIG. 2 depicts a table 200 for LTF subcarriers for 26-tone DRUs with only even- indexed subcarriers in a 40 MHz TB PPDU according to case A as described in FIG. 1 above.x;m; y (e.g., as shown in DRU subcarrier column 204 and LTF subcarriers column 206) represents subcarrier indices starting from x and ending at y with an increment of m for each of DRU indexes DRU 1, DRU 3, DRU 6, DRU 8, DRU 11 , DRU 13, DRU 14, DRU 16 and DRU 18 (see DRU index column 202). FIG. 3 further depicts an illustration 300 of the DRU and its corresponding LTF subcarriers for 26-tone DRUs with only even-indexed subcarriers in a 40 MHz TB PPDU according to the case A. It will be appreciated that illustration 300 only shows subcarriers from -242 to -222.

[0049] FIG. 4 depicts a table 400 for LTF subcarriers for 26-tone DRUs with only odd- indexed subcarriers in a 40 MHz TB PPDU according to case B as described in FIG. 1 above. x:m: y (e.g., as shown in DRU subcarrier column 404 and LTF subcarriers column 406) represents subcarrier indices starting from x and ending at y with an increment of m for each of DRU indexes DRU 2, DRU 4, DRU 5, DRU 7, DRU 9, DRU 10, DRU 12, DRU 15 and DRU 17 (see DRU index column 402). FIG. 5 further depicts an illustration 500 of the DRU and its corresponding LTF subcarriers for 26-tone DRUs with only odd-indexed subcarriers in a 40 MHz TB PPDU according to the case B. It will be appreciated that illustration 500 only shows subcarriers from -242 to -222.

[0050] FIG. 6 depicts a table 600 for LTF subcarriers for 52-tone DRUs in a 40 MHz TB PPDU according to case C as described in FIG. 1 above. x: m: y (e.g., as shown in DRU subcarrier column 604 and LTF subcarriers column 606) represents subcarrier indices starting from x and ending at y with an increment of m for each of DRU indexes DRU 1 , DRU 2, DRU 3, DRU 4, DRU 5, DRU 6, DRU 7, and DRU 8 (see DRU index column 602). FIG. 7 further depicts an illustration 700 of the DRU and its corresponding LTF subcarriers for 52-tone DRUs in a 40 MHz TB PPDU according to the case C. It will be appreciated that illustration 700 only shows subcarriers from -242 to -222.

[0051] FIG. 8 depicts a flowchart 800 for LTF symbol generation (e.g., a process by which a STA which is assigned a DRU generates LTF symbols for TB PPDU transmission) according to various embodiments of the present disclosure. In a step 802, it is determined whether there are any odd-indexed subcarriers in an assigned DRU. If it is determined that there are no odd- indexed subcarriers in the assigned DRU, the process proceeds to step 806 in which the LTF subcarriers which are the same as the DRU subcarriers are modulated, and then proceeds to step 812 in which half of the OFDM symbol associated with the LTF subcarriers is truncated, and the process ends. On the other hand, if it is determined that there are odd-indexed subcarriers in the assigned DRU in step 802, the process proceeds to step 804 in which it isdetermined whether there are any even-indexed subcarriers in the assigned DRU. If it is determined that there are no even-indexed subcarriers in the assigned DRU, the process proceeds to step 808 in which the LTF subcarriers (e.g., which are the DRU subcarriers shifted by one subcarrier) are modulated, and then proceeds to step 812 in which half of the OFDM symbol associated with the LTF subcarriers is truncated, and the process ends. On the other hand, if it is determined that there are even-indexed subcarriers in the assigned DRU at step 804, the process proceeds to step 810 in which the LTF subcarriers (e.g., which are the even- indexed DRU subcarriers and the odd-indexed DRU subcarriers shifted by one subcarrier) are modulated, and then proceeds to step 812 in which half of the OFDM symbol associated with the LTF subcarriers is truncated, and the process ends.

[0052] FIG. 9 depicts an illustration 900 of an exemplary uplink (UL) multi-user (MU) transmission according to various embodiments of the present disclosure. An AP 902 transmits a trigger frame 904 to solicit a TB PPDU response, and a STA 906 transmits a TB PPDU 908 in response to the trigger frame 904. It will be appreciated that there may be more than one STAs (e.g., up to STA 910) in which each of the more than one STAs are configured to transmit a TB PPDU in response to the trigger frame 904 (e.g., STA 910 also transmitting a TB PPDU 912 in response to the trigger frame 904).

[0053] An example of the TB PPDU may be as shown in TB PPDU format 1000 of FIG. 10, which may comprise of an L-STF field 1002, an L-LTF field 1004, an L-SIG field 1006, an RL- SIG field 1008, a U-SIG field 1010, an STF field 1012, an LTF field 1014, a Data field 1016 (e.g., for carrying one or more PSDU(s)) and a PE field 1018. The SIG, STF and LTF fields may have a prefix derived from the name of a future WLAN generation. For example, in UHR WLAN, these fields may be named as UHR-SIG, UHR-STF and UHR-LTF respectively. Further, the LTF field 1014 may comprise WLTFLTF symbols for multiple-input multiple-output (MIMO) channel estimation at the AP.

[0054] A trigger frame sent by an AP may indicate DRU allocation and a number of spatial streams (Nss) for each STA in a User Info field of the trigger frame, and indicate NLTFin a Common Info field of the trigger frame. In an implementation, NLTFmay be greater than or equal to the maximum value of the initial number of LTF symbols (initial NLTF) for each assigned DRU r, in which r = 0,1, ••• ,NDRU- 1, which is the index of the DRU, and wherein NDRUrepresents the number of assigned DRU(s). An initial NLTFfor a DRU r may be based on a sum of the number of spatial streams at the DRU r (Nss r) and the number of spatial streams at a DRU r' (NSS rl) whose LTF subcarriers are overlapped with the DRU r. NSS rl= 0 if the LTF subcarriers for DRU r are not overlapped with any other assigned DRUs.Referring to table 1100 of FIG. 11, an initial NLTFfor a DRU r (e.g., each entry at column 1104) may be NSS r+ NSS r, when NSS r+ NSS rl(e.g., each entry at column 1102) is 1, 2, 4, 6 or 8 . Further, the initial NLTFfor the DRU r may be NSS r+ NSS r, + 1 when NSS r+ NSS rlis 3, 5 or 7. Advantageously, this enables the AP to estimate the channels for multiple DRUs whose LTF subcarriers are overlapped.

[0055] FIG. 12 depicts a table 1200 illustrating an example DRU allocation in a 40 MHz TB PPDU for an UL MU transmission with non-overlapping LTF subcarriers according to various embodiments of the present disclosure. For each DRU (e.g., each DRU index 0, 1, 2 and 3 shown in column 1202, having DRU subcarriers of 52-tone DRU 1, DRU 3, DRU 2 and DRU 4 respectively as shown in column 1204, with its corresponding LTF subcarriers shown in each respective row in column 1206), its LTF subcarriers are not overlapped with those for the other DRUs. Thus, for each of the DRUs, the corresponding NSS r, = 0 (e.g., as shown in column 1210), and an initial WLTF(e.g., initial NLTF= 2 for each DRU as shown in column 1212) for each DRU is equal to each corresponding NSS r(e.g., NSS r= 2 for each DRU as shown in column 1208). Further, the WLTFfor each DRU is the same and is greater than or equal to 2 as shown in column 1214.

[0056] FIG. 13 depicts a table 1300 illustrating another example DRU allocation in a 40 MHz TB PPDU for an UL MU transmission according to various embodiments of the present disclosure. Each DRU index 0, 1, 2, 3, 4, 5 and 6 is shown in column 1302, having DRU subcarriers of 26 -tone or 52-tone DRU 1 , DRU 2, DRU 5, DRU 3, DRU 7, DRU 6 and DRU 8 respectively as shown in column 1304, with its corresponding LTF subcarriers shown in each respective row in column 1306.

[0057] For DRU 5 and DRU 6, their LTF subcarriers are not overlapped with those for the other DRUs (NSS r, = 0 as shown in the respective row for DRU 5 and DRU 5 in column 1310). Thus, for each of the DRUs 5 and 6, the corresponding NSS r, = 0 (e.g., as shown in their respective row in column 1310), and an initial NLTFfor DRU 5 and DRU 6 (e.g., initial NLTF= 4 for DRU 5 and DRU 6 as shown in column 1312) is equal to each corresponding NSS r(e.g., Nss, r= 4 for DRU 5 and DRU 6 as shown in column 1308). As a further example, for DRU 3 and DRU 4, their LTF subcarriers are overlapped with each other e.g., the carrier indices for the LTF subcarriers of DRU 3 and DRU 4 as shown in column 1306 are identical to one another. It will be appreciated that there is only one DRU (DRU3) that has overlapping LTF subcarriers with DRU4, and the initial number of LTF symbols NLTFwill be based on the sum of Nss,3(e.g., 2) and Nss 4(e.g., 2). For DRU 0 or DRU 1, its LTF subcarriers are overlapped with half of theLTF subcarriers for DRU 2. Furthermore, the NLTFfor all the DRUs is greater than or equal to 4 as shown in column 1314.

[0058] FIG. 14 depicts a flowchart 1400 illustrating a process by which an access point (AP) calculates a number of LTF symbols present in a TB PPDU according to various embodiments of the present disclosure. At step 1402, r is set to zero and incremented for cycling through DRU r e.g., starting from a DRU 0. At step 1404, it is determined whether r > NRU- 1. If it is determined that r is not greater than NDRU- 1, the process proceeds to step 1408 in which it is determined whether LTF subcarriers for DRU r are overlapped with LTF subcarriers for other DRUs. If it is determined that there are LTF subcarriers for DRU r that are overlapped with LTF subcarriers for other DRUs, the process proceeds to step 1410 in which a DRU r' whose LTF subcarriers are overlapped with those for DRU r is identified. The process then proceeds to step 1412 in which an initial NLTFfor DRU r is calculated based on Nss r+ Nss r', and then proceeds to step 1406 in which r is incremented by one, and then the process returns to step 1404. On the other hand, if it is determined at step 1408 that there is no LTF subcarrier for DRU r that is overlapped with LTF subcarriers for other DRUs, the process proceeds to step 1412 in which an initialLTFfor DRU r is calculated based on NSS r+ NSS r, (e.g., NSS r'=0), and then proceeds to step 1406 in which r is incremented by one, and then the process returns to step 1404. Furthermore, if it is determined at step 1404 that r > NRU- 1, the process proceeds to step 1414 e.g., at which NLTFis greater than or equal to the maximum value of the initial NLTFfor each DRU r, and the process ends.

[0059] In an implementation, LTF subcarriers may be modulated by their corresponding values of LTF sequence, and then multiplied by entries of a matrix PLTFbased on the LTF symbol index and spatial stream index. The value of the LTF sequence at subcarrier k (LTFfc) may be 0 if fc does not correspond to one of the LTF subcarriers. For fc corresponding to one of the LTF subcarriers, LTFfcmay be either 1 or -1 to minimize a peak-to-average power ratio (PAPR) associated with the time domain LTF symbols. Further, PLTFis a unitary matrix. For example, PLTF= P4x4when NLTF< 4, PLTF= P6x6when NLTF= 6, PLTF= P8X8when NLTF= 8. It will be appreciated that the matrices P4x4, P6x6, and P8X8are as defined in the 802.11 standard.

[0060] Referring to table 1600 of FIG. 16, if two assigned DRUs (e.g., having DRU 0 and DRU 1 as shown in column 1602) have overlapping LTF subcarriers, different rows of PLTFmay be allocated to each corresponding STA. An indication for the rows of PLTFallocated to aSTA can utilize an SS Allocation subfield of a User Info field in a trigger frame (e.g., the trigger frame may indicate an allocation of a row of a PLTFmatrix for a communication apparatus, and the communication apparatus may apply the PLTFmatrix to an even-indexed LTF subcarrier based on the allocation). An example of an SS Allocation subfield format 1500 is shown in FIG. 15. For example, the Number of Spatial Streams subfield 1504 may be set to Nssminus 1. This is also shown in column 1608 of table 1600, in which the number of SS subfield indicates T since an assigned Nssas shown in column 1604 for both DRU index 0 and 1 is ‘2’. Further, the Starting Spatial Stream subfield 1502 may be set to the starting row of PLTFminus 1 . This is also shown in column 1606 of table 1600, in which the Starting Spatial Stream subfield for DRU index 0 indicates ‘0’ because assigned rows of PLTFis ‘1 to 2’ as shown in column 1610, and the Starting Spatial Stream subfield for DRU index 1 indicates *2' because assigned rows of PLTFfor DRU index 1 is ‘3 to 4’ as shown in column 1610. Advantageously, the existing SS allocation subfield can be utilized to allocate rows of PLTFwithout introducing any new subfield in the trigger frame. Furthermore, it is advantageously possible to maintain orthogonality between the spatial streams.

[0061] FIG. 17 depicts an exemplary transmitter block diagram 1700 for LTF according to various embodiments of the present disclosure. An LTF field may be constructed by the following steps as illustrated in the transmitter block diagram 1700. In a step 1702, an LTF sequence may be generated. In a step 1704, a PLTFmatrix may be applied to the LTF sequence. For example, a LTFfcmay be multiplied by [PLTF]s+m,nfor a n-th symbol in a m-th spatial stream, wherein [PLTF]s+m,nindicates an element in row s + m and column n of the matrix PLTF, and where s may be indicated in a Starting Spatial Stream subfield. In a step 1706, Cyclic Shift Diversity (CSD) may be applied for each spatial stream. In a step 1708, a spatial mapping matrix may be applied. In a step 1710, an inverse discrete Fourier transform (IDFT) may be computed for each of the spatial mapping output. In a step 1712, half of the time domain symbol associated with each IDFT output may be truncated. In a step 1714, a guard interval (Gl) may be inserted and windowing may be applied for each LTF symbol including Gl, e.g., Gl + the truncated output. In a step 1716, a resulting complex baseband waveform associated with each transmit chain may be upconverted to a radio frequency (RF) signal according to a center frequency of a desired channel and transmitted.

[0062] In an UL orthogonal frequency-division multiple access (OFDMA) transmission, for example referring to an exemplary PPDU 1800 of FIG. 18, one or more STAs may be assigned DRUs in one frequency subblock 1802 and one or more other STAs may be assigned RRUs (Regular RUs) in another frequency subblock 1804. RRU refers to an RU whose subcarriersare not spreading across a certain bandwidth, such as the RUs defined in 802.11ax / be. In this scenario, NLTFmay be greater than or equal to a maximum value of an initial NLTFfor each assigned DRU and RRU. The initial NLTFfor a RRU can be calculated using the method in 802.11 ax / be, and the initial NLTFfor a DRU may be calculated based on the above described method in FIG. 11.

[0063] Further, the LTF scheme for TB PPDU transmission may be indicated in a Gl AND LTF Type subfield in a Common Info field of a trigger frame, or other similar subfield in the trigger frame. For example, referring to table 1900 of FIG. 19, Gl AND LTF Type subfield value may be set to 1 (as shown in row 1902) to indicate the proposed LTF scheme + 1.6 ps Gl (under column 1906) for DRU, or to indicate 2x LTF + 1.6 ps Gl (under column 1904) for RRU. Gl AND LTF Type subfield value may be set to 0 to indicate 1x LTF + 1.6 ps Gl for RRU, and to 2 to indicate 4x LTF + 3.2 ps Gl for RRU (as shown in column 1904). 1x LTF, 2x LTF, and 4x LTF for RRU are specified in the technical specifications for Institute of Electrical and Electronics Engineers (IEEE) P802.11-REVme / D6.0 and IEEE P802.11be / D6.0. It will be appreciated that other similar subfields or a new subfield in the trigger frame may be utilized instead of the Gl AND LTF Type subfield, and the value may be set to other values depending on the proposed LTF scheme.

[0064] An AP may determine whether to use the proposed LTF scheme for TB PPDU transmission based on DRU allocation. For example, the AP may be configured to indicate the proposed LTF scheme in the trigger frame if all the allocated DRUs have only even- indexed subcarriers. In another example, the AP may be configured to indicate the proposed LTF scheme in the trigger frame if the LTF subcarriers for all the allocated DRUs are not overlapped with each other.

[0065] FIG. 20 shows an exemplary flow diagram 2000 illustrating a communication method according to various embodiments. At step 2002, a trigger-based physical layer protocol data unit (TB PPDU) comprising a long training field (LTF) and a data field is transmitted, the data field comprising a distributed tone resource unit (DRU) subcarrier of a DRU and the LTF comprising an even-indexed LTF subcarrier that is based on the DRU subcarrier. At step 2004, the TB PPDU is transmitted in the DRU.

[0066] FIG. 21 shows an exemplary flow diagram 2100 illustrating another communication method according to various embodiments of the present disclosure. At step 2102, a trigger frame indicating an allocation of a distributed tone resource unit (DRU) subcarrier and anumber of long training field (LTF) symbols associated with an even-indexed LTF subcarrier for a first communication apparatus, the first communication apparatus configured to modulate the even-indexed LTF subcarrier based on an index of the DRU subcarrier for a trigger-based physical layer protocol data unit (TB PPDU). At step 2104, the trigger frame is transmitted to the first communication apparatus.

[0067] FIG. 22 shows an exemplary schematic view of a communication apparatus 2200 that can be implemented for determining LTF for DRU in accordance with the various embodiments. The communication apparatus 2200 may be implemented as a mobile terminal, application host, router, server, non-AP or AP according to various embodiments.

[0068] Various functions and operations of the communication apparatus 2200 are arranged into layers in accordance with a hierarchical model. In the model, lower layers report to higher layers and receive instructions therefrom in accordance with IEEE specifications. For the sake of simplicity, details of the hierarchical model are not discussed in the present disclosure.

[0069] As shown in FIG. 22, the communication apparatus 2200 may include circuitry 2214, at least one radio transmitter 2202, at least one radio receiver 2204 and at least one antenna 2212 (for the sake of simplicity, only one radio receiver and only one antenna is depicted in FIG. 22 for illustration purposes). The circuitry may include at least one controller 2206 for use in software and / or hardware aided execution of tasks it is designed to perform, including control of communications with one or more other devices in a wireless network. The at least one controller 2206 may control at least one transmission signal generator 2208 for generating frames to be sent through the at least one radio transmitter 2202 to one or more other non- APs or APs and at least one receive signal processor 2210 for processing frames received through the at least one radio receiver 2204 from the one or more other non-APs or APs. The at least one transmission signal generator 2208 and the at least one receive signal processor 2210 may be stand-alone modules of the communication apparatus 2200 that communicate with the at least one controller 2206 for the above-mentioned functions. Alternatively, the at least one transmission signal generator 2208 and the at least one receive signal processor 2210 may be included in the at least one controller 2206. It is appreciable to those skilled in the art that the arrangement of these functional modules is flexible and may vary depending on the practical needs and / or requirements. The data processing, storage and other relevant control apparatus can be provided on an appropriate circuit board and / or in chipsets.

[0070] In various embodiments, when in operation, the at least one radio transmitter 2202, at least one radio receiver 2204, and at least one antenna 2212 may be controlled by the at least one controller 2206. Furthermore, while only one radio transmitter 2202 is shown, it will be appreciated that there can be more than one of such transmitters.

[0071] In various embodiments, when in operation, the at least one radio receiver 2204, together with the at least one receive signal processor 2210, forms a receiver of the communication apparatus 2200. The receiver of the communication apparatus 2200, when in operation, provides functions required for processing an information container. While only one radio receiver 2204 is shown, it will be appreciated that there can be more than one of such receivers.

[0072] The communication apparatus 2200, when in operation, provides functions required for determining LTF for DRU. For example, the communication apparatus 2200 may be a first communication apparatus, and the circuitry 2214 may, in operation, generate a TB PPDU comprising a LTF and a data field, the data field comprising a DRU subcarrier of a DRU and the LTF comprising an even-indexed LTF subcarrier that is based on the DRU subcarrier. The transmitter 2202 may, in operation, transmit the TB PPDU in the DRU.

[0073] The DRU subcarrier may be even-indexed, and the even-indexed LTF subcarrier may be overlapped with the DRU subcarrier, The DRU subcarrier may be odd-indexed, and the even-indexed LTF subcarrier may be overlapped with an even-indexed subcarrier adjacent to the DRU subcarrier. The circuitry 2214 may be configured to modulate a plurality of even- indexed LTF subcarriers including the even-indexed LTF subcarrier based on an index of each of a plurality of DRU subcarriers including the DRU subcarrier, and each of the plurality of even-indexed LTF subcarriers may be overlapped with an even-indexed DRU subcarrier or even-indexed subcarrier adjacent to an odd-indexed DRU subcarrier. The transmitter 2202 may be configured to transmit half of each of a plurality of orthogonal frequency domain modulation (OFDM) symbols associated with the modulated plurality of even-indexed LTF subcarriers when transmitting the TB PPDU.

[0074] The receiver 2204 may, in operation, receive a trigger frame from a second communication apparatus prior to the transmission of the TB PPDU, the trigger frame indicating an allocation of the DRU subcarrier, a number of spatial streams for the communication apparatus, and a number of LTF symbols associated with the even-indexed LTF subcarrier. The TB PPDU may include a number of LTF symbols based on the numberof LTF symbols indicated in the trigger frame. The trigger frame may further indicate an LTF scheme in which the even-indexed LTF subcarrier is based on the allocation of the DRU subcarrier, and the circuitry 2214 may be configured to modulate the even-indexed LTF subcarrier based on the LTF scheme. The trigger frame may further indicate an allocation of a row of a PLTFmatrix for the first communication apparatus, and the circuitry 2214 may be configured to apply the PLTFmatrix to the even-indexed LTF subcarrier based on the allocation.

[0075] The communication apparatus 2200 may be a second communication apparatus. The circuitry 2214 may, in operation, generate a trigger frame indicating an allocation of a DRU subcarrier and a number of LTF symbols associated with an even-indexed LTF subcarrier for a first communication apparatus, the first communication apparatus configured to generate a TB PPDU comprising a LTF and a data field, the data field comprising the DRU subcarrier and the LTF comprising the even-indexed LTF subcarrier. The transmitter 2202 may, in operation, transmit the trigger frame to the first communication apparatus.

[0076] The circuitry 2214 may be configured to calculate an initial number of LTF symbols for the DRU subcarrier based on a sum of a number of spatial streams associated with the even-indexed LTF subcarrier and another number of spatial steams whose LTF subcarrier is overlapped with the even-indexed LTF subcarrier associated with the DRU subcarrier. The number of LTF symbols may be greater than or equal to a maximum value associated with the initial number of LTF symbols. The circuitry 2214 may be configured to assign the DRU subcarrier in one frequency subblock for the first communication apparatus and assign a RRU subcarrier in another frequency subblock to a third communication apparatus, and the number of LTF symbols may be greater than or equal to a maximum value associated with both the initial number of LTF symbols for the DRU subcarrier and an initial number of LTF symbols for the RRU subcarrier. The trigger frame may further indicate an allocation of a row of a PLTFmatrix for the first communication apparatus. The trigger frame may indicate the allocation of the row of the PLTFmatrix in a SS allocation subfield. The trigger frame may further indicate an LTF scheme in which the even-indexed LTF subcarrier is based on the allocation of the DRU subcarrier.

[0077] The present disclosure can be realized by software, hardware, or software in cooperation with hardware. Each functional block used in the description of each embodiment described above can be partly or entirely realized by an integrated circuit (IC) such as LSI (Large Scale Integration), and each process described in each embodiment may be controlled partly or entirely by a same LSI or a combination of LSIs. The LSI may be individually formedas chips, or one chip may be formed so as to include a part or all of the functional blocks. The LSI may include a data input and output coupled thereto. The LSI here may be referred to as an IC, a system LSI, a super LSI, an ultra-LSI, a very-large-scale integration (VLSI), or a system on a chip (SoC) depending on the integration scales. However, the technique of implementing an integrated circuit is not limited to the LSI and may be realized by using a dedicated circuit, a general-purpose processor, or a special-purpose processor. In addition, a FPGA (Field Programmable Gate Array) that can be programmed after the manufacture of the LSI or a reconfigurable processor in which the connections and the settings of circuit cells disposed inside the LSI can be reconfigured may be used. The present disclosure can be realized as digital processing and / or analogue processing. The functional blocks could be integrated with various integrated circuit technologies which are not limited to those mainly used at present. Biotechnology can also be applied.

[0078] The present disclosure can be realized by any kind of apparatus, device or system having a function of communication, which is referred to as a communication apparatus.

[0079] Some non-limiting examples of such communication apparatus may include a phone (e.g., cellular (cell) phone, smart phone), a tablet, a personal computer (PC) (e.g., laptop, desktop, netbook), a camera (e.g., digital still / video camera), a digital player (digital audio / video player), a wearable device (e.g., wearable camera, smart watch, tracking device, head mounted display (HMD), smart glasses), a game console, a digital book reader, a telehealth / telemedicine (remote health and medicine) device, and a vehicle providing communication functionality (e.g., automotive, airplane, ship), and various combinations thereof.

[0080] The communication apparatus is not limited to be portable or movable, and may also include any kind of apparatus, device or system being non-portable or stationary, such as a smart home device (e.g., an appliance, lighting, smart meter, control panel), a vending machine, and any other “things" in a network of an “Internet of Things (loT)’’.

[0081] The communication may include exchanging data through, for example, a cellular system, a wireless LAN system, a satellite system, etc., and various combinations thereof.

[0082] The communication apparatus may comprise a device such as a controller or a sensor which is coupled to a communication apparatus performing a function of communication described in the present disclosure. For example, the communicationapparatus may comprise a controller or a sensor that generates control signals or data signals which are used by a communication apparatus performing a communication function of the communication apparatus.

[0083] The communication apparatus also may include an infrastructure facility, such as a base station, an access point, and any other apparatus, device or system that communicates with or controls apparatuses such as those in the above non-limiting examples.

[0084] According to the present disclosure, various examples below have been described:1. A first communication apparatus comprising: circuitry, which in operation, generates a trigger-based physical layer protocol data unit (TB PPDU) comprising a long training field (LTF) and a data field, the data field comprising a distributed tone resource unit (DRU) subcarrier of a DRU and the LTF comprising an even- indexed LTF subcarrier that is based on the DRU subcarrier; and a transmitter, which in operation, transmits the TB PPDU in the DRU.2. The first communication apparatus of example 1, wherein the DRU subcarrier is even-indexed, and the even-indexed LTF subcarrier is overlapped with the DRU subcarrier.3. The first communication apparatus of example 1 , wherein the DRU subcarrier is odd- indexed, and the even-indexed LTF subcarrier is overlapped with an even-indexed subcarrier adjacent to the DRU subcarrier.4. The first communication apparatus of example 1, wherein the circuitry is configured to modulate a plurality of even-indexed LTF subcarriers including the even-indexed LTF subcarrier based on an index of each of a plurality of DRU subcarriers including the DRU subcarrier, and each of the plurality of even-indexed LTF subcarriers is overlapped with an even-indexed DRU subcarrier or even-indexed subcarrier adjacent to an odd-indexed DRU subcarrier.5. The first communication apparatus of example 4, wherein the transmitter is configured to transmit half of each of a plurality of orthogonal frequency domain modulation (OFDM) symbols associated with the modulated plurality of even-indexed LTF subcarriers when transmitting the TB PPDU.6. The first communication apparatus of example 1 , further comprising a receiver which, in operation, receives a trigger frame from a second communication apparatus prior to the transmission of the TB PPDU, the trigger frame indicating an allocation of the DRU subcarrier, a number of spatial streams for the communication apparatus, and a number of LTF symbols associated with the even-indexed LTF subcarrier.7. The first communication apparatus of example 6, wherein the TB PPDU includes a number of LTF symbols based on the number of LTF symbols indicated in the trigger frame.8. The first communication apparatus of example 6, wherein the trigger frame further indicates an LTF scheme in which the even-indexed LTF subcarrier is based on the allocation of the DRU subcarrier, and the circuitry is configured to modulate the even-indexed LTF subcarrier based on the LTF scheme.9. The first communication apparatus of example 1 , wherein the trigger frame further indicates an allocation of a row of a PLTFmatrix for the first communication apparatus, and the circuitry is configured to apply the PLTFmatrix to the even-indexed LTF subcarrier based on the allocation.10. A second communication apparatus comprising: circuitry, which in operation, generates a trigger frame indicating an allocation of a distributed tone resource unit (DRU) subcarrier and a number of long training field (LTF) symbols associated with an even-indexed LTF subcarrier for a first communication apparatus, the first communication apparatus configured to generate a trigger-based physical layer protocol data unit (TB PPDU) comprising a LTF and a data field, the data field comprising the DRU subcarrier and the LTF comprising the even-indexed LTF subcarrier; and a transmitter, which in operation, transmits the trigger frame to the first communication apparatus.11. The second communication apparatus of example 10, wherein the circuitry is configured to calculate an initial number of LTF symbols for the DRU subcarrier based on a sum of a number of spatial streams associated with the even-indexed LTF subcarrier and another number of spatial steams whose LTF subcarrier is overlapped with the even-indexed LTF subcarrier associated with the DRU subcarrier.12. The second communication apparatus of example 11, wherein the number of LTF symbols is greater than or equal to a maximum value associated with the initial number of LTF symbols.13. The second communication apparatus of example 10, wherein the circuitry is configured to assign the DRU subcarrier in one frequency subblock for the first communication apparatus and assign a regular resource unit (RRU) subcarrier in another frequency subblock to a third communication apparatus, and the number of LTF symbols is greater than or equal to a maximum value associated with both the initial number of LTF symbols for the DRU subcarrier and an initial number of LTF symbols for the RRU subcarrier.14. The second communication apparatus of example 10, wherein the trigger frame further indicates an allocation of a row of a PLTFmatrix for the first communication apparatus.15. The second communication apparatus of example 14, wherein the trigger frame indicates the allocation of the row of the PLTFmatrix in a SS allocation subfield.16. The second communication apparatus of example 10, wherein the trigger frame further indicates an LTF scheme in which the even-indexed LTF subcarrier is based on the allocation of the DRU subcarrier.17. A communication method implemented by a first communication apparatus, comprising: generating a trigger-based physical layer protocol data unit (TB PPDU) comprising a long training field (LTF) and a data field, the data field comprising a distributed tone resource unit (DRU) subcarrier of a DRU and the LTF comprising an even-indexed LTF subcarrier that is based on the DRU subcarrier; and transmitting the TB PPDU in the DRU.18. A communication method implemented by a second communication apparatus, comprising: generating a trigger frame indicating an allocation of a distributed tone resource unit (DRU) subcarrier and a number of long training field (LTF) symbols associated with an even- indexed LTF subcarrier for a first communication apparatus, the first communication apparatus configured to modulate the even-indexed LTF subcarrier based on an index of the DRU subcarrier for a trigger-based physical layer protocol data unit (TB PPDU); and transmitting the trigger frame to the first communication apparatus.

[0085] Thus, it can be seen that the present embodiments provide communication apparatuses and methods for determining LTF for DRU.

[0086] While exemplary embodiments have been presented in the foregoing detailed description of the present embodiments, it should be appreciated that a vast number of variations exist. It should further be appreciated that the exemplary embodiments are examples, and are not intended to limit the scope, applicability, operation, or configuration of this disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing exemplary embodiments, it being understood that various changes may be made in the function and arrangement of steps and method of operation described in the exemplary embodiments and modules and structures of devices described in the exemplary embodiments without departing from the scope of the subject matter as set forth in the appended claims.

Claims

CLAIMS1 . A first communication apparatus comprising: circuitry, which in operation, generates a trigger-based physical layer protocol data unit (TB PPDU) comprising a long training field (LTF) and a data field, the data field comprising a distributed tone resource unit (DRU) subcarrier of a DRU and the LTF comprising an even-indexed LTF subcarrier that is based on the DRU subcarrier; and a transmitter, which in operation, transmits the TB PPDU in the DRU.

2. The first communication apparatus of claim 1 , wherein the DRU subcarrier is even- indexed, and the even-indexed LTF subcarrier is overlapped with the DRU subcarrier.

3. The first communication apparatus of claim 1 , wherein the DRU subcarrier is odd- indexed, and the even-indexed LTF subcarrier is overlapped with an even-indexed subcarrier adjacent to the DRU subcarrier.

4. The first communication apparatus of claim 1 , wherein the circuitry is configured to modulate a plurality of even-indexed LTF subcarriers including the even-indexed LTF subcarrier based on an index of each of a plurality of DRU subcarriers including the DRU subcarrier, and each of the plurality of even-indexed LTF subcarriers is overlapped with an even-indexed DRU subcarrier or even-indexed subcarrier adjacent to an odd-indexed DRU subcarrier.

5. The first communication apparatus of claim 4, wherein the transmitter is configured to transmit half of each of a plurality of orthogonal frequency domain modulation (OFDM) symbols associated with the modulated plurality of even-indexed LTF subcarriers when transmitting the TB PPDU.

6. The first communication apparatus of claim 1 , further comprising a receiver which, in operation, receives a trigger frame from a second communication apparatus prior to the transmission of the TB PPDU, the trigger frame indicating an allocation of the DRU subcarrier, a number of spatial streams for the communication apparatus, and a number of LTF symbols associated with the even-indexed LTF subcarrier.

7. The first communication apparatus of claim 6, wherein the TB PPDU includes a number of LTF symbols based on the number of LTF symbols indicated in the trigger frame.

8. The first communication apparatus of claim 6, wherein the trigger frame further indicates an LTF scheme in which the even-indexed LTF subcarrier is based on the allocation of the DRU subcarrier, and the circuitry is configured to modulate the even- indexed LTF subcarrier based on the LTF scheme.

9. The first communication apparatus of claim 1 , wherein the trigger frame further indicates an allocation of a row of a PLTFmatrix for the first communication apparatus, and the circuitry is configured to apply the PLTF matrix to the even-indexed LTF subcarrier based on the allocation.

10. A second communication apparatus comprising: circuitry, which in operation, generates a trigger frame indicating an allocation of a distributed tone resource unit (DRU) subcarrier and a number of long training field (LTF) symbols associated with an even-indexed LTF subcarrier for a first communication apparatus, the first communication apparatus configured to generate a trigger-based physical layer protocol data unit (TB PPDU) comprising a LTF and a data field, the data field comprising the DRU subcarrier and the LTF comprising the even-indexed LTF subcarrier; and a transmitter, which in operation, transmits the trigger frame to the first communication apparatus.11 . The second communication apparatus of claim 10, wherein the circuitry is configured to calculate an initial number of LTF symbols for the DRU subcarrier based on a sum of a number of spatial streams associated with the even-indexed LTF subcarrier and another number of spatial steams whose LTF subcarrier is overlapped with the even- indexed LTF subcarrier associated with the DRU subcarrier.

12. The second communication apparatus of claim 11, wherein the number of LTF symbols is greater than or equal to a maximum value associated with the initial number of LTF symbols.

13. The second communication apparatus of claim 10, wherein the circuitry is configured to assign the DRU subcarrier in one frequency subblock for the first communicationapparatus and assign a regular resource unit (RRU) subcarrier in another frequency subblock to a third communication apparatus, and the number of LTF symbols is greater than or equal to a maximum value associated with both the initial number of LTF symbols for the DRU subcarrier and an initial number of LTF symbols for the RRU subcarrier.

14. The second communication apparatus of claim 10, wherein the trigger frame further indicates an allocation of a row of a PLTFmatrix for the first communication apparatus.

15. The second communication apparatus of claim 14, wherein the trigger frame indicates the allocation of the row of the PLTFmatrix in a SS allocation subfield.

16. The second communication apparatus of claim 10, wherein the trigger frame further indicates an LTF scheme in which the even-indexed LTF subcarrier is based on the allocation of the DRU subcarrier.

17. A communication method implemented by a first communication apparatus, comprising: generating a trigger-based physical layer protocol data unit (TB PPDU) comprising a long training field (LTF) and a data field, the data field comprising a distributed tone resource unit (DRU) subcarrier of a DRU and the LTF comprising an even-indexed LTF subcarrier that is based on the DRU subcarrier; and transmitting the TB PPDU in the DRU.

18. A communication method implemented by a second communication apparatus, comprising: generating a trigger frame indicating an allocation of a distributed tone resource unit (DRU) subcarrier and a number of long training field (LTF) symbols associated with an even-indexed LTF subcarrier for a first communication apparatus, the first communication apparatus configured to modulate the even-indexed LTF subcarrier based on an index of the DRU subcarrier for a trigger-based physical layer protocol data unit (TB PPDU); and transmitting the trigger frame to the first communication apparatus.

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