EP4342258A1

EP4342258A1 - Device and method for multi ap coordinated transmissions

Info

Publication number: EP4342258A1
Application number: EP21940248.4A
Authority: EP
Inventors: Genadiy Tsodik; Shimon SHILO; Arik Klein; Oded Redlich; Jian Yu
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2021-05-21
Filing date: 2021-05-21
Publication date: 2024-03-27
Also published as: CN117413614A; WO2022241795A1

Abstract

The present disclosure relates to AP-to-AP communication in wireless communications. To this end, the disclosure proposes a wireless transmitting device being configured to: transmit a PPDU to at least one wireless receiving device, wherein the PPDU comprises at least one of: a first indication that indicates that the PPDU includes an AP-to-AP communication, intended for at least one other AP and not intended for any non-AP station; a second indication that indicates that the PPDU is not intended for any other AP; and a third indication that indicates that the PPDU is intended for at least one other AP and at least one non-AP station. (FIG. 2)

Description

DEVICE AND METHOD FOR MULTI AP COORDINATED TRANSMISSIONS

TECHNICAL FIELD

The present disclosure relates generally to wireless communications, and particularly to wireless transmissions between access points (APs) . This disclosure proposes a device and method for supporting a Multi-AP (M-AP) coordinated communication in a wireless network.

BACKGROUND

The IEEE 802.11be (Wi-Fi) standard introduces M-AP coordinated transmission operations, wherein multiple APs share resources, to allow parallel transmissions and utilize their resources more efficiently. Coordinated transmission may include physical layer protocol data units (PPDUs) exchange between APs and stations (STAs) , as well as between APs and APs. Frame exchange between APs is new to Wi-Fi, in particular, previous standard versions defined formats that were focused on AP-to-STA or STA-to-AP transmissions.
In a Wi-Fi network that supports M-AP coordination, there are three types of exchanged frames: AP to AP (s) , AP (s) to STA (s) , and STA (s) to AP (s) . The PPDU exchange between AP and STA (s) or STA (s) and AP are done within a Basic Service Set (BSS) , e.g., in the cases of coordinated Time Division Multiple Access (Co-TDMA) , coordinated Orthogonal Frequency Division Multiple Access (Co-OFDMA) , or coordinated spatial reuse (Co-SR) ) . Alternatively, the PPDU exchange may also be done between BSSs, as in a Joint Transmission (JT) case.
Communication between APs is a new type of WiFi communication. Non-AP STA devices are not supposed to detect any PPDU exchanged between APs. Currently, APs are not supposed to detect most frames having a neighbor BSS color. The main issue of reusing existing physical layer (PHY) indication fields is that they cannot uniquely indicate AP-to-AP communications. As the AP-to-AP communication is irrelevant for STAs, if it can be uniquely indicated, the STAs are allowed to skip this packet and thus save power. Therefore, PHY level indications dedicated for indicating AP-to-AP (s) PPDU exchange are desired.
SUMMARY
In view of the above, embodiments of the present disclosure aim to introduce special PHY level indications that can distinguish a new type of communication, in particular, AP-to-AP communication, from all other communication types. An objective is to introduce PHY level changes required to support AP-to-AP transmissions. One aim is thereby to allow new methods of PHY resource allocation for AP-to-AP PPDUs.
These and other objectives are achieved by embodiments as provided in the enclosed independent claims. Advantageous implementations of the embodiments are further defined in the dependent claims.
A first aspect of the disclosure provides a wireless transmitting device for an AP, wherein the wireless transmitting device is configured to transmit a PPDU to at least one wireless receiving device, wherein the PPDU comprises at least one of: a first indication that indicates that the PPDU includes an AP-to-AP communication intended for at least one other AP and not intended for any non-AP station; a second indication that indicates that the PPDU is not intended for any other AP; and a third indication that indicates that the PPDU is intended for at least one other AP and at least one non-AP station.
For instance, embodiments of this disclosure propose adding a new field that can indicate the type of the current communication, particularly, can indicate whether an AP-to-AP communication is included in the current PPDU or not. The wireless transmitting device may be integrated with the AP. The wireless transmitting device may also act as the AP. It should be noted that if the PPDU includes the AP-to-AP communication, it means that the PPDU includes information (data frames or management frames) for at least one other AP. At least one other AP that receives the PPDU is supposed to detect the PPDU and obtain the information for it. According to this disclosure, if the wireless receiving device is a non-AP station, the wireless receiving device knows that the current PPDU is not intended for it when it receiving the PPDU that comprises the first indication.
In an implementation form of the first aspect, the first indication further indicates a variant of the PPDU that is used for the AP-to-AP communication, wherein the variant of the PPDU includes one of: AP to single AP; OFDMA; multi-user multiple-input multiple-output (MU-MIMO) ; and trigger-based (TB) . Advantageously, this allows to transmit different variants of communication under same PPDU format
Notably, AP-to-AP communication may address different needs and requirements of coordination. It may support management and control of M-AP set, from establishment stage till particular coordinated transmission. It can also be used for data exchange, including a large payload to be used in more complex coordination schemes. This disclosure further defines different variants of the PPDU that may be used to support different types of AP-to-AP communication.
In an implementation form of the first aspect, the PPDU comprises a universal signal (U-SIG) field, and the U-SIG field comprises the first indication, or the second indication, or the third indication. Advantageously, this provides an indication that can be detected by any neighbor device, including overlapping BSS (OBSS) devices.
Notably, the indications defined in this disclosure may be carried in the U-SIG field in the PHY preamble.
In an implementation form of the first aspect, the U-SIG field comprises a compressed mode field.
In an implementation form of the first aspect, the U-SIG field further comprises a reserved bit, wherein when the reserved bit is set to 1, the U-SIG field comprises the first indication, wherein the compressed mode field includes a PPDU type that indicates the variant of the PPDU; and when the reserved bit is set to 0, the U-SIG field comprises the second indication, wherein the compressed mode field indicates that the PPDU is a multi-user (MU) PPDU or a TB PPDU as defined by the IEEE 802.11be standard. Advantageously, this allows to efficiently distinguish between the AP-to-AP communication and other communication types by a single bit.
The present disclosure proposes different design options for indicating AP-to-AP communication. As described above, in an option 1, a reserved bit that currently is not used by U-SIG (e.g., validate or disregard bit) is designed to be dedicated to indicating AP-to- AP communication. When the PPDU includes an AP-to-AP communication, i.e., the U-SIG field comprises the first indication, the variant of the PPDU may be further indicated using the compressed mode field.
In an implementation form of the first aspect, the U-SIG field comprises a specific field dedicated to indicating the AP-to-AP communication, wherein the specific field comprises the first indication or the second indication. Advantageously, it allows to efficiently include all the indications of AP-to-AP communication in the new dedicated field with no change to the existing fields.
Accordingly, in an option 2, AP-to-AP PPDU can be indicated by a new field (the specific field) that includes all the possible PHY variants. The new field may include one or more options, for instance one option that indicates that this PPDU is not of AP-to-AP type, and additional options to indicate at least one of the PHY variants as previously defined.
In an implementation form of the first aspect, the compressed mode field of the U-SIG field is an extended compressed mode field comprising a dedicated bit for indicating the AP-to-AP communication, wherein the extended compressed mode field comprises the first indication or the second indication. Advantageously, it efficiently reuses the compressed field design with additional options indicating AP-to-AP communication.
Accordingly, in an option 3, the compressed mode field may be extended to include new AP-to-AP PPDU variants, i.e., by including the dedicated bit.
In an implementation form of the first aspect, when the dedicated bit is set to one of ‘1’ and ‘0’ , the U-SIG field comprises the first indication, wherein the extended compressed mode field indicates the variant of the PPDU; and when the extended bit is set to the other one of ‘1’ and ‘0’ , the U-SIG field comprises the second indication, wherein the extended compressed mode field indicates that the PPDU is a MU PPDU or a TB PPDU as defined by the IEEE 802.11be standard. Advantageously, it efficiently reuses the compressed field design with additional options indicating AP-to-AP communication.
In particular, if a conventional compressed mode field has 2 bits, it may be extended to have 3 bits according to this embodiment. In this case, the extra one bit may be used to indicate whether the current PPDU includes AP-to-AP communication, for instance, by setting the extended bit to 1. When the extended bit is set to 1 (or 0) , the other 2 bits indicate the variant of the PPDU. When the current PPDU does not include AP-to-AP communication (indicated by setting the extended bit to 0 (or 1) ) , the other 2 bits may reuse the existing format of the conventional compressed mode field (e.g., as defined by the IEEE 802.11be) .
In an implementation form of the first aspect, the U-SIG field further comprises a BSS color field, wherein the BSS color field and the compressed mode field comprise the first indication or the second indication. Advantageously, it allows to efficiently design a new indication of AP-to-AP communication without adding new fields to U-SIG.
Accordingly, in an option 4, it is proposed to use the BSS color field to indicate AP-to-AP transmission.
In an implementation form of the first aspect, a set of BSS color options is preserved for the AP-to-AP communication, wherein when the BSS color field comprises a BSS color option from the preserved set of BSS color options, the U-SIG field comprises the first indication, wherein the compressed mode field indicates the variant of the PPDU; when the BSS color field does not comprise a BSS color option from the preserved set of BSS color options, the U-SIG field comprises the second indication, wherein the compressed mode field indicates that the PPDU is a multi-user PPDU or a trigger-based PPDU as defined by the IEEE 802.11be standard. Advantageously, it allows to efficiently use a BSS Color field with full backward compatibility.
This embodiment of the disclosure defines a set of preserved BSS color options for AP-to-AP communication. Notably, AP that supports M-AP Coordination should refrain from choosing BSS Color from the preserved list for its BSS. When the M-AP Set is established, members (APs) of the M-AP Set may choose a new BSS Color from the list of preserved BSS Colors for AP-to-AP communication within this M-AP Set.
In an implementation form of the first aspect, the U-SIG field further comprises a DL/UL field, wherein the DL/UL field and the compressed mode field comprise the first indication or the second indication. Advantageously, it efficiently reuses a DL/UL field.
Accordingly, in an option 5, it is proposed to use the DL/UL field to indicate AP-to-AP transmission.
In an implementation form of the first aspect, when the DL/UL field is set to 1, the U-SIG field comprises the first indication, wherein at least one reserved option of the compressed mode field indicates the variant of the PPDU. Advantageously, it efficiently reuses the reserved options of the DL/UL field.
It may be worth mentioning that the DL/UL field can indicate whether the current PPDU is addressed to AP. In this embodiment, such “to AP transmission” option of the DL/UL field is reused. In addition, two validate options of the compressed mode field may be used to indicate two PHY variants of AP-to-AP communication.
In an implementation form of the first aspect, the wireless transmitting device is for a sharing AP or a shared AP.
It should be noted that the current IEEE 802.11be standard agrees on coordination between multiple APs and defined an initial terminology. In particular, an extremely high throughput (ETH) AP which obtains a Transmit Opportunity (TXOP) and initiates the M-AP coordination is the Sharing AP, and an EHT AP which is coordinated for the Multi-AP transmission by the Sharing AP is the Shared AP.
In an implementation form of the first aspect, the U-SIG field comprises a DL/UL field, wherein when the DL/UL field is set to 0, the wireless transmitting device is the sharing AP; and when the DL/UL field is set to 1, the wireless transmitting device is not the sharing AP; or when the DL/UL field is set to 1, the transmitting of the PPDU is triggered by a sharing AP; and when the DL/UL field is set to 0, the transmitting of the PPDU is not triggered by a sharing AP. Advantageously, it efficiently reuses the DL/UL field to indicate the properties of AP-to-AP PPDU.
For options 1 to 4, the DL/UL field may be reused as defined by the IEEE 802.11be standard. Alternatively, the DL/UL field may be designed with further interpretations in these embodiments. For instance, if the PPDU includes AP-to-AP communication, the DL/UL field may be used to indicate whether the wireless transmitting device is for the sharing AP, or indicate whether the PPDU is triggered by the sharing AP.
In an implementation form of the first aspect, the U-SIG field further comprises a reserved bit, wherein the reserved bit of the U-SIG field comprises the third indication. Advantageously, it allows to combine between AP-to-AP and AP-to-STA communications in the same PPDU.
This disclosure further proposes a new indication to indicate that the current PPDU is a mixed PPDU that includes AP-to-AP transmission and also AP-to-STA transmission. This indication will require APs and also STA to detect the frames.
In an implementation form of the first aspect, the PPDU further comprises an ETH-SIG field, and a user field of the ETH-SIG field indicates an identification of AP that is assigned to a coordinated Multi-AP set. Advantageously, it provides an ability of every AP to determine the relevancy of the PPDU.
Notably, in current 802.11 standards, a user field of the ETH-SIG field includes information of specific resource unit (RU) and information of STA (e.g., STA_ID) that is assigned to the RU. In this embodiment, STA_ID is replaced with the ID of AP that is assigned to the M-AP set. This ID is a unique identifier for each AP member within the M-AP Set.
In an implementation form of the first aspect, the wireless transmitting device and at least one wireless receiving device for another AP belong to the same coordinated Multi-AP set.
In an implementation form of the first aspect, the PPDU comprises an ETH-SIG field, wherein the ETH-SIG field comprises at least a common field and an AP-specific field.
As defined in current 802.11 standards, the ETH-SIG field comprises a common field and a user-specific field. The AP-specific field described here is similar to the user-specific field.
In an implementation form of the first aspect, when the variant of the PPDU that is used for the AP-to-AP communication is OFDMA, a number of APs allocated to the PPDU is not larger than a predetermined value, and each AP allocated to the PPDU is assigned with a bandwidth (BW) not less than a first predetermined BW, the ETH-SIG field is in a short format, wherein a resource allocation indication is omitted in the common field of the EHT-SIG field. Advantageously, it allows efficient indication of all the OFDMA allocations.
This disclosure further defines a short format or a short mode of the ETH-SIG field. In particular, in the short mode, RU allocations are not explicitly indicated. Therefore, the length of the ETH-SIG field may be reduced since fewer bits are required.
In an implementation form of the first aspect, the number of APs allocated to the PPDU is not larger than 8, and each AP allocated to the PPDU is assigned with a BW not less than 20MHz.
Optionally, the short format may be applied for EHT-SIG if certain conditions are satisfied.
In an implementation form of the first aspect, the PPDU is transmitted over a second predetermined BW, wherein in the short format, the common field of the EHT-SIG field includes a field that indicates a number of APs allocated at each half of the second predetermined BW.
In an implementation form of the first aspect, the second predetermined BW is 20MHz, 40MHz, 80MHz, 160MHz, or 320MHz, when the number of APs allocated to the PPDU is 1, the AP allocated to the PPDU is assigned with the second predetermined BW; when the number of APs allocated to the PPDU is 2, each AP allocated to the PPDU is assigned with a half of the second predetermined BW; when the number of APs allocated to the PPDU is 3 or 4, each AP allocated to the PPDU is assigned with at least a quarter of the second predetermined BW. Advantageously, it allows efficient implicit indication of the allocated RUs.
In an implementation form of the first aspect, the AP specific field of the ETH-SIG field comprises one or more AP blocks, each AP block comprising one or two AP fields.
For instance, if the number of allocated APs is odd (e.g. 5) , the AP specific field may comprise 2 AP Blocks each consisting of two AP fields, and one AP Block comprising only one AP field.
In an implementation form of the first aspect, each AP field corresponds to a particular AP allocated to the PPDU, and the AP field indicates a resource allocated to the AP, and an identification of a coordinated Multi-AP set to where the AP belongs. Advantageously, it allows efficient reuse of EHT-SIG format.
Optionally, the AP field may reuse the existing format of the user field (in the EHT-SIG field) with STA_ID, by replacing the STA_ID with the ID of AP that is assigned to the M-AP set.
In an implementation form of the first aspect, when the second predetermined BW comprises a punctured channel, the AP filed indicates multiple resources allocated to the AP.Advantageously, it provides a support to all the punctured scenarios.
According to this embodiment, the punctured channel may also be supported in the short mode.
In an implementation form of the first aspect, the common field is divided into a first content channel and a second content channel, and the first content channel includes AP fields of APs that are allocated in a lower half of the second predetermined BW, and the second content channel includes AP fields of APs that are allocated in an upper half of the second predetermined BW. Advantageously, it allows efficient implicit indication of the allocated RUs.
In an implementation form of the first aspect, the AP-specific field of the ETH-SIG field comprises a zero AP field indicating that a resource is not allocated to any AP. Advantageously, it provides a support to all the punctured scenarios.
A second aspect of the disclosure provides a wireless receiving device, the wireless receiving device being configured to: receive a PPDU from a wireless transmitting device for an AP, wherein the PPDU comprises at least one of: a first indication that indicates that the PPDU includes an AP-to-AP communication intended for at least one other AP and not intended for any non-AP station; a second indication that indicates that the PPDU is not intended for any other AP; and a third indication that indicates that the PPDU is intended for at least one other AP and at least one non-AP station.
That is, an embodiment of this disclosure proposes a wireless receiving device that can operate according to what has been described for the first aspect and its implementation forms.
In an implementation form of the second aspect, when the wireless receiving device is for another AP, the wireless receiving device is configured to detect whether the PPDU comprises the first indication or the third indication; and process the PPDU if it is detected that the PPDU comprises the first indication or the third indication.
According to this embodiment, the receiver of the PPDU is also an AP. Therefore, when the wireless receiving device detects that the PPDU includes an AP-to-AP communication (if the first indication or the third indication is detected) , it should process the PPDU accordingly. Possibly, when the wireless receiving device detects that the PPDU does not include an AP-to-AP communication (if the second indication is detected) , it may ignore the PPDU without processing it.
In an implementation form of the second aspect, the wireless receiving device is a sharing AP or a shared AP.
In an implementation form of the second aspect, when the wireless receiving device is for a station, the wireless receiving device is configured to: detect whether the PPDU comprises the first indication, and set a network allocation vector (NAV) if the first indication is detected.
According to this embodiment, the receiver of the PPDU is the station. Therefore, when the wireless receiving device detects that the PPDU only includes an AP-to-AP communication (if the first indication is detected) , the station may save power by setting NAV immediately for the entire AP-to-AP (s) session after PHY preamble detection.
A third aspect of the disclosure provides a method for a wireless transmitting device for an AP, the method comprising: transmitting a PPDU to at least one wireless receiving device, wherein the PPDU comprises at least one of: a first indication that indicates that the PPDU includes an AP-to-AP communication, intended for at least one other AP and not intended for any non-AP station; a second indication that indicates that the PPDU is not intended for any other AP; and a third indication that indicates that the PPDU is intended for at least one other AP and at least one non-AP station.
Implementation forms of the method of the third aspect may correspond to the implementation forms of the wireless transmitting device of the first aspect described above. The method of the third aspect and its implementation forms achieve the same advantages and effects as described above for the wireless transmitting device of the first aspect and its implementation forms.
A fourth aspect of the disclosure provides a method for a wireless receiving device, the method comprising: receiving a PPDU from a wireless transmitting device, wherein the PPDU comprises at least one of: a first indication that indicates that the PPDU includes an AP-to-AP communication, intended for at least one other AP and not intended for any non-AP station; a second indication that indicates that the PPDU is not intended for any other AP;and a third indication that indicates that the PPDU is intended for at least one other AP and at least one non-AP station.
Implementation forms of the method of the fourth aspect may correspond to the implementation forms of the user device of the second aspect described above. The method of the fourth aspect and its implementation forms achieve the same advantages and effects as described above for the user device of the second aspect and its implementation forms.
A fifth aspect of the disclosure provides a computer program product comprising a program code for carrying out, when implemented on a processor, the method according to the third aspect and any implementation forms of the third aspect, or the fourth aspect and any implementation forms of the fourth aspect.
It has to be noted that all devices, elements, units and means described in the present application could be implemented in the software or hardware elements or any kind of combination thereof. All steps which are performed by the various entities described in the present application as well as the functionalities described to be performed by the various entities are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities. Even if, in the following description of specific embodiments, a specific functionality or step to be performed by external entities is not reflected in the description of a specific detailed element of that entity which performs that specific step or functionality, it should be clear for a skilled person that these methods and functionalities can be implemented in respective software or hardware elements, or any kind of combination thereof.
BRIEF DESCRIPTION OF DRAWINGS
The above described aspects and implementation forms of the present disclosure will be explained in the following description of specific embodiments in relation to the enclosed drawings, in which
FIG. 1 shows an exemplary Wi-Fi network.
FIG. 2 shows a wireless transmitting device according to an embodiment of the disclosure.
FIG. 3 shows content channels in a short mode according to an embodiment of the disclosure.
FIG. 4 shows MRU allocation according to an embodiment of the disclosure.
FIG. 5 shows RU allocation for up to 8 APs for BW of 160MHz according to an embodiment of the disclosure.
FIG. 6 shows RU allocation for up to 8 APs for BW of 320MHz according to an embodiment of the disclosure.
FIG. 7 shows a wireless receiving device according to an embodiment of the disclosure.
FIG. 8 shows a method according to an embodiment of the disclosure.
FIG. 9 shows a method according to an embodiment of the disclosure.
DETAILED DESCRIPTION OF EMBODIMENTS
Illustrative embodiments of methods, devices, and program products for M-AP transmissions in a communication system are described with reference to the figures. Although this description provides a detailed example of possible implementations, it should be noted that the details are intended to be exemplary and in no way limit the scope of the application.
Moreover, an embodiment/example may refer to other embodiments/examples. For example, any description including but not limited to terminology, element, process, explanation and/or technical advantage mentioned in one embodiment/example is applicative to the other embodiments/examples.
To facilitate understanding of the embodiments of the present disclosure, the following describes basic technologies related to the embodiments of the present disclosure.
The current IEEE 802.11be standard agreed on a coordination between multiple APs and defined an initial terminology, i.e., an EHT AP which obtains a TXOP and initiates the M-AP coordination is the Sharing AP, and an EHT AP which is coordinated for the Multi-AP transmission by the Sharing AP is the Shared AP.
FIG. 1 shows a Wi-Fi network that supports M-AP coordination. As shown in FIG. 1, access points AP1, AP2, AP3, and AP4 belong to a M-AP set X, and access points AP5 and AP6 are not members of the M-AP set X.
The IEEE 802.11be specification defines a U-SIG field in a PHY preamble as a field that indicates the parameters of the current PPDU. In particular, it defines PPDU BW, PPDU type and format, TXOP duration, BSS Color, to whom the PPDU is addressed, etc. The U-SIG field defines two types of unused bits –validate bits and disregard bits. Validate bits refer to bits that may be used by future versions of IEEE 802.11 standards, which can be used to indicate that this PPDU is not supposed to be detected by STAs that support previous standard versions. Disregard bits may be used to indicate new options/formats supported by the next versions of 802.11 and supposed to be ignored by STAs that support previous standard versions.
Three U-SIG fields that are relevant for this disclosure are described here.
BSS Color:
This field indicates the BSS network to distinguish an AP and an STA associated with that AP from other APs and STAs associated with the other APs. The size of this field is 6 bits. An AP may choose any combination of 6 bits as its BSS color (all options besides ‘BSS Color = 0’ ) . The BSS color is advertised by the AP and indicated in the PHY preamble of both UL and DL PPDUs as defined by the IEEE 802.11ax/be standard.
DL/UL:
This field indicates whether the current PPDU is addressed to an AP (set to ‘1’ ) or not. In general, every UL PPDU will be indicated with DL/UL field set to ‘1’ .
PPDU Type and Compressed Mode:
This field indicates a PHY format of transmitted packets. There are two types of PPDU (EHT MU, and EHT TB) as defined by the IEEE 802.11be standard, each type may be used with several variants. Each variant has a different specific format of part of U-SIG fields and format of EHT-SIG field (see Table 1)
Table 1: PPDU Type and Compressed Mode field in 802.11be
The U-SIG field is followed by an EHT-SIG field, which defines the PHY structure of the PPDU BW, including RU allocations and specific parameters per RU and per STA allocated with specific RU.
The EHT-SIG field is constructed of three parts: overflow bits (apart of the U-SIG that is transmitted within the EHT-SIG field) , a Common Field that defines the RUs allocated in current PPDU, and a User Specific Field that indicates per-RU parameters and the STA that each RU is allocated to.
The Common Field of the EHT-SIG field includes indication of allocated RUs, wherein the explicit BW division is indicated per 20MHz channel by 9 bits index. This indication refers to RU Allocation Table as defined by the IEEE 802.11be standard.
The User Specific Field contains indications of STAs assigned to each allocated RU that is indicated within the Common Field.
The User Specific Field contains User Blocks, wherein each User Block may include two User Fields or a single User Field if the number of users is odd. Each User Field corresponds to a specific RU and includes information of the STA that is assigned to this RU, and its transmission parameters.
The EHT-SIG is divided into two Content Channels (CC1 and CC2) , wherein each CC is transmitted on 20MHz and repeated over the entire BW. Typically, CC1 includes all the information (Common Field and User Specific Field) that corresponds to allocations within the odds 20MHz channels. CC2 includes all the information that corresponds to allocations within the evens 20MHz channels.
Conventionally, the PPDUs exchanged between AP and AP (s) are always exchanged between BSSs, and may require a coordination regardless of the specific coordination scheme or M-AP Set procedures. The BSS may be signaled by BSS color within the PHY preamble to indicate to neighbor devices that a current packet is not relevant to them. The PPDU exchanged between the APs is not supposed to be received by any STA associated with any AP.
AP-to-AP communication may address different needs and requirements of coordination. It may support management and control of an M-AP set, from an establishment stage to a particular coordinated transmission. It can also be used for data exchange, including a large payload to be used in more complex coordination schemes.
Table 2 shows 4 types of AP-to-AP communication, and also which PHY format of transmission may be used to support each type. Notably, Table 2 includes all possible AP to AP communication cases, while the IEEE 802.11be standard may accept any subset of the listed communication types.
Table 2: Types of AP-to-AP communication
As previously described, the main issue is that the reusing of existing PHY indication fields cannot uniquely indicate an AP-to-AP communication. This means that to be able to cover all the possible scenarios of AP-to-AP PPDU exchanges, and to ensure that only APs be required to detect such type of PPDU, there is a need to modify/extend current PHY preamble fields. Therefore, embodiments of this disclosure propose to include a new field that can indicate AP-to-AP communication in the PHY preamble.
The following describes preferred implementations of the present disclosure in detail with reference to the accompanying drawings in this specification. It should be understood that the preferred embodiments described herein are merely used to describe and explain the present disclosure, but are not intended to limit the present disclosure. In addition, the embodiments in this application and features in the embodiments may be mutually combined if they do not conflict with each other.
FIG. 2 shows a wireless transmitting device 200 according to an embodiment of the disclosure. The wireless transmitting device 200 may comprise processing circuitry (not shown) configured to perform, conduct or initiate the various operations of the wireless transmitting device 200 described herein. The processing circuitry may comprise hardware and software. The hardware may comprise analog circuitry or digital circuitry, or both analog and digital circuitry. The digital circuitry may comprise components such as application-specific integrated circuits (ASICs) , field-programmable arrays (FPGAs) , digital signal processors (DSPs) , or multi-purpose processors. The wireless transmitting device 200 may further comprise memory circuitry, which stores one or more instruction (s) that can be executed by the processor or by the processing circuitry, in particular under control of the software. For instance, the memory circuitry may comprise a non-transitory storage medium storing executable software code which, when executed by the processor or the processing circuitry, causes the various operations of the wireless transmitting device 200 to be performed. In one embodiment, the processing circuitry comprises one or more processors and a non-transitory memory connected to the one or more processors. The non-transitory memory may carry executable program code which, when executed by the one or more processors, causes the wireless transmitting device 200 to perform, conduct or initiate the operations or methods described herein.
In particular, the wireless transmitting device 200 is designed for an AP. The wireless transmitting device 200 is configured to transmit a PPDU 201 to at least one wireless receiving device 210. The PPDU 201 comprises at least one of:
- a first indication that indicates that the PPDU 201 includes an AP-to-AP communication intended for at least one other AP and not intended for any non-AP station;
- a second indication that indicates that the PPDU 201 is not intended for any other AP; and
- a third indication that indicates that the PPDU 201 is intended for at least one other AP and at least one non-AP station.
It may be noted that all the parameters related to the PPDU 201 may be indicated in the U-SIG field following the IEEE 802.11be standard. Thus, embodiments of this disclosure may include adding to the U-SIG field a field that indicates that the current PPDU includes an AP-to-AP communication. For example, according to an embodiment of the disclosure, the PPDU 201 as shown in FIG. 2 may comprise a U-SIG field, and the U-SIG field comprises the first indication, the second indication, or the third indication.
Possible AP-to-AP communication types are shown in Table 2, according to embodiments of the disclosure. Further, Table 3 defines a list of PHY variants that may be supported and used for AP-to-AP transmission. This list defines possible PHY variants of this disclosure, while possibly only a subset of those types may be used.

PHY Variant	Transmission Type
AP to Single AP	Unicast/Broadcast
AP-to-AP OFDMA	Multi-Cast/Data Transmission (used in JT)
AP-to-AP MU-MIMO	Multi-Cast/Data Transmission (used in JT)
AP-to-AP TB	APs Response

Table 3: PHY Variant for AP-to-AP transmissions
According to an embodiment of this disclosure, when the PPDU 201 includes an AP-to-AP communication intended for at least one other AP and not intended for any non-AP STA, i.e., the PPDU 201 comprises the first indication, the first indication may further indicate a variant of the PPDU 201 that is used for the AP-to-AP communication. In particular, the variant of the PPDU 201 may be one of the variants defined in Table 3.
Embodiments of this disclosure propose several options for indicating whether the current PPDU includes an AP-to-AP communication. Details of these indication options are given in the following part.
Indication option 1: using dedicated bit and reuse of PPDU Type and Compressed Mode Field
According to an embodiment of the disclosure, the AP-to-AP PPDU may be indicated by a dedicated bit, which currently is not in use by the U-SIG field (e.g., a validate or disregard bit) . In addition, a PPDU Type and Compressed Mode Field as defined in the IEEE 802.11be standard may be reused, for instance, with the update listed in Table 4 below.
As previously described, the U-SIG field may comprise a compressed mode field. Notably, the U-SIG field may further comprise a reserved bit (avalidate or disregard bit) . In this embodiment, when the reserved bit is set to 1, the U-SIG field comprises the first indication, wherein the compressed mode field includes a PPDU type that indicates the variant of the PPDU 201.
Table 4: PPDU Type and Compressed Mode field for Indication option 1
Accordingly, when the reserved bit is set to 0, the U-SIG field comprises the second indication, which means that the PPDU 201 is not intended for any other AP. In such case, PPDU Type and Compressed Mode Field as defined in the IEEE 802.11be standard can be reused. Optionally, the compressed mode field indicates that the PPDU 201 is a MU PPDU or a TB PPDU as defined by the IEEE 802.11be standard.
Indication option 2 –using a new field
According to an embodiment of the disclosure, the U-SIG field may comprise a specific field dedicated to indicating the AP-to-AP communication, wherein the specific field comprises the first indication or the second indication.
In this embodiment, AP-to-AP PPDU may be indicated by using the new field (the specific field) that includes all the possible PHY variants. Notably, the new field may include an option for indicating that this PPDU is not of AP-to-AP type, and additionally an option to indicate at least one of those PHY variants as defined in Table 3.
Indication option 3 –using extended PPDU Type and Compressed Mode field
According to an embodiment of the disclosure, the compressed mode field of the U-SIG field may be an extended compressed mode field. In particular, the extended compressed mode field may comprise a dedicated bit for indicating the AP-to-AP communication, wherein the extended compressed mode field comprises the first indication or the second indication.
Optionally, when the dedicated bit is set to 1, the U-SIG field comprises the first indication. When the dedicated bit is set to 0, the U-SIG field comprises the second indication.
Alternatively, when the dedicated bit is set to 0, the U-SIG field comprises the first indication. When the dedicated bit is set to 1, the U-SIG field comprises the second indication.
Notably, PPDU Type and Compressed Mode Field may be extended to include new PHY variants as defined in Table 3. In a particular implementation, the extended Compressed Mode Field may have 3 bits. Optionally, when the most significant bit (MSB) of this field is set to ‘1’ (or ‘0’ ) , the AP-to-AP PHY variants may be indicated as depicted in Table 5. That is, the MSB can be used as dedicated bit for indicating the AP-to-AP communication.
When the MSB is set to ‘0’ (or ‘1’ ) , the two least significant bits (LSB) will reuse the options as defined by the IEEE 802.11be standard.
Table 5: Extended Compressed Mode field for Indication option 3
It is worth mentioning that the MSB refers to a bit in a multiple-bit binary number with the largest value. This is usually the bit farthest to the left, or the bit transmitted first in a sequence. The LSB may be referred to as the low-order bit or right-most bit, due to the convention in positional notation of writing less significant digits further to the right. For example, in this embodiment, for the extended Compressed Mode Field ‘100’ , the MSB is 1, and the two LSB bits are ‘00’ .
When the dedicated bit is set to 1, the extended compressed mode field may further indicate the variant of the PPDU 201, as illustrated in Table 5. When the dedicated bit is set to 0, it may indicate that the PPDU 201 is not intended for any other AP. In this case, the extended compressed mode field may indicate that the PPDU 201 is a multi-user PPDU or a trigger-based PPDU as defined by the IEEE 802.11be standard, that is, the existing format as defined by the standard is reused.
Indication option 4: using dedicated BSS Color
Notably, the U-SIG field further comprises a BSS color field. According to an embodiment of the disclosure, the BSS color field and the compressed mode field comprise the first indication or the second indication.
According to an embodiment of this disclosure, a set of BSS color options may be preserved for the AP-to-AP communication. In particular, a set of preserved BSS Color options is defined for AP-to-AP communication. An AP that supports M-AP coordination should refrain from choosing BSS Color from the preserved list for its BSS. When an M-AP Set is established, members of the M-AP Set may choose a new BSS Color from the list of preserved BSS Colors for AP-to-AP communication within this M-AP Set.
Optionally, when the BSS color field comprises a BSS color option from the preserved set of BSS color options, the U-SIG field comprises the first indication. That is, it indicates the PPDU 201 includes an AP-to-AP communication intended for at least one other AP and not intended for any non-AP STA. In this embodiment, the compressed mode field indicates the variant of the PPDU 201 as listed in Table 4. This is similar to the indication option 1.
Optionally, when the BSS color field does not comprise a BSS color option from the preserved set of BSS color options, the U-SIG field comprises the second indication. That means that the PPDU 201 is not intended for any other AP. In this case, the compressed mode field may indicate that the PPDU 201 is a MU PPDU or a TB PPDU as defined by the IEEE 802.11be standard (the existing format as defined by the standard is reused) .
Indication option 5: using DL/UL field and the reserved PPDU Type and Compressed Mode field options
Notably, the U-SIG field further comprises a DL/UL field. According to an embodiment of the disclosure, the DL/UL field and the compressed mode field comprise the first indication or the second indication.
As previously mentioned, if the DL/UL field is set to ‘1’ , it may indicate that the current PPDU is addressed to an AP (as shown in Table 1) . In this embodiment, the DL/UL field option of ‘to AP transmission’ is reused. In addition, two validate options may be reused to indicate two PHY variants of an AP-to-AP communication, for example, as shown in Table 6. For instance, when the DL/UL field is set to ‘1’ , the reserved bits of the PPDU Type and Compressed Mode are further defined to indicate which variant of the PPDU is used for the AP-to-AP communication. In this embodiment, bit ‘2’ indicates the variant AP-to-AP OFDMA, and bit ‘3’ indicates the variant AP to Single AP.
Table 6: PPDU Type and Compressed Mode field for Indication option 5
Notably, the wireless transmitting device 200 as shown in FIG. 2 may be a sharing AP or a shared AP in an M-AP set.
It is worth mentioning that for Indication options 1-4, the DL/UL field may be reused as defined by the IEEE 802.11be standard. Alternatively, the DL/UL field may be designed with further interpretations in these embodiments. For instance, it may be preconfigured that when the DL/UL field is set to ‘0’ , the wireless transmitting device 200 is the sharing AP; and when the DL/UL field is set to 1, the wireless transmitting device 200 is not the sharing AP. In another example, it may be preconfigured that when the DL/UL field is set to 1, the transmitting of the PPDU 201 is triggered by a sharing AP; and when the DL/UL field is set to 0, the transmitting of the PPDU 201 is not triggered by a sharing AP.
Possibly, an AP-to-AP transmission and an AP-to-STA transmission may be mixed within the same PPDU. In this case, the PHY preamble may not indicate explicitly an AP-to-AP PPDU, but may indicate that this PPDU is a mixed PPDU. Such an indication may require an AP to detect the frame. This is referred to as the third indication as described in the previous embodiments.
According to an embodiment of the disclosure, the U-SIG field further comprises a reserved bit, wherein the reserved bit of the U-SIG field comprises the third indication. The reserved bit may be one disregard bit of the U-SIG field.
Notably, the PPDU 201 may further comprise an ETH-SIG field. The ETH-SIG field may include a user field, which indicates an identification (ID) of AP that is assigned to an M-AP set. This ID of an AP is a unique identifier for each AP member within the M-AP Set. It should be noted that in current 802.11 standards, the user field of the ETH-SIG field includes information of specific RU and information of STA (e.g., STA_ID) that is assigned to the RU. In the embodiment of this disclosure, STA_ID is replaced with the ID of AP that is assigned to the M-AP set.
When the PPDU 201 includes an AP-to-AP communication, the at least one wireless receiving device 210 that receives the PPDU 201 may be for another AP. Optionally, the wireless transmitting device 200 and at least one wireless receiving device 210 belong to the same M-AP set.
According to embodiments of this disclosure, modifications in the EHT-SIG field for indicating the AP-to-AP communication are also proposed as following.
U-SIG Overflow Bits:
The overflow bits of the EHT-SIG field for an AP-to-AP PPDU may be defined based on Table 7.

PHY Variant	U-SIG Overflow Bits
AP to Single AP	As in EHT non-OFDMA
AP-to-AP OFDMA	As in EHT OFDMA
AP-to-AP MU-MIMO	As in EHT non-OFDMA
AP-to-AP TB	As in EHT non-OFDMA

Table 7: U-SIG overflow bits for an AP-to-AP PPDU
EHT-SIG field for AP to Single AP and AP-to-AP TB Variants:
· EHT-SIG format in Single AP PHY variant may reuse the EHT-SIG format of SU variant of EHT MU transmission.
· EHT-SIG format in AP TB PHY variant may reuse the EHT-SIG format of EHT TB transmission.
EHT-SIG field for AP-to-AP MU-MIMO:
In the case of MU-MIMO AP-to-AP transmission, the EHT-SIG field will reuse the compressed mode defined for a single MU-MIMO allocation that occupies an entire BW.
EHT-SIG field for AP-to-AP OFDMA:
In the case of AP-to-AP OFDMA transmission, the EHT-SIG field may comprise Common Field and AP Specific Field.
AP Specific Field may consist of AP Blocks, which are similar to User Blocks as defined by the IEEE 802.11be standard, while each AP Block will reuse the structure and encoding rules of User Block. In particular, each AP Block may consist of one or two AP Fields. If the number of allocated APs is odd, there may be one AP Block comprising only one AP Field. For instance, when 5 APs are allocated to the PPDU 201, the AP Specific Field may comprise 2 AP Blocks each consisting of two AP Fields, and one AP Block comprising only one AP Field. AP Field may reuse the existing format of User Field with STA_ID by replacing the STA_ID with the ID of AP that is assigned to the M-AP set.
According to embodiments of the disclosure, each AP field corresponds to a particular AP allocated to the PPDU 201, and the AP field indicates a resource allocated to the AP, and an ID of a coordinated M-AP set to where the AP belongs.
The Common Field may be of two formats: reuse of EHT-SIG of EHT MU with OFDMA (including RU allocations indicated within the common field) ; and a short format where RU allocations are not implicitly indicated using BW (indicated within U-SIG) and the number of allocations.
According to embodiments of the disclosure, when the variant of the PPDU 201 that is used for the AP-to-AP communication is OFDMA, a number of APs allocated to the PPDU 201 is not larger than a predetermined value (e.g., 8) , and each AP allocated to the PPDU 201 is assigned with a BW not less than a first predetermined BW (e.g., 20MHz) , the ETH-SIG field may be in the short format, wherein a resource allocation indication is omitted in the common field of the EHT-SIG field.
For instance, the short format or short mode may be applied for the EHT-SIG field in OFDMA case if the following conditions are satisfied:
· Maximum number of APs allocated to current PPDU is less or equal to 8.
· Every AP allocated to the current PPDU assigned to RU of size 242-tone (20MHz) or larger.
The rules for short mode RU allocation may include one or more of the following:
· Common Field of the EHT-SIG field includes no RU Allocation indication.
· Common Field of the EHT-SIG field includes a field that indicates a number of APs allocated at each half of the entire BW, e.g., 2 bits per half of the entire BW to indicate up to 4 APs at each half.
· Unique RU Allocation may be defined by the entire BW indicated by the U-SIG field and the number of the APs indicated by the EHT-SIG field (e.g., as defined in Table 8) .
· CC1 shall include AP Fields of APs that are allocated in the lower half of the BW (as shown in FIG. 3) .
· CC2 shall include AP Fields of APs that are allocated in the upper half of the BW (as shown in FIG. 3) .
Table 8: RU combinations for up to 4 APs
According to an embodiment of the disclosure, the PPDU 201 may be transmitted over a second predetermined BW, wherein in the short format the common field of the EHT-SIG field includes a field that indicates a number of APs allocated at each half of the second predetermined BW. The second predetermined BW here may be referred to as the entire BW.
FIG. 3 shows content channels in the short format according to this embodiment. In this example, when the entire BW of the PPDU 201 is 80Mhz, CC1 (the lower 40MHz) includes AP Field for AP1 and AP2, and CC2 (the lower 40MHz) includes AP Field for AP3 and AP4.
Table 8 defines RU allocations of the short format for up to 4 APs according to an embodiment of the disclosure. RU1 refers to the RU allocated to AP1, RU2 refers to the RU allocated to AP2, etc. Optionally, as defined in Table 8, the second predetermined BW, i.e., the entire BW allocated to the PPDU 201, may be 20MHz, 40MHz, 80MHz, 160MHz, or 320MHz. Notably, when the number of APs allocated to the PPDU 201 is 1, the AP allocated to the PPDU 201 is assigned with the second predetermined BW.
Optionally, when the number of APs allocated to the PPDU 201 is 2, each AP allocated to the PPDU 201 is assigned with half of the second predetermined BW; when the number of APs allocated to the PPDU 201 is 3 or 4, each AP allocated to the PPDU 201 is assigned with at least a quarter of the second predetermined BW.
For instance, when the entire BW is 80MHz, for the case of 3 APs, if CC1 includes one AP, the lower 484-tone RU may be allocated, otherwise the upper 484-tone RU is allocated.
It is worth mentioning that a punctured channel may be supported in the short Mode according to the following rules. According to an embodiment of the disclosure, when the second predetermined BW comprises a punctured channel, the AP filed may indicate multiple resources allocated to the AP.
Any multi-RU (MRU) supported by the IEEE 802.11be can be allocated to AP by allocating it to the entire RU with punctured channel. FIG. 4 (a) shows an MRU allocation according to an embodiment of the disclosure. In the example depicted on FIG. 4 (a) , AP is allocated with 80MHz BW (996-tone RU) , however, the actual allocated MRU is 242-tone RU plus 484-tone RU (because of the punctured channel) .
FIG. 4 (b) shows RU allocations according to an embodiment of the disclosure. In one case, one RU is allocated to AP1, and one RU is allocated to AP2, while the entire BW comprises punctured channels. In another case, there may be a RU that is not allocated to any AP. In particular, the AP-specific field of the ETH-SIG field may comprise a zero AP field indicating that a resource is not allocated to any AP.
FIG. 5 shows RU allocations for up to 8 APs for a BW of 160MHz according to an embodiment of the disclosure. FIG. 6 shows RU allocations for up to 8 APs for a BW of 320MHz according to an embodiment of the disclosure.
To summarize, embodiments of this disclosure define a field in U-SIG that indicates AP-to-AP communication. Such field may be implemented using different options. In this way, the meaning of existing U-SIG fields can be modified to support AP-to-AP communication. Further, specific AP-to-AP communication types can also be indicated by modifying/extending further PHY Preamble fields.
FIG. 7 shows a wireless receiving device 210 according to an embodiment of the disclosure. The wireless receiving device 210 may comprise processing circuitry (not shown) configured to perform, conduct or initiate the various operations of the wireless receiving device 210 described herein. The processing circuitry may comprise hardware and software. The hardware may comprise analog circuitry or digital circuitry, or both analog and digital circuitry. The digital circuitry may comprise components such as application-specific integrated circuits (ASICs) , field-programmable arrays (FPGAs) , digital signal processors (DSPs) , or multi-purpose processors. The wireless receiving device 210 may further comprise memory circuitry, which stores one or more instruction (s) that can be executed by the processor or by the processing circuitry, in particular under control of the software. For instance, the memory circuitry may comprise a non-transitory storage medium storing executable software code which, when executed by the processor or the processing circuitry, causes the various operations of the wireless receiving device 210 to be performed. In one embodiment, the processing circuitry comprises one or more processors and a non-transitory memory connected to the one or more processors. The non-transitory memory may carry executable program code which, when executed by the one or more processors, causes the wireless receiving device 210 to perform, conduct or initiate the operations or methods described herein.
In particular, the wireless receiving device 210 may be configured to receive a PPDU 201 from a wireless transmitting device 200 for an AP. Possibly, the wireless transmitting device 200 shown in FIG. 7 may be the wireless transmitting device shown in FIG. 2. The PPDU 201 comprises at least one of: a first indication that indicates that the PPDU 201 includes an AP-to-AP communication intended for at least one other AP and not intended for any non-AP STA; a second indication that indicates that the PPDU 201 is not intended for any other AP; and a third indication that indicates that the PPDU 201 is intended for at least one other AP and at least one non-AP STA.
Notably, the wireless receiving device 210 shown in FIG. 7 may be the wireless receiving device shown in FIG. 2. That is, the wireless receiving device 210 may operate accordingly as described in the previous embodiments.
Optionally, according to an embodiment of this disclosure, when the wireless receiving device 210 is for another AP, the wireless receiving device 210 may be configured to detect whether the PPDU 201 comprises the first indication or the third indication; and process the PPDU 201 if it is detected that the PPDU 201 comprises the first indication or the third indication.
In this way, when an AP receiving an AP-to-AP PPDU, the AP is informed to detect the PPDU despite the difference in received BSS Color value.
Optionally, the wireless receiving device 210 is for a sharing AP or a shared AP.
According to another embodiment of this disclosure, when the wireless receiving device 210 is for an STA, the wireless receiving device 210 is configured to detect whether the PPDU 201 comprises the first indication; and set a network allocation vector (NAV) if the first indication is detected.
In this way, when an STA receiving an AP-to-AP PPDU, it can distinguish this new type of communication from all the other communication types. By setting NAV immediately after PHY preamble detection for the entire AP-to-AP (s) session, STAs are allowed to save power.
FIG. 8 shows a method 1000 according to an embodiment of the disclosure. In a particular embodiment of the disclosure, the method 800 is performed by a wireless transmitting device 200 shown in FIG. 2. The method 800 comprises: a step 801 of transmitting a PPDU 201 to at least one wireless receiving device 210. In particular, the PPDU 201 comprises at least one of: a first indication that indicates that the PPDU 201 includes an AP-to-AP communication, intended for at least one other AP and not intended for any non-AP STA; a second indication that indicates that the PPDU 201 is not intended for any other AP; and a third indication that indicates that the PPDU 201 is intended for at least one other AP and at least one non-AP STA. Possibly, the at least one wireless receiving device 210 is the wireless receiving device shown in FIG. 2 or FIG. 7.
FIG. 9 shows a method 900 according to an embodiment of the disclosure. In a particular embodiment of the disclosure, the method 900 is performed by a wireless receiving device 210 shown in FIG. 7. The method 900 comprises: a step 901 of receiving a PPDU 201 from a wireless transmitting device 200. In particular, the PPDU 201 comprises at least one of: a first indication that indicates that the PPDU 201 includes an AP-to-AP communication, intended for at least one other AP and not intended for any non-AP STA; a second indication that indicates that the PPDU 201 is not intended for any other AP; and a third indication that indicates that the PPDU 201 is intended for at least one other AP and at least one non-AP STA. Possibly, the wireless transmitting device 200 is the wireless transmitting device shown in FIG. 2 or FIG. 7.
The present disclosure has been described in conjunction with various embodiments as examples as well as implementations. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed disclosure, from the studies of the drawings, this disclosure and the independent claims. In the claims as well as in the description the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation.
Furthermore, any method according to embodiments of the disclosure may be implemented in a computer program, having code means, which when run by processing means causes the processing means to execute the steps of the method. The computer program is included in a computer readable medium of a computer program product. The computer readable medium may comprise essentially any memory, such as a ROM (Read-Only Memory) , a PROM (Programmable Read-Only Memory) , an EPROM (Erasable PROM) , a Flash memory, an EEPROM (Electrically Erasable PROM) , or a hard disk drive.
Moreover, it is realized by the skilled person that embodiments of the wireless transmitting device 100 and the wireless receiving device 210, respectively, comprises the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing the solution. Examples of other such means, units, elements and functions are: processors, memory, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selecting units, switches, interleavers, de-interleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiver units, transmitter units, DSPs, trellis-coded modulation (TCM) encoder, TCM decoder, power supply units, power feeders, communication interfaces, communication protocols, etc. which are suitably arranged together for performing the solution.
Especially, the processor (s) of the wireless transmitting device 200 and the wireless receiving device 210, respectively, may comprise, e.g., one or more instances of a Central Processing Unit (CPU) , a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC) , a microprocessor, or other processing logic that may interpret and execute instructions. The expression “processor” may thus represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above. The processing circuitry may further perform data processing functions for inputting, outputting, and processing of data comprising data buffering and device control functions, such as call processing control, user interface control, or the like.

Claims

A wireless transmitting device (200) for an access point, AP, wherein the wireless transmitting device (200) is configured to:

transmit a physical layer protocol data unit, PPDU (201) , to at least one wireless receiving device (210) , wherein the PPDU (201) comprises at least one of:

- a first indication that indicates that the PPDU (201) includes an AP-to-AP communication intended for at least one other AP and not intended for any non-AP station;

- a second indication that indicates that the PPDU (201) is not intended for any other AP; and

- a third indication that indicates that the PPDU (201) is intended for at least one other AP and at least one non-AP station.
The wireless transmitting device (200) according to claim 1, wherein the first indication further indicates a variant of the PPDU (201) that is used for the AP-to-AP communication, wherein the variant of the PPDU (201) includes one of:

- AP to single AP;

- orthogonal frequency division multiple access, OFDMA;

- multi-user multiple-input multiple-output, MU-MIMO; and

- trigger-based.
The wireless transmitting device (200) according to claim 1 or 2, wherein the PPDU (201) comprises a universal signal, U-SIG, field, and the U-SIG field comprises the first indication, or the second indication, or the third indication.
The wireless transmitting device (200) according to claim 3, wherein the U-SIG field comprises a compressed mode field.
The wireless transmitting device (200) according to the claims 2 and 4, wherein the U-SIG field further comprises a reserved bit, wherein

when the reserved bit is set to 1, the U-SIG field comprises the first indication, wherein the compressed mode field includes a PPDU type that indicates the variant of the PPDU (201) ; and

when the reserved bit is set to 0, the U-SIG field comprises the second indication, wherein the compressed mode field indicates that the PPDU (201) is a multi-user PPDU or a trigger-based PPDU as defined by the IEEE 802.11be standard.
The wireless transmitting device (200) according to claim 3, wherein the U-SIG field comprises a specific field dedicated for indicating the AP-to-AP communication, wherein the specific field comprises the first indication or the second indication.
The wireless transmitting device (200) according to claim 4, wherein the compressed mode field of the U-SIG field is an extended compressed mode field comprising a dedicated bit for indicating the AP-to-AP communication, wherein the extended compressed mode field comprises the first indication or the second indication.
The wireless transmitting device (200) according to the claims 2 and 7, wherein

when the dedicated bit is set to one of ‘1’a nd ‘0’ , the U-SIG field comprises the first indication, wherein the extended compressed mode field indicates the variant of the PPDU (201) ; and

when the dedicated bit is set to the other one of ‘1’a nd ‘0’ , the U-SIG field comprises the second indication, wherein the extended compressed mode field indicates that the PPDU (201) is a multi-user PPDU or a trigger-based PPDU as defined by the IEEE 802.11be standard.
The wireless transmitting device (200) according to claim 4, wherein the U-SIG field further comprises a basic service set, BSS, color field, wherein the BSS color field and the compressed mode field comprise the first indication or the second indication.
The wireless transmitting device (200) according to the claims 2 and 9, wherein a set of BSS color options is preserved for the AP-to-AP communication, wherein

when the BSS color field comprises a BSS color option from the preserved set of BSS color options, the U-SIG field comprises the first indication, wherein the compressed mode field indicates the variant of the PPDU (201) ;

when the BSS color field does not comprise a BSS color option from the preserved set of BSS color options, the U-SIG field comprises the second indication, wherein the compressed mode field indicates that the PPDU (201) is a multi-user PPDU or a trigger-based PPDU as defined by the IEEE 802.11be standard.
The wireless transmitting device (200) according to claim 4, wherein the U-SIG field further comprises a downlink/uplink, DL/UL, field, wherein the DL/UL field and the compressed mode field comprise the first indication or the second indication.
The wireless transmitting device (200) according to claim 2 and 11, wherein when the DL/UL field is set to 1, the U-SIG field comprises the first indication, wherein at least one reserved option of the compressed mode field indicates the variant of the PPDU (201) .
The wireless transmitting device (200) according to one of claims 1 to 12, wherein the wireless transmitting device (200) is for a sharing AP or a shared AP.
The wireless transmitting device (200) according to one of the claims 3 to 10 and claim 13, wherein the U-SIG field comprises a downlink/uplink, DL/UL, field, wherein

when the DL/UL field is set to 0, the wireless transmitting device (200) is for the sharing AP; and when the DL/UL field is set to 1, the wireless transmitting device (200) is not for the sharing AP; or

when the DL/UL field is set to 1, the transmitting of the PPDU (201) is triggered by a sharing AP; and when the DL/UL field is set to 0, the transmitting of the PPDU (201) is not triggered by a sharing AP.
The wireless transmitting device (200) according to claim 3, wherein the U-SIG field further comprises a reserved bit, wherein the reserved bit of the U-SIG field comprises the third indication.
The wireless transmitting device (200) according to claim 15, wherein the PPDU (201) further comprises an extremely high throughput signal, ETH-SIG, field, and a user field of the ETH-SIG field indicates an identification of AP that is assigned to a coordinated Multi-AP set.
The wireless transmitting device (200) according to claim 16, wherein the wireless transmitting device (200) and at least one wireless receiving device (210) for another AP belong to the same coordinated Multi-AP set.
The wireless transmitting device (200) according to claim 2, wherein the PPDU (201) comprises an extremely high throughput signal, ETH-SIG, field, wherein the ETH-SIG field comprises at least a common field and an AP-specific field.
The wireless transmitting device (200) according to claim 18, wherein when the variant of the PPDU (201) that is used for the AP-to-AP communication is OFDMA, a number of APs allocated to the PPDU (201) is not larger than a predetermined value, and each AP allocated to the PPDU (201) is assigned with a bandwidth not less than a first predetermined bandwidth, the ETH-SIG field is in a short format, wherein a resource allocation indication is omitted in the common field of the EHT-SIG field.
The wireless transmitting device (200) according to claim 19, wherein the number of APs allocated to the PPDU (201) is not larger than 8, and each AP allocated to the PPDU (201) is assigned with a bandwidth not less than 20MHz.
The wireless transmitting device (200) according to claim 19 or 20, wherein the PPDU (201) is transmitted over a second predetermined bandwidth, wherein in the short format,

the common field of the EHT-SIG field includes a field that indicates a number of APs allocated at each half of the second predetermined bandwidth.
The wireless transmitting device (200) according to claim 21, wherein the second predetermined bandwidth is 20MHz, 40MHz, 80MHz, 160MHz, or 320MHz,

when the number of APs allocated to the PPDU (201) is 1, the AP allocated to the PPDU (201) is assigned with the second predetermined bandwidth;

when the number of APs allocated to the PPDU (201) is 2, each AP allocated to the PPDU (201) is assigned with a half of the second predetermined bandwidth;

when the number of APs allocated to the PPDU (201) is 3 or 4, each AP allocated to the PPDU (201) is assigned with at least a quarter of the second predetermined bandwidth.
The wireless transmitting device (200) according to one of claims 18 to 22, wherein the AP specific field of the ETH-SIG field comprises one or more AP blocks, each AP block comprising one or two AP fields.
The wireless transmitting device (200) according to claim 23, wherein each AP field corresponds to a particular AP allocated to the PPDU (201) , and the AP field indicates a resource allocated to the AP, and an identification of a coordinated Multi-AP set to where the AP belongs.
The wireless transmitting device (200) according to claim 21 and claim 23, wherein when the second predetermined bandwidth comprises a punctured channel, the AP filed indicates multiple resources allocated to the AP.
The wireless transmitting device (200) according to one of claims 18 to 25 and claim 21, wherein,

the common field is divided into a first content channel and a second content channel, and

the first content channel includes AP fields of APs that are allocated in a lower half of the second predetermined bandwidth, and the second content channel includes AP fields of APs that are allocated in an upper half of the second predetermined bandwidth.
The wireless transmitting device (200) according to claim 26, the AP-specific field of the ETH-SIG field comprises a zero AP field indicating that a resource is not allocated to any AP.
A wireless receiving device (210) , being configured to:

receive a physical layer protocol data unit, PPDU (201) , from a wireless transmitting device (200) for an access point, AP, wherein the PPDU (201) comprises at least one of:

- a first indication that indicates that the PPDU (201) includes an AP-to-AP communication intended for at least one other AP and not intended for any non-AP station;

- a second indication that indicates that the PPDU (201) is not intended for any other AP; and

- a third indication that indicates that the PPDU (201) is intended for at least one other AP and at least one non-AP station.
The wireless receiving device (210) according to claim 28, wherein when the wireless receiving device (210) is for another AP, the wireless receiving device (210) is configured to:

detect whether the PPDU (201) comprises the first indication or the third indication; and

process the PPDU (201) if it is detected that the PPDU (201) comprises the first indication or the third indication.
The wireless receiving device (210) according to claim 29, wherein the wireless receiving device (210) is a sharing AP or a shared AP.
The wireless receiving device (210) according to claim 28, wherein when the wireless receiving device (210) is for a station, the wireless receiving device (210) is configured to: detect whether the PPDU (201) comprises the first indication; and

set a network allocation vector if the first indication is detected.
A method (800) for a wireless transmitting device (200) for an AP, the method comprising:

transmitting (801) a physical layer protocol data unit, PPDU (201) , to at least one wireless receiving device (210) , wherein the PPDU (201) comprises at least one of:

- a first indication that indicates that the PPDU (201) includes an AP-to-AP communication, intended for at least one other AP and not intended for any non-AP station;

- a second indication that indicates that the PPDU (201) is not intended for any other AP; and

- a third indication that indicates that the PPDU (201) is intended for at least one other AP and at least one non-AP station.
A method (900) for a wireless receiving device (210) , the method comprising:

receiving (901) a physical layer protocol data unit, PPDU (201) , from a wireless transmitting device (200) , wherein the PPDU (201) comprises at least one of:

- a first indication that indicates that the PPDU (201) includes an AP-to-AP communication intended for at least one AP and not intended for any non-AP station;

- a second indication that indicates that the PPDU (201) is not intended for any other AP; and

- a third indication that indicates that the PPDU (201) is intended for at least one other AP and at least one non-AP station.
A computer program comprising a program code for performing, when running on a computer, the method according to claim 32 or 33.