Patent Description:
IEEE-<NUM>-based WLANs have become popular at an unprecedented rate. 11be introduces a Multi AP (M-AP) coordinated transmission, where a group of APs may initiate concurrent frame exchange within a limited time period and one or more APs of the group of APs may share one or more transmission opportunities (TXOPs). The group of APs that have decided to cooperate and perform coordinated transmissions is called an M-AP set. One or more parameters of a coordinated transmission may change between TXOPs including the list of participating APs from the M-AP set, the coordination scheme, resource allocation and the like. However, known or proposed procedures require to re-indicate and re-agree on the coordination parameters at each TXOP regardless of a previous TXOP or any other previous information exchange between the APs. In other words, all or most of the coordination parameters have to be indicated by the TXOP holder to other APs at the beginning of each TXOP. As a consequence, even if some of parameters remain constant over long time periods covering several TXOPs, they still need to be indicated every TXOP resulting in a signaling overhead.

<CIT> describes an access point (AP)that includes circuitry, which, in operation, generates a frame that includes joint transmission (JT) data and a JT identity that uniquely identifies the JT data. The access point further includes a transmitter, which, in operation, transmits the frame to one or more APs that jointly transmit the JT data to a communication apparatus. If the joint transmission is expected to take place for more than one or two frames, set up is a joint transmission session between the Master AP and the participating Slave APs prior to the actual joint transmission. During the joint transmission session negotiation, the Master AP and Slave APs exchange information about the Target STAs involved in the joint transmission. The Master AP and Slave APs also specify the joint transmission parameters that are expected to be used throughout the session, for example the channel to be used, the PPDU format (HT, VHT or HE etc.), pre-coding schemes for MU-MIMO etc. Each joint transmission session is identified by a unique Session ID.

<CIT> describes systems, methods, and devices related to multi-AP resource sharing. A device may participate in a set of coordinated access points (APs) for coordinating a sharing of one or more resources. The device may evaluate whether there is data to be transmitted to at least one associated station device. The device may, based on the evaluation, perform an action associated with acquiring a first transmit opportunity (TXOP) to be shared with one or more candidate APs of the set of coordinated APs.

<CIT> describes that an access point (AP) may transmit, to a second AP and during a first portion of a transmission opportunity (TxOP), a request to participate in a multi-user (MU) transmission. The AP may receive, from the second AP and during the first portion of the TxOP, an indication of intent to participate in the MU transmission during the second portion of the TxOP, the indication of intent including a resource request of the second AP for participation in the MU transmission. The AP may transmit, during an initial period of the second portion of the TxOP, a trigger signal to the second AP indicating a set of one or more resources for the second AP during the MU transmission. The AP may participate, in conjunction with the second AP and during the second portion of the TxOP, in the MU transmission.

It is an objective to provide improved devices and methods for Multi-Access Point (M-AP) coordinated transmission in a wireless communication network allowing for a reduced signaling overhead.

The foregoing and other objectives are achieved by the subject matter of the independent claims.

According to a first aspect, a wireless AP under the role of Sharing AP is configured to share at least a portion of a TXOP, namely its obtained TXOP, with at least one further wireless AP within an M-AP set for participating in one or more coordinated transmissions for communicating with a plurality of wireless non-AP stations. For participating in the one or more coordinated transmissions the wireless APs of the M-AP set have decided upon a coordination agreement of a plurality of agreeable coordination agreements within the MAP set, which define one or more communication parameters to be used for the one or more coordinated transmissions. The wireless AP comprises a processing circuitry configured to generate an M-AP agreement-based announcement frame. The M-AP agreement-based announcement frame comprises a coordination agreement identifier within the M-AP set, wherein the coordination agreement identifier identifies the coordination agreement. Moreover, the wireless AP comprises a communication interface configured to transmit the M-AP agreement-based announcement frame to the at least one further wireless AP within the M-AP set, wherein the Sharing wireless AP and the further wireless AP within the M-AP set operate under, i.e. according to, the same coordination agreement identified by the coordination agreement identifier within the M-AP set. Thus, advantageously, an improved wireless AP in a wireless communication network is provided allowing to reduce the signalling overhead for M-AP coordinated transmission. This is because, one or more of the coordination agreement parameters to be used for the coordinated transmissions may be agreed in advance and, thus, are not required to be explicitly signalled.

In a further possible implementation form of the first aspect, the M-AP agreement-based announcement frame further comprises an M-AP set identifier for identifying the M-AP set including the coordination agreement identified by the coordination agreement identifier. Advantageously, the M-AP agreement-based announcement frame allows identifying both the coordination agreement as well as the corresponding M-AP set.

In a further possible implementation form of the first aspect, the M-AP agreement-based announcement frame further comprises information about a number of a plurality of further wireless APs which are proposed to participate in the coordinated transmission in the current TXOP and are operating under the same coordination agreement within the M-AP set.

In a further possible implementation form of the first aspect, the M-AP agreement-based announcement frame further comprises an identifier of the at least one further wireless AP operating under the coordination agreement within the M-AP set which is proposed to participate in the coordinated transmission in the current TXOP. Advantageously, this allows each wireless AP receiving the M-AP agreement-based announcement frame to efficiently determine whether the M-AP agreement-based announcement frame is relevant for the respective wireless AP.

In a further possible implementation form of the first aspect, the M-AP agreement-based announcement frame further comprises AP-specific resource allocation information about communication resources allocated to the at least one further wireless AP operating under the coordination agreement within the M-AP set which is to participate in the coordinated transmission in the current TXOP. Advantageously, this allows the Sharing AP to define a resource allocation to the Shared APs for the current TXOP.

In a further possible implementation form of the first aspect, the M-AP agreement-based announcement frame further comprises coordination scheme dependent information about one or more parameters to be included, if required by a specific coordination scheme under the coordination agreement within the M-AP set.

The coordination agreement defines one or more parameters of the one or more coordinated transmissions that follow the coordinated agreement setting, till the agreement is either torn down or becomes invalid. By identifying the coordination agreement using the M-AP agreement-based announcement frame, advantageously, no further messaging is required to define the one or more coordinated transmission parameters which are invariant along the coordinated agreement duration. In other words, one or more of the coordination agreement parameters to be used for the coordinated transmissions may be agreed in advance and, thus, are not required to be explicitly signalled.

In a further possible implementation form of the first aspect, the M-AP agreement-based announcement frame further comprises a response type indicator indicative of a response type to be used by the at least one further solicited wireless AP operating under the coordination agreement within the M-AP set for responding to the M-AP agreement-based announcement frame. Advantageously, this allows to efficiently coordinate the expected response type from the further solicited wireless AP(s) receiving the M-AP agreement-based announcement frame.

In a further possible implementation form of the first aspect, the response type indicator is indicative of a parallel response, a sequential response or no response from the at least one further solicited wireless AP operating under the same coordination agreement within the M-AP set.

In a further possible implementation form of the first aspect, the at least one further responding wireless AP operating under the same coordination agreement within the MAP set comprises a plurality of further wireless APs operating under the same coordination agreement within the M-AP set, wherein the response type indicator is indicative of the parallel response from the plurality of further wireless APs operating under the same coordination agreement within the M-AP set. The communication interface of the wireless AP is further configured to transmit an M-AP trigger frame to the plurality of wireless APs operating under the same coordination agreement within the MAP set for triggering the parallel response from the plurality of further wireless APs operating under the same coordination agreement within the M-AP set. Advantageously, the trigger frame enables a synchronized simultaneous response from the plurality of further wireless APs.

In a further possible implementation form of the first aspect, the M-AP trigger frame comprises the coordination agreement identifier. Advantageously, this allows any further wireless AP that is not included in the coordination agreement identified by the coordinated agreement identifier to stop their reception of the soliciting M-AP trigger frame and avoid any response thereto.

In a further possible implementation form of the first aspect, the M-AP trigger frame further comprises at least one of a M-AP set identifier for identifying the M-AP set, information about the duration of the response to the M-AP agreement-based announcement frame, an identifier of each of the plurality of further wireless APs operating under the same coordination agreement within the M-AP set, resource allocation information about communication resources allocated to each of the plurality of further wireless APs operating under the same coordination agreement within the M-AP set for replying to the M-AP agreement-based announcement frame, and/or information about a modulation and coding scheme to be used by each of the plurality of further wireless APs operating under the same coordination agreement within the M-AP set for replying to the M-AP agreement-based announcement frame. Advantageously, this allows the further wireless APs to obtain the required format of the response frame.

In a further possible implementation form of the first aspect, the at least one further wireless AP operating under the same coordination agreement within the M-AP set comprises a plurality of further wireless APs operating under the same coordination agreement within the M-AP set, wherein the type indicator is indicative of the sequential response from the plurality of further wireless APs operating under the same coordination agreement within the M-AP set, wherein the communication interface is further configured, in response to receiving a first immediate sequential response to the M-AP agreement-based announcement frame from a first wireless AP of the plurality of further wireless APs operating under the same coordination agreement within the M-AP set, to sequentially transmit a poll frame to a further wireless AP of the plurality of further wireless APs operating under the same coordination agreement within the M-AP set, which has not responded yet, for requesting a response to the M-AP agreement-based announcement frame. Advantageously, this allows to efficiently coordinate the expected response type from the further solicited wireless AP(s) receiving the M-AP agreement-based announcement frame.

In a further possible implementation form of the first aspect, the M-AP agreement-based announcement frame comprises an identifier of the first wireless AP of the plurality of further wireless APs operating under the same coordination agreement within the M-AP set which is configured to respond immediately to the M-AP agreement-based announcement frame. Advantageously, this allows to the Sharing AP to determine which of the further wireless APs will respond immediately.

In a further possible implementation form of the first aspect, the poll frame comprises the coordination agreement identifier and a corresponding M-AP set identifier. Advantageously, this allows a respective further wireless AP receiving the poll frame to associate the poll frame with the previously received M-AP agreement-based announcement frame including the response type indicator.

In a further possible implementation form of the first aspect, the response type indicator is indicative of no response from the at least one further solicited wireless AP operating under the same coordination agreement within the M-AP set, wherein the communication interface is configured to start transmitting within its BSS in accordance with the coordination agreement identified by the coordination agreement identifier.

In a further possible implementation form of the first aspect, the communication interface is configured to receive a response frame from the at least one further wireless AP within the M-AP set, wherein the processing circuitry is configured to extract from the response frame at least one of the coordination agreement identifier, the corresponding M-AP set identifier, an identifier of the at least one further wireless AP and an indicator whether the at least one further wireless AP participates in the one or more coordinated transmissions in the current TXOP in accordance with the coordination agreement within the M-AP set. Advantageously, this allows to efficiently ensure a controlled message exchange between the wireless APs of the M-AP set.

According to a second aspect a method of operating a wireless AP under the role of Sharing AP is provided, wherein the wireless AP is configured to share at least a portion of a TXOP, namely its obtained TXOP with at least one further wireless AP within a M-AP set for participating in one or more coordinated transmissions for communicating with a plurality of wireless stations. The method comprises the steps of:.

In a further possible implementation form of the second aspect, the method further comprises the steps of:
receiving a response from each of the further solicited wireless APs within the M-AP set that operate under, i.e. according to the same coordination agreement; and processing the response content for the approval or disapproval of the parameters specified in the solicited M-AP agreement-based announcement frame.

The method according to the second aspect can be performed by the wireless AP according to the first aspect of the present disclosure. Thus, further features of the method according to the second aspect of the present disclosure result directly from the functionality of the wireless AP according to the first aspect of the present disclosure as well as its different implementation forms described above and below.

According to a third aspect a wireless AP (herein also referred to as "Shared AP") configured to participate in one or more coordinated transmissions for communicating with a plurality of wireless stations making use of at least a portion of a TXOP shared by a further wireless AP (i.e. the "Sharing AP") operating under one of a plurality of coordination agreements within a M-AP set. The wireless AP (i.e. the "Shared AP") comprises a communication interface configured to receive an M-AP agreement-based announcement frame from the further wireless AP and a processing circuitry configured to extract a coordination agreement identifier from the M-AP agreement-based announcement frame. The coordination agreement identifier identifies the coordination agreement of the plurality of agreeable coordination agreements within the M-AP set, and the coordination agreement defines one or more coordinated transmission parameters of the one or more coordinated transmissions. The communication interface is further configured to participate in the one or more coordinated transmissions in the current TXOP in accordance with the coordination agreement within the M-AP set.

In a further possible implementation form of the third aspect, the processing circuitry is further configured to extract in addition to the coordination agreement identifier an M-AP set identifier from the M-AP agreement-based announcement frame for identifying the MAP set. As already described above, the coordination agreement identified by the coordination agreement identifier is between the wireless APs that are members of the MAP set identified by the M-AP set identifier.

In a further possible implementation form of the third aspect, the processing circuitry is further configured to extract a response type indicator from the M-AP agreement-based announcement frame, wherein the response type indicator is indicative of a response type to be used by the solicited wireless AP under the same coordination agreement within the M-AP set for possibly responding to the M-AP agreement-based announcement frame.

In a further possible implementation form of the third aspect, the response type indicator is indicative of a parallel response, a sequential response or no response from the solicited wireless AP.

In a further possible implementation form of the third aspect, the response type indicator is indicative of a parallel response, wherein the communication interface is further configured to receive a M-AP trigger frame from the further wireless AP operating under the same coordination agreement within the M-AP set for triggering the parallel response from the solicited wireless AP with other wireless APs operating under the same coordination agreement within the M-AP set.

In a further possible implementation form of the third aspect, the processing circuitry is further configured to extract the coordination agreement identifier and an M-AP set identifier for identifying the M-AP set from the M-AP trigger frame.

In a further possible implementation form of the third aspect, the processing circuitry is further configured to extract from the M-AP trigger frame at least one of: information about the duration of the response to the M-AP agreement-based announcement frame, an identifier of the wireless AP, resource allocation information about communication resources allocated to the wireless AP for responding to the M-AP agreement-based announcement frame, and/or information about a modulation and coding scheme to be used by the wireless AP for responding to the M-AP agreement-based announcement frame.

In a further possible implementation form of the third aspect, the communication interface is configured to transmit a response frame to the further soliciting wireless AP, in response to the M-AP trigger frame.

In a further possible implementation form of the third aspect, the response type indicator is indicative of the sequential response, wherein the processing circuitry is further configured to determine that an immediate response is required from the wireless AP.

In a further possible implementation form of the third aspect, the communication interface is configured to transmit an immediate response frame to the M-AP agreement-based announcement frame solicited by the further soliciting wireless AP.

In a further possible implementation form of the third aspect, the response type indicator is indicative of the sequential response, wherein the communication interface is further configured to receive a poll frame from the further wireless AP operating under the same coordination agreement within the M-AP set for requesting the response to the M-AP agreement-based announcement frame from the wireless AP.

In a further possible implementation form of the third aspect, the response type indicator is indicative of the no response, wherein the processing circuitry is further configured to determine that no immediate response is required from the wireless AP.

In a further possible implementation form of the third aspect, the poll frame comprises the coordination agreement identifier and a corresponding M-AP set identifier.

In a further possible implementation form of the third aspect, the communication interface is configured to transmit a response frame to the further soliciting wireless AP, in response to receiving the poll frame.

In a further possible implementation form of the third aspect, the response type indicator is indicative of no response from the solicited wireless AP, wherein the communication interface of the solicited wireless AP is configured to, based on the M-AP agreement-based announcement frame, in particular information contained in the M-AP agreement-based announcement frame, to start the one or more coordinated transmissions.

In a further possible implementation form of the third aspect, the response frame comprises at least one of the coordination agreement identifier, the corresponding M-AP set identifier, an identifier of the wireless AP, an indicator whether the wireless AP participates in the one or more coordinated transmissions in the current TXOP in accordance with the coordination agreement within the M-AP set and coordination scheme dependent information about one or more parameters to be included, if required by a specific coordination scheme under the coordination agreement within the M-AP set.

According to a fourth aspect a method of operating a wireless AP under the role of "Shared AP" is provided, wherein the wireless AP is configured to participate in one or more coordinated transmissions for communicating with a plurality of wireless stations making use of at least a portion of a TXOP shared by a further wireless AP operating under one of a plurality of coordination agreements within a M-AP set. The method according to the fourth aspect comprises the steps of:.

In a further possible implementation form of the fourth aspect, the method further comprises extracting an M-AP set identifier from the M-AP agreement-based announcement frame, in addition to the coordination agreement identifier.

In a further possible implementation form of the fourth aspect, the method further comprises the steps of:.

The method according to the fourth aspect can be performed by the wireless AP according to the third aspect of the present disclosure. Thus, further features of the method according to the fourth aspect of the present disclosure result directly from the functionality of the wireless AP according to the third aspect of the present disclosure as well as its different implementation forms described above and below.

According to a fifth aspect a computer program product is provided, comprising program code which causes a computer or a processor to perform the method according to the second aspect or the method according to the fourth aspect, when the program code is executed by the computer or the processor.

In the following, embodiments of the present disclosure are described in more detail with reference to the attached figures and drawings, in which:.

In the following, identical reference signs refer to identical or at least functionally equivalent features.

In the following description, reference is made to the accompanying figures, which form part of the disclosure, and which show, by way of illustration, specific aspects of embodiments of the present disclosure or specific aspects in which embodiments of the present disclosure may be used. It is understood that embodiments of the present disclosure may be used in other aspects and comprise structural or logical changes not depicted in the figures.

For instance, it is to be understood that a disclosure in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa.

11be a coordination between multiple wireless APs has been agreed (referred to as Multi-AP or M-AP coordination). A wireless AP which obtains a transmission opportunity (TXOP) and initiates the Multi-AP coordination is called the sharing AP. A wireless AP which is coordinated for the Multi-AP transmission by the sharing AP is called the shared AP. Thus, in a WiFi communication network which supports coordination between APs, the wireless AP obtaining the TXOP, i.e. the TXOP holder may share the resources with other wireless APs within the same M-AP set. This scenario is described in more detail in the following in the context of the exemplary WiFi communication system <NUM> shown in <FIG>. By way of example, the wireless, in particular WiFi communication network <NUM> shown in <FIG> comprises a plurality of wireless APs 110a-f, wherein the wireless APs 110a-d are part of a M-AP set (referred to as "M-AP Set X" in <FIG>), while the wireless APs 110e and 110f are not part of this M-AP set (but may be part of a different M-AP set). For participating in one or more coordinated transmissions the wireless APs 110a-d of the M-AP have set a coordination agreement of a plurality of agreeable coordination agreements within the M-AP set, which define one or more communication parameters to be used for the one or more coordinated transmissions.

In the exemplary scenario illustrated in <FIG>, a TXOP may have been obtained, by way of example, by the wireless AP 110a (i.e. the sharing wireless AP 110a), which initiates the coordinated transmission with the further wireless APs of the M-AP set, namely the further wireless APs 110b-d (i.e. the shared wireless APs) for communicating with one or more wireless non-AP stations <NUM>. In other words, the wireless AP 110a under the role of sharing AP is configured to share at least a portion of its obtained TXOP with the sharing wireless APs 110b-d within the M-AP set for participating in one or more coordinated transmissions for communicating with the plurality of wireless non-AP stations <NUM>.

As illustrated in <FIG>, the wireless AP 110a (i.e. the sharing AP) according to an embodiment comprises a processing circuitry 111a for processing data and a communication interface 113a for exchanging data with the other wireless APs 110b-f and the one or more wireless non-AP stations <NUM>. In an embodiment, the communication interface 113a may comprise an antenna for wireless communication with the other wireless APs 110b-f and the one or more wireless non-AP stations <NUM>. The processing circuitry 111a may be implemented in hardware and/or software. The hardware may comprise digital circuitry, or both analogue and digital circuitry. Digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), digital signal processors (DSPs), or general-purpose processors. The wireless AP 110a may further comprise a memory 115a, e.g. a Flash memory 115a, configured to store executable program code which, when executed by the processing circuitry 111a, causes the sharing wireless AP 110a to perform the functions and operations described herein.

Likewise, the further wireless apparatuses 110b-d (as illustrated in <FIG> for the exemplary further wireless AP 110b) comprise a processing circuitry 111b for processing data, a communication interface 113b for exchanging data with the wireless AP 110a and the one or more wireless non-AP stations <NUM>. In an embodiment, the communication interface 113b may comprise one or more antennas for wireless communication with the one or more wireless non-AP stations <NUM>. The processing circuitry 111b may be implemented in hardware and/or software. The hardware may comprise digital circuitry, or both analogue and digital circuitry. Digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), digital signal processors (DSPs), or general-purpose processors. The further wireless APs may further comprise a memory 115b, e.g. a Flash memory 115b, configured to store executable program code which, when executed by the processing circuitry 111b, causes each further wireless AP 110b-d to perform the functions and operations described herein.

As will be appreciated, while in the exemplary coordinated transmission scenario shown in <FIG> the wireless AP 110a is the sharing AP and the further wireless apparatuses 110b-d are the shared APs, in a further coordinated transmission one of the shared APs 110b-d may become the sharing AP and the sharing AP 110a may become one of the shared APs. Thus, the plurality of wireless APs 110a-d may be identical or very similar devices that are configured to provide the functionality of both the shared AP and one of the sharing APs that will be described in more detail in the following.

As will be described in more detail in the following, the processing circuitry 111a of the sharing wireless AP 110a is configured to generate an M-AP agreement-based announcement frame 130a (herein also referred to as "MAPA frame"). The M-AP agreement-based announcement frame 130a comprises a coordination agreement identifier within the M-AP set. The coordination agreement identifier contained within the M-AP agreement-based announcement frame 130a identifies one coordination agreement of a plurality of agreeable coordination agreements within the M-AP set. In an embodiment, the M-AP agreement-based announcement frame 130a may further comprise an M-AP set identifier identifying the M-AP set including the wireless APs 110a-d.

As illustrated in <FIG>, the communication interface 113a of the sharing wireless AP 110a is configured to transmit the M-AP agreement-based announcement frame 130a to the shared wireless APs, including the shared wireless AP 110b within the M-AP set. As already described above, the sharing wireless AP 110a and the shared wireless APs have set a coordination agreement that has a unique identifier within the M-AP set, namely the coordination agreement identifier, and may comprise a specific set of invariant parameters. In other words, the sharing wireless AP 110a and the shared wireless AP 110b within the M-AP set operate under, i.e. in compliance with the same coordination agreement identified by the coordination agreement identifier within the M-AP set. Thus, by means of the M-AP agreement-based announcement frame 130a the TXOP holder, i.e. the sharing wireless AP 110a, is able to efficiently inform other APs of the M-AP set, for instance, the wireless AP 110b that may participate in a current coordination transmission regarding proposed coordination parameters (as defined by the coordination agreement). In an embodiment, the communication interface 113a of the sharing wireless AP 110a at the beginning of a TXOP or during a TXOP.

Complementary to the sharing wireless AP 110a, the communication interface 113b of the shared wireless AP 110b is configured to receive the M-AP agreement-based announcement frame 130a from the sharing wireless AP 110a and the processing circuitry 111b is configured to extract, i.e. parse the coordination agreement identifier (and, if present, the M-AP set identifier) from the M-AP agreement-based announcement frame 130a. In accordance with the coordination agreement within the M-AP set identified by the extracted coordination agreement identifier the shared wireless AP 110b, more specifically its communication interface 113b is configured to participate in the one or more coordinated transmissions of the current TXOP.

<FIG> shows an exemplary sequence of coordinated transmissions 201a-c that may be performed by the plurality of wireless APs 110a-d of the M-AP set shown in <FIG>. As can be taken from <FIG>, once the M-AP set has been established in a stage <NUM>, the wireless APs 110a-d of the M-AP set in a stage 205a may set a specific coordination agreement, which may comprise agreeing on a plurality (not necessarily all) of invariant parameters for the coordinated transmission, i.e. parameter settings to be used by the wireless APs 110a-d of the M-AP set during the coordinated transmissions 201a,b. In an embodiment, some of the coordinated transmission parameters, e.g. parameters depending on the dynamics of the WiFi network <NUM> may be updated for every TXOP by means of the M-AP agreement-based announcement frame 130a. The M-AP agreement-based announcement frame 130a may be transmitted during a respective pre-"coordinated transmission" stage 207a-c. As illustrated, after one or more coordinated transmission in accordance with a first coordination agreement, the same M-AP set of wireless APs 110a-d or a modified M-AP set of wireless APs (possibly including the wireless APs 110e or 110ffrom <FIG>) may set a new coordination agreement. As will be appreciated, while during one coordinated transmission duration the wireless AP 110a may be the sharing AP and the wireless AP 110b one of the shared APs, during the same or another coordinated transmission duration involving a new coordination agreement the wireless AP 110b may be the sharing AP (and perform the operations described in the context of the wireless AP 110a) and the wireless AP 110a one of the shared APs.

<FIG> shows a schematic diagram illustrating the sharing of exemplary communication resources during one or more coordinated transmissions of the plurality of APs 110a-d of the M-AP set according to an embodiment. More specifically, several TXOPs are illustrated in <FIG> (as frequency resources over time), wherein a first portion of these TXOPs are obtained by APs that are members of a M-AP set under the same coordination agreement and a second portion of these TXOPs are obtained by those that are not in the M-AP set (such as the wireless APs 110e, 110f of <FIG>). When the TXOP holder is an AP which is part of the coordination agreement within the M-AP set, such as the wireless AP 110a of <FIG>, it shares its overall frequency resources with several APs for the entire duration of the TXOP and each AP transmits on the frequency portion that is allocated to it. However, when the TXOP holder is not a member of the M-AP set (such as the wireless APs 110e, 110f of <FIG>) the entire frequency resources are utilized solely by this TXOP holder without sharing it with other APs. As can be further taken from <FIG>, frequency may be shared differently between APs within different TXOPs which illustrates that shared resources may be changed over the coordination agreement duration.

As illustrated in <FIG>, a coordination agreement period may include several TXOPs where each TXOP may start with the transmission of the M-AP agreement-based announcement frame 130a and several coordinated transmissions.

In an embodiment, the M-AP agreement-based announcement frame 130a may further comprise information about a number of the plurality of shared wireless APs 110b-d which are proposed to participate in the coordinated transmission 201a-c in each of the TXOPs and are operating under the coordination agreement within the M-AP set. In a further embodiment, the M-AP agreement-based announcement frame 130a may further comprise a respective identifier of the respective shared wireless AP 110b-d operating under the coordination agreement within the M-AP set. In an embodiment, the M-AP agreement-based announcement frame 130a further comprises resource allocation information about communication resources allocated by the Sharing AP to the respective shared wireless AP 110b-d operating under the coordination agreement within the M-AP set for the current TXOP.

As illustrated in <FIG>, in an embodiment, the communication interface 113a of the sharing wireless AP 110a is configured to receive one or more response frames <NUM> from the shared wireless APs 110b-d under the same coordination agreement within the M-AP set. In an embodiment, the processing circuitry 111a of the sharing wireless AP 110a is configured to extract from the respective response frame <NUM> at least one of the coordination agreement identifier, the M-AP set identifier, an identifier of the respective shared wireless AP 110b-d and an indicator whether the respective shared wireless AP 110b-d is going to participate in the one or more coordinated transmissions 201a-c in the TXOP in accordance with the coordination agreement within the M-AP set.

As will be described in more detail in the following under further reference to <FIG> and <FIG>, in an embodiment, the M-AP agreement-based announcement frame 130a further comprises a response type indicator indicative of a response type to be used by each of the shared wireless APs 110b-d for returning the response frame <NUM> to the sharing wireless AP 110a. In an embodiment, the response type indicator is indicative of a parallel response (illustrated in <FIG>), a sequential response (illustrated in <FIG>) or no response from the shared wireless APs (as illustrated in <FIG>) 110b-d operating under the coordination agreement within the M-AP set.

In the embodiment shown in <FIG>, the response type indicator is indicative of a parallel response 603a-n from the shared wireless APs 110b-d operating under the coordination agreement within the M-AP set. As illustrated in <FIG>, in an embodiment, the communication interface 113a of the sharing AP 110a may be further configured to transmit an M-AP trigger frame <NUM> to the shared wireless APs 110b-d for triggering the parallel response 603a-c from the shared wireless APs 110b-d operating under the coordination agreement within the M-AP set. In an embodiment, the M-AP trigger frame <NUM> may comprise the coordination agreement identifier for allowing the shared wireless APs to associate the M-AP trigger frame <NUM> with the preceding M-AP agreement-based announcement frame 130a.

In an embodiment, the M-AP trigger frame <NUM> may further comprise at least one of the M-AP set identifier, information about the duration of the response 603a-c to the M-AP agreement-based announcement frame 130a, an identifier of each of the shared wireless APs 110b-d, resource allocation information about communication resources allocated to each of the shared wireless APs 110b-d for replying to the M-AP agreement-based announcement frame 130a, and/or information about a modulation and coding scheme to be used by each of the shared wireless APs 110b-d for replying to the M-AP agreement-based announcement frame 130a.

As already mentioned above, in the embodiment shown in <FIG>, the response type indicator is indicative of a sequential response 703a-cfrom the shared wireless APs 110b-d operating under the coordination agreement within the M-AP set. In this embodiment, the communication interface 113a of the sharing wireless AP 110a is configured, after it has received a first sequential response 701a to the M-AP agreement-based announcement frame 130a from a first shared wireless AP, e.g. the shared wireless AP 110b, to transmit a poll frame <NUM> to a further shared wireless AP, e.g. the shared wireless AP 110c, which has not responded yet, for requesting a response 703c to the MAP agreement-based announcement frame 130a. In the embodiment illustrated in <FIG>, the M-AP agreement-based announcement frame 130a may comprises an identifier of the first shared wireless AP, e.g. the shared wireless AP 110b to respond immediately to the M-AP agreement-based announcement frame 130a. In an embodiment, the poll frame <NUM> may comprise the coordination agreement identifier and the M-AP set identifier.

Thus, when the response type indicator is indicative of a sequential response, the communication interface 113b of the shared wireless AP 110b, i.e. the first shared wireless AP 110b identified by the M-AP agreement-based announcement frame 130a is configured to immediately (i.e. without awaiting any further triggers) transmit the response frame 703a to the M-AP agreement-based announcement frame 130a solicited by the sharing wireless AP 110a. For the second shared wireless AP identified by the M-AP agreement-based announcement frame 130a, e.g. the shared wireless AP 110c its processing circuitry is configured to determine that for the time being no immediate response is required from the sharing wireless AP 110b (until the poll frame <NUM> is received).

In an embodiment, where the response type indicator is indicative of no response from the shared wireless APs 110b-d, the communication interface 113a of the sharing wireless AP 110a is configured to immediately start transmitting in accordance with the coordination agreement identified by the coordination agreement identifier (i.e. once the M-AP agreement-based announcement frame 130a has been transmitted). When the response type indicator is indicative of no response, the communication interface 113b of the shared wireless AP 110b may, based on the M-AP agreement-based announcement frame 130a, start the one or more coordinated transmissions 201a-c.

<FIG> is a flow diagram illustrating a method <NUM> of operating the sharing wireless AP 110a according to an embodiment.

The method <NUM> may further comprise the steps of receiving a response, such as the parallel or sequential responses 603a-c, 703a-c described above, from each of the shared wireless APs 110b-d within the M-AP set that operate under the same coordination agreement as the sharing wireless AP 110a processing the content of the respective response 603a-c, 703a-c for the approval or disapproval of one or more parameters specified in the M-AP agreement-based announcement frame 130a.

<FIG> is a flow diagram illustrating a method <NUM> of operating the shared wireless AP 110b according to an embodiment.

The method <NUM> may further comprise extracting a response type indicator from the M-AP agreement-based announcement frame 130a and transmitting a possible response 603a-c, 703a-c to the sharing wireless AP 110a based on the response type indicator. As already described above, in an embodiment, the response type indicator may indicate "no response", in which case there will be no response and the coordinated transmission will immediately begin.

The person skilled in the art will understand that the "blocks" ("units") of the various figures (method and apparatus) represent or describe functionalities of embodiments of the present disclosure (rather than necessarily individual "units" in hardware or software) and thus describe equally functions or features of apparatus embodiments as well as method embodiments (unit = step).

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus, and method may be implemented in other manners. For example, the described embodiment of an apparatus is merely exemplary. For example, the unit division is merely logical function division and may be another division in an actual implementation.

Claim 1:
A method (<NUM>) of operating a wireless access point, AP, (110a) configured to share at least a portion of a transmission opportunity, TXOP, with at least one further wireless AP (110b-d) within an multi access point, M-AP, set for participating in one or more coordinated transmissions (201a-c), the method (<NUM>) comprising:
generating (<NUM>) an M-AP agreement-based announcement frame (130a), wherein the M-AP agreement-based announcement frame (130a) comprises a coordination agreement identifier within the M-AP set, wherein the coordination agreement identifier identifies one coordination agreement of a plurality of coordination agreements within the M-AP set, and the coordination agreement defines one or more coordinated transmission parameters of the one or more coordinated transmissions (201a-c); and
transmitting (<NUM>) the M-AP agreement-based announcement frame (130a) to the at least one further wireless AP (110b-d) within the M-AP set, wherein the wireless AP (110a) and the at least one further wireless AP (110b-d) within the M-AP set operate under the coordination agreement identified by the coordination agreement identifier within the M-AP set.