Method and apparatus for coordinating multi-access point communication

Abstract

To provide a communication device, a control method and a pull thereof for effectively coordinating communication of multiple access points (multiple APs) in a wireless network, and in particular in an IEEE 802.11 network.SOLUTION: In a method for coordinating communications including a group of access points (APs) sharing resources during a transmission opportunity (TXOP) acquired by a first AP of the group, the first AP assigns resources within the TXOP to a second AP of the group and forms the group on the basis of the APs' capabilities to share resources and / or use the shared resources and / or on the basis of an enablement state of the APs' capabilities to share resources and / or use the shared resources.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to the technical field of wireless communication networks, and more particularly to a method and device for coordinating communication of multiple access points (multiple APs) in an IEEE 802.11 network. [Background technology]

[0002] Multi-AP technology consists in a degree of cooperation between neighboring access points (APs) for more efficient utilization of available time, frequency, and space resources. This is especially important when neighboring APs operate on the same selected channel. With such technology, two neighboring APs can share resources in terms of frequency and / or time, and in this way they avoid interference. APs that cooperate to share resources are called coordinated APs. The AP that manages the cooperation is called coordinator AP. Typically, the coordinator AP is a sharing AP, i.e., an AP that acquires medium access rights for a given period (called a transmission opportunity or TXOP) in a given channel, and the coordinated AP is a shared AP, i.e., an AP that uses resources shared by the shared AP. The coordinator AP can then share time / frequency resources among the coordinated APs within a given period. The coordinated AP schedules downlink (DL) and / or uplink (UL) transmissions for associated non-AP stations within the constraints of assigned resources.

[0003] However, how neighboring APs and associated basic service sets (BSSs) cooperate to share common resources is not addressed in the prior art. It is desirable to define an efficient mechanism for implementing multi-AP operation. Summary of the Invention

[0004] In this context, a general object of the present invention is a communication method for coordinating multiple access points.

[0005] According to one aspect of the present invention, there is provided a method for coordinating communications in a wireless network including a group of access points (APs) sharing resources during a transmission opportunity (TXOP) acquired by a first AP of the group, the first AP being configured to allocate resources within the range of the TXOP to a second AP of the group, the group being formed based on capabilities of APs to share resources and / or use shared resources and / or based on an enablement state of features in the APs for sharing resources and / or using shared resources.

[0006] In a preferred implementation, the first AP is a coordinator AP of the communication, and the second AP is a coordinated AP.

[0007] In one implementation, the resources are any one or a combination of time resources, spatial resources, and frequency resources.

[0008] According to a further aspect of the present invention, there is provided a frame designed to be transmitted by an Access Point (AP) of a first Basic Service Set (BSS) to an AP of a second BSS, the frame including an enablement field indicating whether the AP of the first BSS has enabled a capability to allocate and / or share resources acquired by the AP of the first BSS during a transmission opportunity (TXOP) with an AP of the second BSS.

[0009] In particular, the AP of the first BSS is configured to support resource allocation and / or sharing functionality.

[0010] In a preferred implementation, the frame is a management frame.

[0011] According to a further aspect of the present invention, there is provided a coordinator AP in a wireless network including a group of access points (APs) that share resources during a transmission opportunity (TXOP) acquired by a coordinator AP of the group of APs, the coordinator AP being configured to allocate resources to coordinated APs of the group within the range of the TXOP, the group being formed based on the capabilities of the APs to share resources and / or use shared resources and / or based on an enablement state of the APs' capabilities to share resources and / or use shared resources.

[0012] According to a further aspect of the present invention, there is provided a coordinated AP in a wireless network including a group of access points (APs) that share resources during a transmission opportunity (TXOP) acquired by a coordinator AP among a group of APs, the coordinated APs being configured to use resources shared by the coordinator AP within the range of the TXOP, the group being formed based on the capabilities of the APs to share resources and / or use shared resources and / or based on an enablement state of the APs' capabilities to share resources and / or use shared resources.

[0013] Any feature of one aspect of the invention may be applied to other aspects of the invention in any appropriate combination, in particular method aspects may be applied to apparatus aspects and apparatus aspects may be applied to method aspects.

[0014] Additionally, hardware implemented features may be implemented in software and vice versa, and any references herein to software and hardware features should be interpreted accordingly.

[0015] Additionally, any apparatus features described herein may be provided as method features, and vice versa. As used herein, means-plus-function features may alternatively be expressed in terms of their corresponding structure, such as a suitably programmed processor and associated memory.

[0016] It should also be understood that specific combinations of the various features described and defined in any aspect of the present invention may be implemented and / or provided and / or used independently. [Brief description of the drawings]

[0017] Further advantages of the present invention will become apparent to those skilled in the art upon examination of the drawings and detailed description.Embodiments of the present invention will now be described, by way of example, and with reference to the following drawings, in which: FIG. [Figure 1] FIG. 1 illustrates an example of a network environment in which embodiments of the present disclosure in various aspects may be implemented. [Figure 2a] 1A and 1B are diagrams illustrating the formats of a MAC management frame and a data frame of IEEE 802.11. [Figure 2b] 1A and 1B are diagrams illustrating the formats of a MAC management frame and a data frame of IEEE 802.11. [Figure 3a] 11A-11C illustrate various exemplary format examples for signaling an AP's multi-AP capability and / or activation status. [Figure 3b] 11A-11C illustrate various exemplary format examples for signaling an AP's multi-AP capability and / or activation status. [Figure 3c] 11A-11C illustrate various exemplary format examples for signaling an AP's multi-AP capability and / or activation status. [Figure 4]2 illustrates, by way of a flow chart, the steps performed by a coordinator AP for coordinating multi-AP transmissions according to an embodiment of the present invention. [Figure 5a] FIG. 2 is a sequence diagram showing the operation of APs involved in multi-AP transmission according to an embodiment of the present invention. [Figure 5b] FIG. 2 is a sequence diagram showing the operation of APs involved in multi-AP transmission according to an embodiment of the present invention. [Figure 6a] FIG. 1 illustrates, by means of a flow chart, a possible implementation of an embodiment of the present invention for coordinating multi-AP transmissions. [Figure 6b] FIG. 1 illustrates, by means of a flow chart, a possible implementation of an embodiment of the present invention for coordinating multi-AP transmissions. [Figure 6c] FIG. 1 illustrates, by means of a flow chart, a possible implementation of an embodiment of the present invention for coordinating multi-AP transmissions. [Figure 7a] FIG. 2 illustrates, by means of a flow chart, management of a group of APs according to an embodiment of the present invention. [Figure 7b] FIG. 2 illustrates, by means of a flow chart, management of a group of APs according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] FIG. 1 illustrates an example of a network environment in which embodiments of the present disclosure in various aspects may be implemented.

[0019] The illustrated network environment includes a multi-AP system 100 formed by a group of adjacent wireless networks. A first wireless network includes an access point (AP) 110 and two non-AP stations (STAs) 115 and 118, a second wireless network includes an AP 130 and one non-AP STA 135, and a third wireless network includes an AP 150 and one non-AP STA 155. In this disclosure, the APs 110, 130, and 150 are also referred to as AP1, AP2, and AP3, respectively.

[0020] However, although not illustrated, it is not excluded that a device may act as an AP in one wireless network and at the same time belong to another wireless network as an associated STA.

[0021] The wireless network of the present system may operate on a common communication channel that the APs can share and that the APs must cooperate to avoid interference. The APs may also use the common communication channel to exchange messages with each other to coordinate multi-AP communication. The common communication channel may correspond to a portion (e.g., 20 MHz) or all (e.g., 20 MHz, 40 MHz, 80 MHz, or 160 MHz) of the operating channel.

[0022] Resources are defined on a common communication channel shared between APs. Resources may include spatial, frequency, and time resources and may be obtained according to various orthogonal multiplexing procedures. Examples of such procedures include Spatial Division Multiple Access (SDMA) systems, Time Division Multiple Access (TDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, and Single Carrier Frequency Division Multiple Access (SC-FDMA) systems. The amount of shared resources may be measured in time units, frequency bandwidth, number of streams, amount of data or traffic (e.g., number of bytes), and / or any other suitable units.

[0023] In the IEEE 802.11 wireless local area networking standard, the multi-AP system 100 can support wireless networks into an Extended Service Set (ESS) and a Basic Service Set (BSS), respectively.

[0024] Although the description of the embodiments of the present invention is provided in the context of IEEE 802.11, the embodiments are not so limited and may be applied to other types of wireless networks and protocols.

[0025] Multi-AP Capability and Activation According to an embodiment of the present invention, APs in a group of neighboring wireless networks (neighboring APs) may have different capabilities and may be in different enablement states with respect to coordination of multi-AP communication. An AP may not have multi-AP capability by design, i.e., it does not support or implement the basic functionality for multi-AP communication and therefore operates as a legacy AP. Or, an AP may have multi-AP capability, i.e., it implements one or more basic functions of multi-AP capability.

[0026] According to embodiments of the present invention, a multi-AP capable AP may further have the ability to enable or disable its multi-AP functionality. In other words, a multi-AP capable AP may be configured to disable (or enable) multi-AP, for example, when one or more conditions are met.

[0027] Multi-AP capability may be treated as either supported or not supported, and multi-AP enablement may be treated as either enabled or not enabled. In variations, capability and enablement states may apply partially to multi-AP functionality. In other words, some basic functionality may be supported or enabled, and others may not be supported or enabled.

[0028] For example, multi-AP functionality may include a basic functionality of sharing resources with other APs and other functionality of using resources shared by other APs.

[0029] The resources shared by the first AP and used by the second AP may represent any kind of resources (e.g., frequency, space and / or time resources) acquired by the first AP during a transmission opportunity (TXOP). Preferably, the device that coordinates the multi-AP communication (coordinator) is the AP that acquires the medium (first AP), and the device that responds to the coordination (coordinated) is the AP that uses the shared resources (second AP).

[0030] According to an embodiment of the present invention, an AP that does not support the multi-AP function does not support any of the basic functions. Conversely, an AP that supports the multi-AP function supports at least one basic function. Also, an AP that supports the multi-AP function may enable some or all of the basic functions.

[0031] According to an embodiment of the present invention, the activation of various basic features may be interdependent, i.e. the activation must follow certain rules.

[0032] Rules can impose requirements. For example, an AP that disables its sharing capabilities must also disable the ability to use resources shared by other APs. Conversely, an AP that enables the ability to use shared resources must enable the sharing capabilities. This ensures fairness between APs.

[0033] The rules may be flexible and preferences may be given. For example, an AP that disables the sharing feature may only be encouraged to disable the ability to use resources shared by other APs. In a variant, an AP that enables the sharing feature may not be required to use resources shared by other APs. Conversely, an AP that disables the ability to use shared resources may not disable the sharing feature.

[0034] According to embodiments of the present invention, the enablement of various basic functions may be independent of each other.

[0035] For example, an AP may enable or disable the sharing functionality, i.e., the ability to share frequency, time, and / or spatial resources acquired by that AP during a TXOP, independently of the enabling / disabling of the functionality to use resources shared by other APs. Conversely, an AP may enable or disable the functionality to use shared resources, i.e., the ability to use frequency, time, and / or spatial resources shared by other (coordinator) APs, independently of the enabling / disabling of the functionality to share resources.

[0036] As discussed above, enabling the multi-AP functionality may depend on one or more conditions being met, such as, for example, any of the following: BSS load (i.e., the amount of data for which an AP must or expects to allocate resources in its BSS), the number of neighboring APs, the number of neighboring APs that support the multi-AP functionality, the number of neighboring APs that have the multi-AP functionality enabled, etc.

[0037] Multi-AP capability and activation state signaling According to an embodiment of the present invention, an AP may signal its multi-AP capability and / or state (enabled / disabled) using data frames, management frames, control frames, or dedicated frames.

[0038] Signaling can be performed by an AP by sending unicast or multicast frames, respectively, directed to another AP (e.g., a coordinator AP) or a group of APs. Signaling may also be performed by an AP by sending broadcast frames directed to all APs.

[0039] 3a illustrates an example format of an information element 301 that may be used to signal multi-AP capability and / or activation status. The information element may be included in a management frame, such as a beacon frame.

[0040] The information element 301 may include the following subfields: an Element ID subfield 310, a Length subfield 311, a Coordinator AP ID subfield 312, a Multi-AP capabilities (support) subfield 313, and a Multi-AP Enable subfield 314. Note that the information element 301 may include only one of the Multi-AP capabilities subfield 313 and the Multi-AP Enable subfield 314.

[0041] The Element ID subfield 310 identifies this element as a multi-AP element. It can take on values ​​in the range [245-254], which is currently reserved in the 802.11 standard. For illustrative purposes, the value 246 is chosen in this embodiment of the invention.

[0042] The Length subfield 311 indicates the number of bytes in this element excluding the Element ID subfield 310 and the Length subfield 311 .

[0043] The Coordinator AP ID subfield 312 corresponds to the identifier of the coordinator AP. Preferably, it is equal to the BSS of the coordinator AP. In a variant, it is equal to a unique AID.

[0044] The Multi-AP capabilities subfield 313 indicates whether the AP supports multi-AP capabilities. For example, if this subfield has a value equal to 1, multi-AP is supported, and if it is 0, multi-AP is not supported.

[0045] The Multi-AP Enable subfield 314 indicates whether the AP has multi-AP capability enabled, e.g., if this subfield has a value equal to 1, multi-AP capability is enabled, and if it is 0, multi-AP capability is not enabled.

[0046] In variants, support and / or enablement of multi-AP basic functionality may be signaled. For example, to signal support of multi-AP basic functionality, the Multi-AP capabilities subfield 313 may include multiple subfields (not shown) for signaling support or non-support of one basic functionality, respectively. The subfield for support of multi-AP (overall) functionality may be kept in addition to the other subfields or may be omitted since support of multi-AP functionality is derivable from support of the basic functionality.

[0047] Also, to signal the enablement of multi-AP basic functionality, the Multi-AP Enable subfield 314 may include multiple subfields (not shown), each for signaling whether one basic functionality is enabled or not. The subfield for enabling multi-AP (overall) functionality may be kept in addition to the other subfields, or may be omitted since enabling multi-AP functionality is derivable from enabling the basic functionality.

[0048] The basic functions of a multi-AP may be, for example, a function of sharing resources, a function of using resources, a function of operating as a coordinator AP, a function of operating as a coordinated AP, and so on.

[0049] As described above, the information element 301 can, for example, be included in a management frame, such as a beacon frame or a new type of management frame that can be exchanged between APs, to signal the AP's multi-AP capability and / or activation status to neighboring APs.

[0050] As an example, the information element 301 may be included in the frame body field 210 of the IEEE 802.11 MAC management frame 201 (FIG. 2a).

[0051] FIG. 3b illustrates an example format of a Control Information subfield in the Operating Mode (OM) subfield of IEEE 802.11 adapted in accordance with an embodiment of the present invention.

[0052] The Control Information subfield within the OM Control subfield contains information regarding the Operational Mode (OM) change of the device transmitting the frame. The OM Control subfield is included in the HT Control field 220 of the IEEE 802.11 MAC data frame 201 (FIG. 2b).

[0053] The Control Information subfield is modified according to an embodiment of the present invention to signal the multi-AP enabled state.

[0054] For example, two subfields may be added: a "Multi-AP Enable" subfield 320 and a "Multi-AP Disable" subfield 321. The "Multi-AP Enable" subfield 320 is added to enable the multi-AP functionality of a multi-AP capable AP, and the "Multi-AP Disable" subfield 321 is added to disable the multi-AP functionality of a multi-AP capable AP.

[0055] In a variant, only one subfield, "Multi-AP Enable", is added to signal whether the multi-AP functionality is enabled (1) or not (0). In another variant, the "Multi-AP Enable" subfield is not present and the multi-AP functionality is considered enabled by default if it is supported. And the "Multi-AP Disable" subfield is set to 1 if it is desired to disable the multi-AP functionality.

[0056] In a variant, the enablement state of the basic multi-AP features can be signaled. For example, the Multi-AP Enabled subfield 320 may include multiple subfields (not shown), each signaling whether one basic feature is enabled or not. The subfield for enabling the multi-AP (overall) feature may be kept in addition to the other subfields, or may be omitted, since enabling the multi-AP feature can be derived from enabling the basic features.

[0057] Additionally, modified OM Control fields can be inserted into MAC frames addressed to various destinations. The multi-AP functionality of an AP can be disabled for one neighboring AP, a set of neighboring APs, or all neighboring APs.

[0058] FIG. 3c illustrates an example format of an Action frame 330 for signaling a multi-AP enabled state, in accordance with an embodiment of the present invention.

[0059] As specified in the IEEE 802.11 standard, the Action frame provides a mechanism for specifying enhanced management operations. According to these embodiments, Category field 331 indicates that it is dedicated to multi-AP functionality, and field 332 includes a multi-AP enabled status that indicates whether multi-AP functionality is enabled or disabled.

[0060] The Action frame can be unicast, multicast, or broadcast, allowing advertising the state of the multi-AP feature to one neighboring AP, a set of neighboring APs, or all neighboring APs.

[0061] Coordinator AP / Coordinated AP Operation FIG. 4 illustrates, by way of a flow chart, the steps performed by a coordinator AP to coordinate multi-AP transmissions according to an embodiment of the present invention.

[0062] In step S410, an AP gains access to the medium resources (space, time, and / or frequency) for the TXOP period and becomes the coordinator of the multi-AP transmission.

[0063] In step S420, the coordinator AP obtains a group of APs that will participate in the multi-AP transmission. The group may be formed from a list of APs maintained by the coordinator AP. The list may include detected neighboring APs. The list may further include information such as the multi-AP capability and enablement status of the detected APs. The group may then be formed based on the list, for example by including all detected APs when no further information is available about the APs' capabilities and enablement status. If information about the enablement status of the multi-AP functionality is available, it is preferable for the coordinator to configure the group based on whether the APs have enabled their multi-AP functionality. In particular, only APs that have signaled that they have enabled the multi-AP functionality (or at least the basic functionality of using shared resources) are included in the group. The group may be established before or after the coordinator AP has acquired medium access.

[0064] In step S430, the coordinator AP allocates the acquired resources to one or more APs in the group.

[0065] Thus, an embodiment of the present invention relates to a method for coordinating communications in a wireless network including a group of Access Points (APs) sharing resources during a transmission opportunity (TXOP) acquired by a coordinator AP in the group of APs, the coordinator AP being configured to allocate resources within the TXOP to the coordinated APs of the group, where the groups are formed based on their ability to share resources and / or use the shared resources and / or based on an enablement state of the APs' capabilities to share resources and / or use the shared resources.

[0066] Each AP in the group is itself configured to manage a basic service set (BSS) of stations.

[0067] 5a and 5b illustrate, by means of a sequence diagram, the operation of APs involved in a multi-AP transmission according to an embodiment of the present invention. In the illustrated example, the multi-AP operation involves one coordinator AP (AP1) and two coordinated APs (AP2 and AP3), but the present embodiment applies to any number of APs.

[0068] Block 510 of the diagram corresponds to step S410 of FIG. 4, where AP1 gains access to the medium resource for the TXOP period and becomes the coordinator of the multi-AP transmission.

[0069] In Fig. 5a, sequence 520 corresponds to an initialization phase in which the coordinator is implemented to accomplish one or both of two main functions. The first one is for the coordinator AP to indicate / signal to the coordinated APs that it has acquired the medium over the channel during the period TXOP and is ready to start the multi-AP transmission. The second one is for the coordinator AP to optionally request responses from the coordinated APs to know which coordinated APs are willing to participate in the multi-AP transmission. It may also request the resource needs of each coordinated AP that is willing to participate.

[0070] The resource needs may correspond to an amount of required resources measured in time units, frequency bandwidth, number of streams, amount of data or traffic, and / or any other suitable units.

[0071] Thus, two types of messages SETUP_REQ and SETUP_RESP may be exchanged during the initialization phase 520: a SETUP_REQ (521) message is sent by the coordinator AP, and a SETUP_RESP (522) message is sent by the coordinated AP in response to the SETUP_REQ. The SETUP_REQ (521) may contain the indication mentioned above (e.g., a request for a response). The SETUP_RESP (522) may contain whether the coordinated AP is willing to participate in the multi-AP transmission and, optionally, its resource needs. In a variant, the coordinated AP responds to the coordinator AP's request only if it is willing to participate, i.e., no response indicates that the coordinator AP is not willing to participate. This variant is advantageous in that it makes it possible to handle the case where the coordinator AP is not available to send its response.

[0072] The SETUP_REQ message can be sent by the coordinating AP to a target specific AP (e.g., by using as many unicast frames as necessary, multicast / group addressed frames), or the SETUP_REQ message can be sent by the coordinating AP using a broadcast frame addressed to all of the APs configured to decode the frame.

[0073] After the initialization phase 520, the coordinator AP forms a resource allocation by allocating resources to a group of coordinated APs (530). The resource allocation may include any information for the AP that is required to discover the resources that are assigned to it. Basically, the allocation may include one or more of the following: the BSSID of the AP to which the resource is assigned, the channel number or width (e.g. number of tones) of the frequency band to which it is assigned, the start time / duration or TXOP of the resource. Note that one or more of the information items may be implicit or predefined and therefore not communicated to the coordinated AP (cf. 540). For example, an AP may set aside certain resources for sharing if it does not use them (pre-agreement between APs). In this case, the AP only needs to indicate the availability of the resources.

[0074] The group of APs to which resources are assigned may be based on the group of APs to which the SETUP_REQ message was sent. The group of APs to which resources are assigned may be a subset or a superset of that initial group. Details of group formation are described later in this specification.

[0075] Once the coordinator AP has collected the resource needs of the coordinated APs, e.g., via the SETUP_RESP message, the coordinator may use the resource needs to form a resource allocation, and in particular to decide how much resources to allocate to each coordinated AP. Alternatively or additionally, the coordinator AP may take into account a set of rules, which may be predefined, for example, to allocate resources.

[0076] The coordinator AP then shares the created allocation to the participating APs using a dedicated message SHARE_ALLOCATION (540). The allocated resources are used by each coordinated AP within the BSS used by the AP or STA to transmit data (550).

[0077] 5a illustrates a multi-AP operation in which the coordinator AP forms the resource allocation after gaining access to the media resource, which is advantageous in that it allows the AP to form the resource allocation based on the actual amount of resources it has acquired and the latest needs of the coordinated APs, thus improving the efficiency of resource utilization.

[0078] Figure 5b illustrates a multi-AP operation in which the coordinator AP forms the resource allocation before gaining access to the medium resources, which has the advantage that the coordinated AP that has obtained the resource allocation has time to schedule transmissions within the BSS.

[0079] The formation of resource allocation (530) and sharing of the allocation (540) takes place before the coordinating AP acquires access to the medium resources (510). The allocation may be formed based on the resource needs of the coordinated APs collected in advance. Alternatively or in addition, the coordinating AP may take into account a set of rules, which may for example be predefined, for the allocation of resources. The SETUP_REQ message (523) is optionally used to indicate / signal to the coordinated APs that its function is that the coordinating AP has acquired the medium on the channel for the period TXOP. It may also be used to signal that the AP is ready to start multi-AP transmission.

[0080] 6a, 6b and 6c illustrate, by way of a flow chart, a possible implementation of an embodiment of the present invention in one AP for coordinating multi-AP transmissions.

[0081] The flowchart of Figure 6a depicts a sequence of steps similar to those discussed with reference to Figure 5a. In this implementation, an AP gains access to media resources (S610a), obtains the participation intentions of coordinated APs (S620a), optionally obtains their resource needs (S630a), forms a resource allocation (S640a), and shares the formed resource allocation to a group of APs (S650a).

[0082] The flowchart of Figure 6b illustrates a variant sequence of steps in which obtaining the intentions of coordinated APs (S620b) and obtaining their resource needs (S630b) are performed before gaining access to the medium (S610b), and forming resource allocations (S640b) and sharing the formed resource allocations to a group of APs (S650b) are performed thereafter.

[0083] The flowchart of Figure 6c illustrates a further variation of the sequence of steps, in which the AP forms a resource allocation (S640c) without explicit or immediate input from a coordinated AP. After the AP gains access to the medium (S610c), the AP shares the formed resource allocation to a group of APs (S650c).

[0084] Multi-AP group formation In multi-AP operation, the coordinator obtains a group of APs with which the resource may be shared by the AP that has gained access to the resource. This may correspond to step S420 of the flowchart of FIG. 4 according to an embodiment of the present invention. The obtained group is hereinafter referred to as a candidate group or set. It may also be referred to as a qualified group or set. The coordinator then forms a group of APs to which the resource is assigned for use in the respective BSS based on the candidate group (e.g., step S430 in FIG. 4). The formed group is referred to as an assignee group or set. The assignee group may be the same as the candidate group, may be a part of the candidate group, or may extend the candidate group with additional APs as described in detail later in this specification.

[0085] The coordinator function may be hosted by a master device or an AP elected for a period of time according to defined rules, or may be taken over by each AP that has gained access to a media resource (a shared AP) to give the responsibility for coordinating the multi-AP operation to the AP that owns the resource. The latter is illustrated, for example, by the embodiment of Fig. 4. In the following, for simplicity of explanation, it is assumed that the coordinator is a shared AP, i.e., the AP that has gained access to the resource.

[0086] According to an embodiment of the present invention, the candidate group is formed by a list of multi-AP capable APs, hereafter referred to as L0, which is maintained by each multi-AP capable or multi-AP enabled AP and can be obtained by various methods.

[0087] The coordinator may collect the multi-AP capabilities of the APs using signaling sent by the APs or by their associated STAs. The transmission may be over the air over a unicast, multicast, or broadcast link between the coordinator and the APs. Alternatively or additionally, the transmission may be over a wired link, for example over a backhaul network or via an internal connection in case the coordinator and the AP are hosted by the same device (e.g., in case of a physical AP hosting multiple virtual APs).

[0088] The signaling may be done using a multi-AP capability field (e.g., field 313 shown in FIG. 3a) indicating support for multi-AP operation and / or support for one or more basic multi-AP features. This field may be embedded in an information element (e.g., information element 301 shown in FIG. 3a) or any suitable signaling field.

[0089] The multi-AP capability field can be transmitted in existing or new types of frames exchanged between APs, for example, if the transmission is over a wireless link, a management frame (e.g., a frame as illustrated in FIG. 2a) or a newly defined management frame can be used.

[0090] According to an embodiment of the present invention, the candidate group is formed by a list of APs that have enabled their multi-AP functionality, hereafter referred to as list L1. L1 can be obtained in various ways.

[0091] For example, L1 can be obtained by checking the multi-AP enabled status of L0's APs. Alternatively, L1 may be configured independently of L0 by listing all APs that have enabled their multi-AP capability.

[0092] Determining which APs have enabled their multi-AP functionality may depend on signaling received from the AP (or STA) by the coordinator in response to a request from the coordinator or without the AP being requested.

[0093] The coordinator may collect the multi-AP enabled state of the AP through signaling sent by the AP or a STA associated with the AP. Signaling the multi-AP enabled state may be done by means similar to that of signaling the multi-AP capability described above.

[0094] In particular, the signaling may be done using a Multi-AP Enabled field (e.g., field 314 shown in FIG. 3a) indicating the enabled state of multi-AP operation and / or the enabled state of one or more basic multi-AP features. This field may be embedded in an information element (e.g., information element 301 shown in FIG. 3a), in a Control Information subfield of the Operating Mode (OM) subfield defined in IEEE 802.11 (e.g., field 320 / 321 shown in FIG. 3b), in an action frame specified according to IEEE 802.11 (e.g., field 332 of frame 330 shown in FIG. 3c), or in any suitable signaling field embedded in management frames exchangeable between existing or new types of BSSs.

[0095] The multi-AP enablement field can be sent in existing or new types of frames exchanged between APs, such as management frames (e.g., frames such as those illustrated in FIG. 2a or newly defined management frames), control frames, data frames (e.g., FIG. 2a), or action frames (e.g., FIG. 3c).

[0096] Signaling the multi-AP enabled state may be addressed to all APs (without distinction), potentially including APs that voluntarily share their resources. Alternatively, the signaled state may be applied on a per-AP basis, i.e., an AP may signal its multi-AP enabled state to a specific AP or to multiple APs.

[0097] As discussed above in this specification, the signaled enabled state may apply to the entire multi-AP functionality, including all of the basic functionality, such as using shared resources and sharing resources, or specifically to one or more of the basic functionality.

[0098] According to one implementation, L1 may be configured to include only APs that have enabled their basic capabilities of using shared resources. This implementation is advantageous because APs that maintain candidate groups based on L1 have better knowledge of the needs or willingness of other APs to use shared resources and thus allocate resources more efficiently to reduce unused resources.

[0099] Relying on the multi-AP enabled state as a whole may not be sufficient. In fact, an AP that has enabled its multi-AP functionality may not have enough data to be exchanged within its BSS at a given time to justify using resources shared by other APs. Also, an AP that is not configured or does not implement basic capability signaling but is configured or does implement multi-AP capability signaling needs to be able to signal its willingness to share its resources (if it grants access to media resources) while not willing to use resources currently shared by the coordinator AP.

[0100] According to an embodiment of the invention, the candidate group is formed by a list of APs indicating their locations participating in the multi-AP transmission, hereafter referred to as list L2. L2 can be obtained in various ways.

[0101] An AP may signal its willingness to join using a control frame. This signaling may be done in response to a request control frame from the coordinator (e.g., control frame SETUP_RESP 522 following control frame SETUP_REQ 521 in FIG. 5a), or the signaling may be AP-initiated.

[0102] The signaled intent may apply to one, the current, or the next multi-AP transmission (i.e., the multi-AP transmission that is relevant when the AP gains medium access and can allocate resources to other APs). Alternatively, it may last for a predefined number of multi-AP transmissions or for a period of time. In a further variation, an AP's intent to join or not join may last until the AP updates its intent in a subsequent control frame.

[0103] The willingness to be signaled may apply indiscriminately to all APs willing to share their resources, or alternatively, the willingness to be signaled may apply on a per-AP basis, i.e., an AP may signal whether it is willing to use resources shared by a particular AP or multiple APs.

[0104] The signaled intention may apply to the multi-AP functionality as a whole, i.e., may include basic functionality such as intending to use shared resources and to share resources when an AP gains access to a media resource, etc. Alternatively, the signaled intention may apply specifically to one or more basic functionality, e.g., intending to use shared resources.

[0105] According to an embodiment of the present invention, the two groups are identical since the assigned group is formed by all APs of the candidate group, i.e. by any one of lists L0, L1 or L2. Thus, the selected list forming the assigned group according to this embodiment is called L3.

[0106] According to an embodiment of the invention, the assigned group is formed by a list of APs called L4 that is a sublist of L3, i.e. only a part of the APs of L3 are included in L4. The APs selected to form L4 can be based on different criteria and can serve different purposes.

[0107] For example, the amount of resources that an AP can share may not be sufficient to serve all APs in the candidate group, in which case the selection of APs to form L4 may be random, arbitrary, or based on priorities.

[0108] Additionally or alternatively, the types of resources that an AP can share may not match what a candidate AP can use, for example because the candidate AP is capable or configured to use the spatially shared resources or to operate in a given frequency band in which the shared resources are located. In this case, the selection of APs to form L4 may take into account APs that are capable or most likely to use the shared resources.

[0109] Additionally or alternatively, the amount of resources that an AP previously shared with a given AP may reach a limit (window), and the given AP may be removed from the list of APs to which resources are assigned. The removal may be permanent or temporary, e.g., for a defined time period. Also, fairness between coordinated APs may be considered depending on the amount of resources assigned to other APs. The amount of resources may be evaluated in time units, frequency bandwidth, number of streams, amount of data or traffic (e.g., number of bytes), and / or any other suitable units. The amount of resources previously shared by an AP may be counted only during its last multi-AP transmission (TXOP). In a variant, the amount of resources may be counted for more than one multi-AP transmission in which the AP shared the resources. For example, the resources may be counted during a defined time period, e.g., a target beacon transmission time (TBTT), or in multiple multi-AP transmissions. In this variant, the removal occurs when the cumulative amount of resources reaches a limit.

[0110] Additionally or alternatively, an AP may be removed from the list of APs to which resources are assigned because it has not reciprocated by sharing its own resources. In this case, reciprocity criteria may be applied to maintain a certain level of fairness. For example, an AP that has been assigned resources and has not shared its own resources in a subsequent multi-AP transmission may not be kept in the list. An AP may be reintroduced when it finally shares resources during a multi-AP transmission or after a certain time interval has elapsed since it was assigned resources (cf. e.g. Figs. 7a and 7b). Thus, the coordinator AP may maintain one timer per coordinated AP. In a variant, an offset of the window of shared resources may be set between pairs of APs. When a first AP as a sharing AP assigns a first resource to a second AP (as a shared AP), the offset is increased by the amount of the assigned first resource, and when the second AP as a sharing AP assigns a second resource to the first AP (as a shared AP) in return, the offset is decreased by the amount of the assigned second resource. When the offset reaches the window offset, no more resources are assigned. The amount of resources may be measured in time units, frequency bandwidth, number of streams, and / or any other suitable units.

[0111] In a variant, a first AP (acting as a shared AP) to which resources are specifically assigned by a second AP (acting as a sharing AP) must, when operating as a sharing AP, assign resources to the second AP (acting as a shared AP) for a defined period of time.

[0112] In a variant, a sharing AP that removes a shared AP from its candidate group informs the shared AP of the removal, for example by using a message.

[0113] In a variant, a sharing AP that adds a shared AP to its candidate group notifies the shared AP of the addition, e.g., by using a message. In a variant, a sharing AP may notify a shared AP only if the shared AP was added (i.e., reintroduced) after it was previously removed.

[0114] According to an embodiment of the invention, an assignment group is formed by a list of APs called L5 that extends L3, i.e., in addition to the APs in L3, one or more APs are included in L5. The additional one or more APs may be based on various criteria. For example, if more resources are available than should be assigned to the APs of the candidate group (e.g. based on the needs of the APs of the candidate group), the additional APs may be added to benefit from the resource surplus. The additional APs may be requested to participate in the multi-AP transmission for them to be included in the transmission. In a variant, the additional APs are APs that have enabled their multi-AP functionality and joined the network, or APs that are considered high priority after the candidate group is formed.

[0115] According to an embodiment of the present invention, the assignment group is formed by a list of APs called L6 which is a combination of lists L4 and L5, i.e. L6 includes some of the APs in L3 and one or more APs which are not part of L3.

[0116] Figures 7a and 7b illustrate the management of a group of APs according to an embodiment of the invention by means of a flow chart. The flow chart illustrates the management of a candidate group of APs, but can also be applied to an assigned group of APs.

[0117] Figure 7a illustrates the removal of an AP from the candidate group if it has shared resources instead for a defined period of time, and Figure 7b illustrates the inclusion of an AP into the candidate group if it has shared resources (e.g., after having previously been removed).

[0118] In step 710, the sharing AP obtains a candidate group, for example according to any of the embodiments described herein for forming a group. After the sharing AP allocates resources to the APs of the group (S720), a timer is started (S730) to monitor whether the shared AP to which the resources have been allocated allocates resources in exchange for the first sharing AP during a period T. If the timer expires (S735) without the shared AP sharing resources instead, the shared AP is removed from the candidate group (S737). Optionally, the sharing AP may check a condition to see if the shared AP should be removed (S736). The condition may be, for example, that the shared AP is not bound by the reciprocity rule, is a high priority AP, or forms an exception. If the condition is met, the shared AP is not removed. Before the expiration of the timer (i.e., during the period T), the first sharing AP acquires the resources from the shared AP (S740), and the timer is stopped (S741) without removing the shared AP from the group.

[0119] According to the embodiment of Fig. 7b, following or independently of the exclusion, if an AP shares resources and is not in the group of candidate APs among those APs with which the resource is shared (S750), the AP is included in the group (S752). Optionally, a condition can be checked to see if the AP that shared the resource should be added (S751). If the condition is met, the AP is not added to the group.

Claims

1. A communication device operating as an access point, An acquisition means for acquiring a transmission opportunity (TXOP); A transmitting means for transmitting a first frame during a period of the acquired TXOP to notify another access point of an intention to share at least a part of the acquired TXOP; receiving means for receiving a response from another access point indicating whether the other access point intends to accept allocation of at least a portion of the TXOP from the communication device as a response to the first frame; having the transmitting means transmits a second frame for allocating at least a portion of the TXOP to other access points that have transmitted responses indicating an intention to accept allocation of at least a portion of the TXOP; A communication device comprising:

2. 2. The communication device according to claim 1, wherein the receiving means receives a response from the other access point indicating that the other access point does not intend to accept allocation of at least a portion of the TXOP from the communication device.

3. 2. The communication device according to claim 1, wherein the transmitting means transmits the first frame specifying a specific access point as the communication device that should respond to the first frame.

4. 2. The communication device of claim 1, wherein if the communication device does not receive a response to the first frame from another access point, the communication device assumes that the other access point has no intention of accepting allocation of at least a portion of the TXOP.

5. 2. The communication device according to claim 1, wherein said receiving means receives a third frame from another access point, the third frame including capability information indicating that said access point has a capability of performing cooperative operation among a plurality of access points.

6. 2. The communication device according to claim 1, wherein the communication device performs wireless communication in accordance with the IEEE 802.11 standard.

7. 2. The communication device according to claim 1, wherein the communication device is a sharing AP conforming to the IEEE 802.11 standard.

8. A communication device operating as an access point, receiving means for receiving a first frame from another access point during a transmission opportunity (TXOP) for notifying the other access point of its intention to share at least a portion of the TXOP; a transmitting means for transmitting a response indicating whether the other access point intends to accept an allocation of at least a portion of the TXOP from the other access point as a response to the first frame to the other access point; having The receiving means receives a second frame for allocating at least a portion of the TXOP from the other access point in response to transmitting a response indicating an intention to accept allocation of at least a portion of the TXOP. A communication device comprising:

9. 9. The communication device according to claim 8, wherein the transmitting means transmits a response to the other access point indicating that the communication device has no intention of accepting allocation of at least a portion of the TXOP from the other access point.

10. 9. The communication device according to claim 8, wherein said receiving means receives said first frame identifying said communication device as the specific communication device that should respond to said first frame.

11. The communication device of claim 8, wherein the communication device does not transmit a response to the first frame to the other access point if the communication device does not intend to accept allocation of at least a portion of the TXOP.

12. 9. The communication device according to claim 8, wherein the transmitting means transmits to the other access points a third frame including capability information indicating that the other access points have a capability of performing cooperative operations among a plurality of access points.

13. 9. The communication device according to claim 8, wherein the communication device performs wireless communication in compliance with the IEEE 802.11 standard.

14. 9. The communication device according to claim 8, wherein the communication device is a shared AP conforming to the IEEE 802.11 standard.

15. A method for controlling a communication device operating as an access point, comprising the steps of: acquiring a transmission opportunity (TXOP); a first transmission step of transmitting a first frame during the acquired TXOP to notify other access points of an intention to share at least a portion of the acquired TXOP; receiving a response from the other access point in response to the first frame indicating whether the other access point is willing to accept an allocation of at least a portion of the TXOP from the communication device; a second transmission step of transmitting a second frame for allocating at least a portion of the TXOP to other access points that have transmitted responses indicating an intention to accept the allocation of at least a portion of the TXOP; A control method comprising the steps of:

16. A method for controlling a communication device operating as an access point, comprising the steps of: a first receiving step of receiving a first frame from another access point during a transmission opportunity (TXOP) to notify the other access point of its intention to share at least a portion of the TXOP; a transmitting step of transmitting a response to the first frame to the other access point indicating whether the other access point intends to accept an allocation of at least a portion of the TXOP from the other access point; a second receiving step of receiving a second frame for allocating at least a portion of the TXOP from the other access point in response to transmitting a response indicating an intention to accept allocation of at least a portion of the TXOP; A control method comprising the steps of:

17. A computer included in a communication device that operates as an access point acquiring a transmission opportunity (TXOP); a first transmission step of transmitting a first frame during the acquired TXOP to notify another access point of an intention to share at least a portion of the acquired TXOP; receiving a response from the other access point in response to the first frame indicating whether the other access point is willing to accept an allocation of at least a portion of the TXOP from the communication device; a second transmission step of transmitting a second frame for allocating at least a portion of the TXOP to other access points that have transmitted responses indicating an intention to accept the allocation of at least a portion of the TXOP; A program for executing.

18. A computer included in a communication device that operates as an access point a first receiving step of receiving a first frame from another access point during a transmission opportunity (TXOP) to notify the other access point of its intention to share at least a portion of the TXOP; transmitting a response to the first frame to the other access point indicating whether the other access point intends to accept an allocation of at least a portion of the TXOP from the other access point; a second receiving step of receiving a second frame for allocating at least a portion of the TXOP from the other access point in response to transmitting a response indicating an intention to accept allocation of at least a portion of the TXOP; A program for executing.

Images