COMMUNICATIONS DEVICE AND METHOD

Abstract

A first communication device acting as a source node transmits a cooperative transmission (CT) link metric query to a relay node, asking the relay node to feed back measurements / estimates of several cooperative transmission data rates, which causes at least one second communication device acting as a relay node to send a CT link metric response to the source node. The CT link metric response includes measurements / estimates of several cooperative transmission data rates between the relay node and a sink node (non-AP STA).

Description

[Technical field]

[0001] TECHNICAL FIELD The present disclosure relates to communications devices and methods, and in particular to multi-access point (multi-AP) devices and methods for use in multi-AP networks. [Background technology]

[0002] A multi-AP device is generally understood to be a wireless access point (AP) that can cooperate with other APs to transmit and / or receive signals. This cooperation includes joint processing, meaning that several multi-AP devices can transmit or receive signals simultaneously to obtain better performance by utilizing spatial diversity. Multi-AP has been considered in particular to extend the coverage and / or improve the robustness of wireless networks.

[0003] A wireless network utilizing multi-AP may include a source node (also referred to herein as a "first multi-AP device"), one or more relay nodes (also referred to herein as a "second multi-AP device"), and one or more sink nodes (also referred to herein as a "third communication device" or "non-AP STA"). A source node is a communication device that is the source of data sent, a relay node is a communication device that relays data to other communication devices, and a sink node is a communication device that is the destination of the data.

[0004] The "Background" statements provided herein are intended to generally indicate the context of the present disclosure. To the extent that they are provided in this Background section, aspects of the description, currently named inventors' work, and which may not be admitted as prior art at the time of filing, are not admitted expressly or impliedly as prior art to the present disclosure.

[0005] Summary of the Invention [Problem to be solved by the invention]

[0006] It is an object to improve data throughput in wireless networks using cooperative transmission. A further object is to provide a corresponding communication device and method, as well as a corresponding computer program and non-transitory computer readable recording medium for implementing the method. [Means for solving the problem]

[0007] According to one aspect, a first communication device configured to operate as a source node and communicate with one or more second communication devices, the second communication device configured to operate as a relay node and communicate with one or more third communication devices, the first communication device comprising: - transmitting a cooperative transmission (CT) link metric query to a plurality of second communication devices requesting them to collect CT link metric information regarding cooperative transmissions from two or more of the second communication devices to one or more third communication devices, the CT link metric query including one or more CT instructions, each CT instruction indicating a different combination of two or more second communication devices and / or a different beamforming (BF) type for which CT link metric information should be collected; receiving a CT link metric response from at least one of the plurality of second communication devices in response to the transmitted CT link metric query, the CT link metric response including the collected CT link metric information; - determining a BF type to be used by a plurality of second communication devices for cooperative transmission to one or more third communication devices based on the CT link metric response; - transmitting BF type information indicating the determined BF type to a plurality of second communication devices; A first communications device is provided, the first communications device including circuitry configured according to the following:

[0008] According to a further aspect, a second communication device configured to operate as a relay node, the second communication device configured to communicate with a first communication device configured to operate as a source node, one or more other second communication devices configured to operate as relay nodes, and / or one or more third communication devices configured to communicate with the one or more second communication devices, - receiving a cooperative transmission (CT) link metric query from a first communication device requesting to collect CT link metric information for cooperative transmissions from the second communication device and one or more other second communication devices to one or more third communication devices, the CT link metric query including one or more CT instructions, each CT instruction indicating a different combination of two or more second communication devices and / or a different beamforming (BF) type for which CT link metric information should be collected; - transmitting a CT link metric response to the first communication device in response to the transmitted CT link metric query, the CT link metric response including the collected CT link metric information; receiving, from the first communication device, BF type information indicating a determined BF type to be used by the second communication device for a cooperative transmission to the third communication device; - transmitting data to a third communication device in cooperation with one or more other second communication devices using a BF type indicated for the second communication device in the received BF type information; A second communications device is provided that includes circuitry configured according to the following:

[0009] According to further aspects of the corresponding method, there is provided a computer program comprising program means for causing a computer to perform the steps of the methods disclosed herein, when the computer program is executed on a computer, as well as a non-transitory computer readable recording medium having stored therein a computer program product which, when executed by a processor, causes a computer to perform the methods disclosed herein.

[0010] Embodiments are defined in the dependent claims. It is to be understood that the disclosed method, the disclosed computer program and the disclosed computer-readable recording medium have further embodiments similar and / or identical to the claimed devices and those defined in the dependent claims and / or disclosed herein.

[0011] One aspect of the present disclosure is to foresee a scheme of link metric indication from a relay node to a source node, such that the relay device can perform optimized cooperative transmission (sometimes also referred to as joint transmission) depending on the data traffic and / or the intended sink node.

[0012] The preceding paragraphs have been provided by way of general introduction and are not intended to limit the scope of the following claims. The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings, in which:

[0013] A more complete understanding of the present disclosure and many of the attendant advantages will be readily obtained as the same becomes better understood by reference to the following detailed description, when considered in connection with the accompanying drawings. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic diagram of a multi-AP network in which a communication device according to the present disclosure may be used. [Figure 2A]FIG. 2 is a schematic diagram showing different types of cooperative transmission, non-cooperative transmission, and dynamic point selection. [Figure 2B] FIG. 2 is a schematic diagram showing different types of cooperative transmission, non-cooperative transmission, and dynamic point selection. [Figure 2C] FIG. 2 is a schematic diagram showing different types of cooperative transmission, non-cooperative transmission, and dynamic point selection. [Figure 2D] FIG. 2 is a schematic diagram showing different types of cooperative transmission, non-cooperative transmission, and dynamic point selection. [Figure 2E] FIG. 2 is a schematic diagram showing different types of cooperative transmission, non-cooperative transmission, and dynamic point selection. [Figure 2F] FIG. 2 is a schematic diagram showing different types of cooperative transmission, non-cooperative transmission, and dynamic point selection. [Diagram 3] 4 is a flow chart illustrating one embodiment of a first communication method according to the present disclosure. [Figure 4] 4 is a flow chart illustrating one embodiment of a second communication method according to the present disclosure. [Diagram 5] FIG. 2 illustrates a more detailed embodiment of a communication scheme for communication between different communication devices according to the present disclosure. [Figure 6] FIG. 2 illustrates one embodiment of a CT link metric query frame in accordance with the present disclosure. [Figure 7] FIG. 13 illustrates another embodiment of a communication scheme for communication between different communication devices according to the present disclosure. [Figure 8A] FIG. 1 illustrates one embodiment of a CT link metric response frame in accordance with the present disclosure. [Figure 8B] FIG. 1 illustrates one embodiment of a CT link metric response frame in accordance with the present disclosure. [Figure 8C] FIG. 1 illustrates one embodiment of a CT link metric response frame in accordance with the present disclosure. [Figure 8D] FIG. 1 illustrates one embodiment of a CT link metric response frame in accordance with the present disclosure. [Figure 8E] FIG. 1 illustrates one embodiment of a CT link metric response frame in accordance with the present disclosure. [Figure 8F] FIG. 1 illustrates one embodiment of a CT link metric response frame in accordance with the present disclosure. [Figure 8G] FIG. 1 illustrates one embodiment of a CT link metric response frame in accordance with the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Before referring to the drawings, some terminology is explained. The term "multi-AP device" refers to a wireless access point (AP) that can cooperate with other APs to transmit and / or receive signals. This cooperation includes joint processing, meaning that several multi-AP devices can transmit or receive signals simultaneously to exploit spatial diversity and obtain better performance. The term "multi-AP entity" refers to a logical entity that performs AP control functions, provides multi-AP specific control information, and controls the operation of the multi-AP network. The terms "fronthaul AP" and "backhaul STA" generally refer to entities that are included in a multi-AP device and communicate with each other when communicating between multi-AP devices. In a multi-AP network, a "fronthaul AP" is connected to a "backhaul STA" or to a non-AP STA.

[0016] The term "source node" refers to a communication device (also referred to herein as a "first communication device") that is the source of sent data. The term "relay node" refers to a communication device (also referred to herein as a "second communication device") that relays data to another communication device (another relay node or a sink node (also referred to herein as a "third communication device")). Each of the source node and relay node has at least one fronthaul AP. Typically, a source node has a fronthaul AP and an Ethernet port, and a relay node has a backhaul STA and a fronthaul AP.

[0017] Referring now to the drawings, where like reference numerals indicate the same or corresponding parts throughout the several views, Figure 1 shows a schematic diagram of a multi-AP network in which communication devices according to the present disclosure may be used. In this example network, multi-AP device 10 acts as a source node and multi-AP devices 11 and 12 act as relay nodes.

[0018] The multi-AP device 10 has a multi-AP entity and a fronthaul AP, and can transmit signals generated by the fronthaul AP to a non-AP STA 13 (operating as a sink node, also referred to herein as a "third communication device"), the multi-AP device 11, and the multi-AP device 12. If the multi-AP device 10 is connected by Ethernet, it may have an Ethernet port instead of a backhaul STA. In FIG. 1, the entity of the Ethernet port is shown as a "logical Ethernet port". Each of the multi-AP devices 11 and 12 has a backhaul STA, a multi-AP entity, and a fronthaul AP. As shown in FIG. 1, each performs signal processing of the received signal from the multi-AP device 1. The multi-AP devices 11 and 12 can communicate with each other. For example, when the multi-AP device 11 sends control information to the multi-AP device 12, a signal is sent from the fronthaul AP of the multi-AP device 11 to the backhaul STA of the multi-AP device 12, as shown by the dotted line in FIG. 1. Each fronthaul AP configures its own BSS (Basic Service Set) to distinguish links. For example, the fronthaul AP of the multi-AP device 10 has a first BSS including the fronthaul AP of the multi-AP device 10, non-AP STAs 13, backhaul STAs of the multi-AP device 11, and backhaul STAs of the multi-AP device 12. Similarly, the fronthaul APs of the multi-AP devices 11 and 12 have different BSSs and communicate with other non-AP STAs 14 and 15.

[0019] Multi-AP has been considered for coverage extension and robust network. In fact, Easy Mesh, like IEEE 802.11s, is standardized to provide the functionality for multi-AP network. Multi-AP network uses collected link metrics so that multi-AP device can decide which route to choose to relay data to non-AP STA. "Link metric" refers to the link quality between communication devices that does not depend on wireless or tethered link. In Easy Mesh, several formats are standardized to notify link metric depending on the version of multi-AP device profile, but basically, estimated data rate and / or measured data rate are selected as link metric. The same is true for IEEE 802.11s, and the airtime of the link is used as follows:

number

[0020] Especially in downlink communication, cooperative transmission (CT), usually called joint processing in 3GPP (3rd Generation Partnership Project), is mainly divided into three groups: 1) joint transmission (JT), 2) dynamic point selection (DPS), and 3) a combination of JT and DPS. DPS refers to selecting an access point to associate with depending on channel conditions, etc., and JT refers to sending signals from different APs to non-AP STAs. Generally, JT requires strict synchronization in frequency and time domain between APs. This is a difficult requirement for WLAN communication devices to meet, but the residual carrier frequency offset (CFO) error between two WLAN devices can be suppressed to within only 30 Hz, which is a sufficient synchronization level for JT.

[0021] In particular, JT can be further divided into several types, as shown in Figure 2, which shows a schematic diagram showing different types of joint transmission. These types are 1) coherent joint transmission (CJT, Figure 2A), 2) non-coherent joint transmission (NCJT, Figure 2B), and 3) cooperative beamforming (CBF, Figure 2C). In CJT, several multi-AP devices operate as if they were one large multi-AP device, resulting in the most spatial streams and beam gains in JT. However, each AP of the multi-AP device is required to have the same transmission data distributed through the backhaul CJT. In NCJT, each multi-AP device does not need to share the data sent, but the performance may be worse than CJT. In CBF, each multi-AP device sends data to different non-AP STAs, but may null unintended receivers. Since each multi-AP device nulls at the expense of spatial freedom, the performance may be even worse than CJT. The above performance relationships may differ if overhead such as data sharing is taken into account, but performance may differ depending on the JT type.

[0022] 2D and 2E are diagrams of non-joint transmission, particularly for single-user (SU) MIMO and multi-user (MU) MIMO. FIG 2F is a diagram of dynamic point selection (DPS).

[0023] As mentioned above, in CJT, transmitters need to share the data to be sent. Referring to Fig. 1, the multi-AP device 10 can send data to the multi-AP devices 11 and 12 in a multicast manner. Because, if the multi-AP device 10 sends data to the multi-AP devices 11 and 12 with different space / frequency / time resources, it will waste resources.

[0024] In a multi-AP network as shown in FIG. 1, the multi-AP devices 11 and 12 can perform JT, and the multi-AP device 10 does not know the channel quality between other multi-AP devices and non-AP STAs. To achieve the best end-to-end data rate performance (from the source node to the relay node to the sink node), the multi-AP device 10 needs to know what type of JT the multi-AP devices 11 and 12 perform, because the data transmitted to the multi-AP devices 11 and 12 differs depending on the type of JT. Furthermore, the multi-AP devices 11 and 12 can perform different JT depending on the non-AP STA, such as performing CJT to non-AP STA 14 but not JT to non-AP STA 15.

[0025] According to the above scenario, only the estimated data rate of one of the multi-AP devices 11 and 12 and the non-AP STAs 14 and 15 can be notified to the multi-AP device 10. Therefore, the multi-AP device 10 does not know which is the optimal JT scheme for the multi-AP devices 11 and 12. Furthermore, the optimal JT type varies depending on the data traffic to the non-AP STAs that the multi-AP device 10 has.

[0026] According to the present disclosure, a scheme of link metric indication from the multi-AP devices 11 and 12 to the multi-AP device 10 is illustrated so that the multi-AP devices 11 and 12 can perform optimal CT according to data traffic and / or intended non-AP STAs.

[0027] 3 shows a flowchart of an embodiment of a first communication method 100 performed by a first communication device (e.g., a multi-AP device 10) according to the present disclosure. In a first step 101, a CT link metric query (also simply referred to as a link metric query) is sent by the first communication device to a plurality of second communication devices, requesting to collect CT link metric information (also simply referred to as link metric information) from two or more of the second communication devices regarding cooperative transmissions to one or more third communication devices (e.g., non-AP STAs 14 or 15). The CT link metric query includes one or more CT instructions, each CT instruction indicating a different combination of two or more second communication devices and / or BF types for which CT link metric information should be collected.

[0028] In a second step 102, in response to the transmitted CT link metric query, a CT link metric response (also simply referred to as a link metric response) is received from at least one of the multiple second communication devices. The CT link metric response includes the collected CT link metric information. In a third step 103, the first communication device determines a BF type to be used by the multiple second communication devices for cooperative transmission to one or more third communication devices based on the CT link metric response. In a fourth step 104, BF type information indicating the determined BF type is transmitted to the multiple second communication devices. In this context, the BF type includes coherent joint transmission, non-coherent joint transmission, joint transmission, cooperative beamforming, and non-joint transmission. The BF type can be determined independently for any RU.

[0029] Beamforming (BF) shall generally be understood as a technique for directional signal transmission and reception, such as MRC (maximum ratio combining). Cooperative transmission, such as CJT, NCJT, and CBF, may also be considered as part of BF, because transmitters basically form beams jointly or non-jointly to exploit spatial degrees of freedom. Here, BF type shall be understood as a type of beamforming and cooperative transmission. In other words, in this specification, "CT type" shall be understood as "BF type" assuming multiple transmitters, but "CT type" does not include BF type with only one transmitter.

[0030] Since the definition of the term "joint transmission" varies among standardization groups, such as 3GPP and IEEE 802.11, in this specification the term "cooperative transmission type" (or "CT type") is understood to refer to types of cooperative transmission, such as CJT, NCJT, CBF, etc., but is not to be understood as a type of beamforming without cooperative transmission.

[0031] 4 shows a flowchart of an embodiment of a second communication method 200 performed by a second communication device (e.g., multi-AP device 11 or 12) according to the present disclosure. In a first step 201, a CT link metric query is received from the first communication device requesting to collect CT link metric information regarding cooperative transmissions from the second communication device and one or more other second communication devices to a third communication device.

[0032] In a second step 202, in response to the transmitted CT link metric query, a link metric response is transmitted to the first communication device. In a third step 203, BF type information is received from the first communication device, indicating the determined BF type used by the second communication device for cooperative transmission to one or more third communication devices. In a fourth step 204, the BF type indicated for the second communication device in the received BF type information is used to transmit data to the third communication device in cooperation with another second communication device. The "BF type" refers to 1) a variant of cooperative transmission (also referred to herein as CT type) as shown in Figures 2A, 2B, 2C, and 2) beamforming without cooperative processing (i.e., non-cooperative transmission) as shown in Figures 2D and 2E. Essentially, cooperative transmission can also be regarded as beamforming of multiple transmitters.

[0033] FIG. 5 illustrates a more detailed embodiment of a communication scheme 300 for communication between different communication devices according to the present disclosure. In this communication scheme, there is one multi-AP device 10 (also a source node), several multi-AP devices 11, 12 (also relay nodes) connected with the multi-AP device 10, and a non-AP STA 14 associated with the multi-AP device. For simplicity, acknowledgement for each step is not illustrated in FIG. 5, but acknowledgement may be performed after each step. Furthermore, two relay nodes are illustrated in FIG. 5 as an example. In general, one or more relay nodes may be provided.

[0034] In the first step 301, the source node, the relay node and the non-AP STA exchange capabilities including association. "Capability" refers to the type of function each communication device has, for example, whether the multi-AP device can operate as a source node and / or a relay node, which cooperative transmissions can be performed in each multi-AP device, which BF type each non-AP STA can receive the transmission signal, etc. In one embodiment, the capability exchange between the relay node and the non-AP STA follows the capability exchange between the source node and the relay node, but the order may be different. Furthermore, although it is not shown in FIG. 5 that the capability of each non-AP STA is relayed through the relay node, the capability can be sent directly from the non-AP STA to the source node. In this step, routing can also be determined.

[0035] After the capability exchange is performed, in the second and third steps 302, 304, the source node sends NDP-A (Null Data Packet Announcement) and NDP to the relay node so that the source node can know the channel state between the source node and the relay node. The format of NDP-A and the frame can be the same as the protocol and control frame standardized in IEEE 802.11. In general, NDP-A may constitute the subsequent NDP and hold a channel estimation sequence for the receiver to perform channel estimation. In FIG. 5, another transmission of NDP-A / NDP from the multi-AP devices 11 and 12 to the non-AP STA 14 is provided as step 308. The framework of NDP-A and NDP transmission will be described in more detail below.

[0036] After receiving the NDP, the relay node sends channel state information between the source node and the relay node ("sounding feedback FBCK") to the source node (steps 303 and 305). In FIG. 5, another sounding FBCK is provided in step 307, in which the non-AP STA sends channel state information between the relay node to the non-AP STA. The format of the sounding FBCK and frame may be the same as the protocol and frame standardized in IEEE 802.11. The channel state information may include data rate information, particularly about the estimated data rate for the channel between the relay node and the non-AP STA.

[0037] After the capability exchange is performed, the source node asks the relay node to feed back link metrics between the relay node and non-AP STAs to the source node by sending a CT link metric query in step 306. After receiving the link metric query, the relay node shall send a CT link metric response to the source node within a certain duration (step 312). This duration may be signaled in the CT link metric query and / or may be determined in the capability exchange.

[0038] 6 illustrates one embodiment of a CT link metric query frame 20 according to the present disclosure. The frame may include one or more of the following fields (in one embodiment, all of these fields are included, in other embodiments, only a single field or group of fields are included, and additional fields may be included as well): Frame Control: Indicates the type of this frame. Essentially, this field is interpreted as the element ID of the Multi-AP Link Metric Query Element. - RA (Received STA Address): Indicates to which non-AP STA this frame is sent (in Figure 3, this field indicates both relay nodes 11 and 12). -TA (Sending STA Address): Indicates which non-AP STA this frame is sent from. -CT Link Metric Query element: indicates the BSS for which link metrics should be responded to.

[0039] A CT link metric query element may include one or more of the following fields: - Element ID: Indicates which element this is. - Length: Indicates the bits or octets used in the CT Link Metric Query element. - Comeback policy: indicates how soon each intended receiver indicated by the RA will respond to this frame (the value can be set to different values ​​depending on the joint transmission type for which the relay node estimates the data rate. This field can be omitted if this value is already known between the transmitter and receiver, i.e. if it is a standardized value). - Number of BSSIDs: Indicates the number of consecutive BSSID fields that follow. - BSSID#k: indicates the kth BSSID that responds with the link metric. - Number of CT BSSIDs: Indicates the number of consecutive CT BSSID fields that follow. -CT BSSID#k: indicates a combination of BSSIDs that respond with link metrics for cooperative transmission (each BSSID can be understood as an identifier of a multi-AP device, and "CT BSSID" can be understood as an identifier of a combination of multi-AP devices).

[0040] When the number of BSSIDs indicates four BSSIDs, the CT BSSID field can be expressed in four bits (e.g., as a bitmap, the kth bit indicates that the BSSID indicated in the BSSID#k field is included in the combination of BSSIDs to respond). This is because it is possible to express each of all possible combinations of CTs between multi-AP devices indicated by the number of BSSID fields. For example, when the CT BSSID#m field is expressed as "1001", this field indicates that the BSSIDs indicated in the BSSID#1 field and the BSSID#4 field should respond with a link metric based on cooperative transmission.

[0041] If the number of multi-AP devices involved in CT is already predetermined, the CT BSSID field does not need to indicate it, for example, by a bitmap. For example, if the number of BSS ID fields indicates 6 and the CT BSS ID#k indicates two multi-AP devices, each is indicated in the BSSID#2 field and the other is indicated in the BSSID#4 field, and the number of all possible combinations is 15, so each CT BSSID#i field can be represented by 4 bits. Also, which number corresponds to which combination of multi-AP devices indicated in the BSSID subfield is determined between the transmitter and the receiver.

[0042] In one embodiment, the CT link metric query frame may specify resource units (RUs) whose estimated data rates are fed back from the relay node to the source node in a CT link metric response. For example, the relay node may respond to the query with a CT link metric response that includes measured or estimated data rates for a number of RUs.

[0043] Referring again to FIG. 5, after receiving the link metric query in step 306, each relay node may implement NDP-A / NDP in step 308 according to the age of the channel state information it has. The decision of whether the relay node implements NDP-A / NDP for cooperative transmission is made by one of the relay nodes, which may be called the "shared AP". The shared AP is the device that obtains the earliest transmission opportunity (TXOP) among the relay nodes after the link metric query is sent. If the shared AP decides to perform the trigger of NDP-A / NDP, the trigger of NDP-A / NDP is sent to the other relay nodes, which may be called the "shared AP", in step 307 before sending the NDP-A / NDP in step 308.

[0044] FIG. 7 illustrates another embodiment of a communication scheme for communication between different communication devices according to the present disclosure. FIG. 7 illustrates an embodiment of steps from a CT link metric query to a CT link metric response, particularly under the assumption that the CT link metric query includes a CT BSSID#k field indicating relay nodes 11 and 12. Also, in FIG. 7, it is assumed that relay node 11 obtains a TXOP and sends a sounding trigger to relay node 12 faster than any other relay node. Thus, relay node 11 can be referred to as a shared AP, and relay node 12 can be referred to as a shared AP. The TXOP can be obtained by exchanging RTS and CTS frames between relay nodes 11 and 12 after sending a JT link metric query, for example, as standardized in IEEE 802.11. Note that the source node does not need to be a TXOP holder after sending a JT link metric query.

[0045] After receiving the sounding trigger in step 307, the relay nodes 11 and 12 send the NDP-A (subsequently or preferably simultaneously) and the NDP (subsequently or preferably simultaneously) to the non-AP STA 14 (step 308). Known sequences for estimating channel conditions at the non-AP STAs may be included in the NDP, which may be orthogonal to each other so that each non-AP STA can estimate each channel from each antenna of the relay node to each antenna of the non-AP STA.

[0046] A BFRP (Beamforming Feedback Report) trigger may optionally follow the transmission of the NDP (step 309) to ask non-AP STAs to feed back channel estimates (sounding FBCK) at least to the shared AP (in this embodiment, relay node 11) in step 310. The BFRP trigger may be sent from relay node 11 (shared AP) but may also be sent simultaneously from relay node 12 (shared AP). The content of the BFRP trigger may be identical to the BFRP trigger standardized in IEEE 802.11. The relay node 12 may be included as one of the intended recipient non-AP STAs of the transmitted sounding FBCK in step 310.

[0047] After receiving the sounding FBCK from the non-AP STA, the relay node 11 estimates the data rate of at least one of the cooperative transmission types, such as SU (single user) MIMO or MU (multi-user) MIMO and non-cooperative transmission (step 311). The data rate may be estimated based on 1) each RU (resource unit) that the relay node 11 can arbitrarily determine or that is indicated in the JT link metric query frame, and 2) each combination of the non-AP STAs. The relay node 11 may refer to a PER (packet error rate) table when estimating the data rate. For example, if PER=0.1 is set as the basis for each transmission, the relay node 11 may calculate a channel gain based on CSI (channel state information) for the channel between the relay node and the STA. There are various algorithms for determining the channel gain, but one well-known scheme is a combination of SVD (singular vector decomposition) and water-filling algorithm under the constraint of MCS (modulation and coding scheme) capability of each communication device. When considering PER, the packet size can be assumed to be 1500 bits.

[0048] As exemplified above, the CT link metric query can specify an RU, of which the estimated data rate shall be included in the CT link metric response. If the CT link metric query specifies an RU, the data rate of each RU shall be indicated in the CT link metric response. The reason is that when the source node sends data to the relay node, the data size of each non-AP STA is usually different, for example, some data is sent by the relay node in CJT in RU#1, while other data is sent in a different BF type or non-CT in a different RU. In order to provide flexibility in the transmission path and realize efficient transmission at the relay node, it is preferable that the estimated data rate is indicated in RU units.

[0049] After estimating the data rate based on the sounding feedback, the relay node 11 transmits data rate information regarding the estimated data rate to the source node 10 in a CT link metric response in step 312. Figure 8 shows an example embodiment of a CT link metric response frame 30 and the different fields.

[0050] 8A illustrates an exemplary general layout of a CT link metric response frame 30 according to the present disclosure, which may include one or more of the following fields (in one embodiment, all of these fields are included; in other embodiments, only a single field or group of fields are included; additional fields may be included as well): -Frame Control: indicates the type of this frame. Basically, this field is interpreted as a CT Link Metrics Response Element or an Element ID of a Link Metrics Response Element. - RA (Received STA Address): Indicates to which non-AP STA this frame is sent. -TA (Sent from STA Address): Indicates which non-AP STA this frame is sent from. - Link metric response element 31: Contains the link metric between the BSSIDs for which notification is requested in the CT Link Metric Query. -CT Link Metric Response element 32: Contains the link metrics of the CT by the multi-AP device. The combination of the multi-AP device is specified in the CT BSSID field of the CT Link Metric Query. The difference between a link metric response element and a CT link metric response element is that a link metric response element contains non-CT link metrics, while a CT link metric response element contains CT link metrics. A link metric response element does not need to be included in a CT link metric response.

[0051] The link metric response element 31 is shown in FIG. 8B and may include one or more of the following fields: - Element ID: Indicates which element this is. -Length: Indicates the bits or octets used in the Link Metric Response element. Number of BSSIDs: indicates the number of BSSID fields in the element, this information is included in the Link Metric Query Element. For example, this field indicates the value of N. -BSSID#k: Indicates the transmitter of the estimated data rate indicated in the Estimated Data Rate #(k,i) (i is any integer value) field, and the BSS of the transmitter's fronthaul AP shall be within the BSS indicated in that field. -STA Info #k33: Indicates non-AP STAs that may be included in the STA Set #(k,t) field. -STA Set #(k,i): indicates the receiver of the estimated data rate indicated in the Estimated Data Rate #(k,i) field. If the number of STA Set #k subfields indicates a value of R, this field can be represented by an R bit, and the l-th bit indicates whether the non-AP STAs indicated in the STA ID #l field of the STA Info #k field are counted as receivers of the estimated data rate indicated in the Estimated Data Rate #(k,i) field (e.g., if the number of STA Set #k subfields indicates 4 and the STA Set #(k,i) field contains "1001", the non-AP STAs indicated in the STA ID #1 and STA ID #4 subfields of the STA Info #k field are counted as receivers of the estimated data rate indicated in the Estimated Data Rate #(k,i) field). - Estimated Data Rate #(k,i) 34: indicates the estimated data rate of the transmitter and receiver. The transmitter is the device with the fronthaul AP of the BSS whose BSSID#k field indicates the BSSID, and the receiver is the device indicated in the STA Set #(k,i) field (there are some variations of non-cooperative transmissions, but the data rate indicated in this field can be determined based on which data rate is better than any other non-cooperative transmission).

[0052] The STA Info #k field 33 may include one or more of the following subfields, as shown in FIG. 8C: Number of STA#k: indicates the number of the following consecutive STA ID subfields. STA ID#j: indicates the jth (j is any integer) STA that may be included in STA set #(k,i). Number of STA Sets #k: indicates the number of Estimated Data Rate #(k,i) fields. In FIG. 8C, the number of STA Sets #k subfields is the L that can be determined by the transmitter of the Link Metric Response element. k Indicates the value of.

[0053] The estimated data rate #(k,i) field 34 may include one or more of the following subfields, as shown in FIG. 8D: Number of RUs: Indicates the number of RU ID subfields in the Estimated Data Rate #(k,i) field. - RU ID #l: indicates the lth RU of the estimated data rate indicated in the estimated data rate of the RU#l subfield. - Estimated Data Rate of RU#l: Indicates the estimated data rate of the RU indicated in the RU#l subfield. The intended transmitter is the device with the fronthaul AP with the BSS indicated in the BSSID#k field, and the intended receiver is the device indicated in the STA Info#k field. The above parameters i, j, k, and l are arbitrary integer values.

[0054] The CT link metric response element 32 is shown in FIG. 8E and may include one or more of the following fields: - Element ID: Indicates which element this is. - Length: Indicates the bits or octets used in the CT Link Metric Query element. Number of BSSIDs: Indicates the consecutive number following the BSSID#i element. - BSSID#i: indicates the i-th BSSID whose elements include the link metric for cooperative transmission. -CT BSSID count: Indicates the number of BSSID combinations among the link metrics of cooperative transmission included in the element. -CT BSSID Info #k' 35: indicates information about the k'th combination of BSSIDs, of which the estimated data rate of the cooperative transmission is included in the Estimated Data Rate #(k',i) field (i is any integer value). - STA Set #(k',j): Indicates the intended receiver of the estimated data rate indicated in the Estimated Data Rate #(k',j) field. - Estimated Data Rate #(k',j) 36: indicates the estimated data rate between the transmitter and receiver indicated in the CT BSS ID #k' subfield and the STA Set #(k',j) field, respectively. It should be noted that the CT link metric response frame may further include information indicating the transmitter's buffer status.

[0055] The CT BSSID Info #k′ field 35 may include one or more of the following subfields, as shown in FIG. 8F: -CT BSSID#k': Indicates the k'-th combination of BSSIDs for which the multi-AP device is the intended transmitter of the estimated data rate indicated in the Estimated Data Rate #(k',j) field (j is any integer value). Number of STA#k': indicates the number of the following consecutive STA ID subfields. - STA ID#i: indicates the kth STA, the estimated data rate is included in the Estimated Data Rate#(k',i) field. Number of STA sets #k': indicates the number of STA set #(k',j) fields. As shown in the figure, for example, the number of STA set #(k',j) fields is L i If , this value is included in the number of STA set #k' subfields (where j is any integer value).

[0056] The estimated data rate #(k',j) field 36 may include one or more of the following subfields, as shown in FIG. 8G: Number of CT types: indicates the number of CT type subfields in the Estimated Data Rate #(k',j) field. -CT Type #l: indicates the intended CT type of the estimated data rate indicated in the estimated data rate CT Type #1 of the RU #m subfield (l and m are any integer values). This field may have three variations indicating CJT, NCJT, and CBF. Number of RUs: Indicates the number of RU ID subfields included in the Estimated Data Rate #(k',j) field. - RU ID#m: indicates the mth RU for which the estimated data rate is indicated in the estimated data rate CT type #l of the RU#m subfield. Estimated Data Rate CT Type #l of RU #m: indicates the estimated data rate. The CT type is that indicated in the CT Type #1 subfield, and the RU is that indicated in the RU ID #m subfield.

[0057] Note that the relay node decides which link metrics of which BF type are fed back, since NDP sounding is assumed to be done by multiple relay nodes simultaneously so that the sink node knows the global CSI (e.g., a 4×2 channel matrix instead of 2×2 channel matrix if each device has two antennas).

[0058] Referring again to FIG. 5, in step 312, after receiving the CT link metric response from the relay node, the source node determines the BF type to use to relay data through the relay node. As mentioned above, the optimal BF type at the relay node depends on the data traffic and / or buffer status of the relay node. The source node may select the BF type on a RU basis.

[0059] In a non-limiting embodiment, the determination of the source node may be performed as follows: The data traffic of the source node can be considered in the BF type determination. In the following example, there are two sink nodes to which data is sent from the source node via a relay node (e.g., as shown in FIG. 1), and the source node is a D 2 [bit] and D for non-AP STA15 3 Assume that the non-AP STAi from relay node j in “estimated data rate CT type #k in RU #l” has [bits]. Furthermore, the indicated value of C (i,j,k,l) [bps / Hz], and the indicated value of non-AP STAi from relay node j in “Estimated data rate in RU#l” is C (i,j,0,l) It shall be [bps / Hz].

[0060] First, the source node can estimate the optimal BF type for communication between the relay node and the sink node on a RU-by-RU basis. The following formula (2) is an example for determining the BF type, in which the RU is selected for all BF types, but it can also be seen that the BF type can be selected for each RU in principle.

number

number

[0061] Then, the source node may select the optimal BF type on a RU basis for communication from the source node to the relay node such that the transmission time is the shortest among all possibilities. The following equation (4) is an example for determining the BF type, where C' (i,k,l) [bps / Hz] is the estimated data rate of communication between source node #i with BF type #k' in RU #l and relay node #i.

number

number

number

[0062] After determining the BF type, the source node sends data whose final destination is a non-AP STA to the relay node in step 313. The applied BF type can be changed on a RU basis. In particular, if the source node sends the same data to the relay node that is intended to be sent from the relay node to a non-AP STA in CJT, the source node can send the data in a multicast BF. The source node can simultaneously inform the relay node which data to send in which BF type. This part is similar to CJT, with one shared AP and two shared APs.

[0063] After receiving the data to send to the non-AP STA, the relay node sends the data to the non-AP STA in step 314. The BF type may vary on a per RU basis.

[0064] In summary, according to the present disclosure, a first communication device acting as a source node sends a link metric query to a relay node, asking the relay node to feed back measurements / estimates of some joint transmission data rates. This causes at least one second communication device acting as a relay node to send a link metric response to the source node. The link metric response includes measurements / estimates of some joint transmission data rates between the relay node and a sink node (non-AP STA). The data rates may be indicated on a per-RU basis.

[0065] Thus, the foregoing discussion discloses and describes merely exemplary embodiments of the present disclosure. As will be understood by those skilled in the art, the present disclosure may be embodied in other specific forms without departing from its spirit or essential characteristics. Accordingly, the disclosure of the present disclosure, as well as the other claims, are intended to be illustrative rather than limiting on the scope of the present disclosure. The present disclosure defines in part the scope of the preceding claim terms so as not to subject the subject matter of the invention to the public, including readily identifiable variations of the teachings herein.

[0066] In the claims, the word "comprise" does not exclude other elements or steps, and the indefinite article "a" does not exclude a plurality. A single element or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0067] To the extent that embodiments of the present disclosure have been described as being implemented, at least in part, by a software-controlled data processing apparatus, it will be understood that non-transitory machine-readable media bearing such software, such as optical disks, magnetic disks, semiconductor memories, etc., are also considered to represent embodiments of the present disclosure. Moreover, such software may be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0068] The elements of the disclosed devices, apparatus and systems may be implemented by corresponding hardware and / or software elements, such as suitable circuits or circuitry. A circuit is a structural collection of electronic components, including conventional circuit elements, application specific integrated circuits, standard integrated circuits, application specific standard products, and integrated circuits, including field programmable gate arrays. Furthermore, a circuit includes a central processing unit, a graphics processing unit, and a microprocessor, which are programmed or configured according to software code. A circuit includes the above hardware that executes software, but does not include pure software. A circuit or circuitry may be implemented by a single device or unit, or by multiple devices or units, or by a chipset, or by a processor.

[0069] Further embodiments of the disclosed subject matter are listed below. 1. A first communication device configured to operate as a source node and communicate with one or more second communication devices, the second communication device configured to operate as a relay node and communicate with one or more third communication devices, the first communication device being: - transmitting a cooperative transmission (CT) link metric query to a plurality of second communication devices requesting collection of CT link metric information related to cooperative transmission from two or more of the second communication devices to one or more third communication devices, the link metric query including one or more CT instructions, each CT instruction indicating a different combination of two or more second communication devices and / or a different beamforming (BF) type for which CT link metric information should be collected; - receiving a CT link metric response from at least one of the plurality of second communication devices in response to the transmitted CT link metric query, the link metric response including the collected CT link metric information; - determining a BF type to be used by the second communication devices for cooperative transmission to one or more third communication devices based on the CT link metric response; - transmitting BF type information indicating the determined BF type to the plurality of second communication devices; A first communications device comprising circuitry configured according to the above. 2. A first communication device as defined in embodiment 1, wherein the circuit configuration is configured by the step of determining a BF type to be used by selecting one BF type from a group of BF types including coherent joint transmission, non-coherent joint transmission, joint transmission, coordinated beamforming, and non-joint transmission. 3. The first communications device defined in any one of the preceding embodiments, wherein the circuit configuration is configured by including in the CT link metric query CT number information indicating the number of the CT indications included in the CT link metric query. 4. A first communications device as defined in any one of the preceding embodiments, wherein the circuit configuration is configured by including one or more first AP instructions and / or one or more second AP instructions in the CT link metric query, each first AP instruction indicating a different set of one or more second communications devices for which CT link metric information regarding transmissions from the respective second communications device to one or more third communications devices should be collected, and each second AP instruction indicating a different second communications device for which CT link metric information regarding transmissions from the respective second communications device to the third communications devices should be collected. 5. A first communications device as defined in embodiment 4, wherein the circuit configuration is configured by a step of including AP number information in the CT link metric query indicating the number of the first and / or second AP indications included in the CT link metric query. 6. The circuitry responds to the link metric query by: - received information indicating to which second communication device the link metric query is addressed; - transmission information indicating the first communications device to which the link metric query is to be transmitted and / or indicating a first communications device to which the link metric response is to be transmitted; - comeback policy information indicating a time frame during which the CT link metric response should be transmitted by at least one of the plurality of second communication devices; and Resource unit (RU) information indicating one or more RUs for which collected CT link metric information should be included in the CT link metric response 4. The first communication device as defined in any one of the preceding embodiments, 7. The first communications device as defined in any one of the preceding embodiments, wherein the circuit configuration is configured by determining the BF type to be used by the second communications device based on data rate information included in the CT link metric response, the data rate information indicating estimated data rates for different BF types. 8. The first communication device as defined in embodiment 7, wherein the circuit configuration is configured by the step of determining the BF type to be used by the second communication device by minimizing transmission time from the second communication device to each third communication device based on data traffic to the third communication device. 9. The first communications device as defined in any one of the preceding embodiments, wherein the CT link metric information includes data rate information for an estimated data rate for a channel between the second communications device and a third communications device. 10. A second communication device configured to operate as a relay node, the second communication device configured to communicate with a first communication device configured to operate as a source node, one or more other second communication devices configured to operate as relay nodes, and / or one or more third communication devices configured to communicate with the one or more second communication devices, - receiving a cooperative transmission (CT) link metric query from the first communication device requesting to collect CT link metric information for cooperative transmissions from the second communication device and one or more other second communication devices to one or more third communication devices, the CT link metric query including one or more CT instructions, each CT instruction indicating a different combination of two or more second communication devices and / or a different beamforming (BF) type for which CT link metric information should be collected; - transmitting a CT link metric response to the first communication device in response to the transmitted CT link metric query, the CT link metric response including the collected CT link metric information; receiving, from the first communication device, BF type information indicating a determined BF type to be used by the second communication device for a cooperative transmission to a third communication device; - transmitting data to a third communication device in cooperation with one or more other second communication devices using the BF type indicated for the second communication device in the received BF type information; A second communications device comprising circuitry configured according to the above. 11. A second communication device as defined in embodiment 10, wherein the circuit configuration is configured by: in response to receiving the CT link metric query, transmitting a null data packet to one or more third communication devices; and in response to the transmitted null data packet, receiving data information from the one or more third communication devices regarding an estimated data rate for a channel between the second communication device and each of the third communication devices. 12. A second communications device as defined in embodiment 10 or 11, wherein the circuit configuration is configured by: obtaining a transmission opportunity in response to receiving the CT link metric query; and transmitting a sounding trigger to one or more other second communications devices to transmit a null data packet to the one or more third communications devices simultaneously with the second communications device transmitting a null data packet to the one or more third communications devices. 13. The second communications device as defined in embodiment 12, wherein the circuitry is configured by: transmitting a sounding trigger to the other second communications device indicated in the CT link metric query. 14. A second communication device as defined in embodiment 11, wherein the circuit configuration is configured by the step of transmitting, after transmitting the null data packet, a feedback trigger to the one or more third communication devices to feed back to at least the second communication device data rate information regarding an estimated data rate for a channel between the third communication device that transmitted the null data packet to the third communication device and the second communication device. 15. A second communications device as defined in embodiment 11, wherein the circuit configuration is configured to: determine estimated data rates for different types of CT transmissions and non-CT transmissions based on the received data rate information; and include the estimated data rates in the CT link metric response. 16. The circuit configuration includes a CT link metric response, - received information indicating to which first communication device the CT link metric response is addressed; - transmission information indicating from which second communication device the CT link metric response is transmitted; link metric response information indicating link metric information for non-CT transmissions from different second communication devices to respective third communication devices; and - CT link metric response information indicating CT link metric information regarding CT transmissions from different second communication devices to respective third communication devices. 16. The second communication device as defined in any one of embodiments 10 to 15, further comprising one or more of: 17. The second communications device defined in embodiment 16, wherein the circuit configuration is configured by including the link metric information and / or the CT link metric information per resource unit (RU) in the link metric response information and / or the CT link metric response information. 18. A first communication method of a first communication device configured to operate as a source node and communicate with one or more second communication devices, the second communication device configured to operate as a relay node and communicate with one or more third communication devices, the first communication method comprising: - transmitting cooperative transmission (CT) link metric queries to a plurality of second communication devices requesting the plurality of second communication devices to collect CT link metric information regarding cooperative transmissions from two or more of the second communication devices to one or more third communication devices, the link metric queries including one or more CT instructions, each CT instruction indicating a different combination of two or more second communication devices and / or a different beamforming (BF) type for which CT link metric information should be collected; - receiving a CT link metric response from at least one of the plurality of second communication devices in response to the transmitted CT link metric query, the link metric response including the collected CT link metric information; - determining a BF type to be used by the second communication devices for cooperative transmission to one or more third communication devices based on the CT link metric response; - transmitting BF type information indicating the determined BF type to the plurality of second communication devices; A first communication method comprising: 19. A second communication method for a second communication device configured to operate as a relay node, the second communication device configured to communicate with a first communication device configured to operate as a source node, one or more other second communication devices configured to operate as relay nodes, and / or one or more third communication devices configured to communicate with the one or more second communication devices, the second communication device comprising: - receiving a cooperative transmission (CT) link metric query from the first communication device requesting to collect CT link metric information for cooperative transmissions from the second communication device and one or more other second communication devices to one or more third communication devices, the CT link metric query including one or more CT instructions, each CT instruction indicating a different combination of two or more second communication devices and / or a different beamforming (BF) type for which CT link metric information should be collected; - transmitting a CT link metric response to the first communication device in response to the transmitted CT link metric query, the CT link metric response including the collected CT link metric information; receiving, from the first communication device, BF type information indicating a determined BF type to be used by the second communication device for a cooperative transmission to a third communication device; - transmitting data to a third communication device in cooperation with one or more other second communication devices using the BF type indicated for the second communication device in the received BF type information. 20. A non-transitory computer-readable recording medium having stored therein a computer program product which, when executed by a processor, causes the method according to embodiment 18 or 19 to be performed. 21. A computer program comprising program code means for causing a computer to carry out the steps of the method according to embodiment 18 or 19, when said computer program is run on a computer. 22. The first communication device defined in any one of embodiments 1 to 9, wherein the circuit configuration is configured by performing a capability exchange with one or more second multi-APs and / or one or more other communication devices. 23. A first communications device as defined in any one of embodiments 1 to 9 and 22, wherein the circuit configuration is configured by: transmitting a null data packet to one or more second multi-AP devices; and receiving channel state information from the one or more second multi-AP devices regarding a channel between the first multi-AP device and each of the second multi-AP devices in response to the transmitted null data packet. 24. The first communications device as defined in any one of embodiments 1 to 9, 22 and 23, wherein the circuit configuration includes a multi-access point entity and a fronthaul access point. 25. A second communication device as defined in any one of embodiments 10 to 17, wherein the circuit configuration is configured by a step of performing a capability exchange with the first multi-AP device and one or more other communication devices configured to operate as sink nodes. 26. A second communications device defined in any one of embodiments 10 to 17 and 25, wherein the circuit configuration is configured by: receiving a null data packet from the first multi-AP device; and in response to the received null data packet, transmitting channel state information regarding a channel between the second multi-AP device and the first multi-AP device to the first multi-AP device. 27. The second communications device as defined in any one of embodiments 10 to 17, 25 and 26, wherein the circuit configuration includes a multi-AP entity, a backhaul station and a fronthaul access point.

Claims

1. A first communication device configured to operate as a source node and to communicate with one or more second communication devices, the second communication device configured to operate as a relay node and to communicate with one or more third communication devices, the first communication device being: - sending a cooperative transmission (CT) link metric query to a plurality of the second communication devices requesting them to collect CT link metric information related to cooperative transmissions from two or more of the second communication devices to one or more of the third communication devices, the link metric query including one or more CT instructions, each CT instruction indicating a different combination of two or more second communication devices and / or a different beamforming (BF) type for which CT link metric information should be collected; receiving a CT link metric response from at least one of the plurality of second communication devices in response to the transmitted CT link metric query, the link metric response including the collected CT link metric information; - determining a BF type to be used by the second communication devices for cooperative transmission to one or more third communication devices based on the CT link metric response; - transmitting BF type information indicating the determined BF type to the plurality of second communication devices; A first communications device comprising circuitry configured according to the following:

2. The first communication device of claim 1 , wherein the circuit configuration is configured to determine a BF type to be used by selecting one BF type from a group of BF types including coherent joint transmission, non-coherent joint transmission, joint transmission, coordinated beamforming, and non-joint transmission.

3. The first communications device of claim 1 , wherein the circuitry is configured to include, in the CT link metric query, CT number information indicating a number of the CT indications included in the CT link metric query.

4. 2. The first communications device of claim 1, wherein the circuit configuration is configured to include one or more first AP indications and / or one or more second AP indications in the CT link metric query, each first AP indication indicating a different set of one or more second communications devices for which CT link metric information regarding transmissions from the respective second communications device to one or more third communications devices should be collected, and each second AP indication indicating a different second communications device for which CT link metric information regarding transmissions from the respective second communications device to the third communications device should be collected.

5. The first communication device of claim 4 , wherein the circuit configuration is configured by a step of including AP number information in the CT link metric query indicating the number of the first and / or second AP indications included in the CT link metric query.

6. The circuitry may further include, - received information indicating to which second communication device the link metric query is addressed, - transmission information indicating the first communications device to which the link metric query is to be sent and / or indicating the first communications device to which the link metric response should be sent; - comeback policy information indicating a time frame during which the CT link metric response should be transmitted by at least one of the plurality of second communication devices; and Resource Unit (RU) information indicating one or more RUs for which collected CT link metric information should be included in the CT link metric response. The first communication device of claim 1, wherein the first communication device is a first communication device.

7. The first communication device of claim 1, wherein the circuit configuration is configured to determine the BF type to be used by the second communication device based on data rate information included in the CT link metric response, the data rate information indicating estimated data rates for different BF types.

8. The first communication device of claim 7, wherein the circuit configuration is configured to determine the BF type to be used by the second communication device by minimizing transmission time from the second communication device to each third communication device based on data traffic to the third communication device.

9. The first communications device of claim 1 , wherein the CT link metric information includes channel condition information regarding a channel between one or more second communications devices and a third communications device.

10. A second communication device configured to operate as a relay node, the second communication device configured to communicate with a first communication device configured to operate as a source node, one or more other second communication devices configured to operate as relay nodes, and / or one or more third communication devices configured to communicate with the one or more second communication devices, receiving a cooperative transmission (CT) link metric query from a first communication device requesting to collect CT link metric information for cooperative transmissions from the second communication device and one or more other second communication devices to one or more third communication devices, the CT link metric query including one or more CT indications, each CT indication indicating a different combination of two or more second communication devices and / or a different beamforming (BF) type for which CT link metric information should be collected; - transmitting a CT link metric response to the first communications device in response to the transmitted CT link metric query, the CT link metric response including the collected CT link metric information; receiving, from the first communication device, BF type information indicating a determined BF type to be used by the second communication device for a cooperative transmission to a third communication device; - transmitting data to a third communication device in cooperation with one or more other second communication devices using the BF type indicated for the second communication device in the received BF type information; A second communication device comprising circuitry configured according to the above.

11. 11. The second communications device of claim 10, wherein the circuit configuration is configured to: transmit a null data packet to one or more third communications devices in response to receiving the CT link metric query; and receive channel state information from the one or more third communications devices regarding a channel between the second communications device and each of the third communications devices in response to the transmitted null data packet.

12. 11. The second communications device of claim 10, wherein the circuit configuration is configured to: obtain a transmission opportunity in response to receiving the CT link metric query; and transmit a sounding trigger to one or more other second communications devices to transmit a null data packet to the one or more third communications devices simultaneously with the second communications device transmitting a null data packet to the one or more third communications devices.

13. The second communications device of claim 12 , wherein the circuitry is configured for transmitting a sounding trigger to the other second communications device indicated in the CT link metric query.

14. 12. The second communication device of claim 11, wherein the circuit configuration is configured to transmit, after transmitting the null data packet, a feedback trigger to at least the second communication device for feeding back channel state information regarding a channel between the second communication device and a third communication device that transmitted the null data packet to the third communication device.

15. 12. The second communications device of claim 11, wherein the circuitry is configured to: determine an indicated estimated data rate for different types of CT and non-CT transmissions based on the received data rate information; and include the estimated data rate in the CT link metric response.

16. The circuitry responds to the CT link metric response by receiving information indicating to which first communications device the CT link metric response is addressed; - transmission information indicating from which second communication device the CT link metric response is transmitted; link metric response information indicating link metric information for non-CT transmissions from different second communication devices to respective third communication devices; and - CT link metric response information indicating CT link metric information regarding CT transmissions from different second communication devices to respective third communication devices. The second communication device of claim 10, further comprising one or more of the following steps:

17. The second communications device of claim 16, wherein the circuit configuration is configured to include the link metric information and / or the CT link metric information per resource unit (RU) in the link metric response information and / or the CT link metric response information.

18. 1. A first communication method of a first communication device configured to operate as a source node and to communicate with one or more second communication devices, the second communication device configured to operate as a relay node and to communicate with one or more third communication devices, the first communication method comprising: - transmitting cooperative transmission (CT) link metric queries to a plurality of second communication devices requesting the plurality of second communication devices to collect CT link metric information regarding cooperative transmissions from two or more of the second communication devices to one or more third communication devices, the link metric queries including one or more CT indications, each CT indication indicating a different combination of two or more second communication devices and / or a different beamforming (BF) type for which CT link metric information should be collected; receiving a CT link metric response from at least one of the plurality of second communication devices in response to the transmitted CT link metric query, the link metric response including the collected CT link metric information; - determining a BF type to be used by the second communication devices for cooperative transmission to one or more third communication devices based on the CT link metric response; - transmitting CT type information indicating the determined BF type to the plurality of second communication devices; A first communication method comprising:

19. A second communication method for a second communication device configured to operate as a relay node, the second communication device configured to communicate with a first communication device configured to operate as a source node, one or more other second communication devices configured to operate as relay nodes, and / or one or more third communication devices configured to communicate with the one or more second communication devices, the second communication method comprising: receiving a cooperative transmission (CT) link metric query from the first communication device requesting to collect CT link metric information for cooperative transmissions from the second communication device and one or more other second communication devices to one or more third communication devices, the CT link metric query including one or more CT indications, each CT indication indicating a different combination of two or more second communication devices and / or a different beamforming (BF) type for which CT link metric information should be collected; - transmitting a CT link metric response to the first communications device in response to the transmitted CT link metric query, the CT link metric response including the collected CT link metric information; receiving, from the first communication device, BF type information indicating a determined BF type to be used by the second communication device for a cooperative transmission to a third communication device; - a step of transmitting data to a third communication device in cooperation with one or more other second communication devices using the BF type indicated for the second communication device in the received BF type information.

20. A non-transitory computer readable storage medium having stored therein a computer program product which, when executed by a processor, causes the processor to perform the method according to claim 18 or 19.

Images