Communication control devices and methods

Abstract

A first communication control device configured to control a first wireless communication circuitry of a first communication device configured to communicate with one or more third communication devices to obtain a transmission opportunity (TXOP), transmit an initial control frame (ICF) to a second communication device with which the TXOP shall be shared for a coordinated transmission, receive an initial control response frame (ICR) from the second communication device, and allocate at least a part of the obtained TXOP for the coordinated transmission, wherein the number of spatial streams and the number of spatial degrees of freedom for reception nulling are configured based on the ICF and / or ICR.

Description

WITTEWELLERPAT E N TA N WA LT EApplicants:Sony Group Corporation 13.03.20261-7-1 Konan 4727P381 WO - SK Minato-KuTokyo 108-0075JAPAN SONY Europe LimitedThe Heights, Brooklands,Weybridge, SurreyKT130XWUNITED KINGDOMCOMMUNICATION CONTROL DEVICES AND METHODSBACKGROUNDFIELD OF THE DISCLOSURE

[0001] The present disclosure relates to first and second communication control devices and methods for controlling a wireless communication circuitry of a respective communication device configured to communicate with other (third and fourth, respectively) communication devices.DESCRIPTION OF RELATED ART

[0002] Multi Access Point (Multi-AP) has been paid attention as a typical Wireless LAN (WLAN) deployment even for home use scenario. High reliability and extremely high throughputare required for future wireless extended reality (XR) application such as high definition image transmission forXR. Multi-AP coordination is thus one of key features for improving wireless communication performance.

[0003] The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventor(s), to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.SUMMARY

[0004] It is an object to enhance reliability and / or throughput in a coordinated transmission (CT) in which multiple APs transmit data to intended receivers while mitigating interference for unintended receivers. It is a further object to provide corresponding communication control devices, corresponding communication control methods as well as a corresponding computer program and a non-transitory computer-readable recording medium that stores therein a computer program product for implementing said methods.

[0005] According to an aspect there is provided a first communication control device configured to control a first wireless communication circuitry of a first communication device configured to communicate with one or more third communication devices to:obtain a transmission opportunity (TXOP);transmit an initial control frame (ICF) to a second communication device with which the TXOP shall be shared fora coordinated transmission, the ICF including an indication ofi) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / orii) a maximum number of spatial degrees of freedom for reception nulling, which isless than the number of receive antennas at each of the one or more third communication devices;receive an initial control response frame (ICR) from the second communication device, the ICR including an indication ofa) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / or a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices, andb) an indication which communication devices are scheduled to perform reception nulling; andallocate at least a part of the obtained TXOP for the coordinated transmission, wherein the number of spatial streams and the number of spatial degrees of freedom for reception nulling are configured based on the ICF and / or ICR.

[0006] According to a further aspect there is provided a second communication control device second communication control method of a second communication control device configured to control a second wireless communication circuitry of a second communication device configured to communicate with one or more fourth communication devices to:receive an initial control frame (ICF) from a first communication device with which the TXOP shall be shared fora coordinated transmission, the ICF including an indication ofi) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / orii) a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices;transmit an initial control response frame (ICR) to the first communication device, the ICR including an indication ofa) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / or a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices, andb) an indication which communication devices are scheduled to perform reception nulling; andreceive an allocation of at least a part of the obtained TXOP for the coordinated transmission from the first communication device, wherein the number of spatial streams and the number of spatial degrees of freedom for reception nulling are configured based on the ICF and / or ICR.

[0007] According to still further aspects corresponding methods, a computer program comprising program means for causing a computer to carry out the steps of the method disclosed herein, when said computer program is carried out on a computer, as well as a non-transi- tory computer-readable recording medium that stores therein a computer program product, which, when executed by a processor, causes the method disclosed herein to be performed are provided. Further, in aspects of the present disclosure first and second communication devices are presented comprising a respective communication control device and respective wireless communication circuitry.

[0008] Embodiments are defined in the dependent claims. It shall be understood that the disclosed methods, the disclosed computer program and the disclosed computer-readable recording medium have similar and / or identical further embodiments as the claimed devices and as defined in the dependent claims and / or disclosed herein.

[0009] One of the aspects of the disclosure is to provide a Multi-AP with a degree of freedom to perform transmission nulling (also called Tx nulling or transmit nulling) and reception nulling (also called Rx nulling or receive nulling) and to enable the Multi-AP to establish the configuration for an upcoming / intended CT. The configuration may include, e.g., how many spatial streams are set for Rx nulling in the CT. Such a protocol, as pre-TXoperation, does currently not exist and has not been disclosed as WLAN protocol, but is provided by the present disclosure.

[0010] According to embodiments of the present disclosure, at least a part of an obtained transmission opportunity (TXOP) is allocated for the CT and the number of spatial streams and the number of spatial degrees of freedom (DoF) for Rx nulling by the second and / or fourth communication devices (and, optionally, for Tx nulling by the first and / or second communication devices) are configured based on the an initial control frame (ICF) and / or an initial control response frame (ICR). This allows the second communication device (in an embodiment one of the APs) to transmit one or more frames to one or more fourth communication devices (in an embodiment one or more stations, STAs, associated with the second communication device) concurrently with a transmission of one or more frames to one or more third communication devices (in an embodiment one or more STAs associated with the first communication device) by the first communication device (in an embodiment another AP). This transmission may thus be in line with the indications in the ICF and / or ICR and concurrently with a transmission of one or more frames to one or more third communication devices by the first communication device.

[0011] The foregoing 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.BRIEF DESCRIPTION OF THE DRAWING

[0012] A more complete appreciation of the disclosure and many of the attendant advantages thereof 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, wherein:Fig. 1 shows a diagram illustrating Tx nulling.Fig. 2 shows a diagram illustrating Rx nulling.Fig. 3 shows diagrams illustrating different allocations of DoFs for Tx nulling.Fig. 4 shows a diagram illustrating an example of transmissions between two APs and their associated STAs.Fig. 5 shows a diagram illustrating the allocation of DoFs for the example of transmissions shown in Fig. 4.Fig. 6 shows a diagram illustrating the lack of antennas of an AP.Fig. 7 shows a diagram of the conventional allocation of DoFs.Fig. 8 shows a diagram illustrating the desired Rx nulling according to the present disclosure.Fig. 9 shows a diagram illustrating a protocol using CT according to an embodiment of the present disclosure.Fig. 10 shows a diagram of a configuration setup protocol according to a first embodiment of the present disclosure.Fig. 11 shows a flowchart of an embodiment of a method for determining the number of spatial streams for data transmission from the second communication device to a fourth communication device.Fig. 12 shows a diagram of a configuration setup protocol according to a second embodiment of the present disclosure.Fig. 13 shows a diagram illustrating an embodiment of the layout of the main communication devices in an embodiment of the present disclosure.Fig. 14 shows a flowchart of an embodiment of a first communication control method according to the present disclosure.Fig. 15 shows a flowchart of an embodiment of a second communication control method according to the present disclosure.DETAILED DESCRIPTION OF THE EMBODIMENTS

[0013] Before details of the present disclosure are discussed, it shall be noted that in the context of the present disclosure the term ‘basic service set (BSS)’ refers to a set of stations (STAs) that have successfully synchronized, the term ‘beamformee’ refers to a station that receives a physical layer (PHY) protocol data unit (PPDll) that was transmitted using a beamforming steering matrix and the term ‘beamformer’ refers to a station that transmits a physical layer protocol data unit using a beamforming steering matrix.

[0014] The term ‘precoding matrix’ refers to a matrix determined using knowledge of the channel between a transmitter and intended receiver(s) that maps from space-time streams to transmit antennas with the goal of improving signal-to-noise ratio (SNR) at the intended receiver. It can also be determined with knowledge of the channel among a transmitter, intended receiver(s) and unintended receiver(s), and in this case the aim is improving SNR at the intended receiver(s) as well as interference reduction at the unintended receivers).

[0015] The term ‘postcoding matrix’ refers to a matrix determined with knowledge of the channel between a transmitter and intended receiver(s) that maps from receive antennas to spacetime streams with the goal of improving signal-to-noise ratio (SNR) at the receiver. It can also be determined with knowledge of the channel among a transmitter, intended receivers) and unintended receiver(s), and in this case the aim is improving signal-to-inter- ference-and-noise ratio (SINR) at the receiver.

[0016] Further, the term ‘Tx nulling’ refers to beamforming with steering null to unintended receivers, and the term ‘Rx nulling’ refers processing at a receiver to reduce interference from unintended transmitters.

[0017] One of the solutions to enhance reliability and / or throughput is coordinated transmission (CT) from Multi-AP, where each AP transmits data to intended receivers while mitigating interference for unintended receivers. Interference mitigation can be achieved with leveraging multiplexing in spatial domain, where each AP steers null to unintended receivers and / or each receiver applies MMSE (Minimizing-Mean-Square-Error) postcoding with the knowledge of the channel from an intended transmitter as well as interferes. The MMSE postcoding is essentially steering null to interferes from the receiver, and steering null generally requires the STA that steers null to consume its spatial degree of freedoms (DoFs).

[0018] Especially in CT from Multi-AP, the way of spatial multiplexing by the Multi-AP is called Coordinated Beamforming (CBF), where each AP steers null to unintended receiver. Typically, AP has more antennas than non-AP STAs, which means AP has more spatial DoFs, and thus it is AP that steers null in CT instead of steering null by receiver (i.e. non-AP STAs).

[0019] In IEEE 802.11 Task Group bn, candidates of basic protocol for CBF have been discussed, and it has been suggested that the following four stages should be conducted before CT from Multi-AP is carried out:Stage 1: Multi-AP Discovery: Each AP discovers (an)other AP(s) which support CT, and required parameters and supported capabilities are exchanged between Multi-AP.Stage 2: Multi-AP Coordination agreement setting: The Multi-AP establishes agreement for CT.Stage 3: Pre-TX operation: Channel sounding and CSI (Channel State Information) feedback would take place as well as obtaining TXOP by the APs. Channel sounding and CSI feedback may be skipped if the channel is stable over time.Stage 4: Multi-AP Coordinated T ransmission (Multi-AP CT): With a trigger by the initiator of CT, the CT takes place.

[0020] In Stage 3, Multi-AP may obtain CSI from both intended receivers and unintended receivers. It’s also suggested that Multi-AP exchange information for Stage 4 such as MCS (Modulation and Coding Scheme), number of spatial streams to be used as well as receivers to let the Multi-AP to select QoS (Quality of Service) parameters, PHY parameters etc., The information is suggested to be exchange with ICF (Initial Control Frame) and ICR (Initial Control Response frame), and those frames can also be used to obtain TXOP (Transmission opportunity) until Stage 4 is terminated, nevertheless primary channel of each AP is different or not[3’4]. It is also suggested that information on spatial stream for preceding CT is exchanged among the Multi-AP. However, it is not assumed that at least one of the receivers might perform Rx nulling as illustrated in later part.

[0021] In Stage 4, each of APs would apply precoding matrix IV such that HIV = 0, where H is channel matrix between the AP and unintended receivers, to steer null to unintended receivers. The basic null steering requires AP to consume N spatial DoFs for steering null, where N is the summation of receive antennas of the unintended receivers, and if N is greater than maximum available spatial DoFs of the AP, the AP no more can steer null to all unintended receivers. However, some techniques such as Interference Alignment (IA)[4]or predetermined postcoding enable to achieve interference mitigation even in this case, but interference vectors / spaces at unintended receivers should be determined before the CT with whichever techniques. One of the example ways to set predetermined postcoding is that the unintended receiver sets MMSE (Minimum Mean Square Error) postcoding matrices P, which are already computed prior to CT. The MMSE postcoding matrices are computed from acquired CSI toward the AP by receiving training signal from AP as a part of channel sounding within Pre-TX operation. If PH or P are informed to the AP after channel sounding and the rank of PH is less than the number of receive antenna of the unintended receiver, AP uses precoding matrices which are parts of kernel space of PH.

[0022] The fundamental issue still lies on CBF, which is that AP requires to obtain CSI for steering null. In general, null performance is more sensitive to channel aging than main beam level because null is sharper than main beam in terms of array factor, and thus it’s difficult to ensure higher SINR during long period undertime-varying channel.

[0023] To cope with sensitiveness to channel aging, Null Space Expansion (NSE) can provide robust nulling while sacrificing more spatial DoFs. The background of this algorithm is that channel is most likely to vary linearly, and thus future channel vectors are most likely in the same space containing past channel vectors. With this solution, a beamformer steers null to several past CSIs of unintended receivers, while existing precoding algorithms can be reused.

[0024] The following IV is one of examples for a precoding matrix, where equation (1) is an SLNR (Signal-to-Leakage-and-Noise Ratio)-based precoding scheme:where H is the channel matrix of a channel between beamformer and an intended receiver and o is the noise level at the receiver while H contains more past channels between beamformer and unintended receivers as shown in equation (2), where H(tt) is channel obtained at ti (j = 1,2), and tg and t2are different time instances.

[0025] One of the other promising solutions to tackle this issue is to perform interference reduction at receivers because every receiving PPDll (PHY Protocol data unit) contains LTFs (Long Training Fields) that allow a receiver to estimate a fresh channel from the transmitter. To work with interference reduction at receivers, all LTFs from APs should be orthogonal to each other to allow receivers to estimate every channel, and the receiver can reduce interference with, for example, a MMSE postcoding matrix P.P = HH(HHH+ HHH+ CT / )1(3)where H is the channel matrix of a channel from an intended transmitter, H is the channel matrix from unintended transmitters and o is the noise level at the receiver. Below, thereceiver’s operation for interference reduction with leveraging Ml MO and channel state information of interference link is also called ‘Rx nulling’.

[0026] To ensure a low interference level, the number of interference spatial streams should be less than the number of maximum available spatial DoFs of the receiver. In a typical case, a non-AP STA has a few receiving antennas, and thus the number of interference spatial streams should be managed to allow the receivers with a few receiving antennas to implement interference reduction.

[0027] In IEEE 802.11 TGbn, interference mitigation in spatial domain is considered as one of the approaches for high reliability communication. In the followings specific approaches are described, but essentially each approach requires that the AP / STA consume more spatial DoFs. Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, Fig. 1 shows a diagram illustrating Tx nulling (also called ‘CBF’ or ‘null steering’ as part of CT). ForTx nulling the transmitter (AP) steers null to unintended receivers (STA2), for which it should know the channel to the unintended receivers (e.g. h2in Fig. 1). Fig. 2 shows a diagram illustrating Rx nulling (also called ‘MIMO Interference Suppression’ (MIMO-IS) or ‘Interference Mitigation’). For Rx nulling the receiver (STA) steers null to unintended transmitters (AP2). The receiver, which should have two or more antennas should know at least the covariance matrices of the channel from unintended receivers (e.g. h2h2in Fig. 2; also works with just h2).

[0028] Spatial DoFs generally mean how many antennas are to be allocated for beamform- ing / nulling. Regarding Tx nulling, the transmitter (AP or beamformer) can allocate spatial DoFs to beamforming and / or nulling. In an example, the AP has four antennas and can allocate four spatial DoFs at most. Fig. 3 shows diagrams illustrating different allocations of DoFs for Tx nulling where the AP allocates one DoF to each of two STAs (Fig. 3A), in which case the AP still has two extra spatial DoFs. In the example shown in Fig. 3B, the AP allocates two DoFs to each of the two STAs, in which case the AP has no extra spatial DoF. Regarding Rx nulling, the receiver (STA or beamformee) can allocate spatial DoFs to 1) receiving spatial streams and / or 2) nulling. However, these approaches for Rx nulling essentially require consumption of more spatial DoFs.

[0029] The required spatial DoF allocation can conventionally be done as follows. Fig. 4 shows a diagram illustrating an example of transmissions between two APs and their associated STAs. As shown in Fig. 4, AP1 sends data to STA1 in one spatial stream (SS), and that AP2 sends data to STA2 in one SS. In Tx nulling, each AP steers null to unintended receivers with a number of spatial DoFs equal to the number of the unintended receiver’s antennas. Fig. 5 shows a diagram illustrating the allocation of DoFs for the example of transmissions shown in Fig. 4. As shown in Fig. 5, AP2 allocates two spatial DoFs for Tx nulling to STA1. The number of spatial DoFs for Tx nulling should be equal to or greater than two, which corresponds to the number of Rx antennas of the unintended receiver.

[0030] However, this technique requires that the AP is implemented with more antennas. In some cases, the AP does not have enough antennas, and the basic Tx nulling cannot work anymore. Fig. 6 shows a diagram illustrating the lack of antennas of AP2. As illustrated, AP2 cannot allocate two spatial DoFs for Tx nulling and one spatial DoF for the STA at the same time, because the AP2 only has two antennas and thus two spatial DoFs. Hence, as illustrated in Fig. 7 showing a diagram of the conventional allocation of DoFs, each AP steers null to unintended receivers with a number of spatial DoFs equal to the number of SS that the unintended receiver receives from another AP.

[0031] The AP2 allocates two spatial DoFs for Rx nulling to STA1. The number of spatial DoFs should be equal to or greater than two. However, this conventional approach is still based on the assumption that the channels are stable and that both APs are aware of a postcoding vector at the STAs, wherein predetermined postcoding is one of options for this.

[0032] One aim of the present disclosure is to utilize Rx nulling as much as possible because Rx nulling yields better interference reduction due to leveraging fresh CSI (= LTFs in received PPDll) and enables the AP to reduce the consumed number of spatial DoFs for nulling. Fig. 8 shows a diagram illustrating the desired Rx nulling according to the present disclosure. STA1 and 2 perform Rx nulling, but need to exchange configuration beforehand between APs, which is addressed by the present disclosure.

[0033] In Fig. 8 and for the following explanations, it is assumed that AP1 establishes a Basic Service Set (BSS) where STA1 is associated with AP1, which is called BSS1, and AP2 establishes another BSS where STA2 is associated with AP2, which is called BSS2. In a typical example, each STA has one or more receiving antennas and / or RF (Radio Frequency) chains. To perform Rx nulling at STAs, ideally each STA should have more receiving antennas and RF chains. STA1 and STA2 are receivers in CT from AP1 and AP2. In CT, AP1 transmits data to STA1, while AP2 transmits data to STA2 simultaneously. The transmission of AP1 may cause interference at STA2 and the transmission of AP2 may cause interference at STA1. Further STAs (not shown) may be associated with AP1 and / or AP2.

[0034] Fig. 9 shows a diagram illustrating a protocol 100 using CT according to a first embodiment of the present disclosure. In this example, AP1 comprises four antennas, AP2 and STA1 each comprises two antennas, and STA2 includes one antenna.

[0035] Initially, a capabilities exchange stage (not shown in Fig. 9) may be provided. To perform CT from Multi-AP, several stages may take place in advance. In a capabilities exchange stage AP1 and STA1 exchange their capabilities within association, and AP2 and STA2 exchange their capabilities as well. AP1 and AP2 may further exchange information which frequency channel(s) is (are) used for signaling with respect to the configuration for CT. Fig. 9 illustrates the exemplary case that in CT one or more spatial streams are allocated for transmission from AP1 to STA1 , one or more spatial DoFs are allocated for Tx nulling from AP1 to STA2, one or more spatial streams are allocated for transmission from AP2 to STA2, and one or more spatial DoFs are allocated for Rx nulling from STA2 to AP1.These numbers of spatial stream and spatial DoF allocation generally depend on a configuration setting determined by a procedure as explained below. In Fig. 9, solid lines mean data transmission to intended receivers from APs in CT, and dashed lines mean AP(s) and / or non-AP STA(s) steering null to unintended transmitter(s) and / or receiver(s).

[0036] Subsequently, an optional channel sounding and CSI Feedback Stage 10 is provided. After capabilities exchange, both APs and STAs optionally perform channel sounding and CSI Feedback for upcoming CT. This stage can be triggered by either AP1 or AP2 with sending trigger to the counterpart. STA1 and STA2 obtain CSI from both AP1 and AP2,and both STAs feedback the CSI to both APs. It is also possible that AP1 and AP2 exchange capabilities of their associated STAs to let the APs know capabilities of potential receivers in CT before the channel sounding. It shall be noted that this stage may be skipped, if the channel is considered stable. Further, this stage may take place within or after the Exchange of Configuration Info for CT stage 20.

[0037] Next, an Exchange of Configuration Info for CT stage 20 is provided, which represents a Configuration Setup Stage. In this stage, AP1 and AP2 exchange configuration information for the upcoming CT. Prior to this stage or in this stage, AP1 and AP2 may obtain TXOP by exchanging ICF and ICR, as will be explained below in more detail. Each of ICF and ICR can contain a Mll-RTS (Multi-User Ready-to-Send) frame, an RTS frame, or a CTS (Clear-to-send) frame. If primary channels of BSS1 and BSS2 are different, both RTS frame and CTS frame may be transmitted on both primary channels.

[0038] There are various embodiments how to perform the configuration setup in stage 20. Fig.10 shows a diagram of a configuration setup protocol 20 according to a first embodiment of the present disclosure. In this embodiment, three or four steps take place. In a first step 21 , AP1 sends an ICF to AP2 for a setup request to inform parameters about spatial stream allocation for API’s data transmission as part of the upcoming CT. In a second step 22, AP2 sends an ICR to AP1 to inform AP1 of parameters about spatial stream allocation for AP2’s transmission in the upcoming CT. In a third step 23, AP1 may calculate or derive the number of spatial DoFs for nulling and spatial streams for the upcoming CT. In the fourth step 24, AP1 optionally informs AP2 of parameters about at least AP2’s transmission in the upcoming CT. AP2 configure the number of spatial streams and spatial DoFs in step 25 (e.g. after step 21) for nulling in the upcoming CT. IAP2 may configure the number of spatial streams and spatial DoFs for nulling in the upcoming CT, as indicated in the information 21c in the ICF described below.

[0039] With the ICF sent in the first step 21 , in an example AP1 informs AP2 about the following information:21a: an indication of the number of spatial streams and resource units (RUs) to be intended for transmission to which STA(s) associated with AP1 in the upcoming CT;21b: an indication of a maximum number of spatial DoFs for Tx nulling from AP1 to potential STA(s), to which AP2 would transmit data in the upcoming CT; and21c: an indication of a maximum number of spatial DoFs for Rx nulling from each of the indicated STA(s) to AP2 in the upcoming CT, or a maximum number of spatial streams to be allocated for AP2’s transmission in the upcoming CT.

[0040] If the information 21c indicates a maximum number of spatial DoFs for Rx nulling from each of the indicated STA(s), AP2 may set the number of spatial streams for upcoming CT to the number equal to or less than the maximum number of spatial DoFs for Rx nulling from each of the indicated STA(s). In this case, AP2 may set the spatial DoFs to the number equal to or less than the number of AP2’s transmit antennas minus the number of spatial streams for upcoming CT.

[0041] If the information 21c indicates a maximum number of spatial streams to be allocated for AP2’s transmission in the upcoming CT, AP2 may set the number of spatial streams for upcoming CT to the number equal to or less the number indicated in information 21c. In this case. In this case, AP2 may set the spatial DoFs to the number equal to or less than the number of AP2’s transmit antennas minus the number of spatial streams for upcoming CT.

[0042] If the maximum number of spatial DoFs for Tx nulling from AP1 is already informed to AP2, for example through capabilities information exchange among the APs, the indication 21b may not be contained in the ICF. The maximum number of spatial DoFs for Tx nulling from AP may be equal to the number of transmit antennas of AP1.

[0043] If AP1 is informed of the maximum number of spatial DoFs for Rx nulling from each of the indicated STA(s) before the ICF, the indication 21c may not be contained in the ICF. The maximum number of spatial DoFs for Rx nulling from the STA(s) may be equal to the number of receive antennas of the STA(s), respectively.

[0044] In addition, the ICF may contain one or more of following indications:21 d: an indication that whether STA(s) indicated indication 21a can receive a signal with predetermined postcoding matrices in the upcoming CT;21e: an indication whether channel sounding and CSI Feedback is scheduled after the Exchange of Configuration Info for CT stage 20;21f: an indication, if indication of 21e indicates channel sounding and CSI Feedback is scheduled, which STA associated with AP1 can apply predetermined postcoding matrices, which is determined through channel sounding, in the upcoming CT; and21g: an indication of a duration for the upcoming CT.

[0045] The predetermined postcoding matrices shall also be known at AP2, and the postcoding matrices can be informed as part of CSI Feedback. If the indication 21c indicates the maximum number of spatial streams to be allocated for AP2’s transmission in the upcom ing CT, this indication also indicates one spatial stream as predetermined parameter. In other words, it can be assumed that only one spatial stream is allowed for AP2’s transmission for CT. If the number of spatial streams for AP1 ’s transmission to each STA in CT shall be restricted to one, the indication 21a may not include the number of spatial streams. In this case, the indication 21a indicates a total number of receiving STAs associated with AP1 in the upcoming CT instead of each number of spatial stream for transmission to each of the STA(s).

[0046] Under the assumption illustrated in Fig. 8, STA1 is indicated in each of the indications 21a and 21c. AP1 may transmit a (MU-)RTS frame to at least AP2, and AP2 sends, in response to the (MU-)RTS frame, a CTS frame to AP1 to let other STAs associated with AP2 set NAV (Network Allocation Vector). If primary channels of AP1 and AP2 are different, the (MU-)RTS frame and the CTS frame may be transmitted on both primary channels. The (MU-)RTS frame can be contained in ICF, and the CTS frame can be contained in ICR.

[0047] After receiving the ICF from AP1 in step 21 , AP2 may send CTS (Clear-to-send) frame to inform STAs associated with AP2 for TXOP acquisition on its primary channel. The CTS frame may be identical to the CTS frame defined in IEEE 802.11 standards. Subsequently, AP2, in response to the ICF, sends ICR in step 22 to inform AP1 about the following information:22a: an indication of the number of spatial streams and RUs to be intended or allocated for AP2’s transmission to which STA(s) among STAs associated with AP2 in the upcoming CT;22b: an indication of a maximum number of spatial DoFs to be allocated for Tx nulling from AP2 to STA(s), which are indicated in indication 21a in ICF, while AP2 performs transmission indicated in indication 22a; and22c: an indication of a maximum number of spatial DoFs that each of the STAs indicated in indication 22a can be allocated for Rx nulling in the upcoming CT, while the STAs receive data streams with the configuration indicated in indication 22a.

[0048] If the maximum number of spatial DoFs for Tx nulling from AP2 is already informed to AP1, for example through capabilities information exchange among the APs, the indication 22b may not be contained in the ICF. The maximum number of spatial DoFs for Tx nulling from AP may be equal to the number of transmit antennas of AP1. If AP2 is informed of the maximum number of spatial DoFs for Rx nulling from each of the indicated STA(s) before the ICF, the indication 22c may not be contained in the ICF. The maximum number of spatial DoFs for Rx nulling from the STA(s) may be equal to the number of receive antennas of the STA(s), respectively.

[0049] In addition, the ICR may contain one or more of following indications:22d: an indication that whether STA(s) indicated in 1-2) can receive a signal, with predetermined postcoding matrices, in the upcoming CT;22e: an indication whether channel sounding and CSI Feedback is scheduled after the Exchange of Configuration Info for CT stage 20;22f: an indication, if indication 22e indicates that channel sounding and CSI Feedback is scheduled, which STA associated with AP1 can apply predetermined postcoding matrices, which is determined through the channel sounding, in the upcoming CT.

[0050] The predetermined postcoding matrices shall also be known at AP1 , and the postcoding matrices can be informed as part of CSI Feedback. Under the assumption illustrated in Fig. 8, STA1 is indicated in indication 22b, and STA2 is the STA indicated in each of indications 22a and 22c. If at least indication 22e indicates that channel sounding and CSI Feedback is scheduled, channel sounding and CSI Feedback take place after ICR istransmitted to AP1. Through the CSI Feedback, STAs may inform APs about part of postcoding matrices which will be applied in the upcoming CT.

[0051] After receiving ICR in step 22, AP1 may determine (step 23) the number of spatial streams, which will be allocated at AP1 and AP2, in the upcoming CT. One of the reasons why AP1 determines the parameter in this step is that AP1 may not be aware whether STA2 supports Rx nulling, and thus AP1 can allocate more spatial streams for transmission to AP1 in the upcoming CT while STA2 performs Rx nulling.

[0052] In this step, the followings variants for the upcoming CT may be determined:23a: number of spatial streams to be allocated for transmission from AP1 to STA1 , referred t23b: number of spatial streams to be allocated for transmission from AP2 to STA2, referred to as n®;23c: number of spatial DoFs be allocated for Tx nulling from AP1 to STA2, which is equal to or greater than T ,?-’, if Tx nulling is performed;23d: minimum number of spatial DoFs to be allocated at STA1 for Rx nulling to AP2 from STA1, which is equal to / v < , if Rx nulling is performed;23e: minimum number of spatial DoFs to be allocated for Tx nulling from AP2 to STA1 , which is equal to N^\ if Tx nulling is performed; and23f: minimum number of spatial DoFs to be allocated for Rx nulling to AP1 from STA2, which is equal to n®, if Rx nulling is performed.

[0053] All of these variants do not have to be informed from AP1 to AP2 because variants 23c to 23f are known to both APs by exchange of ICF and ICR and / or by receiving CSI Feedback from STAs. AP1 should use the number of spatial streams in the upcoming CT as indicated in 23a in ICF, while other variants are determined with constraints on spatial DoFs at each device.

[0054] Fig. 11 shows a flowchart 200 of an embodiment of a method for determining the number n® of spatial streams for data transmission from AP2 to STA2. The following parameters are used (the variants with capital letters means fixed value): / Vt(1,2): maximum number of spatial DoFs for Tx nulling and transmission at AP1 and AP2, respectively; typically, it is equal to the number of Tx antennas;maximum number of spatial DoFs for Rx nulling and reception at STA1 and STA2, respectively; typically, it is equal to be number of Rx antennas; / V® : number of spatial streams for data transmission from AP1 to STA1 ;n^: number of spatial streams for data transmission from AP2 to STA2, which is one of the variants determined through the flowchart; andTV, '2-’: required number of spatial DoFs for Tx nulling to STA1 and STA2, respectively; these numbers are basically equal to N^l2respectively; if AP1 is aware of predetermined postcoding matrices at STA2 to be used in the upcoming CT, and STA2 also applies the postcoding matrices in the upcoming CT, / V,(2)is equal to n®; if AP2 is aware of predetermined postcoding matrices at STA1 to be used in the upcoming CT, and STA1 also applies the postcoding matrices in the upcoming CT, / V,® is equal to / V®.

[0055] At first (step 201), after AP1 receives ICR from AP2, it sets / V®. / V® can be the same number that AP1 has been informed to AP2 with ICF. In the second step 202, AP1 determines whether STA2 can perform Rx nulling in the upcoming CT. If STA2 supports Rx nulling, AP1 further determines in step 202 whether the following condition (4) is met

[0056] If the equation (4) is met, AP1 further determines (step 203) that STA1 can perform Rx nulling in the upcoming CT. If STA1 can support Rx nulling, AP determines whether the following condition (5) is met where> 1:Then, STA1 and STA2 both perform Rx nulling.

[0057] If equations (4) and (5) are met, AP1 sets n® to one of positive integer numbers which meet both equations (4) and (5), and informs AP2 of the following information in step 204:an indication that STA1 and STA2 are scheduled to perform Rx nulling in the upcoming CT;NgllTotal number of spatial streams to be used in the upcoming CT; and n®: number of spatial streams to be used for transmission from AP2 to STA2 in the upcoming CT.

[0058] The above three indications can be sent to AP2 in ‘Setup Announce’ step 24 illustrated in Fig. 10. By receiving the above information, AP2 recognizes that AP2 does not have to allocate spatial DoFs for Tx nulling but may allocate extra spatial DoFs for Tx nulling in upcoming CT, if JV® > n®. AP1 can also allocate part of extra spatial DoFs for Tx nulling in upcoming CT, if N® > N^.

[0059] If equation (4) is met while equation (5) is not met, AP2 determines (step 206) whether AP2 can perform Tx nulling in the upcoming CT. If AP2 can support Tx nulling, AP1 further determines whether the following condition (6) is met where n® > 1:In step 207, AP1 informs AP2 accordingly. Then, AP2 performs Tx nulling and STA2 performs Rx nulling.

[0060] If equations (4) and (6) are met while equation (5) is not met, AP1 sets (step 207) n® to one of positive integer numbers which meet both equations (4) and (6), and informs AP2 of the following information:an indication that AP2 and STA2 are scheduled to perform Tx nulling and Rx nulling, respectively, in the upcoming CT;NgllTotal number of spatial streams to be used in the upcoming CT;n®: number of spatial streams to be used for transmission from AP2 to STA2 in the upcoming CT; andminimum number of spatial DoFs for Tx nulling from AP2 to STA1 in the upcoming CT.

[0061] The above three indications can be sent to AP2 in ‘Setup Announce’ step 24 illustrated in Fig. 10. By receiving the above information, AP2 recognizes that AP2 does not have to allocate spatial DoFs for Tx nulling but may allocate extra spatial DoFs for Tx nulling in upcoming CT, if / Vt(2)> n® . AP2 shall also allocate at least n® spatial DoFs for Tx nulling in upcoming CT, if> N^\

[0062] If equation (4) is not met in step 202, AP1 determines (step 209) whether AP1 can perform Tx nulling. If AP1 can support Tx nulling, AP1 determines whether following condition (7) is metIf equation (4) is not met while equation (7) is, AP1 further determines (step 210) whether STA1 can perform Rx nulling. If STA1 supports Rx nulling, AP1 determines whether equation (5) is met where> 1. AP1 informs AP accordingly (step 211). Then, AP1 performs Tx nulling and STA1 performs Rx nulling.

[0063] If equation (4) is not met while equations (5) and (7) are met, AP1 sets (step 213) n® to one of positive integer numbers which meet both equations (5) and (7) while they do not meet equation (4), and informs AP2 of the following information:an indication that AP1 and STA1 are scheduled to perform Tx nulling and Rx nulling, respectively, in the upcoming CT;NgllTotal number of spatial streams to be used in the upcoming CT; andn2number of spatial streams to be used for transmission from AP2 to STA2 in the upcoming CT.

[0064] If equations (4) and (5) are not met while equation (7) is met, AP determines whether AP2 can perform Tx nulling. If AP2 can support Tx nulling AP1 determines (step 212) whether equation (6) is met where> 1. Then, AP1 and AP2 perform Tx nulling.

[0065] If equations (4) and (5) are not met while equations (6) and (7) are met, AP1 sets n® to one of positive integer numbers which meet both equation (6) and (7) while they do not meet equations (4) and (5), and informs AP2 of the following information:an indication that AP1 and AP2 are scheduled to perform Tx nulling, in the upcoming CT;NgllTotal number of spatial streams to be used in the upcoming CT; and minimum number of spatial DoFs for Tx nulling from AP2 to STA1 in the upcoming CT.

[0066] If one of the following conditions are met, CT is not scheduled:a) equations (5) and (6) are not met while equation (4) is met where= 1; b) equations (4), (5) and (6) are not met while equations (7) is met where= 1; andc) equation (4) and (7) are not metIn these cases, AP1 may inform (steps 208, 214) AP2 that CT is not scheduled in ‘Setup Announce’ step 24.

[0067] AP2 can also determine n® through the same procedure described above with reference to Fig. 11. In this case, the indications in ICR are computed after AP2 determines n®. Furthermore, in this case, AP2 shall setto the same number as AP1 informed AP2 with ICF, and shall inform the following information with ICR:an indication that which APs and which STAs are scheduled to perform Tx nulling and / or Rx nulling in the upcoming CT;NgllTotal number of spatial streams to be used in the upcoming CT;n®: number of spatial streams to be used for transmission from AP2 to STA2 in the upcoming CT; andan indication whether AP2 joins CT.In this case, AP1 shall set N® in the upcoming CT as AP1 informs AP2 it with ICF, ‘Setup Announce’ as illustrated in latter may be skipped, and spatial stream allocation and spatial DoFs allocation for nulling in the upcoming CT follow parameters indicated in both ICF and ICR.

[0068] After n® is determined by AP1 , e.g. as explained above with reference to Fig. 11 , AP1 may inform AP2 of as Setup Announce in step 24 (see Fig. 10) of an indication whether CT is scheduled and a trigger for CT. If the indication indicates that CT is scheduled, the following indications may also be contained in Setup Announce:an indication which APs and which STAs are scheduled to perform Tx nulling and / or Rx nulling, respectively, in the upcoming CT;Nglltotal number of spatial streams to be used in the upcoming CT ;n® : number of spatial streams to be used for transmission from AP2 to STA2 in the upcoming CT;minimum number of spatial DoFs for Tx nulling from AP2 to STA1 in the upcoming CT, if AP2 is scheduled to perform Tx nulling; andminimum number of spatial DoFs for Rx nulling from STA2 to AP1 , if STA2 is scheduled to perform Rx nulling.

[0069] AP1 and AP2 shall follow whether they perform Tx nulling and configure the number or spatial streams in the upcoming CT, as indicated in Setup Announce in step 24.

[0070] Referring again to Fig. 9, after the configuration exchange in stage 20, the concurrent transmission (CT) is performed in stage 30. In the upcoming CT, a sufficient number of LTFs (Long Training Fields) shall be inserted in the transmitted PPDll (PHY Protocol Data Unit) to allow STA1 and STA2 to estimate the channel from AP1 and AP2 to perform Rx nulling at those STAs. The number of LTFs shall be equal to or greater than N^llandthe same preamble part of the PPDll, including the LTFs, shall be transmitted from AP1 and AP2 in the CT.

[0071] It may be applicable that some parts of the preamble, which indicate user specific information, appended to the LTFs are multiplexing in spatial / frequency domain such that those parts can be separately decoded at each STA by estimated CSI with leveraging LTFs. The user specific information may contain the following information to inform receiving STAs of parameters for Rx nulling: minimum number of spatial DoFs where each STA shall steer null in receiving / decoding PSDU in the upcoming CT.

[0072] Fig. 12 shows a diagram of a configuration setup protocol 20’ according to a second embodiment of the present disclosure, which may implement stage 20 illustrated in Fig. 9. In this embodiment, AP2 can send preferred configuration beforehand without receiving ICR from AP1 as ‘Request for setup’ step 26. AP2 may contain buffer status report (BSR) in the request to inform AP1 which STAs associated AP2 are candidate destinations in the upcoming CT. The ‘Request for setup’ in step 26 may contain an indication of preferable MCS (Modulation and Coding Scheme) and RU size for the upcoming CT. AP2 shall also send ICF (step 21) and / or ‘Setup Announce’ (step 24 in Fig. 10; not shown in Fig. 12).

[0073] Prior to the ‘Request for setup’ in step 26, AP2 may obtain TXOP on primary channel of AP1 and / or AP2 by RTS and CTS frame exchange with AP1 , but the TXOP does not have to be maintained until the upcoming CT.

[0074] It is not illustrated in Fig. 12, but after receiving ‘Request for Setup’, AP1 may determine n® before sending ICF to AP2 in step 21. n® can be determined as explained above. In this case, AP2 shall configure n® in the upcoming CT, if scheduled. AP2 may configure the number of spatial streams and spatial DoFs in step 25 for nulling in the upcoming CT after receiving ICF from AP1, and inform, in response to ICF, those parameters with ICR in step 22.

[0075] After receiving ICR, AP1 may determine number of spatial streams and DoFs for nulling in the upcoming CT. In this case, AP1 sends ‘Setup Announce’ to AP2 to informconfiguration for the upcoming CT, wherein indications contained in ‘Setup Announce’ may be identical to the indications explained above.

[0076] AP1 may obtain TXOP before transmitting ‘Setup Announce’ by exchanging MU (Multi User)-RTS frame and CTS frame exchange with AP2, STA1 and STA2 on the primary channel of BSS1. If primary channels are different between BSS1 and BSS2, AP1 may send AP2 a request to exchange RTS frame and CTS frame with the STA(s) indicated in the ‘Request for setup’. AP1 may also inform AP2 of preferable TXOP duration with ICF. The TXOP duration can be computed based on i) traffic size indicated in the ‘Request for setup’, ii) traffic size for intended receiver of AP1, and / or iii) the MCS and the RU size indicated in the ‘Request for setup’.

[0077] After AP2 establishes TXOP on its primary channel, which is different from the primary channel of BSS1 , by exchanging RTS frame and CTS frame with the STA(s) in BSS2, AP2 may send AP1 an indication that the exchange of RTS frame and CTS frame is completed. If AP1 does not receive the indication within a certain time from the request, AP1 may defer scheduling CT.

[0078] After AP1 receives from AP2 the indication that AP2 obtains TXOP on its primary channel,AP1 may exchange RTS frame and CTS frame with intended receiver(s) in the upcoming CT to obtain TXOP on its primary channel and send ‘Setup Announce’ to AP2.

[0079] In another embodiment, to implement the configuration setup in a simplified way, n® may be set to one as a predetermined parameter. In this case, ICF may include indications that indicate i) n® is set to one and ii) if n® cannot be set to one, CT is not scheduled.

[0080] In still another embodiment, it is also applicable that upcoming CT is still scheduled even if some of the equations (4) to (7) are not met. In this case, MCS shall be set to below a certain level such as QPSK with 2 / 3 LDPC (Low Density Parity Code) coding rate to ensure low PER (Packet Error Rate) while interference can be observed at each STA due to lack of spatial DoFs.

[0081] Fig. 13 shows a diagram illustrating an embodiment of the layout of the main communication devices in an embodiment of the present disclosure. According to this embodiment the first communication device (AP1) 310, the second communication device (AP2) 320, the third communication device (STA1) 330 and the fourth communication device (STA2) 340 each comprises a communication control device 311, 321, 331 , 341 that controls a wireless communication circuitry 312, 322, 332, 342 of the respective communication device so that AP1 310 can communicate with one or more STA1 330 and AP2 330 can communication with one or more STA2340. The communication control devices 311 , 321 , 331, 341 may each further comprise control circuitry 313, 323, 333, 343 to control the wireless communication circuitry of the respective communication device. The wireless communication circuitry 312, 322, 332, 342 and / or the control circuitry 313, 323, 333, 343 may implement the components of the respective communication device as illustrated hereinafter and may carry out the respective functions of these components.

[0082] Fig. 14 shows a flowchart of an embodiment of a first communication control method 410 according to the present disclosure, which may be carried out by a first communication control device 310, e.g. AP1. In a first step 411, AP1 is controlled to obtain a TXOP. In a second step 412, AP1 is controlled to transmit an ICF to AP2 with which the TXOP shall be shared for a coordinated transmission. In a third step 413, AP1 is controlled to receive an ICR from AP2. In a fourth step 414, AP1 is controlled to allocate at least a part of the obtained TXOP for the coordinated transmission, wherein the number of spatial streams and the number of spatial degrees of freedom for reception nulling are configured based on the ICF and / or ICR.

[0083] Fig. 15 shows a flowchart of an embodiment of a second communication control method 420 according to the present disclosure, which may be carried out by a second communication control device 320, e.g. AP2. In a first step 421, AP2 is controlled to receive an ICF from AP1 with which the TXOP shall be shared for a coordinated transmission. In a second step 422, AP2 is controlled to transmit an ICR to AP1. In a third step 423, AP2 is controlled to receive an allocation of at least a part of the obtained TXOP for the coordinated transmission from AP1 , wherein the number of spatial streams and the number of spatial degrees of freedom for reception nulling are configured based on the ICF and / or ICR.

[0084] In these embodiments of operation, the ICF preferably includes an indication ofi) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / orii) a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices.

[0085] Furthermore, in these embodiments of operation, the ICR preferably includes an indication ofa) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / or a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices, andb) an indication which communication devices are scheduled to perform reception nulling.

[0086] The device may be implemented by respective units or circuitry, e.g. a processor, processing circuitry, a computer, dedicated hardware, etc., that carries out the functions of the device. Alternatively, a common unit or circuitry, e.g. a common processor or computer, may implement the various functions of the device, or separate units or elements may be used that together represent the circuitry.

[0087] 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 the spirit or essential characteristics thereof. Accordingly, the disclosure of the present disclosure is intended to be illustrative, but not limiting the scope of the disclosure, as well as other claims. The disclosure, including any readily discernible variants of the teachings herein,defines, in part, the scope of the foregoing claim terminology such that no inventive subject matter is dedicated to the public.

[0088] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit may fulfill the functions of several 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.

[0089] In so far as embodiments of the disclosure have been described as being implemented, at least in part, by software-controlled data processing apparatus, it will be appreciated that a non-transitory machine-readable medium carrying such software, such as an optical disk, a magnetic disk, semiconductor memory or the like, is also considered to represent an embodiment of the present disclosure. Further, such a software may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

[0090] The elements of the disclosed devices, apparatus and systems may be implemented by corresponding hardware and / or software elements, for instance appropriate circuits or circuitry. A circuit is a structural assemblage of electronic components including conventional circuit elements, integrated circuits including application specific integrated circuits, standard integrated circuits, application specific standard products, and field programmable gate arrays. Further, a circuit includes central processing units, graphics processing units, and microprocessors which are programmed or configured according to software code. A circuit does not include pure software, although a circuit includes the above-described hardware executing software. A circuit or circuitry may be implemented by a single device or unit or multiple devices or units, or chipset(s), or processor(s).

[0091] It follows a list of further embodiments of the disclosed subject matter:1. A first communication control device configured to control a first wireless communication circuitry of a first communication device configured to communicate with one or more third communication devices to:obtain a transmission opportunity (TXOP);transmit an initial control frame (ICF) to a second communication device with which the TXOP shall be shared fora coordinated transmission, the ICF including an indication ofi) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / orii) a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices;receive an initial control response frame (ICR) from the second communication device, the ICR including an indication ofa) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / or a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices, andb) an indication which communication devices are scheduled to perform reception nulling; andallocate at least a part of the obtained TXOP for the coordinated transmission, wherein the number of spatial streams and the number of spatial degrees of freedom for reception nulling are configured based on the ICF and / or ICR.2. The first communication control device according to embodiment 1 , further configured to control the first wireless communication circuitry to additionally include in the ICF an indication of one or more of:the number of spatial streams and resource units allocated to one or more third communication devices in the intended coordinated transmission,a maximum number of spatial degrees of freedom for transmission nulling at the first communication device towards one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, a maximum number of spatial streams to be allocated for transmission by the second communication device in the intended coordinated transmission, andan indication that a number of spatial streams to be allocated for transmission by the second communication device in the intended coordinated transmission is restricted to be one at most.3. The first communication control device according to embodiment 1 or 2, further configured to control the first wireless communication circuitry to additionally include in the ICF one or more of the following indications:whether the one or more third communication devices can receive signals with predetermined postcoding matrices in the intended coordinated transmission,whether channel sounding and an exchange of channel state information feedback is scheduled after receipt of the ICR,which of the one or more third communication devices can apply predetermined postcoding matrices, which is determined through channel sounding, in the intended coordinated transmission, andduration of the intended coordinated transmission.4. The first communication control device according to any preceding embodiment, further configured to control the first wireless communication circuitry to determine, after receipt of the ICR, the number of spatial streams which will be allocated by the first communication device to the one or more third communication devices and / or the number of spatial streams for allocation by the second communication device to the one or more fourth communication devices in the intended coordinated transmission.5. The first communication control device according to any preceding embodiment, further configured to control the first wireless communication circuitry to determine, after receipt of the ICR, one or more of:the number of spatial degrees of freedom to be allocated for transmission nulling at the first communication device towards one or more fourth communication devices towhich the second communication device may transmit in the intended coordinated transmission,a minimum number of spatial degrees of freedom to be allocated at the first communication device for reception nulling to the second communication device from the one or more third communication devices,a minimum number of spatial degrees of freedom to be allocated for transmission nulling from the second communication device to the one or more third communication devices, anda minimum number of spatial degrees of freedom to be allocated for reception nulling towards the first communication device from the one or more fourth communication devices.6. The first communication control device according to any preceding embodiment, further configured to control the first wireless communication circuitry to transmit to the second communication device after receipt of the ICR, a setup announce indication including one or more of:an indication if coordinated transmission is scheduled, anda trigger to initiate coordinated transmission.7. The first communication control device according to embodiment 6, further configured to control the first wireless communication circuitry to include, if the indication indicates that coordinated transmission is scheduled, into the setup announce indication one or more of:an indication which communication devices are scheduled to perform transmission nulling and / or reception nulling in the intended coordinated transmission,the total number of spatial streams to be used in the intended coordinated transmission,the number of spatial streams to be used for transmission from the second communication device to the one or more fourth communication device in the intended coordinated transmission,a minimum number of spatial degrees of freedom for transmission nulling from the second communication device to the one or more third communication device if the second communication device is scheduled to perform transmission nulling, anda minimum number of spatial degrees of freedom for reception towards the first communication device from the one or more fourth communication devices if the one or more fourth communication devices are scheduled to perform reception nulling.8. The first communication control device according to any preceding embodiment, further configured to control the first wireless communication circuitry toinitially receive a setup request from the second communication device including one or more of:- an indication of one or more fourth communication devices as candidate destinations in the intended coordinated transmission,- preferable modulation coding scheme in the intended coordinated transmission, - preferable size of resource units in the intended coordinated transmission; and determine, before transmitting the ICR, the number of spatial streams for allocation by the second communication device to the one or more fourth communication devices in the intended coordinated transmission.9. The first communication control device according to any preceding embodiment, further configured to control the first wireless communication circuitry to carry out one or more of the following steps:initially exchange capabilities with the one or more third communication devices, transmit capabilities received from the one or more third communication devices to the second communication device, andperform channel sounding and exchange channel state information feedback with the one or more third communication devices.10. A second communication control device configured to control a second wireless communication circuitry of a second communication device configured to communicate with one or more fourth communication devices to:receive an initial control frame (ICF) from a first communication device with which the TXOP shall be shared fora coordinated transmission, the ICF including an indication of communicationi) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one ormore fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / orii) a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices;transmit an initial control response frame (ICR) to the first communication device, the ICR including an indication ofa) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / or a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices, andb) an indication which communication devices are scheduled to perform reception nulling; andreceive an allocation of at least a part of the obtained TXOP for the coordinated transmission from the first communication device, wherein the number of spatial streams and the number of spatial degrees of freedom for reception nulling are configured based on the ICF and / or ICR.11. The second communication control device according to embodiment 10, further configured to control the second wireless communication circuitry to transmit one or more frames to one or more fourth communication devices according to the indications in the ICR or a setup announce indication from the first communication device, concurrently with a transmission of one or more frames to one or more third communication devices by the first communication device.12. The second communication control device according to embodiment 10 or 11, further configured to control the second wireless communication circuitry to additionally include in the ICF an indication of one or more of:the number of spatial streams and resource units allocated to one or more fourth communication devices in the intended coordinated transmission, anda maximum number of spatial degrees of freedom for transmission nulling at the second communication device towards one or more third communication devices to which the first communication device may transmit intended coordinated transmission.13. The second communication control device according to any one of embodiments 10 to 12, further configured to control the second wireless communication circuitry to additionally include in the ICR one or more of the following indications:whether one or more fourth communication devices can receive signals with predetermined postcoding matrices in the intended coordinated transmission,whether channel sounding and an exchange of channel state information feedback is scheduled after transmission of the initial control response frame, andwhich one or more third communication devices can apply predetermined postcoding matrices, which is determined through the channel sounding, in the intended coordinated transmission.14. The second communication control device according to any one of embodiments 10 to 13, further configured to control the second wireless communication circuitry to determine, after receipt of the ICF, the number of spatial streams which will be allocated by the second communication device to the one or more fourth communication devices in the intended coordinated transmission.15. The second communication control device according to any one of embodiments 10 to 14, further configured to control the second wireless communication circuitry to initially transmit a setup request to the first communication device including one or more of:an indication of one or more fourth communication devices as candidate destinations in the intended coordinated transmission,preferable modulation coding scheme in the intended coordinated transmission, preferable size of resource units in the intended coordinated transmission.16. A first communication control method of a first communication control device configured to control a first wireless communication circuitry of a first communication device configured to communicate with one or more third communication devices to:obtain a transmission opportunity (TXOP);transmit an initial control frame (ICF) to a second communication device with which the TXOP shall be shared fora coordinated transmission, the ICF including an indication ofi) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / orii) a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices;receive an initial control response frame (ICR) from the second communication device, the ICR including an indication ofa) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / or a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices, andb) an indication which communication devices are scheduled to perform reception nulling; andallocate at least a part of the obtained TXOP for the coordinated transmission, wherein the number of spatial streams and the number of spatial degrees of freedom for reception nulling are configured based on the ICF and / or ICR.17. A second communication control method of a second communication control device configured to control a second wireless communication circuitry of a second communication device configured to communicate with one or more fourth communication devices to:receive an initial control frame (ICF) from a first communication device with which the TXOP shall be shared fora coordinated transmission, the ICF including an indication ofi) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one ormore fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / orii) a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices;transmit an initial control response frame (ICR) to the first communication device, the ICR including an indication ofa) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / or a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices, andb) an indication which communication devices are scheduled to perform reception nulling; andreceive an allocation of at least a part of the obtained TXOP for the coordinated transmission from the first communication device, wherein the number of spatial streams and the number of spatial degrees of freedom for reception nulling are configured based on the ICF and / or ICR.18. A non-transitory computer-readable recording medium that stores therein a computer program product, which, when executed by a processor, causes the method according to embodiment 16 or 17 to be performed.19. A computer program comprising program code means for causing a computer to perform the steps of said method according to embodiment 16 or 17 when said computer program is carried out on a computer.

Claims

CLAIMS1. A first communication control device configured to control a first wireless communication circuitry of a first communication device configured to communicate with one or more third communication devices to:obtain a transmission opportunity (TXOP);transmit an initial control frame (ICF) to a second communication device with which the TXOP shall be shared fora coordinated transmission, the ICF including an indication ofi) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / orii) a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices;receive an initial control response frame (ICR) from the second communication device, the ICR including an indication ofa) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / or a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices, andb) an indication which communication devices are scheduled to perform reception nulling; andallocate at least a part of the obtained TXOP for the coordinated transmission, wherein the number of spatial streams and the number of spatial degrees of freedom for reception nulling are configured based on the ICF and / or ICR.

2. The first communication control device according to claim 1 , further configured to control the first wireless communication circuitry to additionally include in the ICF an indication of one or more of:the number of spatial streams and resource units allocated to one or more third communication devices in the intended coordinated transmission,a maximum number of spatial degrees of freedom for transmission nulling at the first communication device towards one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, a maximum number of spatial streams to be allocated for transmission by the second communication device in the intended coordinated transmission, andan indication that a number of spatial streams to be allocated for transmission by the second communication device in the intended coordinated transmission is restricted to be one at most.

3. The first communication control device according to claim 1 , further configured to control the first wireless communication circuitry to additionally include in the ICF one or more of the following indications:whether the one or more third communication devices can receive signals with predetermined postcoding matrices in the intended coordinated transmission,whether channel sounding and an exchange of channel state information feedback is scheduled after receipt of the ICR,which of the one or more third communication devices can apply predetermined postcoding matrices, which is determined through channel sounding, in the intended coordinated transmission, andduration of the intended coordinated transmission.

4. The first communication control device according to claim 1 , further configured to control the first wireless communication circuitry to determine, after receipt of the ICR, the number of spatial streams which will be allocated by the first communication device to the one or more third communication devices and / or the number of spatial streams for allocation by the second communication device to the one or more fourth communication devices in the intended coordinated transmission.

5. The first communication control device according to claim 1 , further configured to control the first wireless communication circuitry to determine, after receipt of the ICR, one or more of:the number of spatial degrees of freedom to be allocated for transmission nulling at the first communication device towards one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission,a minimum number of spatial degrees of freedom to be allocated at the first communication device for reception nulling to the second communication device from the one or more third communication devices,a minimum number of spatial degrees of freedom to be allocated for transmission nulling from the second communication device to the one or more third communication devices, anda minimum number of spatial degrees of freedom to be allocated for reception nulling towards the first communication device from the one or more fourth communication devices.

6. The first communication control device according to claim 1 , further configured to control the first wireless communication circuitry to transmit to the second communication device after receipt of the ICR, a setup announce indication including one or more of: an indication if coordinated transmission is scheduled, anda trigger to initiate coordinated transmission.

7. The first communication control device according to claim 6, further configured to control the first wireless communication circuitry to include, if the indication indicates that coordinated transmission is scheduled, into the setup announce indication one or more of:an indication which communication devices are scheduled to perform transmission nulling and / or reception nulling in the intended coordinated transmission,the total number of spatial streams to be used in the intended coordinated transmission,the number of spatial streams to be used for transmission from the second communication device to the one or more fourth communication device in the intended coordinated transmission,a minimum number of spatial degrees of freedom for transmission nulling from the second communication device to the one or more third communication device if the second communication device is scheduled to perform transmission nulling, anda minimum number of spatial degrees of freedom for reception towards the first communication device from the one or more fourth communication devices if the one or more fourth communication devices are scheduled to perform reception nulling.

8. The first communication control device according to claim 1 , further configured to control the first wireless communication circuitry toinitially receive a setup request from the second communication device including one or more of:- an indication of one or more fourth communication devices as candidate destinations in the intended coordinated transmission,- preferable modulation coding scheme in the intended coordinated transmission, - preferable size of resource units in the intended coordinated transmission; and determine, before transmitting the ICR, the number of spatial streams for allocation by the second communication device to the one or more fourth communication devices in the intended coordinated transmission.

9. The first communication control device according to claim 1 , further configured to control the first wireless communication circuitry to carry out one or more of the following steps:initially exchange capabilities with the one or more third communication devices, transmit capabilities received from the one or more third communication devices to the second communication device, andperform channel sounding and exchange channel state information feedback with the one or more third communication devices.

10. A second communication control device configured to control a second wireless communication circuitry of a second communication device configured to communicate with one or more fourth communication devices to:receive an initial control frame (ICF) from a first communication device with which the TXOP shall be shared fora coordinated transmission, the ICF including an indication of communicationi) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one ormore fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / orii) a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices;transmit an initial control response frame (ICR) to the first communication device, the ICR including an indication ofa) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / or a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices, andb) an indication which communication devices are scheduled to perform reception nulling; andreceive an allocation of at least a part of the obtained TXOP for the coordinated transmission from the first communication device, wherein the number of spatial streams and the number of spatial degrees of freedom for reception nulling are configured based on the ICF and / or ICR.

11. The second communication control device according to claim 10, further configured to control the second wireless communication circuitry to transmit one or more frames to one or more fourth communication devices according to the indications in the ICR or a setup announce indication from the first communication device, concurrently with a transmission of one or more frames to one or more third communication devices by the first communication device.

12. The second communication control device according to claim 10, further configured to control the second wireless communication circuitry to additionally include in the ICF an indication of one or more of:the number of spatial streams and resource units allocated to one or more fourth communication devices in the intended coordinated transmission, anda maximum number of spatial degrees of freedom for transmission nulling at the second communication device towards one or more third communication devices to which the first communication device may transmit intended coordinated transmission.

13. The second communication control device according to claim 10, further configured to control the second wireless communication circuitry to additionally include in the ICR one or more of the following indications:whether one or more fourth communication devices can receive signals with predetermined postcoding matrices in the intended coordinated transmission,whether channel sounding and an exchange of channel state information feedback is scheduled after transmission of the initial control response frame, andwhich one or more third communication devices can apply predetermined postcoding matrices, which is determined through the channel sounding, in the intended coordinated transmission.

14. The second communication control device according to claim 10, further configured to control the second wireless communication circuitry to determine, after receipt of the ICF, the number of spatial streams which will be allocated by the second communication device to the one or more fourth communication devices in the intended coordinated transmission.

15. The second communication control device according to claim 10, further configured to control the second wireless communication circuitry to initially transmit a setup request to the first communication device including one or more of:an indication of one or more fourth communication devices as candidate destinations in the intended coordinated transmission,preferable modulation coding scheme in the intended coordinated transmission, preferable size of resource units in the intended coordinated transmission.

16. A first communication control method of a first communication control device configured to control a first wireless communication circuitry of a first communication device configured to communicate with one or more third communication devices to:obtain a transmission opportunity (TXOP);transmit an initial control frame (ICF) to a second communication device with which the TXOP shall be shared fora coordinated transmission, the ICF including an indication ofi) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / orii) a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices;receive an initial control response frame (ICR) from the second communication device, the ICR including an indication ofa) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / or a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices, andb) an indication which communication devices are scheduled to perform reception nulling; andallocate at least a part of the obtained TXOP for the coordinated transmission, wherein the number of spatial streams and the number of spatial degrees of freedom for reception nulling are configured based on the ICF and / or ICR.

17. A second communication control method of a second communication control device configured to control a second wireless communication circuitry of a second communication device configured to communicate with one or more fourth communication devices to:receive an initial control frame (ICF) from a first communication device with which the TXOP shall be shared fora coordinated transmission, the ICF including an indication ofi) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one ormore fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / orii) a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices;transmit an initial control response frame (ICR) to the first communication device, the ICR including an indication ofa) a maximum number of spatial degrees of freedom for transmission nulling, which is less than the number of transmit antennas of the first communication device, to one or more fourth communication devices to which the second communication device may transmit in the intended coordinated transmission, and / or a maximum number of spatial degrees of freedom for reception nulling, which is less than the number of receive antennas at each of the one or more third communication devices, andb) an indication which communication devices are scheduled to perform reception nulling; andreceive an allocation of at least a part of the obtained TXOP for the coordinated transmission from the first communication device, wherein the number of spatial streams and the number of spatial degrees of freedom for reception nulling are configured based on the ICF and / or ICR.

18. A non-transitory computer-readable recording medium that stores therein a computer program product, which, when executed by a processor, causes the method according to claim 16 or 17 to be performed.

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