Patent ID: 12237886

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

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following description, reference is made to the accompanying figures, which form part of the disclosure, and which show, by way of illustration, aspects of embodiments of the present disclosure or aspects in which embodiments of the present disclosure may be used. It is understood that embodiments of the present disclosure may be used in other aspects and comprise structural or logical changes not depicted in the figures. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims.

For instance, it is to be understood that a disclosure in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if one or a plurality of method steps is described, a corresponding device may include one or a plurality of units, e.g. functional units, to perform the described one or plurality of method steps (e.g. one unit performing the one or plurality of steps, or a plurality of units each performing one or more of the plurality of steps), even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, for example, if a specific apparatus is described based on one or a plurality of units, e.g. functional units, a corresponding method may include one step to perform the functionality of the one or plurality of units (e.g. one step performing the functionality of the one or plurality of units, or a plurality of steps each performing the functionality of one or more of the plurality of units), even if such one or plurality of steps is not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary embodiments and/or aspects described herein may be combined with each other, unless noted otherwise.

Before describing different embodiments in more detail, in the following some technical background as well as terminology concerning wireless transmitters, in particular wireless transmitters in accordance with the IEEE 802.11 WLAN standard will be introduced making use of the following abbreviations:AID Association IdentifierAP Access PointBF Beam-formingBSS Basic Service SetBW BandwidthCA Certification Authority/Collision Avoidance/Carrier AggregationCCA Clear Channel AssessmentCSMA Carrier Sense Multiple AccessHD High DensityHEW High Efficient Wi-FiIP Internet ProtocolMAC Medium Access ControlMCS Modulation and Coding SchemeMIMO Multiple Input Multiple OutputMU Multi-UserNDP Null Data PacketNDPA NDP AnnouncementOBSS Overlapping Basic Service SetPER Packet Error Ratio/Packet Error RatePHY Physical LayerPPDU PHY Protocol Data UnitRRM Radio Resource ManagementRX Receive or ReceiverSIFS Short Inter-frame SpaceSINR Signal to Interference plus Noise RatioSR Spatial ReuseSTA StationTX Transmit or TransmitterTxOP Tx OpportunityVHD Very High DensityWLAN Wireless local area network based on IEEE 802.11 and related standards

Multiple WIFI access points (APs) of a basic service set (BSS) may use the same communication channel and space (fewer channels than APs) sharing the medium by using a CSMA/CA access method such that only one device transmits at a time, while the others are idle. Using a CSMA/CA access method, however, increases the collision and hidden nodes probability, which, in turn, result in an increased PER and noise level. In high-density (HD) and very high density (VHD) WIFI deployments, the distance between cells may be short (10 to 30 meters), which increases the unused time of Wi-Fi devices (or “Time Shared”). As long as the WIFI devices “hear” a signal larger than the clear channel assessment (CCA) threshold, they will refrain from using the medium. Therefore, in many HD/VHD deployments the throughput per channel is almost fixed and declines when the number of APs per channel increases. Therefore, adding more APs to the deployment usually does not increase the network data rate, as illustrated inFIG.1.

The standard 802.11 TGax (also referred to as High-Efficiency Wireless (HEW)) focuses on implementing mechanisms to serve more users with a consistent and reliable stream of data (average throughput) in the presence of many other users. To improve the system level performance and the efficiency due to the CSMA/CA access method in WLAN scenarios, the 802.11ax standard implements a SR technique. SR enables the sharing of the medium between two or more Tx devices using the same channel, time and space. In order for an Rx device to select its transmitter in a SR environment, wireless stations can identify signals by using the BSS coloring scheme. When a wireless station that is actively listening to the medium detects an 802.11ax frame, it checks the BSS color bits. If the BSS color in the detected PPDU is the same color as its associated AP has announced, then the STA considers that frame as an intra-BSS frame. However, if the detected frame has a BSS color different from its own color, then the STA considers that frame as an inter-BSS frame from an overlapping BSS. Moreover, 802.11ax devices treat the medium as CCA-BUSY only during the time it takes the STA to validate that the frame is from an inter-BSS, but not longer than the time indicated as the length of the frame's payload.

SR is used in 802.11ax to utilize the medium (frequency, time and space) by multiple devices and to avoid collisions between those devices. In an example, SR allows multiple devices to share the same frequency, time and space by using a different BSS color and ID.

A SR session is initiated by the wireless AP that got access to the medium, i.e. has obtained a transmission opportunity (TxOP). This AP is referred to herein as the SR IAP that indicates that it is willing to share the medium with other devices. InFIG.2andFIG.5, the IAP is identified by the reference sign101(or AP1). Other APs that have data to transmit, may start using the medium. Those APs are referred to herein as Participator APs (PAPs). InFIG.2andFIG.5, a PAP is identified by the reference sign111(or AP2). The major SR challenge is the adjustment of the CCA threshold and Tx power level to prevent mutual interferences between the IAP101and the PAP111. The main idea behind these adjustments is that the CCA threshold should be at a maximum level and the transmit power should be at a minimum level, i.e. working only with the STAs120a-h(illustrated inFIG.2andFIG.5) at close distance.

Based on this approach, the PAP111conventionally decreases its TX power in order to reduce interference with the IAP101. However, a conventional reduction of the TX power of the PAP111significantly decreases the radius of its cell coverage, with the result that only the small number of wireless stations associated with the PAP111will benefit from the spatial reuse approach, while the other wireless stations will be out of coverage (as illustrated by the wireless stations120a-hshown inFIG.2). Using a low Tx power by the PAP111may also require using a lower MCS (both for the IAP101and the PAP111), because of a lower SINR, more retransmissions, an inferior performance and a decreased efficiency.

BF and MU-MIMO have been introduced in the standard 802.11ac/ax. As already described above, a WLAN device (AP or STA) may steer its antenna beam to the receiver's direction by applying a MIMO digital beam-forming technique. In an example, a beam-former may steer more energy towards a desired direction, while suppressing the energy in other directions. Applying N Spatial Streams (SS) per user MU-MIMO enables sending different information to multiple receivers at the same time. Using beam-forming allows nulling or creating NULL per streams per direction (STA). In an example, BF allows spatial selectivity and better power exploitation.

As will be described in more detail in the following under reference toFIG.3,FIG.4, andFIG.5, embodiments of the present disclosure provide a wireless initiator access point (IAP)101and a wireless participator access point (PAP)111that make use of beam-forming and MU MIMO for improving the SR efficiency by reducing the interference at the IAP101due to the PAP111as well as improving the SINR of the wireless stations120a-h. According to an embodiment, both the IAP101and the PAP111are configured to obtain BF precoder information from all OBSS STAs120a-h(that support a BF report), and use that information to send NULL data to the neighboring STA(s)120a-hwhile in SR transaction time. In an embodiment, the wireless IAP101and the wireless PAP111are configured to operate in accordance with the IEEE 802.11 WLAN standard or a standard evolved therefrom, in particular 802.11ax or 802.11ac.

In an example, according to an embodiment the wireless initiator AP101comprises a communication interface with an array of antennas. The communication interface of the wireless initiator AP101is configured to operate the array of antennas with an adjustable precoding configuration for MU-MIMO communication with the plurality of multi-antenna wireless stations120a-h, i.e. wireless clients or terminals. The communication interface of the wireless IAP101is configured to send an NDP Announcement frame301(as illustrated inFIGS.3and4) to the plurality of wireless stations120a-hand to trigger the wireless PAP111to send an NDP frame303to the plurality of wireless stations120a-h. The communication interface of the wireless IAP101is further configured to receive a plurality of Compressed Beamforming frames (i.e. precoder information)305a-cfrom the plurality of wireless stations120a-hand to forward the plurality of Compressed Beamforming frames (i.e. the precoder information)305a-cto the wireless PAP111.

In an embodiment, the communication interface of the wireless IAP101is configured to send the NDP Announcement frame301to the plurality of wireless stations120a-hand the wireless PAP111for triggering the wireless PAP111to send the NDP frame303to the plurality of wireless stations120a-h. In other words, in an embodiment, the NDP Announcement frame301itself may be used as a triggering signal/message for the wireless PAP111. In a further embodiment, the communication interface of the wireless IAP101may be configured to send a triggering signal or message via the IP backbone network to the wireless PAP111for triggering the wireless PAP111to send the NDP frame303to the plurality of wireless stations120a-h.

Likewise, the wireless PAP111comprises a communication interface with an array of antennas, wherein the communication interface is configured to operate the array of antennas with an adjustable precoding configuration for MU-MIMO communication with the plurality of multi-antenna wireless stations, i.e. clients120a-h. The communication interface of the wireless PAP111is further configured to be triggered to send an NDP frame303to one or more of the plurality of wireless stations120a-hand/or to one or more of a further plurality of wireless stations120a-hfor triggering the one or more of the plurality of wireless stations120a-hand/or the one or more of the further plurality of wireless stations120a-hto send a plurality of Compressed Beamforming frames (including the precoder information)305a-cto the wireless IAP101. Moreover, the communication interface of the wireless PAP111is configured to receive the plurality of Compressed Beamforming frames305a-cfrom the wireless IAP101. The wireless PAP111further comprises a processing circuitry configured to determine the precoding configuration for operating its antenna array based on the precoder information included in the plurality of Compressed Beamforming frames305a-creceived from the wireless IAP101.

In an embodiment, the wireless PAP111is configured to be triggered by the NDP Announcement frame301from the wireless PAP111. In an example, in an embodiment, the communication interface of the wireless PAP111is configured to receive the NDP Announcement frame301from the wireless PAP111and to send, in response to the NDP Announcement frame301, the NDP frame303to the one or more of the plurality of wireless stations120a-hand/or to the one or more of the further plurality of wireless stations120a-h. As described above, the NDP frame303from the wireless PAP111triggers the one or more of the plurality of wireless stations120a-hand/or the one or more of the further plurality of wireless stations120a-hto send a plurality of Compressed Beamforming frames (including the precoder information)305a-cto the wireless IAP101.

In an example, advantageously, using the existing 802.11 BF and MU-MIMO schemes of BF the wireless IAP101and the wireless PAP111may obtain precoder information from all relevant wireless stations120a-h. Thereby, the wireless PAP111may increase its spatial reuse coverage, while reducing the interference between transmissions and maintaining a high SINR level with its wireless stations120a-hby using the precoder information from the stations of the IAP101. By increasing the SR coverage and SINR the SR efficiency is improved.

In an embodiment, the wireless PAP111may create NULL(s) to a plurality of neighboring wireless STA(s)120a-hwhile sending data to one or more of the target STA(s)120a-h. This ensures a minimal interference with all the target STA(s)120a-hof the IAP101, while enabling a higher SINR and data rate. By increasing its TX power, the wireless PAP111may send data to STAs120a-hlocated at larger distances and, thereby, increase the number of candidate stations120a-havailable for SR availability (with a larger TX power and data rate). The station candidates for transmission may be any of the AP STAs120a-h, which, however, may require a frequency and time synchronization.

In an example, for being able to send a NULL to a specific non-associated STA120a-h, the wireless IAP101and the wireless PAP111collaborate for obtaining the precoder information from all STAs120a-h. As illustrated inFIG.3in the context of a sounding scheme in compliance with the 802.11ac standard, the IAP101prepares its STAs120a-hfor precoder measurements by sending the NDP announcement frame301to these stations120a-h. In an embodiment, the wireless IAP101is configured to send the NDP announcement frame301only to those wireless STAs120a-hthat can be part of the SR process with the wireless PAP111. In order to find out which of the STAs120a-hhear the wireless PAP111, the wireless IAP101may be configured to request an AP Beacon measurement from all associated STAs120a-h. As illustrated inFIG.3, a SIFS time interval after the NDP announcement frame301was sent, the wireless PAP111sends the pilots (NDP frame)303instead of the initiator AP101(the STAs120a-hwill receive and calculate the compressed BF). Each STA120a-hwill respond (send) to the wireless IAP101a beam-forming report305a-c(including the precoder information), possibly in response to a Beamforming report Poll307a,bfrom the wireless IAP101. Upon collecting the compressed BF reports305a-cfrom all stations120a-h, the wireless IAP101sends the precoder information to the wireless PAP111. In an embodiment, the wireless IAP101may be configured to forward the plurality of Compressed Beamforming frames305a-cvia an IP backbone network to the wireless PAP111.

FIG.4illustrates a further sounding scheme implemented by the wireless IAP101and the wireless PAP111in compliance with the 802.11ax standard, wherein the sounding scheme is performed as part of the multi user uplink (MU UL).

As will be appreciated, for enabling the wireless PAP111to send the pilots (NDP frame(s)303), the wireless PAP111should be able to know that the NDP Announcement (NDPA) frame301, also referred to as NDPA301, emitted by the wireless IAP101started the sounding process for the wireless PAP111. In an embodiment, this may be achieved by reserving several AIDs for neighboring APs, and when such a sounding process starts, the NDPA301will include the AID, i.e. an identifier of the wireless PAP111. In an embodiment, the wireless PAP111may send the NDP frame303according to the NDPA transmitter address (TA) and the above AID.

In the exemplary sounding scenario illustrated inFIG.5AP1is the wireless IAP101, i.e. the SR initiator that transmits to the exemplary wireless station120c(i.e. S11) while utilizing the traffic and using BF. AP2as the wireless PAP111transmits, by way of example, to the wireless stations120band120f, i.e. S21and S23. The wireless PAP111may decide whether to join the SR session and select the STAs120a-hto transmit to. The wireless PAP111maximizes its SR efficiency by creating a NULL to the wireless station120c(i.e. STA11) and using a higher Tx power as well as beam-forming for transmitting to the wireless stations120band120f, i.e. S21and S23. As will be appreciated, the total number of spatial stream(s) (SS(s)) and NULL(s) that can be used by the wireless PAP111may have to be less than the number of antennas of the wireless PAP111.

FIG.6shows a flow diagram illustrating a corresponding method600for MU-MIMO communication with the plurality of multi-antenna wireless stations, i.e. clients120a-h. The method600comprises the steps of operating601the array of antennas of the wireless IAP101with an adjustable precoding configuration for MU-MIMO communication with the plurality of wireless stations120a-h; sending603an NDPA frame301to the plurality of wireless stations, i.e. clients120a-h; triggering605the multi-antenna wireless PAP111to send an NDP frame303to the plurality of wireless stations120a-h; receiving607a plurality of Compressed Beamforming frames305a-c(including precoder information) from the plurality of wireless stations120a-h; and forwarding609the plurality of Compressed Beamforming frames305a-c(including the precoder information) to the wireless PAP111.

In an embodiment, the step of sending603the NDP Announcement frame301comprises sending the NDP Announcement frame301to the plurality of wireless stations120a-hand the wireless PAP111for triggering605the wireless PAP111to send the NDP frame303to the plurality of wireless stations120a-h.

Further features of the method600result directly from the structure and/or functionality of the wireless IAP101and the wireless PAP111as well as their different embodiments described above.

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

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus, and method may be implemented in other manners. For example, the described embodiment of an apparatus is merely exemplary. For example, the unit division is merely logical function division and may be another division in an actual implementation. For example, a plurality of units or components may be combined or integrated into another system, or some features may be ignored or not performed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections may be implemented by using some interfaces. The indirect couplings or communication connections between the apparatuses or units may be implemented in electronic, mechanical, or other forms.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one position, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solutions of the embodiments.

In addition, functional units in the embodiments of the present disclosure may be integrated into one processing unit, or each of the units may exist alone physically, or two or more units are integrated into one unit.