Changing steering matrix corresponding to MU-MIMO group to allow access points transmit on wireless communication channel simultaneously

In high density wireless local area network (WLAN) deployments, non-overlapping frequency bands could be scarce. As a result, adjacent access points (APs) in the WLAN may need to share access to the wireless communication channel, which may lead to channel interference to one AP in the WLAN caused by a neighboring AP's transmission.

The following detailed description references the drawings, wherein:

FIG. 1 is a block diagram of an example system environment for changing a steering matrix corresponding to MU-MIMO group to allow access points transmit on wireless communication channel simultaneously;

FIG. 2 is a sequence diagram illustrating example communication sequences for changing a steering matrix corresponding to MU-MIMO group to allow access points transmit on wireless communication channel simultaneously;

FIG. 3 is a sequence diagram illustrating example communication sequences for changing a steering matrix corresponding to MU-MIMO group to allow access points transmit on wireless communication channel simultaneously;

FIG. 4 is a flowchart of an example process of changing a steering matrix corresponding to MU-MIMO group to allow access points transmit on wireless communication channel simultaneously;

FIG. 5 is a flowchart of an example process of changing a steering matrix corresponding to MU-MIMO group to allow access points transmit on wireless communication channel simultaneously; and

FIG. 6 is a block diagram of an example network device to change a steering matrix corresponding to MU-MIMO group to allow access points transmit on wireless communication channel simultaneously.

In a typical enterprise WLAN deployment, access points adjacent to each other can use different non-overlapping frequency bands (or channels) for operation either via manual configuration or through the APs' automatic radio resource management features. However, in high density WLAN deployments, especially when the available non-overlapping channels are scarce (e.g., 2.4 GHz or via administrator imposed restrictions), nearby APs may need to operate on the same wireless frequency band. While the medium access protocols can allow sharing the access to the wireless medium, they do not increase channel reuse. Examples of the present disclosure can increase channel reuse by managing interferences from one AP's transmissions to another. Specifically, techniques disclosed in examples herein can allow neighboring APs to transmit at the same time when operating on the same channel that is within the range of each other, thereby increasing the capacity.

According to IEEE 802.11 standards, when two APs are sufficiently located close to each other physically that a clear channel assessment threshold is triggered, the two APs cannot transmit data on the channel together to avoid channel contentions. Generally, clear channel assessment (CCA) may refer to a logical function found within physical layers of a wireless communication device (e.g., an access point) which determines the current state of use of a wireless medium. In some implementations, the CCA detection threshold can be adjusted to a less sensitive value by a network administrator. However, the less sensitive CCA threshold value may cause the APs to serve a reduced set of client devices, because the AP can no longer receive requests from client devices that are located outside the reduced CCA range.

According to examples of the present disclosure, as illustrated in FIG. 1 , two access points (e.g., AP 1 110 and AP 2 120 ) can transmit simultaneously on the same wireless channel even though AP 2 120 is within the CCA range 160 of AP 1 110 . In FIG. 1 , client devices Client 1 130 and Client 2 135 are associated with AP 1 110 ; and, client devices Client 3 140 and Client 4 145 are associated with AP 2 120 . The dotted lines may show the range to which the CCA is triggered because of a respective AP. For example, CCA range 160 may indicate the range when CCA is triggered for AP 1 110 . Moreover, the solid line may show the range up to which transmitted frames can be decoded. For example, TX range 150 may indicate the transmission range up to which a frame transmitted by an access point or a client device (e.g., Client 1 130 or Client 2 135 ) can be decoded by AP 1 110 . Note that when AP 1 110 detects wireless signals on its wireless operating channel from another AP (e.g., AP 2 120 ) that is located within CCA range 160 , without techniques described herein, AP 1 110 shall refrain from transmitting on the wireless operating channel for a period of time.

As used herein, “access point” (AP) generally refers to receiving points for any known or convenient wireless access technology which may later become known. Specifically, the term AP is not intended to be limited to IEEE 802.11-based APs. APs generally function as an electronic device that is adapted to allow wireless devices to connect to a wired network via various communications standards. As used herein, a “client device” may include a notebook, tablet, mobile phone, and/or other mobile device that can utilize a WLAN connection. As used herein, “wireless local area network” (WLAN) generally may refer to a communications network links two or more devices using some wireless distribution method (for example, spread-spectrum or orthogonal frequency-division multiplexing radio), and usually providing a connection through an access point to the Internet; and thus, providing users with the mobility to move around within a local coverage area and still stay connected to the network.

In order to transmit data to Client 1 130 and Client 2 135 , AP 1 110 can create a MU-MIMO group 170 that includes both Client 1 130 and Client 2 135 . Likewise, in order to transmit data to Client 3 140 and Client 4 145 , AP 2 120 can create a MU-MIMO group 180 that includes both Client 3 140 and Client 4 145 .

The multi-user MIMO technique works by taking advantage of beamforming to send frames to spatially diverse locations at the same time. As used herein, “beamforming” generally may refer to a way of wireless transmission that allows a transmitter to focus energy toward a receiver. Beamformees can be selected by calculating a steering matrix for an antenna array of the access point. The steering matrix generally may refer to a mathematical description of how the antenna array uses each individual element to select a spatial path for the data transmission.

However, as AP 1 110 forms the MU-MIMO group 170 including Client 1 130 and Client 2 135 , AP 1 110 may also trigger the CCA at AP 2 120 , which is located within CCA range 160 but outside Tx range 150 . As mentioned above, if CCA is triggered at AP 2 120 , which means that AP 2 120 detects a transmission signal from AP 1 110 that is stronger than the CCA threshold value, then AP 2 120 cannot transmit simultaneously on the same wireless communication channel as AP 1 110 .

To increase the likelihood of simultaneous transmission on the same wireless communication channel by AP 1 110 and AP 2 120 , when AP 1 110 forms the MU-MIMO group, AP 1 110 may treat AP 2 120 as one of its client devices. Therefore, the MU-MIMO group 170 formed by AP 1 110 can be modified to include Client 1 130 , Client 2 135 , and AP 2 120 . Then, AP 1 110 will follow a MU-MIMO sounding protocol to sound the channel between AP 110 and each of Client 1 130 , Client 2 135 , and AP 2 120 . In a MU-MIMO transmission towards multiple client devices, one intended client device will receive the data transmission, whereas the other client devices in the same MU-MIMO group will receive a NULL frame. Therefore, when AP 2 120 is a member of the MU-MIMO group 170 , when AP 1 110 transmission data frames to Client 2 135 , both Client 1 130 and AP 2 120 will receive NULL frames, e.g., NULL message 180 . As a result of the MU-MIMO sounding between AP 1 110 and AP 2 120 , AP 1 110 can be informed of the channel condition between AP 1 110 and AP 2 120 .

Since in this example, AP 1 110 and AP 2 120 operate on the same channel, sounding frames sent by AP 2 120 to its own clients (e.g., Client 3 140 and Client 4 145 ) can be heard by AP 1 110 as well. Assuming that the channel is symmetric, the beamforming steering matrix V generated at AP 1 110 can be used to create a NULL message 180 to transmit in AP 2 120 's direction, which can reduce the chance that the CCA is triggered at AP 2 120 . In summary, by changing the MU-MIMO steering matrix based on the explicit sounding process between AP 1 110 and AP 2 120 , AP 1 110 can selectively isolate AP 2 120 while maintaining connections to the farthest client device of AP 1 110 .

FIG. 2 is a sequence diagram illustrating example communication sequences for changing a steering matrix corresponding to MU-MIMO group to allow access points transmit on wireless communication channel simultaneously. FIG. 2 includes, for example, AP 1 220 , AP 2 225 , and a plurality of client devices, such as, Client 1 200 , Client 2 212 , Client 3 214 , and Client 4 216 . In this example, assuming that Client 1 200 and Client 2 212 are associated with AP 1 220 ; and, Client 3 214 and Client 4 216 are associated with AP 2 225 . According to techniques described above, AP 1 220 can form a MU-MIMO group that includes Client 1 200 , Client 2 212 , and AP 2 225 . Similarly, AP 2 can form a MU-MIMO group that includes Client 3 214 , Client 4 216 , and AP 1 220 .

At time point t 1 , AP 2 225 sends a Null Data Packet Announcement (NDPA) 230 . NDPA 230 is received by Client 3 214 and Client 4 216 at time point t 2 . Moreover, AP 1 220 also receives the NDPA 230 at time point t 3 . Upon transmission of NDPA 230 , AP 2 225 next transmits a Null Data Packet (NDP) frame 232 , which is the frame used to calibrate the channel. NDP 232 is subsequently received by Client 3 214 and Client 4 216 at time point t 5 . Also, AP 1 220 can receive the NDP 232 at time point t 6 .

In some examples, AP 2 225 can transmit from each of its antennas one at a time. The header of NDP 232 can identify which antenna the frame is sent from. A beamformee device can record information about how it receives a sounding frame on each of its antennas individually. This results in an M to N relation over the number of antennas at AP 2 225 and the number of antennas at the client device (e.g., Client 3 214 ). The client device may record the following data for every MN relation: (1) the strength of the signal measured by its amplitude; and (2) the time it received the signal. The differences in these times can be recorded in a matrix, which is also known as Channel State Information (CSI). CSI can then be compressed and returned to AP 2 225 in a compressed beamforming action feedback frame (CBAF) 234 . The targeted beamformees need to reply with CBAF 234 . In some examples, the intended client device may reply immediately whereas the other beamformees in the MU-MIMO group may wait to be polled by the beamformer (e.g., AP 2 225 ). In the example, illustrated in FIG. 2 , Client 3 214 returns CBAF 234 at time point t 7 , and thereafter, Client 4 216 returns CBAF 236 to AP 2 225 at time point t 8 . AP 2 225 can then calculate steering matrix that determines how to beamform to Client 3 214 and Client 4 216 based on CBAF 234 and 236 .

On the other hand, at time point t 3 , when AP 1 220 receives NDPA 230 from AP 2 225 on the same operating channel as AP 1 220 , AP 1 220 may indicate the channel as reserved 250 . Thereafter, when AP 1 220 receives NDP 232 at time point t 6 , AP 1 220 can calculate a NULL frame in AP 2 's direction 260 based on information received within NDP 232 . The calculation of NULL frame is similar to how a client device calculates the CBAF based on a NDP frame, although no actual frame is transmitted from AP 1 220 to AP 2 225 in this example. However, AP 1 220 can adjust its steering matrix for MU-MIMO group based at least in part on the NULL frame calculation. With the adjusted steering matrix, data transmissions targeted to Client 1 200 and Client 2 212 can have little interference to AP 2 225 .

Note that the channel reservation, calibration, and NULL frame calculation can be done symmetrically by AP 2 225 in the same fashion. Therefore, both AP 1 220 and AP 2 225 can adjust their respective steering matrix to reduce interference to each other. As a result, at time point t 9 , AP 1 220 and AP 2 225 can start simultaneous transmission 270 on the same wireless communication channel. Specifically, AP 1 220 can transmit Data 1 240 to Client 1 200 , Data 2 242 to Client 2 212 ; and, AP 2 225 can transmit Data 3 244 to Client 3 214 , Data 4 246 to Client 4 216 .

FIG. 3 is a sequence diagram illustrating example communication sequences for changing a steering matrix corresponding to MU-MIMO group to allow access points transmit on wireless communication channel simultaneously. FIG. 3 includes, for example, AP 1 320 , AP 2 330 , and AP 3 335 , as well as a plurality of client devices, such as, Client 1 300 , Client 2 312 , Client 3 314 , and Client 4 316 . In this example, assuming that Client 1 300 , Client 2 312 , Client 3 314 , and Client 4 316 are associated with AP 1 320 . Also, assuming that AP 2 330 and AP 3 335 are within the neighborhood of AP 1 320 and operate on the same wireless communication channel as AP 1 320 so that the APs can hear the signals transmitted from each other. In this example, the APs are connected to each other via wired connections, which is common in wireless local area network (WLAN) deployment. Here, AP 1 320 can form a MU-MIMO group that includes Client 1 300 , Client 2 312 , Client 3 314 , and Client 4 316 in order to simultaneously transmit data to those client devices.

At time point t 1 , AP 1 320 sends a Null Data Packet Announcement (NDPA) 340 . NDPA 340 may be received by Client 1 300 , Client 2 312 , Client 3 314 , and Client 4 316 at time point t 2 . Moreover, AP 2 330 and AP 3 335 can also receive the NDPA 340 . Upon transmission of NDPA 340 , at time point t 3 , AP 1 320 next transmits a Null Data Packet (NDP) frame 342 , which is the frame used to calibrate the channel state. NDP 342 is subsequently received by Client 1 300 , Client 2 312 , Client 3 314 , and Client 4 316 at time point t 4 . Also, AP 1 220 can receive the NDP 232 at time point t 6 .

Each beamformee need to reply with compressed beamforming action feedback (CBAF) frame 234 . In some examples, the intended client device may reply immediately, whereas the other beamformees in the MU-MIMO group may wait to be polled by the beamformer (e.g., AP 1 320 ). In the example, illustrated in FIG. 3 , Client 4 316 returns CBAF 350 at time point t5; Client 3 314 returns CBAF 352 at time point t 6 ; Client 2 312 returns CBAF 354 at time point t 7 ; and thereafter, Client 1 300 returns CBAF 356 to AP 1 320 at time point t 8 .

Then, AP 1 320 can determine how much nulling AP 2 330 and AP 3 335 may affect data transmissions to Client 1 300 , Client 2 312 , Client 3 314 , and Client 4 316 , vice versa. To make such determination, AP 1 320 first can determine the channel state information (CSI) between a client device (e.g., Client 1 300 ) and itself based on the CBAFs (e.g., CBAFs 350 - 356 ) received from each client device in the MU-MIMO group.

In addition, AP 1 320 can also determine the channel state between AP 1 320 and AP 2 330 based on a received compressed beamforming feedback (CBF) frame 360 over the wired connection between AP 1 320 and AP 2 330 . In this example, AP 2 330 receives an NDP frame from AP 1 320 and calculates the channel state information based on the signals associated with NDP frame as well as the information stored in the NDP frame. The channel state information is returned to AP 1 320 in the CBF frame 360 by AP 2 330 at time point t 9 . Likewise, AP 1 320 can determine the channel state between AP 1 320 and AP 3 335 based on a CBF 365 transmitted by AP 3 335 over the wired connection between AP 1 320 and AP 3 335 at time point t 10 .

In some examples, if the CBF is not received from AP 2 330 or if the received CBF is stale, AP 1 320 can create channel state by assuming that the channel is symmetric, and calculating the NULL frame in AP 2 330 's direction based on a NDP received from AP 2 330 , and the NULL frame in AP 3 335 's direction based on a different NDP received from AP 3 335 .

Next, AP 1 320 can calculate a steering matrix 370 that determines how to beamform to Client 1 300 , Client 2 312 , Client 3 314 , and Client 4 316 based on CBAFs 350 , 352 , 354 , and 356 . Furthermore, AP 1 320 can create a covariance matrix from the client device (e.g., Client 1 300 ) and AP 2 330 channel matrices. The rank of this covariance matrix may indicate whether the channel state information of a client device in the MU-MIMO group (e.g., Client 1 300 ) and a neighboring AP (e.g., AP 2 330 ) are linearly independent. For example, a high rank may indicate that the channels are independent, which implies that AP 1 320 may null out a neighboring AP (e.g., AP 2 330 ) without affecting data transmission to the client device in its MU-MIMO group (e.g., Client 1 300 ). On the other hand, a low rank may indicate that the channels are not independent with each other, which implies that AP 1 320 may not transfer data simultaneously with a neighboring AP (e.g., AP 2 330 ) without affecting each other. Based on the covariance matrix, AP 1 320 adjust the MU-MIMO group membership and the steering matrix 370 , such that AP 1 320 can simultaneously transmit Data 1 390 to Client 1 300 , Data 2 392 to Client 2 312 , Data 3 394 to Client 3 314 , and Data 4 396 to Client 4 316 . Meanwhile, AP 2 330 and AP 3 335 may be allowed simultaneous data transmission 380 on the same wireless communication channel as well.

Table 1 below shows an example table that AP 1 320 can maintain to indicate channel states between every associated client device in the MU-MIMO group and each neighbor AP operating on the same channel.

AP 1 320 performs such computation, because even if a client device (e.g., Client 1 300 ) and a neighboring AP (e.g., AP 2 330 ) are not in the same location, their channel state might be similar. Thus, data transmissions involving the client device (e.g., Client 1 300 ) may affect data transmissions involving a neighboring AP (e.g., AP 2 330 ), and vice versa. Based on information in Table 1 above, AP 1 320 can send data to client devices. For example, if AP 1 320 plans to transmit a data packet to Client 1 300 , Client 2 312 , and Client 3 314 ; then, AP 1 320 can look up in the table and determine to null out AP 2 330 but not AP 3 335 , in case AP 1 320 plans to send data packet to Client 1 300 , Client 2 312 , and Client 3 314 simultaneously. This is because AP 2 330 has a high rank in the covariance matrix associated with Client 1 300 , Client 2 312 , and Client 3 314 , whereas AP 3 335 has a low rank in the covariance matrix associated with Client 3 314 . Accordingly, AP 1 320 can change its steering matrix 370 based on the CBAFs received from Client 1 300 , Client 2 312 , and Client 3 314 and the CBF received from AP 2 330 . When AP 1 320 use the resulting steering matrix 370 for beamforming, MU-MIMO data transmission from AP 1 320 will be targeted to Client 1 300 , Client 2 312 , and Client 3 314 and away from AP 2 330 . Therefore, the CCA threshold is unlikely to be triggered at AP 2 330 due to AP 1 320 's data transmission. Thus, AP 2 330 can simultaneously transmit data packets to its own associated client devices. AP 3 335 , on the other hand, will refrain from any data transmission during the time when AP 1 320 is transmitting data to its client devices (e.g., Client 1 300 , Client 2 312 , and Client 3 314 ). Here, AP 3 335 has a low rank in the covariance matrix associated with Client 3 314 , possibly because Client 3 314 is in the same direction as AP 3 335 relative to AP 1 320 .

As another example, if AP 1 320 plans to send data packets to Client 1 300 and Client 2 312 , but not to Client 3 314 and Client 4 316 , then AP 1 320 can null out both AP 2 330 and AP 3 335 based on the information in Table 1. This is because both AP 2 330 and AP 3 335 have high rank in the covariance matrix associated with Client 1 300 and Client 2 312 . In other words, both AP 2 330 and AP 3 335 can transmit to its own associated client devices at the same time on the same wireless communication channel as AP 1 320 . In this example, the MU-MIMO group may include all four client devices (e.g., Client 1 300 , Client 2 312 , Client 3 314 , and Client 4 316 ), but AP 1 320 has data packets to transmit to Client 1 300 and Client 2 312 , not Client 3 314 and Client 4 316 . However, the same computation can also apply to the case where the MU-MIMO group includes two client devices, namely, Client 1 300 and Client 2 312 .

In some examples, after AP 1 320 receives CBAFs from client devices, AP 1 320 selects a set of client devices to become members of a MU-MIMO group. During the MU-MIMO group membership selection, AP 1 320 determines a set of neighboring APs that can become a part of the same MU-MIMO group. Also, AP 1 320 determines a subset of its client devices that are compatible with the set of neighboring APs in the MU-MIMO group, so that data transmissions to the subset of client devices can be null out at the neighboring APs in the MU-MIMO group.

In some examples, when AP 1 320 detects that the amount of active traffic associated with its client devices (e.g., Client 1 300 , Client 2 312 , Client 3 314 , and Client 4 316 ) is relatively low, then AP 1 320 may give preference to include a greater number of APs in the MU-MIMO group. In this case, because the neighboring AP has a high priority to be included in the MU-MIMO group, if a client device is incompatible with the neighboring AP, then client device will be excluded from the MU-MIMO group.

In some examples, when AP 1 320 determines that its own associated client devices have high priority data transmissions, then AP 1 320 may give preference to include its client devices in the MU-MIMO group, and exclude any neighboring AP that is incompatible with the client devices from the MU-MIMO group.

In this way, every AP makes a decision to null out a number of its neighboring APs. This can increase the overall spatial reuse in the network. Moreover, this increase in the network's throughput does not lead to any sacrifice of other resources in the network.

Processes of Changing Steering Matrix Corresponding to MU-MIMO Group to Allow Access Points Transmit on Wireless Communication Channel Simultaneously

FIG. 4 is a flowchart of an example process of changing a steering matrix corresponding to MU-MIMO group to allow access points transmit on wireless communication channel simultaneously. During operations, a first access point can receive a plurality of beamforming feedback frames from a plurality of client devices in a wireless local area network (WLAN) (operation 400 ). Subsequently, the first access point can overhear a first beamforming feedback frame from a second access point (operation 420 ). Then, the first access point can calculate a second beamforming feedback frame in response to receiving a sounding frame transmitted from the second access point in the WLAN (operation 440 ). Furthermore, the first access point can select a first subset of the plurality of client devices and the second access point as members of a multi-user multiple input, multiple output (MU-MIMO) group (operation 460 ). Also, the first access point changing a steering matrix corresponding to the MU-MIMO group based on both the received plurality of beamforming feedback frames and the calculated beamforming feedback frame to allow the first access point and the second access point transmit on a particular wireless communication channel simultaneously without interfering each other (operation 480 ).

FIG. 5 is a flowchart of an example process of changing a steering matrix corresponding to MU-MIMO group to allow access points transmit on wireless communication channel simultaneously. Unlike the example in FIG. 4 , the neighboring APs in FIG. 5 provides explicit feedback frame to the access point via a wired and/or wireless connection between the neighboring APs and the access point.

During operations, a network device (e.g., an access point) can receive a plurality of beamforming feedback frames from a plurality of client devices in a wireless local area network (WLAN) (operation 500 ). Subsequently, the network device can receive a particular beamforming feedback frame from a first access point in the WLAN (operation 520 ). Furthermore, the network device can select a first subset of the plurality of client devices and the second access point as members of a multi-user multiple input, multiple output (MU-MIMO) group (operation 540 ). Also, the network device can change a steering matrix corresponding to the MU-MIMO group based on both the received plurality of beamforming feedback frames and the particular beamforming feedback frame to allow the network device and the first access point transmit on a particular wireless communication channel simultaneously without interfering each other (operation 560 ).

In some examples, the plurality of beamforming feedback frames and the second beamforming feedback frame may include a plurality of compressed beamforming action frames (CBAFs). The plurality of CBAFs may be received in response to the first access point transmitting a null data packet (NDP) frame.

In some examples, the first access point may transmit a NDP announcement frame (NDPA) prior to transmitting the NDP frame.

In some examples, selecting the subset of the plurality of client devices and the second access point as members of the MU-MIMO group involves including the second access point in a rank calculation, wherein the second access point is treated as a client device of the first access point for the rank calculation.

The first access point may include a radio comprising multiple spatial streams, each spatial stream is steered toward a respective member of MU-MIMO group except the second access point according to the rank calculation.

In some examples, the first access point can further determine that including the second access point in the MU-MIMO group triggers a clear channel assessment (CCA) threshold, and exclude the second access point from the MU-MIMO group.

In some examples, the first access point can further determine that transmitting to a second subset of client devices interferes with wireless transmission of the second access point, wherein network traffic transmitted to the second subset of client devices is low. Then, the first access point can determine that the second access point serves a number of active client devices, and exclude the second subset of client devices from the MU-MIMO group to allow the first access point and the second access point transmit on the particular wireless communication channel simultaneously without interfering each other.

In some examples, the first access point can determine that transmitting to a particular client device in the first subset of client devices interferes with wireless transmission of a third access point, whereas the particular client device is inactive. Then, the first access point can include the third access point in the MU-MIMO group to allow the first access point, the second access point, and the third access point transmit on the particular wireless communication channel simultaneously without interfering each other.

As used herein, “network device” generally includes a device that is adapted to transmit and/or receive signaling and to process information within such signaling such as a station (e.g., any data processing equipment such as a computer, cellular phone, personal digital assistant, tablet devices, etc.), an access point, data transfer devices (such as network switches, routers, controllers, etc.) or the like. For example, a “network device may refer to a network controller that comprises a hardware or a combination of hardware and software that enables connection between client devices and computer networks. In some implementations, a network device may refer to a server computing device (e.g., on-premise server, private, public, or hybrid cloud server) that comprises a hardware or a combination of hardware and software that can process and/or display network-related information. In some implementations, a network device may refer to an access point acting as a virtual master network controller among a cluster of access points.

As used herein, ‘access point’ (AP) generally refers to receiving points for any known or convenient wireless access technology which may later become known. Specifically, the term AP is not intended to be limited to IEEE 802.11-based APs. APs generally function as an electronic device that is adapted to allow wireless devices to connect to a wired network via various communications standards.

Network Device to Change Steering Matrix Corresponding to MU-MIMO Group to Allow Access Points Transmit on Wireless Communication Channel Simultaneously

FIG. 6 is a block diagram of an example network device to change a steering matrix corresponding to MU-MIMO group to allow access points transmit on wireless communication channel simultaneously.

As used herein, a network device may be implemented, at least in part, by a combination of hardware and programming. For example, the hardware may comprise at least one processor (e.g., processor 610 ) and the programming may comprise instructions, executable by the processor(s), stored on at least one machine-readable storage medium (e.g., 620 ). In addition, a network device may also include embedded memory and a software that can be executed in a host system and serve as a driver of the embedded memory. As used herein, a “processor” may be at least one of a central processing unit (CPU), a semiconductor-based microprocessor, a graphics processing unit (GPU), a field-programmable gate array (FPGA) configured to retrieve and execute instructions, other electronic circuitry suitable for the retrieval and execution instructions stored on a machine-readable storage medium, or a combination thereof.

The at least one processor 610 may fetch, decode, and execute instructions stored on storage medium 620 to perform the functionalities described below in relation to receiving instructions 630 , transmitting instructions 540 , calculating instructions 650 , selecting instructions 660 , and beamforming instructions 670 . In other examples, the functionalities of any of the instructions of storage medium 620 may be implemented in the form of electronic circuitry, in the form of executable instructions encoded on a machine-readable storage medium, or a combination thereof. The storage medium may be located either in the computing device executing the machine-readable instructions, or remote from but accessible to the computing device (e.g., via a computer network) for execution. In the example of FIG. 6 , storage medium 620 may be implemented by one machine-readable storage medium, or multiple machine-readable storage media.

Although network device 600 includes at least one processor 610 and machine-readable storage medium 620 , it may also include other suitable components, such as additional processing component(s) (e.g., processor(s), ASIC(s), etc.), storage (e.g., storage drive(s), etc.), or a combination thereof.

As used herein, a “machine-readable storage medium” may be any electronic, magnetic, optical, or other physical storage apparatus to contain or store information such as executable instructions, data, and the like. For example, any machine-readable storage medium described herein may be any of Random Access Memory (RAM), volatile memory, non-volatile memory, flash memory, a storage drive (e.g., a hard drive), a solid state drive, any type of storage disc (e.g., a compact disc, a DVD, etc.), and the like, or a combination thereof. Further, any machine-readable storage medium described herein may be non-transitory. In examples described herein, a machine-readable storage medium or media may be part of an article (or article of manufacture). An article or article of manufacture may refer to any manufactured single component or multiple components.

Specifically, instructions 630 - 670 may be executed by processor 610 to: receive a plurality of beamforming feedback frames from a plurality of client devices in a wireless local area network (WLAN); overhear a first beamforming feedback frame from a second access point; calculate a second beamforming feedback frame in response to receiving a sounding frame transmitted from the second access point in the WLAN; select a first subset of the plurality of client devices and the second access point as members of a multi-user multiple input, multiple output (MU-MIMO) group; change a steering matrix corresponding to the MU-MIMO group based on both the received plurality of beamforming feedback frames and the calculated beamforming feedback frame to allow the first access point and the second access point transmit on a particular wireless communication channel simultaneously without interfering each other; receive a particular beamforming feedback frame from a first access point in the WLAN; change a steering matrix corresponding to the MU-MIMO group based on both the received plurality of beamforming feedback frames and the particular beamforming feedback frame to allow the network device and the first access point transmit on a particular wireless communication channel simultaneously without interfering each other; etc.

Moreover, instructions 630 - 670 may also be executed by processor 610 to: determine that including the second access point in the MU-MIMO group triggers a clear channel assessment (CCA) threshold; exclude the second access point from the MU-MIMO group; determine that transmitting to a second subset of client devices interferes with wireless transmission of the second access point, wherein network traffic transmitted to the second subset of client devices is low; determine that the second access point serves a number of active client devices; exclude the second subset of client devices from the MU-MIMO group to allow the first access point and the second access point transmit on the particular wireless communication channel simultaneously without interfering each other; determine that transmitting to a particular client device in the first subset of client devices interferes with wireless transmission of a third access point, wherein the particular client device is inactive; include the third access point in the MU-MIMO group to allow the first access point, the second access point, and the third access point transmit on the particular wireless communication channel simultaneously without interfering each other; etc.