CN112787699A - Beamformer requested sounding - Google Patents

Abstract

The application relates to beamformer requested sounding. Example implementations relate to methods and systems employing a requested probing protocol that include receiving, by a second access point, a probing trigger broadcast by a first access point. The method and system further comprise: receiving, by the second access point, a dedicated training signal from the first station in response to a probe trigger broadcast by the first access point; and generating, by the second access point, channel characteristics for a channel based on the first dedicated training signal, the channel comprising a forward channel between the second access point and the first station.

Description

Beamformer requested sounding

Cross Reference to Related Applications

This application claims the benefit of previously filed co-pending application No. 16/403,073 entitled "BEAMFORMER SOLICITED SOUNDING" filed on 3.5.2019 and claims the benefit of provisional application No. 62/667,405 entitled "BEAMFORMER SOLICITED SOUNDING" filed on 4.5.2018, both of which are incorporated herein by reference in their entirety. This application also claims the benefit of previously filed co-pending application No. 62/932,998 entitled "MULTI-ACESS POINT BEAMFORMER SOLICITED SOUNDING" filed on 8.11.2019, which is incorporated herein by reference in its entirety.

Technical Field

Aspects of the present disclosure relate generally to sounding for wireless communication operations, and more particularly, to systems and methods for sounding of beamformer requests and operations thereof.

Background

Home, outdoor and office networks, also known as Wireless Local Area Networks (WLANs), are established using devices known as Wireless Access Points (WAPs). The WAP may include a router. WAP wirelessly couples all devices of a home network (e.g., wireless sites such as computers, printers, televisions, Digital Video (DVD) players, security cameras, and smoke detectors) to each other and to cables or subscriber lines that deliver internet, video, and television to the home. Most WAPs implement the IEEE 802.11 standard, which is a contention-based standard for handling communications between multiple competing devices sharing a wireless communication medium on a selected one of a plurality of communication channels. The frequency range of each communication channel is specified in a corresponding one of the IEEE 802.11 protocols being implemented (e.g., "a," "b," "g," "n," "ac," "ad"). The communication follows a hub and spoke model, with WAPs at the hub and spokes corresponding to wireless links to each "client" device.

After selecting a single communication channel for the associated home network, access to the shared communication channel relies on a multiple access method identified as Collision Sense Multiple Access (CSMA). CSMA is a distributed random access method for sharing a single communication medium, implemented by backoff of competing communication devices and retry access if a collision on the wireless medium is detected (e.g., if the wireless medium is in use).

Communications on a single communication medium are identified as "simplex," meaning one communication flow at a time from a single source node to one or more target nodes, where all remaining nodes are able to "listen" to the subject transmission. Starting from the IEEE 802.1lac standard, and in particular from its 'Wave 2', discrete communications with more than one target node may occur simultaneously using the so-called multi-user (MU) Multiple Input Multiple Output (MIMO) capability of WAP. MU capabilities are added to the standard to enable WAPs to communicate simultaneously with single antenna single stream or multiple antenna multiple stream transceivers, thereby increasing the time available for discrete MIMO video links for wireless HDTV, computer tablets, and other high throughput wireless devices with communication capabilities comparable to those of WAPs. The IEEE 802.11ax standard integrates Orthogonal Frequency Division Multiple Access (OFDMA) into WAP or site capabilities. OFDMA allows WAPs to simultaneously communicate with multiple stations on the downlink over discrete frequency ranges identified as resource units.

The more and more complexity in signal processing required by IEEE 802.11n and 802.11ac standards to support fully compatible WLAN nodes, including beamforming capabilities for focusing user data communications. To characterize the multipath communication channel between the WAP and each station, MIMO sounding is performed. Explicit probing as specified in the IEEE 802.11n and 802.11ac standards involves transmitting a known sequence of packets from the WAP to each associated station, which then processes the sequence of packets to perform measurements and calculations to generate a detailed probe response from the station for characterizing the communication channel between the WAP and itself. WAP traditionally uses explicit probe responses to focus its MIMO antennas in a manner that either or both improves signal strength at the site or improves downlink throughput to the MIMO antennas.

As the variety and number of stations on a wireless network increases, there is an increasing need for improved sounding procedures that can efficiently coordinate communication services to a greater number of devices while reducing the transmission overhead of the sounding and the processing overhead required to probe the stations.

Disclosure of Invention

Among other benefits, methods and systems employing a sounding protocol that includes a request for an active communication sequence also improve the bandwidth used for sounding sessions and reduce the processing required to beamform a receiving end. In one example, a transmitter determines a sounding control schedule for one or more receivers, transmits sounding triggers to the one or more receivers based on the sounding control schedule, receives at least one dedicated training signal from the one or more receivers in response to the sounding triggers, and for each received dedicated training signal, the transmitter estimates forward Channel State Information (CSI) derived based on the dedicated training signal from the associated receiver.

Exemplary implementations include methods and systems for operating a wireless transceiver, the methods and systems including: for each of the received dedicated training signals, a sounding trigger is transmitted to one or more beamforming receivers via a forward channel in response to the sounding trigger, and at least one dedicated training signal is received from the one or more beamforming receivers via a reverse channel. The method also includes estimating forward CSI derived based on the dedicated training signal from the associated beamformee, and may precode subsequent packets with a precoding derived from the forward CSI for transmission to the associated beamformee via the forward channel.

Example implementations include methods and systems having a wireless transceiver device for a wireless local area network supporting wireless communications, and the wireless transceiver device includes a plurality of antennas. The wireless transceiver device further comprises a plurality of components coupled to each other to form a transmit chain and a receive chain; and requester module circuitry to transmit a sounding trigger via the forward channel to request a plurality of dedicated training signals from one or more beamformers, and the dedicated training signals to be processed for estimating forward CSI for transmission of subsequent packets to the associated beamformers.

Exemplary implementations include methods and systems for operating a wireless transceiver, including: for each received dedicated training signal, a sounding trigger is transmitted to one or more beamforming receivers via a forward channel in response to the sounding trigger, and at least one dedicated training signal having timing information is received from the one or more beamforming receivers via a reverse channel in response to the sounding trigger. The method also includes estimating forward channel state information derived based on dedicated training signals from an associated beamforming receiver; and wherein subsequent packets are precoded with a precoding derived from the forward CSI for transmission via the forward channel to the associated beamformed receiving end, and a packet transmission timestamp and a packet reception timestamp are determined based on the timing information. Other embodiments of this aspect include corresponding communication protocols, networked systems, apparatuses, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the methods.

Example implementations include methods and systems employing a sounding protocol that includes a request for multiple beamformers that benefit from a single sounding trigger. For example, such methods may include receiving, by a second access point, a sounding trigger broadcast by a first access point. The method and system further comprise: receiving, by the second access point, a dedicated training signal from the first station in response to a probe trigger broadcast by the first access point; and generating, by the second access point, channel characteristics of a channel based on the first dedicated training signal, the channel comprising a forward channel between the second access point and the first station.

Example implementations include methods and systems that include opportunistically monitoring probe triggers from individual access points without coordinating with individual wireless access points. The method and system also include observing a probe trigger from the individual access points and receiving a first dedicated training signal from the first station generated in response to the probe trigger. The method and system also include generating a first channel characteristic for a first channel based on the first dedicated training signal, the first channel comprising communications between the access point and the first station.

Exemplary implementations include methods and systems that include the operation of beam-shaping a receiving end in the context of a requested probe. The method and system include receiving a sounding trigger from a first beamformer and transmitting a dedicated training signal to a plurality of beamformers in response to the sounding trigger from the first beamformer. The method and system may also include receiving beamformed communications from each of the plurality of beamformers, wherein each of the communications is beamformed based on the transmitted dedicated training signals.

The method and system are implemented using one or more networked devices and/or systems. Other features and advantages of the inventive concept will become more readily apparent to those of ordinary skill in the art after reviewing the following detailed description and accompanying drawings.

Drawings

The construction and operation of the exemplary implementations will be understood from the following detailed description and the accompanying drawings, wherein like reference numerals refer to like parts, and in which:

fig. 1A-B illustrate a prior art example of WLAN channel sounding and beamforming communication.

Figures 2A-D illustrate examples of existing probe and packet maps.

Fig. 3 illustrates a flow diagram of a probe beamformer process according to an exemplary request of an exemplary implementation.

Fig. 4A illustrates a diagram of an exemplary probe requestor system, according to an exemplary implementation.

Fig. 4B illustrates a diagram of an example sounding trigger frame, according to an example implementation.

Fig. 5A-G illustrate exemplary sequences of probes of requests according to various exemplary implementations.

Fig. 6 illustrates a flow diagram of an exemplary requested probe beamforming receive-end procedure in accordance with an exemplary implementation.

7A-B illustrate examples of probing of requests with timing feedback according to example implementations.

Fig. 8A-C illustrate examples of probes requested by another beamformer according to an example implementation.

Fig. 9 illustrates a diagram of an exemplary networked device in accordance with an exemplary implementation.

Fig. 10A-10B illustrate an exemplary system for channel sounding and beamformed communication according to an exemplary implementation.

11A-11D illustrate additional exemplary sequences of probing of requests according to various exemplary implementations.

Fig. 12-15 illustrate flow diagrams of a probe beamforming receive-end process according to an exemplary implementation.

Detailed Description

The following detailed description provides further details of the figures and exemplary implementations of the present application. For clarity, reference numerals and a description of redundant elements between figures are omitted. The terminology used throughout the description is provided by way of example and is not intended to be limiting.

Conventional explicit sounding methods begin with a beamformer (e.g., an access point, a transmitter, etc.) sending a pair of packets with an announcement frame and a dedicated training signal (e.g., a Null Data Packet Announcement (NDPA) followed by a Null Data Packet (NDP)) to a beamforming receiver (e.g., a station, a client, a receiver, etc.), such that the beamforming receiver can measure the received dedicated training signal to obtain characteristics of a forward communication channel (e.g., from the beamformer to the beamforming receiver). Conventionally the beamformed receiver then generates detailed sounding feedback payload back to the beamformer. Traditionally, the beamformer uses the returned sounding feedback to determine the precoding that is available for subsequent transmission to the beamformed receiving end. The beamformer uses sounding feedback to improve subsequent transmissions.

In the complex multipath channel environment encountered by multiple-input multiple-output (MIMO) transmissions, feedback of the link channel matrix consumes a significant amount of air time because a certain amount of data must be transmitted to characterize the multipath channel, and low Modulation and Coding Schemes (MCSs) transmitting conventional detailed sounding feedback consume a significant amount of network resources. Thus, each explicit probe consumes valuable air time of the network.

Since explicit sounding uses sounding feedback of the forward channel to determine precoding of the forward channel, explicit sounding is typically more accurate than estimating the forward channel based on the reverse channel in implicit sounding. However, explicit sounding generally requires additional overhead, and the sounding feedback received from the beamformed receiving end can be quite large, thus reducing the availability of air time for other transmissions.

Conventional implicit sounding methods begin with a beamformed receiver opportunistically transmitting packets to a beamformer so that the beamformer can measure received packets to determine characteristics of reverse channel information (e.g., from the beamformed receiver to the beamformer) which are then used in an attempt to estimate the forward channel back to the beamformed receiver. However, conventional implicit sounding cannot manage sounding between several beamformed receivers in an effectively coordinated framework. For example, since the beamforming receiving end controls the initiation of the sounding process in the conventional implicit sounding method, the beamformer cannot update the CSI when data communication is degraded. In addition, the beamforming receiving end in the implicit sounding method is only interested in its own sounding process, and cannot consider the sounding requirements of other sites or network resources over time.

As the variety and number of nodes on a wireless network increases, there is an increasing need for improved sounding protocols that can efficiently coordinate communication services to a greater number of devices while reducing the transmission overhead from sounding and the processing overhead of sounding required by client nodes (e.g., beamforming receiving ends).

Aspects of the exemplary implementations described herein relate to systems and methods for a requested sounding framework that is initially initiated by a beamformer, requires minimal processing resources on the beamformed receiver, and can coordinate multiple sounding sequences among several beamformed receivers. The requested sounding framework provides improved transmission overhead for sounding and reduces the sounding processing overhead required by the beamformed receiving end. In the exemplary implementation described herein, the beamformer transmits a sounding trigger to request a dedicated training signal frame from the beamforming receiver. A sounding trigger is a packet sent by a transmitter to at least one targeted station that instructs the station to send one or more dedicated training signals to the transmitter. A single probing trigger may instruct a station to transmit multiple dedicated training signals and/or instruct a schedule to transmit dedicated training signals and other configurable parameters related to the dedicated training signals or their transmissions. A single sounding trigger may also instruct multiple stations to transmit multiple dedicated training signals.

The dedicated training signal is a packet transmitted by the beamforming receive end to the beamformer that does not require a payload. The transmitted dedicated training signal may be processed to estimate channel information between the sender and receiver. The beamforming receiving end processes the sounding trigger and responds with one or more dedicated training signals to be transmitted at coordinated times based on instructions indicated by the sounding trigger.

The beamformer can receive multiple responses to a single sounding trigger without additional prompting of the beamformed receive end. The sounding trigger may include additional instructions for the response and does not require the beamformer to send an announcement packet with the sounding trigger or to prompt for additional dedicated training signals. The beamforming receiver responds to the sounding trigger with one or more dedicated training signals based on instructions accompanying the trigger. The dedicated training signal requires significantly less overhead than conventional sounding feedback.

An exemplary aspect of the requested sounding framework includes an efficient sounding sequence between the access point and one or more stations by reducing the number of transmissions initiating a sounding and reducing the amount of bandwidth or air time used to determine CSI for the forward channel as compared to explicit sounding.

In the requested sounding framework, a beamforming receive (e.g., station, receiver, etc.) sends a dedicated training signal to a beamformer (e.g., access point, transmitter, transceiver station, etc.), which may be processed to estimate reverse channel information about the channel in the beamforming receive-to-beamformer direction. The beamformer measures the received dedicated training signals to determine characteristics of the reverse channel information (e.g., from the beamforming receiver to the beamformer) which are then used in an attempt to estimate the forward channel back to the beamforming receiver.

The requested probe framework has improved performance and efficiency compared to conventional explicit probing and conventional implicit probing. For example, rather than requiring the beamformer to send multiple packets (e.g., NDPA and NDP) and hints, the requesting sounding framework uses a single sounding trigger. Furthermore, the dedicated training signal allows the beamformed receiver to respond with minimal processing and bandwidth without the need to measure the channel, generate detailed sounding feedback, and transmit a large amount of detailed sounding feedback (e.g., compressed feedback reports) that can consume a large amount of processing and network resources.

Furthermore, the requested sounding framework allows the beamformer to initiate the sounding process and coordinate several dedicated training signals from multiple beamformers over a period of time without sending several hints or waiting for the beamformers to send packets opportunistically. Additional aspects of the sounding framework of requests as discussed herein include coordinated sounding for several receivers with different capabilities, configurable sounding characteristics, integrated ranging capabilities, and the like.

In one exemplary implementation, the wireless transceiver transmits a sounding trigger to one or more beamforming receiving ends via a forward channel in response to the sounding trigger and receives at least one dedicated training signal from the one or more beamforming receiving ends via a reverse channel. For each of the received dedicated training signals, the transceiver estimates forward CSI derived based on the dedicated training signals from the associated beamformed receiver to improve transmission of subsequent communications of data (e.g., precoded with a forward CSI derived precoding for transmission to the associated beamformed data packet via the forward channel) to the associated beamformed receiver.

The requested sounding framework achieves improved data communication quality by instructing the beamforming receiver to transmit multiple dedicated training signals over time without additional prompting, such that the beamformer can use the multiple dedicated training signals to re-probe the link with updated CSI. In addition, the beamformer may send updated sounding triggers to maintain a coordinated sounding sequence with one or more beamformee receivers, thereby effectively maintaining a communication link within the network. In one example, the beamformer sends another sounding trigger in response to detecting a change in transmission quality, network resources, or performance of one or more of the beamformed receivers. For example, when data communication of one or more of the beamformed receiving ends degrades, the beamformer may send another sounding trigger to update the sounding interval or training signal format indicated by the previous sounding trigger.

In other exemplary implementations, the efficiency of the requested probing framework may be used to streamline or support other networked applications (e.g., motion tracking, building automation, etc.) in addition to probing. In one example, transmissions between the beamformer and the beamformed receiver of the requested sounding framework may be adapted to effectively synchronize timing, ranging functions, etc. between stations.

In addition to implementations involving a single beamformer, the present disclosure includes implementations of multiple beamformers that may benefit from the claimed sounding framework. For example, a single beamformer may transmit a sounding trigger to a beamforming receive end via a forward channel, and multiple beamformers may receive dedicated training signals transmitted in response to the single sounding trigger from the beamforming receive end via a reverse channel. Upon receiving the dedicated training signals, each of the beamformers may estimate its own respective forward CSI derived based on the dedicated training signals from the beamforming receiving end to improve transmission of subsequent communications of data to the beamforming receiving end (e.g., data packets precoded with a precoding derived from the respective forward CSI for transmission to the beamforming receiving end via the forward channel).

In some implementations, the beamformers may operate in a coordinated manner such that a single beamformer transmits sounding triggers on behalf of multiple beamformers listening for dedicated training signals. For example, one beamformer may operate as a master and always send sounding triggers, or may send a schedule or indication of which beamformers will send sounding triggers and when.

In some implementations, the opportunistic beamformer may be decoupled from another beamformer that sends sounding triggers. The opportunistic beamformer may monitor for sounding triggers from other beamformers and, when one sounding trigger is observed, may listen for dedicated training signals sent from the beamforming receive end in response to the sounding trigger from another beamformer. In such implementations, the opportunistic beamformer can use the dedicated training signals to estimate the forward CSI to the beamformed receiver without ever sending a sounding trigger, while still avoiding some of the disadvantages of conventional implicit sounding.

Fig. 1A-B illustrate a prior art example of WLAN channel sounding and beamforming communication. Fig. 1A illustrates channel sounding with intermittent sounding packets sent from a WAP identifying one or more site nodes from which to request existing sounding feedback. Conventional sounding packets include a number of elements, including an advertisement packet with a sounding packet (e.g., an NDP sounding packet). The response to each intermittent probe packet from the receiver station node contains detailed information quantifying the characteristics of the channel between the receiver station node and the station node. The transmitter processes the detailed information. Whether transmitted from a device having a single antenna or multiple antennas, the sounding packet exhibits an RF signal strength to allow the receiving device to identify the link channel characteristics.

In fig. 1A, WAP 102 is shown establishing communication link 120 and communication link 140 with wireless site node 108 and wireless site node 112, respectively, within location 100. Each link pair exchanges capabilities (e.g., 122A-B on link 120 and capabilities exchange, 142A-B on link 140). During this exchange, the number of antennas, number of streams, coding and beamforming support capabilities of each device are exchanged. Next, an initial explicit probe request and response occurs, 122C-D on link 120 and 142C-D on link 140. The sounding packets are transmitted using a Radio Frequency (RF) signal strength 104. Upon receiving the sounding packet, the receiving station determines the changes in amplitude and phase, e.g., fading, attenuation, and phase shift, that caused the sounding transmission of the link channel, and passes indicia of these channel characteristics as a detailed sounding feedback response packet 122D. As shown at 142D, back to the WAP where they are immediately used to establish beamforming for subsequent data communications, as shown in fig. 1B.

The more and more complexity in signal processing required by IEEE 802.11n and 802.11ac standards to support fully compatible WLAN nodes, including beamforming capabilities for focusing user data communications. One of the many capabilities of a fully compatible WLAN node, according to any of these standards, is the ability to focus the signal strength of the transmitted communication to the receiving device. This requires multiple antennas and means for individually controlling the phase and amplitude of the communication signals transmitted thereon. The baseband component of the WAP or station, referred to as a spatial mapper, takes as input the individual communication streams for each antenna along with a steering matrix (also referred to as a beamforming matrix) determined during previous channel sounding, as shown in fig. 1A. The steering matrix contains complex coefficients corresponding to discrete phase and amplitude adjustments of the communication stream for each antenna that provide the desired focused signal strength to the composite of the signals transmitted from all antennas. The steering matrix for subsequent transmissions is derived from previous probes, as shown in FIG. 1A.

In fig. 1B, WAP is shown using probe feedback to establish subsequent data communications with its link partners (e.g., station 108, station 112). Detailed sounding feedback is used to establish subsequently beamformed data communications based on capabilities supported by the transmitter and receiver. Beamforming improves received signal strength and is achieved by using CSI obtained in detailed sounding feedback response packets (see, e.g., 122D, 142D of fig. 1A) through independent variation of phase and/or amplitude of the signals transmitted from each of the transmit antennas, which collectively direct the transmit power coverage area to the intended receiver site.

A detailed sounding feedback response packet is typically received in response to each sounding packet. At time t₀WAP 102 is shown using multiple antennas to beamform 105A downlink data communication packet 142E on link 140 to station 112. Subsequently, at time t₁WAP 102 is shown beamforming 105B downlink data communication packet 122E on link 120 to station 112.

Fig. 2A-D illustrate prior examples of probe and packet maps. Fig. 2A shows a conventional probe map. Wireless communication protocols provide for packet headers to include various preamble fields with known sequences to allow a receiving station to synchronize reception with packet boundaries to determine the channel received. Typical operations of WAP include a transmitter and receiver sounding sequence that begins with a pair of packets (e.g., announcement and NDP) that may be periodically (e.g., at 100 millisecond intervals) sent to begin the sounding sequence, followed by a short interframe space (SIFS) and a sounding response. During a sounding sequence, one or more downstream or upstream links are probed to determine their channel characteristics, and using CSI in feedback from the sounding, a beamforming matrix for each link subject to sounding is determined. Sounding is performed on a per link basis and may also be downlink sounding or uplink sounding. The sounding feedback is different for each link. During the contention-based interval, Carrier Sense Multiple Access (CSMA) serves as a Medium Access Control (MAC) method to allow any station to gain control of the channel and send uplink user data traffic thereon to the transmitter 202.

Conventional explicit sounding protocols cause the transmitter 202 to send sounding packets with an announcement frame 211, a Null Data Packet (NDP)212 frame, and a response frame, as shown at 200A, 200B, and 201C of fig. 2A and 2B. A conventional sounding packet includes a pair of packets, where the NDPA 211 packet precedes the NDP 212 packet, and identifies a receiving station 208 that is requested to share channel analysis (e.g., CSI) performed by a beamforming receiving end (e.g., the receiving station 208) with a beamformer (e.g., the transmitter 202).

In the pair of packets, the NDPA 211 indicates which stations will respond to the next NDP 212 sounding frame and describes the NDP frame size. After the NDPA 211, the transmitter 202 sends the sounding NDP 212 as a broadcast to be processed by the identified receiving station 208. In response to receiving the NDP 212 broadcast, the identified beamformed receiver performs a series of steps to measure the RF channel characteristics, process and generate a steering matrix with the channel measurements as part of the detailed sounding feedback response packet 250. After the beamforming receive end station 208 completes a series of steps, the station 208 responds to the NDPA 211 and NDP 212 with a detailed sounding feedback response packet 250.

Fig. 2B is a prior art probe map 200B and 201B for explicit probing of sequential probes and data communications. Explicit sounding of the link channel between transmitter 202 and station 208 and between transmitter 202 and station 209 is shown in 200B and 201B. The sounding sequence includes the transmitter 202 sending the pair of sounding packets NDPA 211 and NDP 212, and in response, the target station 208 (after extensive processing 260) sends back a compressed detailed sounding feedback response packet 250A. The transmitter must then send a report poll packet 213 in time to prompt the next station 209 from which to request the generation of detailed sounding feedback.

The header of the NDP packet 212 contains a ubiquitous preamble field for channel estimation, which is identified as the VHT-LTF field of fig. 2C in the case of the IEEE 802.11ac standard. The VHT-LTF field (e.g., channel estimation or sounding field) contains a long training sequence for MIMO channel estimation by the receiver station 208. Each receiver station 207, 208, 209 is then required to determine the corresponding beam steering matrix required to adjust the phase and amplitude of the subsequent MIMO transmission for the transmitter 202 in order to update the received signal strength at the receiver station.

Each beamforming receiver site 207, 208, 209 is required to perform the bulk of the processing of the NDP 260 to determine detailed sounding feedback based on the matrix by performing Singular Value Decomposition (SVD) on the H matrix for each subchannel or tone that requires significant processing resources (e.g., power, time, processor cycles, memory, etc.) to complete. A signal-to-noise ratio (SNR) matrix is derived by scaling a sigma L matrix of the SVD. Each station then waits for the transmitter to send another packet (e.g., a report poll 213) to prompt a response before the beamforming receiving end station sends a single detailed sounding feedback in response to each report poll 213. That is, the first target station 208 responds with a detailed beamforming feedback packet 250B containing CSI (e.g., payload) only when prompted. If the receiving station is IEEE 802.11n compliant, the detailed feedback is in the form of a link channel matrix H. If the receiving station is IEEE 802.11ac compliant, the detailed feedback is in the form of the actual unity beam steering matrix V and the diagonal per tone matrix SNR. Any remaining stations for which initial probing is directed respond with the beam steering matrix of their own link when requested to do so by the report poll 213. The next station 209 then responds with a compressed detailed probe feedback response packet 251B. After probing, a communication recovery and downlink communication of user data is sent on the probed link or links. Since each station 207, 208, 209 sends detailed sounding feedback in response to each transmitter request, considerable bandwidth is consumed to maintain a large number of stations with frequent sounding sequences.

In response to each additional sounding packet 211 and 212, the beamforming receive end 209 may transmit additional detailed beamforming feedback packets 251B, 252B, etc. In some approaches, the beamforming receive 209 may transmit additional detailed beamforming feedback packets 251B, 252B in response to each prompt (e.g., report poll 213).

User data packets 266 (e.g., Media Access Control (MAC) service data units (MSDUs) or protocol data units (MPDUs)) are transmitted using precoding based on the associated beamforming matrix. Transmitter 202 resumes transmitting user data packets 266 on the link that has been probed. The time and overhead required to send the detailed sounding feedback response packets 250A and 251B consumes a significant amount of processing and transmission resources.

Fig. 2C is a prior art packet diagram of a transmitter packet with a preamble field for channel estimation. Fig. 2C includes a packet 240 and a corresponding Symbol Interval (SI) required to transmit each field. The header includes a legacy (legacy) portion containing L-STF, L-LTF and L-SIG fields, and a very high throughput portion containing VHT-SIGA, VHT-STF, VHT-LTF and VHT-SIGB fields. The payload portion does not contain user data. The legacy (L), Long (LTF), and Short (STF) training and Signal (SIG) fields are compatible with stations that support only the IEEE 802.11n or earlier standards. The remaining signals and training fields are intended for very high throughput (e.g., IEEE 802.11ac compliant devices). The VHT-SIGA field contains information on the MCS and the number of sounding streams. The VHT-STF field is used for Automatic Gain Control (AGC). The VHT-LTF field (e.g., channel estimate) includes a long training sequence used by the receiver for MIMO channel estimation.

Fig. 2D is a diagram of a sounding channel between an access point as a transmitter 202 and one or more stations 208, 209. The access point and the station may be transceivers that include both a transmitter and a receiver that are combined and share a common circuit or a single enclosure. The access point and station may also be transmitter-receivers with separate circuitry between the transmit and receive functions. The beamformer typically includes multiple antennas for the transmitter and receiver, while the beamformed receiving end may operate with a single antenna or multiple antennas.

In the example where the access point transmitter 202 is a beamformer sounding beamforming receive station 209, the sounding channel may be described as having both a forward channel 220 from the beamformer access point 202 to the beamforming receive station 209 and a reverse channel 221 from the beamforming receive station 209 to the beamformer access point 202. As shown in fig. 2A and 2B, the beamformer access point 202 conventionally transmits a pair of sounding packets with NDPA advertisements 211 and NDP sounding 212 via a forward channel 220 received by a beamforming receiving end station 209. Conventionally, the beamforming station 209, after processing the pair of sounding packets, then sends detailed sounding feedback 250A, 250B, or 251B via the back channel 221.

Multiple stations 208, 209 may also probe each other, for example in a mesh network. In the example where station 208 is a beamformer sounding beamforming receive station 209, the sounding channel may be described as having both a forward channel 230 from the beamformer station 208 to the beamforming receive station 209 and a reverse channel 231 from the beamforming receive station 209 to the beamformer station 208. Accordingly, the beamformer station 208 sends a pair of sounding packets with an NDPA announcement 211 and an NDP sounding 212 via a forward channel 230 received by the beamformer station 209. Conventionally, the beamforming receive end station 209, after processing the pair of sounding packets, then sends detailed sounding feedback via the back channel 231.

Conventional explicit sounding requires a beamformer to transmit multiple packets to a beamforming receiver, which must then process each of the multiple packets to generate detailed sounding feedback, which is then returned upon prompting. Multiple packets consume forward channel 220's air time, thereby preventing the transmitter from using these communication resources to deliver actual user data to other stations. Detailed sounding feedback consumes a large number of processing cycles (e.g., 260), power at the beamforming receive end, and bandwidth of the back channel 231. Regular sounding sequences for beamformed receiving stations with limited resources may reduce the utility and effectiveness of such stations. Moreover, for networks with many stations, probing with multiple packets and detailed probe feedback wastes bandwidth and interferes with the access point, making it unable to efficiently coordinate services to meet the growing station demand. Further, additional detailed sounding feedback packets are transmitted in response to receiving additional hints from the beamformer.

Fig. 3 illustrates a flow diagram of a probe beamformer process according to an exemplary request of an exemplary implementation. The requested sounding framework allows the beamformer to initiate the requested sounding process in a coordinated scheme for several beamformed receiving end stations with different capabilities and configurable sounding characteristics. The requesting sounding framework also coordinates the beamforming receiving site to automatically update the beamformer with the information to accurately precode user data without requiring the beamformer to send repeated update requests or update hints.

The beamformer process may begin at step 310 to determine sounding controls for one or more beamformed receiving ends. In an exemplary implementation, the probe controls may include probe scheduling instructions, training options, and site information, as discussed with reference to fig. 4-8. Since the requested sounding framework is initially initiated by the beamformer, it can coordinate multiple sounding sequences in several beamformed receivers and reduce the sounding processing overhead required by the beamformed receivers. The requested sounding framework provides improved transmission overhead for sounding and requires minimal processing resources at the beamforming receiving end.

The sounding schedule and training options may be based on communication parameters such as the capabilities of the beamformed receiver (e.g., beamforming, MIMO, etc.), the traffic type (e.g., web browsing, video streaming, video conferencing, etc.), or the positioning parameters (e.g., movement, dwell time, etc.). In an exemplary implementation, the sounding schedule enables the beamformer to instruct the beamforming receive end to transmit multiple dedicated training signals at predetermined sounding intervals in a coordinated manner and to avoid transmitting multiple sounding trigger requests. The beamforming receive end receives the sounding trigger with the sounding instructions and provides an initial dedicated training signal response that does not require the payload or significant processing of the beamforming receive end. The beamforming receiver may store instructions and execute the schedule to provide additional dedicated training signals without receiving additional sounding triggers or hints. For example, the beamformer may determine that the sounding control includes a sounding schedule having short time intervals for receivers that previously received video conference traffic data.

At 320, the beamformer process transmits a sounding trigger to one or more beamformed receive ends based on the sounding controls. For example, the single probing trigger may be a null data packet polling frame that is not prior to the announcement frame. Unlike conventional explicit sounding techniques, the requested sounding enables the beamformer to trigger duplicate information based on a single sounding trigger instead of NDPA and NDP.

At 330, the beamformer process receives at least one dedicated training signal from one or more beamformers in response to a sounding trigger. In the requested sounding, the beamforming receiving end does not measure channel information from the received sounding trigger. One or more dedicated training signals transmitted by the beamformed receiver are triggered by the sounding trigger, but the dedicated training signals do not require measurements associated with the transmission of the sounding trigger. For example, the dedicated training signal may be a null data packet without a sounding data payload.

At 340, for each received dedicated training signal, the beamformer process performs steps 350 and 360 to estimate forward channel state information. At step 350, the beamformer process calculates the CSI of the reverse channel by measuring the received dedicated training signals. At 360, the beamformer process derives CSI for the forward channel from CSI for the reverse channel based on characterization of front end parameters of the transmitter. In one example implementation, the beamformer process may use the estimated forward CSI to transmit subsequent packets using precoded packets with precoding derived from the estimated CSI at 370. The beamformer process repeats at least steps 350 and 360 for each received dedicated training signal. Thus, the requested sounding framework requires less beamforming receive-end processing and less bandwidth than traditional sounding methods.

Fig. 4A illustrates a diagram of an exemplary probe requestor system, according to an exemplary implementation. The requestor system 410 includes a trigger generator 415, a scheduler 420, a training option module 430, and a beamforming receive manager 440 for transmitting sounding triggers to one or more beamforming receives. In one exemplary implementation, the trigger generator 415 may create a probe trigger that includes probe controls such as probe scheduling instructions, training options, and site information for one or more receivers. For example, the training options used by the beamforming receive end to format the dedicated training signal may include repeated symbols, partial bandwidth, multiple bits, and so on.

Trigger generator 415 uses beamforming receive end manager 440 to determine site information for the sounding trigger, including a list of receivers that respond to the sounding trigger. The beamforming receive end manager 440 may determine characteristics of stations to receive sounding triggers from the transmitter. In some examples, a station may be associated with a transmitter such that a successful handshake or authentication procedure has been attempted or successfully completed. The beamforming receive end manager 440 may also infer characteristics or assign identifiers to stations that are not associated or authenticated with the transmitter. In some implementations, the beamforming receive end manager 440 uses the data repository 402 or the analyzer module 470 to track or predict the characteristics of the station. For example, the beamforming receive end manager 440 may determine a site Identifier (ID), site capabilities, site type, traffic/service type, location information, predicted dwell time, and the like. Further, the beamforming receive end manager 440 may use the acquired MAC address information to determine or assign an identifier to a station. Using the beamforming receive end manager 440, the trigger generator 415 may include instructions for different receivers in the sounding trigger.

In an exemplary implementation, trigger generator 415 may include different scheduling instructions for different receivers in the probe trigger. The beamforming receive end manager 440 performs functions for coordinating and updating the operations of the other modules of the requestor system 410. For example, beamforming receive end manager 440 works with scheduler 420 to generate a list of one or more receivers associated with a sounding trigger.

Scheduler 420 may generate scheduling instructions for individual target receivers or groups of receivers to provide dedicated training signals in a coordinated manner. For example, scheduler 420 may generate scheduling instructions for different receivers to respond simultaneously in response to sounding triggers at different spatial streams. As discussed further herein with reference to fig. 5, the synthesizer system 410 may create various scheduling configurations.

In an exemplary implementation, trigger generator 415 may include scheduling instructions in a probe trigger for a group of receivers and/or allow the receivers in the group to determine a coordinated response time or interval. The beamforming receive end manager 440 may identify a group of receivers and the scheduler 420 may generate sounding instructions for the group according to the beamforming process discussed herein with reference to fig. 3-5.

In an exemplary implementation, trigger generator 415 may include a training option in the detection trigger for formatting the dedicated training signal by one or more receivers. The beamforming receive end manager 440 may operate with the training option module 430 to generate instructions for different receivers to respond to a sounding trigger with a dedicated training signal of a particular format or communication mode (e.g., repeated symbols, spatial streams, partial bandwidth, multiple bits, etc.). The training options module 430 may also configure a set of training options in the sounding trigger based on the characteristics of the transmitter, observed network behavior or performance, environmental factors, feedback quality, and the like.

Trigger generator 415 generates a probe trigger for one or more receivers to request a dedicated training signal with minimal overhead. In response to a single probe trigger, the requestor system 410 may receive multiple dedicated training signals from a single receiver and/or multiple different receivers.

The requestor system 410 includes a front-end controller 445, a dedicated training signal tracker module 450, a reverse channel CSI module 455, a calibration module 460, and a precoder 465 for processing the received dedicated training signals.

The front end controller 445 and the dedicated training signal tracker module 450 may operate with the beamforming receive end manager 440 to process multiple dedicated training signals received simultaneously. For example, the front-end controller 445 may receive multiple dedicated training signals simultaneously in different spatial streams, and the dedicated training signal tracker module 450 may rank the received dedicated training signals and associate them with a site profile or site information based on information from the beamforming receive end manager 440.

Dedicated training signal tracker module 450 processes the received dedicated training signals to measure channel information from each dedicated training signal, and back channel CSI module 455 calculates the CSI of the back channel from the measured dedicated training signal information. Calibration block 460 uses the characteristics of the transmitter from front-end controller 445 to derive the forward CSI for the forward channel from the reverse channel CSI. The characteristics of the transmitter from the front end controller 445 may be based on the particular hardware or software configuration of the transmitter, such as manufacturing process differences, design parameters, RF hardware and frequency-to-antenna transmission time or delay, delay differences between multiple transmit chains, and the like. The precoder 465 then uses the precoding derived from the forward CSI for subsequent transmission via the forward channel to the associated receiver.

An exemplary implementation of the synthesizer system 410 may also include an analyzer 470, a mapper 475, and a timer module 480. The analyzer 470 can track traffic with each site to generate historical information for predicting the best configuration of probe triggers. For example, based on the historical usage schedule or movement of the stations, analyzer 470 may indicate to scheduler 420 the optimal time interval for scheduling the repetitive dedicated training signals in response to a single probe trigger.

Mapper 475 may optimize probe communications with sites of different capabilities. For example, mapper 475 may coordinate with front-end controller 445 to receive dedicated training signals from multi-user MIMO (MU-MIMO) enabled receivers, beamforming receivers, and/or the like. The timer 480 supports ranging operations with minimal overhead by utilizing requested probe triggers and dedicated training signal responses. For example, timer 480 may be used with training option module 430 to request timestamp feedback from the receiver with a dedicated training signal to perform ranging operations, thereby avoiding or reducing additional triggers or requests by the transmitter.

Fig. 4B illustrates a diagram of an example sounding trigger frame, according to an example implementation. The exemplary sounding trigger 411 includes an initiating procedure 416, which is a preamble to instruct the receiver to respond with a dedicated training signal. The probe trigger 411 is a single frame that is transmitted and includes at least the preamble initiation procedure 416 without any announcement packet. That is, the sounding trigger 411 is not part of a pair of packets or is preceded by an advertisement packet (e.g., an NDPA packet).

The probing triggers 411 may include scheduling information 421 created by scheduler 420 that allows, for example, repeated responses to a single probing trigger 411. The types of scheduling information 421 may include a time interval 421A, a probe position 421B, a packet length 421C, a terminator 421D, and the like.

The time interval 421A of the schedule 421 indicates the frequency at which the beamforming receiver transmits the dedicated training signal after receiving the single sounding trigger 411. For different beamforming receiving a single sounding trigger 411, the synthesizer system 410 may configure the time interval 421A to be static or dynamic based on time period, network conditions, etc. For example, a static time interval 421A of the schedule 421 may instruct the beamforming receiver to repeatedly transmit the dedicated training signal consistently according to the time frame (e.g., every 100 microseconds). The dynamic time interval 421A of the schedule 421 may instruct the beamforming receiving end to repeatedly transmit the dedicated training signal in bursts within a time frame or intermittently depending on timing factors, conditions, particular channel activity, etc.

Sounding location 421B may be used to indicate when the beamforming receiver will transmit dedicated training signals according to relative or defined locations. The sounding location 421B used by the beamforming receiver to transmit the dedicated training signal may be associated with one or more other beamforming receivers (e.g., order, position, rank, group, time slot, etc.) responsive to the sounding trigger 411. For example, sounding trigger 411 may be sent to a list of beamformed receivers, and sounding location 421B indicates the sequence of each beamformed receiver in the list to transmit a dedicated training signal. The beamforming receiving end may repeatedly transmit the dedicated training signal by restarting the sequence without receiving another sounding trigger 411. In another example, sounding location 421B indicates a coordinated time location (e.g., based on a time scale, a reference time, etc.) for each of the beamformed receivers to repeatedly transmit dedicated training signals in groups or at different times without receiving another sounding trigger 411.

In some implementations, the sounding location 421B indicates that the beamforming receiver repeatedly transmits the dedicated training signal by listening to the channel according to the packet length 421C of the sounding trigger 411. For example, a beamforming receiver may monitor a channel to monitor for a preamble from another beamforming receiver or count the number of transmissions heard from other beamforming receivers, determine a previous beamforming receiver based on the sounding location 421B, and calculate a time of transmission after the previous beamforming receiver according to the packet length 421C.

The schedule 421 may include a terminator 421D to instruct or signal one or more of the beamforming receivers to stop or suspend transmission of additional dedicated training signals. In some implementations, a terminator 421D is transmitted with the first sounding trigger 411 to indicate when one or more of the beamformers stop or suspend transmission of dedicated training signals. For example, terminator 421D may indicate a number of dedicated training signals to be transmitted without receiving another sounding trigger. Terminator 421D may also indicate that transmission of the dedicated training signal is suspended after a period of time or condition (e.g., schedule expiration). Other implementations may include a second probe trigger 411 with a terminator 421D that signals stopping or suspending the transmission of the dedicated training signal. The sounding trigger 411 may include a terminator 421D for each target beamformed receiver, a subset of the target beamformed receivers, or all of the response beamformed receivers. In another example, the detection trigger 411 may include training options 431 configured by the training options module 430 to, for example, instruct the receiver how to format or customize the dedicated training signal. Types of training options 431 may include precision parameters 431A, format 431B, timing options 431C, spatial streams 431D, and so on.

For example, the precision parameter 431A may indicate the frequency at which symbols are repeated in the VHT-LTFs as averaged at the receiver. In one example, timing option 431C may indicate a measured arrival time of an incoming packet and a measured departure time of an outgoing packet. Training options 431 may include spatial stream 431D configurations for use with receivers that support MU-MIMO. Other exemplary training options 431 may include configurable format 431B elements as understood in the art.

The sounding trigger 411 may also include site information 441 coordinated by the beamforming receive-end manager 440 to enable, for example, multiple receivers to respond to a single sounding trigger 411. Types of site information 441 may include site list 441A, site identifier 441B, MAC address 441C, site capabilities 441D, and so forth.

An exemplary implementation of probing of requests as described herein may use a probe trigger 411 that contains the initiating program 416 and additionally does not include any, or some or all of the scheduling information 421, training options 431, and/or site information 441 described herein.

Fig. 5A-G illustrate exemplary sequences of probes of requests according to various exemplary implementations. Fig. 5A shows an exemplary sequence 500A and 501A of probes for a targeted site 508A request. The requested sounding procedure can be initiated by the access point 502A to sound a channel for communicating with the station 508A. In the exemplary implementation shown in 500A and 501A of fig. 5A, the access point 502A initiates the requested probe by sending an NDP poll 510A as a probe trigger identifying the access point 502A and the intended recipient station 508A.

In response to receiving the NDP poll 510A, the station 508A sends an NDP 550A to the access point 502A. The NDP 550A is sent within a first interval (e.g., a short interframe space (SIFS) or a portion of a SIFS) of the NDP poll 510A. The access point 502A reserves the channel during a predetermined response period for receiving the dedicated training signal. The NDP 550A response packet is an exemplary dedicated training signal without user data that can be processed to estimate reverse channel information in the reverse direction from the station 508A to the access point 502A. The access point 502A estimates forward CSI using the reverse channel information derived based on the NDP 550A to determine a corresponding link matrix for adjusting forward channel precoding (e.g., user data 566A) for subsequent MIMO transmission by the access point 502A to the targeted site 508A.

Fig. 5B illustrates an exemplary sequence 500B, 501B, and 503B of probe bursts of requests in accordance with various exemplary implementations. In an exemplary implementation, the requested probing may include a separate probing triggered NDP poll 510B to request one or more dedicated training signals (e.g., NDPs 550B, 551B, 552B) from a single site 508B, as shown in sequence 500B and sequence 501B of fig. 5B. The beamformer may send additional NDP polls 511B to update (e.g., add, change, modify, cancel, etc.) the instructions for the single station 508B indicated by the previous NDP poll 510B.

The requested sounding framework achieves improved data communication quality by instructing the beamforming receiver to transmit multiple dedicated training signals over time without additional prompting, such that the beamformer can use the multiple dedicated training signals to re-probe the link with updated CSI. In addition, the beamformer may send another sounding trigger to maintain a coordinated sounding sequence with one or more beamformers, thereby effectively maintaining a communication link within the network. For example, the beamformer may send another sounding trigger to account for variations in transmission quality, network resources, performance of one or more of the beamformed receivers. In one example, as data communication degrades, the beamformer may send another sounding trigger to update the sounding interval or training signal format indicated by the previous sounding trigger.

In another exemplary implementation, the requested probe burst may include separate probe-triggered NDP polls 510B and 511B to request one or more dedicated training signals (e.g., NDPs 550B, 551B, 552B) from different stations 508B, 509B, as shown in sequence 500B and sequence 503B of fig. 5B. According to various exemplary implementations, probe-triggered NDP polls 510B and 511B may be sent to one or more stations 508B, 509B. That is, NDP poll 510B may be directed to first station 508B, and NDP poll 511B may be directed to second station 509B. In another example, NDP poll 510B and NDP poll 511B may be directed to both the first station 508B and the second station 509B. Additionally, NDP poll 510B may be directed to first station 508B and NDP poll 511B may be directed to both first station 508B and second station 509B. Alternatively, NDP poll 510B may be directed to both first station 508B and second station 509B, and NDP poll 511B may be sent to update the sounding instructions for one of the stations (e.g., first station 508B).

The requested sounding procedure is initiated by the access point 502A to sound multiple different stations 508B, 509B with multiple sounding triggered NDP polls 510B and 511B. In the exemplary implementation shown in fig. 5B, the access point 502B initiates the requested probing by sending a first NDP poll 510B to the first station 508B and receives a first NDP 550B within a first interval for probing the first NDP poll 510B. After receiving the first dedicated training signal from the first station 508B, the access point 502B may initiate another requested sounding by sending a second NDP poll 511B and receive a second NDP 551B from the second station 509B.

The first NDP poll 510B and/or the second NDP poll 511B may include a schedule for the respective station 508B and/or station 509B to send additional NDP 552B responses without receiving additional NDP polls. The access point 502B uses each received NDP 550B, NDP 551B and NDP 552B to estimate the forward CSI derived based on each NDP for sounding the associated station 508B or 509B. In another example implementation shown in fig. 5B, the first NDP poll 510B may be used to request one or more dedicated training signals from the target station 508B as an NDP 550B response. Based on the received NDP 550B, the access point 502B derives forward CSI for the forward channel from the reverse channel CSI according to characteristics of the radio frequency front end of the transmitter and precodes subsequent packets with a precoding derived from the forward CSI for transmission.

The NDP poll 510B may include instructions for the targeted station 508B to send additional NDPs without requiring additional NDP polls. The access point 502B may also send another NDP poll 511B to the targeted station 508B to change (e.g., modify, replace, cancel, etc.) the instruction indicated by the previous sounding trigger (e.g., the first NDP poll 510B). The second NDP poll 511B may be used to update parameters for requesting one or more dedicated training signals indicated by the previous NDP poll 510B sent to the one or more recipients.

Fig. 5C shows an exemplary sequence of probing of requests for a series of dedicated training signal responses. In an exemplary specific implementation, the NDP poll 510C may include instructions for the targeted station 508C to send a series of NDPs 550C, 551C, 552C without sending additional NDP polls.

In the exemplary implementation shown in fig. 5C, the first NDP 550C may be sent by the station 508C to the access point 502C as an initial response to the NDP poll 510C from the access point 502C. The target station 508C may send additional dedicated training signals NDP 551C and NDP 552C based on instructions included in the NDP poll 510C. To receive the additional NDPs 551C and 552C, the access point 502C may maintain a timer to anticipate when additional dedicated training signals are expected and reserve a channel.

For example, based on satisfaction of a threshold condition, external measurement resources, predictions, etc., NDP poll 510C may include instructions to coordinate when a series of NDPs 550C, 551C, 552C are expected at fixed or variable intervals, time windows, with target station 508C. Thus, the access point 502C may receive a series of NDPs 550C, 551C, 552C based on a single NDP poll 510C.

Fig. 5D illustrates an exemplary sequence of probes for a series of dedicated training signal responses from one or more stations 550D, 551D, 552D. In an exemplary implementation, the NDP poll 510D may include instructions indicating a schedule for the plurality of different stations 507D, 508D, 509D to transmit the plurality 550D, 551D, 552D without additional NDP polls. In the exemplary implementation shown in fig. 5D, the NDP poll 510D may include a schedule table indicating the response intervals, sounding locations, etc., at which each of the stations 507D, 508D, 509D sent the NDPs 550D, 551D, 552D.

The NDP poll 510D is a sounding trigger that identifies the access point 502 and the targeted receiving station 508 requesting sounding. In the case where the NDP poll 510D is sent to more than one station, the stations 507D, 508D, 509D may use the order in which the recipient stations are listed in the instructions from the sounding trigger 510D to control the order or location for sending the NDPs 550D, 551D, 552D. For example, NDP poll 510D may include a list with the order or probe location of each of the sites 507D, 508D, 509D. The stations 507D, 508D, 509D may repeatedly transmit NDPs 550D, 551D, 552D to the access point 502D according to a sequence or schedule until the schedule expires, a termination command is transmitted, a new NDP poll is received, or the station 507D goes offline.

For example, a scheduling instruction indicated by the NDP poll 510D may allocate station 507D to send a first NDP 550D within a SIFS relative to the NDP poll 510D, allocate station 508D to send another NDP 551D within the SIFS relative to the first NDP 550D, and allocate station 509D to send a third NDP 552D within the SIFS relative to the second NDP 551D.

In another exemplary implementation, the NDP poll 510D may initiate a plurality of different stations 507D, 508D, 509D to transmit a plurality of NDPs 550D, 551D, 552D without additional NDP polls, where the different stations 507D, 508D, 509D determine when to transmit each of the NDPs 550D, 551D, 552D. For example, NDP poll 510D may be received by a plurality of different stations 507D, 508D, 509D, and each station may monitor the network channel to detect preambles that trigger other dedicated training signals from other receivers in response to the probe.

In this example, the station 507D can begin responding to the NDP poll 510D with the NDP 550D, and the station 508D can monitor the network channel and listen for the preamble of the NDP 550D. The station 508D may calculate the packet length of the NDP 550D by listening to the preamble of the NDP 550D. Based on the packet length, station 508D may determine when a channel will become available to transmit access point 502D the next time, and then transmit NDP 551D when a channel is available.

As another example, station 507D and station 508D may contend for the medium before sending the NDP. For example, station 507D and station 508D may each attempt to transmit, detect that the channel is busy, and wait a certain amount of time (e.g., a contention window) before attempting to transmit again. In response to the first station 508D detecting that a channel is available, the NDP 551D is transmitted, while the station 507D waits another amount of time before attempting to transmit. Then, after another amount of time, if the second station 507D detects that a channel is available, the NDP 550D is transmitted.

As described above, the NDPs 550D, 551D, 552D respond with packets as dedicated training signals with no user data that can be processed to estimate the reverse channel information in the direction from each of the stations 507D, 508D, 509D to the access point 502D. Then, for each received NDP 550D, 551D, 552D, the access point 502D estimates forward CSI derived based on the respective NDP to determine a corresponding link matrix needed to adjust forward channel precoding for subsequent MIMO transmissions (e.g., user data 566) by the access point 502 to the associated target station.

FIG. 5E illustrates an exemplary sequence of probes for a request with a variable response schedule. The access point 502E may send an NDP poll 510 to a plurality of different stations 507E, 508E, 509E or groups of stations and receive a plurality of NDPs (e.g., 550E, 551E, 552E) within a response window (e.g., a Network Allocation Vector (NAV) 524).

Access point 502E may establish response window coordinates with stations responding to the probe trigger to transmit unresponsive stations and prevent their attempts to transmit on the channel. For example, the NAV 524 provides a virtual carrier sensing mechanism to control network access by signaling stations on the network that the channel is unavailable or busy for a specified contention period. Stations that are not responding to the NDP poll 510E listen to the wireless medium and use the duration field to set their NAV to indicate the duration for which they must defer from accessing the medium.

The responding stations 507E, 508E, 509E may schedule instructions based on NDP poll 510E at different times (e.g., T₁、T₂、T₃Etc.) to respond. The requesting sounding framework supports various scheduling schemes as described herein. For example, the NDP poll 510E may indicate a probe location relative to other receiver stations, and each station 507E, 508E, 509E may determine one or more response times based on the probe location to transmit one or more dedicated training signals at the calculated response times. As another example, the station 507E, 508E, 509E may coordinate sending multiple NDPs 550E, 551E, 552E in sequence by determining a response time based on the packet length of the NDPs. Each station 507E, 508E, 509E may monitor channel listening to monitor a preamble of an NDP from another one of the stations to determine a score of the NDPThe group length. Based on the determined packet length of the NDP, the second station 508E may calculate the response time T based on a reference time (such as the last detected NDP preamble)₂。

Fig. 5F illustrates an exemplary sequence of requested sounding with uplink MU-MIMO communication. An access point with front-end RF functionality parameters for uplink MU-MIMO communications splits the available bandwidth into separate individual streams (i.e., spatial streams) that share the medium equally. With uplink MU-MIMO, an access point may receive different data from two or more stations simultaneously through the same set of OFDM tones. MU-MIMO access points are characterized by the transmitter's front-end parameters (e.g., multiple transmit and receive chains, antennas, etc.) with up to n × m communication streams being transmitted and received per link of an antenna array.

In an exemplary implementation, the NDP polling trigger 510F may request multiple MU-MIMO capable stations 506F, 507F, 508F, 509F to concurrently schedule NDPs on separate spatial streams (e.g., NDP STAs₁、NDP STA₂…NDP_N-1、NDP_N) To an access point 502F supporting MU-MIMO. The NDP polling trigger 510F may indicate or allocate a target spatial stream for each station 506F, 507F, 508F, 509F to transmit a respective NDP (e.g., NDP STA)₁、NDP STA₂…NDP_N-1、NDP_N) And thus access point 502F receives each response simultaneously. The NDP polling trigger 510F may also be used by stations 506F, 507F, 508F, 509F as a time reference point to coordinate multiple NDPs (e.g., NDP STAs₁、NDP STA₂…NDP_N-1、NDP_N) Simultaneous transmission on different spatial streams so that an access point 502F supporting MU-MIMO can properly handle NDP (e.g., NDP STA)₁、NDP STA₂…NDP_N-1、NDP_N) To estimate the forward channel information.

In the exemplary implementation shown in fig. 5F, the first NDP STA₁A second NDP STA, which may be transmitted by station 506F on a first spatial stream₂… NDP may be sent on a second spatial stream by station 507F_N-1NDP, which may be sent by station 508F on spatial stream N-1_NCan be composed ofStation 509F transmits on spatial stream N up to the number of available spatial streams indicated by access point 502F.

Fig. 5G shows an exemplary sequence of probes requested with different types of stations. In the exemplary implementation shown in fig. 5G, the NDP poll 510G may request a number of different stations that are grouped to transmit dedicated training signals. In one example, different stations (e.g., 506G-50NG) may be grouped based on their capabilities and scheduled to send NDPs at different times.

For example, the NDP poll 510G may indicate that a first group of MU-MIMO capable stations 506G-50NG simultaneously send NDPs (e.g., NDP STAs) on separate spatial streams within a first response interval₁、NDP STA₂…NDP_N-1、 NDP_N) And further instructs the second group of beamforming capable stations 508G and 509G to sequentially transmit NDPs 552G, 553G after the response interval. Exemplary implementations may include a combination of different scheduling and training options as discussed herein.

Fig. 6 illustrates a flow diagram of an exemplary requested probe beamforming receive-end procedure in accordance with an exemplary implementation. The sounding process 600 for a request to beamform a receiving end may include receiving a sounding trigger from a wireless transmitter and transmitting at least one dedicated training signal in response to the sounding trigger 650, at 615. In one example, at 655, the beamforming receiving end receives a subsequent packet with a precoding derived from CSI information of at least one dedicated training signal.

In an exemplary implementation, the beamformed receiving end determines a response time for the transmission at 625. The beamforming receive end may process a single sounding trigger to provide multiple dedicated training signals used to determine precoding for subsequent packets sent from the transmitter via the forward channel. The beamforming receive end may determine the response time for transmissions without a sounding schedule by, for example, responding immediately, using contention-based transmissions, invoking a schedule from memory, monitoring a channel to monitor information from other stations, etc.

The beamforming receive end may also process the sounding trigger at 620 to set up a scheduler for providing additional dedicated training signals and configure the dedicated training signals. In one exemplary implementation, the wireless receiver receives a probe trigger at 615 indicating a probe schedule at 625 and training options for the format of the dedicated training signal. The beamforming receiving end stores a sounding schedule and calculates a response time of each of the one or more dedicated training signals based on the sounding schedule.

In one exemplary implementation, the at least one dedicated training signal from one or more beamformed receivers comprises a plurality of dedicated training signals from associated beamformed receivers in response to a sounding trigger. The sounding trigger indicates a sounding schedule of additional dedicated training signals from the associated beamformed receiving end, and receives a plurality of dedicated training signals from the associated beamformed receiving end at timing intervals based on the sounding schedule.

At 635, the beamforming receive end may also format the dedicated training signal based on the training options from the sounding trigger. In one example, the beamforming receive end may determine the time to transmit the dedicated training signal by monitoring network traffic of a preamble that triggers other dedicated training signals from other receivers in response to the sounding. The beamforming receiving end may then derive a packet length for the dedicated training signal based on the other dedicated training signals and determine a response time based on the packet length.

In another example, where the sounding trigger may indicate a sounding location relative to other receivers, the beamforming receiving end calculates one or more response times based on the sounding location and transmits one or more dedicated training signals at the calculated response times.

7A-B illustrate examples of probing of requests with timing feedback according to example implementations. In other exemplary implementations, the beamforming receiver may adapt the requested sounding framework to streamline or support other networking applications besides sounding (e.g., motion tracking, building automation, etc.). In one example, the beamforming receive end may determine timing feedback based on the measured arrival time of the incoming packet and the measured departure time of the outgoing packet. The beamforming receive end may then utilize at least one of the dedicated training signals to transmit a timestamp or other timing information. The timing and ranging functions between stations can be effectively synchronized by utilizing the special training signals including additional timing feedback, and meanwhile, the transmission overhead between a beam forming receiving end and a beam forming device is increased to the minimum extent.

Fig. 7A shows an exemplary sequence of probing of requests with timing feedback. In other exemplary implementations, the sites 707, 708, 709 may adapt the requesting probe framework to streamline or support other networked applications besides probing (e.g., motion tracking, building automation, etc.). In one example, the stations 707, 708, 709 can determine additional feedback parameters 781, 782, 783 transmitted with the NDPs 751, 752, 753 to the access point 702E. For example, the stations 751, 752, 753 can determine timing feedback parameters 781, 782, 783 transmitted with the NDPs 751, 752, 753 that the access point 702 can use for other network applications or coordination, such as effectively synchronizing timing between stations, ranging functions, and so forth.

The NDPs 751, 752, 753 do not include payload or user data for the purpose of probing of requests. However, additional feedback timing feedback parameters 781, 782, 783 may optionally be transmitted with the NDPs 751, 752, 753 to refine or support other networked applications (e.g., motion tracking, building automation, etc.) in addition to detection. By transmitting the additional feedback parameters 781, 782, 783 with the NDPs 751, 752, 753, the access point 702 can initiate multiple functions with a single trigger. For example, the access point 702 may extract or determine timing information from data (e.g., additional feedback parameters 781, 782, 783) attached to the NDPs 751, 752, 753. The beamformer does not need additional feedback parameters 781, 782, 783 and does not need to use these additional feedback parameters to complete the requested sounding process. However, by operably coupling the additional feedback parameters 781, 782, 783 that are appended to the NDPs 751, 752, 753, the number of overhead transmissions between the beamformer and the beamformed receive end may be further reduced.

Fig. 7B shows an exemplary time sequence of probing of a request with timing feedback. In an exemplary implementation, the station 708 bases its arrival time T of the incoming packet on the measurement₁And measured outgoing packet departure time T₂To determine timing feedback 780. In one example, the timing feedback 780 can be a time, one or more timestamps, or other calculated difference. When responding to the NDP poll 710, the station 708 may optionally include timing feedback 780 as additional information 781 during the transmission of the NDP 751. By transmitting the timing feedback 780 as additional information 781 during the transmission of the NDP 751, the requested sounding framework may be utilized to eliminate or avoid separate additional transmissions of the timing feedback 780 to effectively provide additional functionality. In addition to the requested sounding of a single transmission from station 708, the beamformed receiver may enable the access point 702 to process other applications 760, thereby increasing the availability of the channel.

Fig. 8A-C illustrate examples of probes requested by another beamformer according to an example implementation. In an example implementation, sounding requested by a first beamformer (e.g., access point 802) may enable one or more other beamformers (e.g., stations 808) to estimate a forward channel 830 to the same station 809 without sending any sounding triggers.

Fig. 8A illustrates an exemplary sequence of probes of a request according to an exemplary implementation. In the example where the access point 802 is a beamformer sounding beamforming receiver station 809, an access point-to-station (AP-STA) sounding channel may be described as having both an AP-STA forward channel 820 from the beamformer access point 802 to the beamforming receiver station 809 and an STA-AP reverse channel 821 from the beamforming receiver station 809 to the beamformer access point 802. As described above, the beamformer access point 802 may transmit a single sounding trigger via the AP-STA forward channel 820 received by the beamforming receive site 809. The beamforming receiving site 809 may transmit multiple dedicated training signals via the STA-AP reverse channel 821 with minimal processing required in response to a single sounding trigger from the AP-STA forward channel 820.

In an exemplary implementation, multiple beamformers may probe one or more beamformed receiving ends based on a single requested probing trigger. The sounding requested by a first beamformer (e.g., access point 802) may enable one or more other beamformers (e.g., station 808) to estimate an STA-STA forward channel 830 to the same station 809 without sending any sounding triggers. For example, the first beamformer access point 802 may send a sounding trigger via the AP-STA forward channel 820, and the beamforming receiver station 809 may respond to the first beamformer access point 802 via the STA-AP reverse channel 821 with an NDP that is overheard by the second beamforming receiver station 808 via the STA-STA reverse channel 831.

In the example where station 808 is a beamformer in communication with beamforming receive station 809, the sounding channel may be described as having an STA-STA forward channel 830 from the beamformer station 808 to the beamforming receive station 809 and an STA-STA reverse channel 831 from the beamforming receive station 809 to the beamformer station 808. For example, as in a mesh network, the second station 808 may be a beamforming receive end of the beamformer access point 802 and the second station 808 may be a beamformer of the beamforming receive end station 809, among other combinations.

It should be noted that the beamformer and beamformed receiving end and channels are not limited to any number or combination of access points and stations. The examples described herein are exemplary and apply to any combination of communication devices having means for beamformer operation and/or means for beamforming receive end operation.

In some implementations, the second station 808 can also receive a sounding trigger from the first beamformer (e.g., access point 802) via the second AP forward channel 822. In other implementations, the second station 808 can receive the dedicated training signal from the first station 809 independent of receiving the sounding trigger from the access point 802. The second station 808 may monitor the medium for the dedicated training signal from the beamforming receive station 809 (e.g., via the STA-STA reverse channel 831) to estimate the STA-STA forward channel 830 without sending a sounding trigger.

The beamformer station 808 may perform sounding of the STA-STA forward channel 830 based on overhearing the dedicated training signal sent by the beamforming receive end station 809 to the access point 802 via the AP reverse channel 821 via the STA-STA reverse channel 831.

Fig. 8B illustrates an exemplary sequence of multiple beamformers probing a receiving end based on a single requested probe trigger according to an exemplary implementation. At 810, the access point 802 transmits a sounding trigger to the first station 809 via the AP-STA forward channel 820. The second station 808 may or may not also receive the same sounding trigger via another AP-STA forward channel 822 at 811.

At 836, the second station monitors the STA-STA reverse channel 831 for the frequency of the dedicated training signal. Monitoring the frequency of the STA-STA reverse channel 831 may detect transmissions broadcast or transmitted on other sounding channels in the network (e.g., AP-STA forward channel 820, STA-AP reverse channel 821, STA-STA reverse channel 831, another AP-STA forward channel 822, etc.). At 850, the first station 809 transmits one or more dedicated training signals to the access point 802 via the AP reverse channel 821 based on the sounding trigger. At 870, the second station 808 overhears the one or more dedicated training signals transmitted by the first station 809 via the STA-STA reverse channel 831. At 875, the second station 808 processes the overheard dedicated training signal to estimate the forward CSI of the STA-STA forward channel 830. At 880, the second station 808 may transmit subsequent packets to the associated beamforming receiving end first station 809 via the STA-STA forward channel 830 based on the estimated forward CSI of the STA-STA forward channel 830.

At 860, the access point 802 processes the received dedicated training signal to estimate the forward CSI of the AP-STA forward channel 820. At 866, the access point 802 may transmit a subsequent packet to the associated beamforming receiving end first station 809 via the AP-STA forward channel 820 based on the estimated forward CSI of the AP-STA forward channel 820. Thus, multiple beamformers may probe one or more beamformed receive ends based on a single requested probe trigger.

Fig. 8C shows a flow diagram of an exemplary sequence of a secondary beamformer probing a beamformed receive based on a single requested probe trigger from a primary beamformed receive. The auxiliary beamformer process 840 begins at step 841 where an auxiliary beamformer (e.g., an unsolicited beamformer, a piggyback beamformer, etc.) will monitor the communication medium as discussed with reference to fig. 8A-B.

At 842, the auxiliary beamformer process detects at least one dedicated training signal from one or more beamforming receive ends in response to a probe trigger sent by another beamformer (e.g., a primary beamformer or a requesting beamformer). The auxiliary beamformer does not transmit a sounding trigger.

At 843, for each overhead dedicated training signal, the auxiliary beamformer process performs steps 844 and 845 to estimate forward channel state information. At step 844, the auxiliary beamformer process calculates CSI for the reverse channel by measuring the received dedicated training signals. At 845, the auxiliary beamformer process derives CSI for the forward channel from the CSI for the reverse channel based on the characterization of the front end parameters of the transmitter.

In one example implementation, the auxiliary beamformer process may use the estimated forward CSI at 846 to transmit subsequent packets using precoded packets with precoding derived from the estimated CSI. The auxiliary beamformer process repeats at least steps 844 and 845 for each overhead dedicated training signal associated with the beamformee with which the auxiliary beamformer intends to communicate. Thus, the requested sounding framework requires less beamformer processing and less bandwidth than conventional sounding methods.

FIG. 9 illustrates a diagram of an exemplary networked device or system that may be used in conjunction with the various exemplary implementations described herein. For example, system 915 may be used as or in conjunction with one or more of the mechanisms or processes described above, and may represent components of a processor, one or more user systems, and/or other devices described herein. The system 915 may be a networked device, a router, a server, a laptop, a mobile device, or any conventional computer, or any other processor-enabled device capable of wired or wireless data communication. Other computer systems and/or architectures may also be used, as will be apparent to those skilled in the art.

The system 915 preferably includes one or more processors, such as a processor 925. Additional processors may be provided, such as an auxiliary processor for managing input/output, an auxiliary processor for performing floating point mathematical operations, a special purpose microprocessor having an architecture suitable for fast execution of signal processing algorithms (e.g., digital signal processors), a slave processor subordinate to the main processing system (e.g., a back-end processor), additional microprocessors or controllers or co-processors for dual or multi-processor systems. Such auxiliary processors may be discrete processors or may be integrated with the processor 925.

The processor 925 is preferably connected to a communication bus 920. The communication bus 920 may include a data channel for facilitating the transfer of information between the storage device and other peripheral components of the system 920. The communication bus 920 may also provide a set of signals used for communication with the processor 925, including a data bus, an address bus, and a control bus (not shown). The communication bus 920 may include any standard or non-standard bus architecture, such as Industry Standard Architecture (ISA) -compliant, Extended Industry Standard Architecture (EISA), Micro Channel Architecture (MCA), Peripheral Component Interconnect (PCI) local bus, or standards promulgated by the Institute of Electrical and Electronics Engineers (IEEE) including IEEE 802.11, IEEE 1188 general interface bus (GPIB), IEEE 696/S-30, and so forth.

The processor 925 may execute under any Operating System (OS) (not shown) in a local or virtual environment. One or more applications including logic units, Application Programming Interface (API) units, and the like may be deployed.

System 915 preferably includes main memory 930 and may also include secondary memory 935. The main memory 930 provides storage of instructions and data for programs executing on the processor 925, such as one or more of the functions and/or modules described above. It should be appreciated that programs stored in memory and executed by processor 925 may be written and/or compiled in accordance with any suitable language, including but not limited to C/C + +, Java, JavaScript, Pearl, Visual Basic,. NET, and so forth. The main memory 930 is typically a semiconductor-based memory such as a Dynamic Random Access Memory (DRAM) and/or a Static Random Access Memory (SRAM). Other semiconductor-based memory types include, for example, Synchronous Dynamic Random Access Memory (SDRAM), Rambus Dynamic Random Access Memory (RDRAM), Ferroelectric Random Access Memory (FRAM), and the like, including Read Only Memory (ROM).

The secondary memory 935 may optionally include internal memory 940 and/or a removable media 945 such as a Digital Versatile Disk (DVD) drive, other optical disk drives, flash memory drive, or the like. Removable media 945 is read from and/or written to by it in a well-known manner. Removable storage medium 945 may be, for example, a floppy disk, magnetic tape, CD, DVD, SD card, or the like. Removable storage medium 945 is a non-transitory computer-readable medium having stored thereon computer-executable code (i.e., software) and/or data.

Other examples of the auxiliary memory 935 may include a semiconductor-based memory such as a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable read-only memory (EEPROM), or a flash memory (block-oriented memory similar to EEPROM). Also included are any other removable storage media 945 and communication interfaces 955 that allow software and data to be transferred from external media 960 to system 915.

System 915 may include a communication interface 955. Communication interface 955 allows software and data to be transferred between system 915 and external devices (e.g., printers), networks, or information sources. For example, computer software or executable code may be transferred to system 915 from a network server via communication interface 955. Examples of communication interface 955 include a built-in network adapter, a Network Interface Card (NIC), a Personal Computer Memory Card International Association (PCMCIA) network card, a card bus network adapter, a wireless network adapter, a Universal Serial Bus (USB) network adapter, a modem, a Network Interface Card (NIC), a wireless data card, a communication port, an infrared interface, an IEEE 1394 firewire, or any other device capable of interfacing system 915 with a network or another computing device.

Communication interface 955 preferably implements industry-promulgated protocol standards such as the ethernet IEEE 802 standard, fiber optic channels, Digital Subscriber Lines (DSL), Asynchronous Digital Subscriber Lines (ADSL), frame repeaters, Asynchronous Transfer Mode (ATM), integrated digital services network (ISDN), Personal Communication Services (PCS), transmission control protocol/internet protocol (TCP/IP), serial internet protocol/point-to-point protocol (SLIP/PPP), etc., although custom or non-standard interface protocols may also be implemented.

Software and data transferred via communications interface 955 are typically in the form of electrical communications signals 970. These signals 970 are preferably provided to the communication interface 955 via a communication channel 965. In an exemplary implementation, the communication channel 965 may be a wired or wireless network, or any other type of communication link. By way of example, communication channel 965 carries signals 970 and may be implemented using a variety of wired or wireless communication means including wire or cable, fiber optics, a conventional telephone line, a cellular telephone link, a wireless data communication link, a radio frequency ("RF") link, or an infrared link.

Computer executable code (i.e., computer programs or software) is stored in main memory 930 and/or secondary memory 935. Computer programs may also be received via communication interface 955 and stored in main memory 930 and/or secondary memory 935. Such computer programs, when executed, enable the system 915 to perform the various functions of the present invention as previously described.

For example, the communication interface 955 coupled to the processor 925 may be configured to operate the wireless transceiver, including transmitting a sounding trigger to one or more receivers and receiving at least one dedicated training signal from the one or more receivers via a back channel in response to the sounding trigger. For each received dedicated training signal, the dedicated training signal may estimate forward CSI based on the dedicated training signal from the associated receiver; and wherein subsequent packets are precoded with a precoding derived from the forward CSI for transmission to an associated receiver via the forward channel.

According to one exemplary implementation, the processor 925 may be configured to transmit additional sounding triggers to the target additional receivers, wherein in response to each additional sounding trigger, a separate additional dedicated training signal is received from each of the additional receivers, and wherein for each separate additional dedicated training signal received, the processor further estimates CSI for the additional receiver associated with the separate additional dedicated training signal; and transmitting additional pilot packets to additional receivers based on the CSI. The sounding trigger is not preceded by an announcement frame and the receiver does not process the sounding trigger to generate detailed sounding feedback (e.g., SVD based on compressed beamforming feedback).

In another example, the communication interface 955 coupled to the processor 925 may be configured to operate the wireless receiver, including receiving a probe trigger from the wireless transmitter, transmitting at least one dedicated training signal in response to the probe trigger; and receiving a subsequent packet with a precoding derived from CSI information of the at least one dedicated training signal.

Transmitting the at least one dedicated training signal in response to the probing trigger may include transmitting a plurality of dedicated training signals without receiving another probing trigger. In one example, the probing trigger indicates a probing schedule and training options for the dedicated training signal format, and the processor 925 is configured to store the probing schedule, calculate a response time for each of the one or more dedicated training signals based on the probing schedule, and format the dedicated training signals based on the training options. The sounding schedule instructions may indicate sounding times for transmission of dedicated training signals coordinated (e.g., sequentially, continuously, simultaneously, bursty, etc.) with a group of receivers. In other exemplary implementations, the processor 925 is configured to determine response times for transmitting additional dedicated training signals without receiving additional hints from the beamformer. In this example, the wireless transceiver may transmit additional sounding triggers to target additional beamformed receiving ends. For example, the additional sounding triggers a series of separate additional dedicated training signals from each of the additional beamformed receivers. Further, in response to each additional sounding trigger, the additional sounding trigger initiates a series of separate additional dedicated training signals from each of the additional beamformed receivers.

In one example, operating a wireless transceiver for estimating forward CSI includes measuring channel information from a dedicated training signal received via a reverse channel, calculating CSI for the reverse channel from the measured channel information, and deriving forward CSI for a forward channel from the CSI for the reverse channel according to characteristics of a radio frequency front end of the transceiver, wherein subsequent packets are transmitted via the forward channel to an associated beamformed receiving end.

In some examples, a wireless transceiver apparatus includes multiple sets and/or subsets of antennas, multiple components coupled to one another to form transmit and receive chains, and a requester module circuit to transmit a sounding trigger via a forward channel to request multiple dedicated training signals from one or more beamforming receive ends. For example, the dedicated training signals may be processed to improve subsequent transmission of data to the associated beamformed receiver (e.g., to estimate forward Channel State Information (CSI) for transmission of subsequent packets to the associated beamformed receiver).

A wireless transceiver having a requester module circuit generates a sounding trigger indicating a control schedule (e.g., a training option for a format of at least one of a plurality of dedicated training signals based on communication parameters of a target beamforming receive end). For example, the communication parameters of the target beamforming receiving end include one or more combinations of target beamforming capabilities, traffic types, positioning parameters, and the like.

In further examples, a wireless transceiver having a requester module circuit may include a probe module circuit coupled to a plurality of components. In other examples, a wireless device without transceiver requester module circuitry may include probe module circuitry coupled to a plurality of components. The detection module circuitry may process the dedicated training signals, e.g., as each received dedicated training signal, the detection module circuitry will: channel information of a dedicated training signal received via a reverse channel is measured, CSI of the reverse channel is calculated from the measured channel information, and forward CSI of a forward channel is derived from the CSI of the reverse channel according to characteristics of a radio frequency front end of a transceiver.

In other examples, a wireless transceiver apparatus includes multiple sets and/or subsets of antennas, multiple components coupled to one another to form transmit and receive chains, and a sounding module circuit coupled to the multiple sets and/or subsets of antennas. The wireless transceiver in this example does not require a requester module circuit and may use a wireless transceiver that is initially populated with another wireless transceiver (e.g., a wireless transceiver with a requester module circuit). The detection module circuitry may detect at least one dedicated training signal from one or more beamformers, where the at least one dedicated training signal is based on a detection trigger from another beamformer.

The wireless transceiver device of claim 15, wherein the sounding trigger indicates a sounding schedule with time intervals configured based on communication parameters of a target beamforming receiving end, the communication parameters of the target beamforming receiving end including at least one of: target beamforming receiver capabilities, traffic types, and positioning parameters.

Transmitting the at least one dedicated training signal may be performed at timed intervals by the communication interface 955 based on a probing schedule indicated by the probing trigger. In another example, transmitting the at least one dedicated training signal may be based on monitoring preambles of other dedicated training signals from other receivers in response to the sounding trigger; deriving a packet length for a dedicated training signal based on the other dedicated training signals; and determining a response time based on the packet length.

In another embodiment, any of the examples may include receiving at least one dedicated training signal having timing information. Such timing information may indicate packet transmission and reception timestamps. The timing information may be used for applications other than the probing process, such as motion tracking, position mapping, and the like.

In this specification, the term "computer-readable medium" is used to refer to any non-transitory computer-readable storage medium for providing computer-executable code (e.g., software and computer programs) to the system 915. Examples of such media include main memory 930, secondary memory 935 (including internal memory 940, removable media 945, and external storage media 945), and any peripheral devices (including a network information server or other network device) communicatively coupled to communication interface 955. These non-transitory computer-readable media are means for providing executable code, programming instructions, and software to the system 915.

In an exemplary implementation using software implementations, the software may be stored on a computer-readable medium and loaded into system 915 via removable media 945, I/O interface 950, or communications interface 955. In such exemplary implementations, software is loaded into system 915 in the form of electrical communication signals 970.

In an exemplary implementation, the I/O interface 950 provides an interface between one or more components of the system 915 and one or more input and/or output devices. Exemplary input devices include, but are not limited to, a keyboard, touch screen or other touch sensitive device, biometric sensing device, computer mouse, trackball, pen-based pointing device, and the like.

System 915 also includes optional wireless communication components that facilitate wireless communication via voice and via a data network. The wireless communication components include an antenna system 975, a radio system 980, and a baseband system 985. In system 915, Radio Frequency (RF) signals are transmitted and received over the air by antenna system 975 under the management of radio system 980.

In one exemplary implementation, the antenna system 975 may include one or more antennas and one or more multiplexers (not shown) that perform switching functions to provide transmit and receive signal paths for the antenna system 975. In the receive path, the received RF signals may be coupled from the multiplexer to a low noise amplifier (not shown) that amplifies the received RF signals and sends the amplified signals to the radio system 980.

In alternative exemplary implementations, the radio system 980 may include one or more radios configured to communicate over various frequencies. In one exemplary implementation, radio system 980 may combine a demodulator (not shown) and a modulator (not shown) in one Integrated Circuit (IC). The demodulator and modulator may also be separate components. In the incoming path, the demodulator strips away the RF carrier signal leaving a baseband receive audio signal that is sent from the radio system 980 to the baseband system 985.

If the received signal contains audio information, the baseband system 985 decodes the signal and converts it to an analog signal. The signal is then amplified and sent to a speaker. The baseband system 985 also receives analog audio signals from the microphone. These analog audio signals are converted to digital signals and encoded by the baseband system 985. The baseband system 985 also encodes digital signals for transmission and generates baseband transmission audio signals that are routed to the modulator portion of the radio system 980. The modulator mixes the baseband transmit audio signal with an RF carrier signal that generates an RF transmit signal that is routed to the antenna system and may pass through a power amplifier (not shown). The power amplifier amplifies and routes the RF transmit signal to the antenna system 975, where it is switched to the antenna port for transmission.

The baseband system 985 is also communicatively coupled to the processor 925. The central processing unit 925 can access the data storage areas 930 and 935. The central processing unit 925 is preferably configured to execute instructions (i.e., computer programs or software) that may be stored in the memory 930 or the secondary memory 935. Computer programs may also be received from the baseband processor 985 and stored in the data storage area 930 or the auxiliary memory 935, or executed upon receipt. Such computer programs, when executed, enable the system 915 to perform the various functions of the present invention as previously described. For example, data storage area 930 may include various software modules (not shown).

Fig. 10A-10B illustrate exemplary systems 1000A/1000B for channel sounding and beamforming communication according to an exemplary implementation. The system 1000a may include first and second beamformers 1010a, 1010b in communication with a first beamformed receive end 1020a, and the system 1000b may include first and second beamformers 1010a/1010b and first and second beamformed receive ends 1020a, 1020 b.

In operation, the first beamformer 1010a may transmit a sounding trigger signal to the first beamformed receive end 1020a in a manner similar or equivalent to that described in this disclosure, such as shown in fig. 5A-5G. For example, the probe trigger may be a null data packet polling frame that is not prior to the announcement frame. Unlike conventional explicit sounding techniques, the requested sounding enables the beamformer 1010a to trigger duplicate information based on a single sounding trigger. In these and other embodiments, the first beamformed receiver 1020a may respond to the sounding trigger with a dedicated training signal. As described herein, in requested sounding, the first beamformed receiver 1020a does not measure channel information from the received sounding trigger. One or more dedicated training signals transmitted by the first beamformed receiver 1020a are triggered by the sounding trigger, but the dedicated training signals do not require measurements associated with the transmission of the sounding trigger. For example, the dedicated training signal may be a null data packet without a probe data payload. In these and other implementations, the first beamformer 1010a may derive channel information to facilitate beamforming for communication between the first beamformer 1010a and the first beamformed receiving end 1020 a. The derivation of such channel information by the first beamformer 1010a may be performed according to any of the examples described in this disclosure, e.g., the first beamformer 1020a may follow the beamformer process described with reference to fig. 3.

In addition to being received at the first beamformer 1010a transmitting the sounding trigger, the dedicated training signal may be received by the second beamformer 1010b even if the second beamformer 1010b does not transmit the sounding trigger. By listening for dedicated training signals from the first beamformed receiver 1020a, the second beamformer 1010b may derive its own corresponding channel information in a manner similar or equivalent to that derived by the first beamformer 1010 a. However, the second beamformer 1010b may obtain a dedicated training signal even without sending a sounding trigger. Such an arrangement may be beneficial in a mesh network or other arrangement where multiple beamformers 1010 may serve a given beamformed receiving end 1020. An explanation of an exemplary message series for an embodiment with a single beamformed receive end and multiple beamformers may be described in more detail with reference to fig. 11A.

In some implementations, the second beamformer 1010b may have some form of relationship with the first beamformer 1010 a. For example, a developer or manager of a WLAN may deploy and configure the first beamformer 1010a/1010b at a location such that the first beamformer 1010a sends a sounding trigger to cause the first beamformee receiver 1020a to generate a dedicated training signal that is received by both the first beamformer and the second beamformer 1010a/1010 b. Such physical configurations may include mesh networks or other networks having multiple beamformers with overlapping coverage. As another example, the first beamformer 1010a and the second beamformer 1010b may be in a master/slave or master/slave relationship, where the first beamformer 1010a actively issues a sounding trigger and/or indicates when the second beamformer 1010b issues a sounding trigger.

Fig. 10B illustrates a system 1000B in which multiple beamformers 1020 (such as a first beamformed receiver 1020a and a second beamformed receiver 1020B) may be configured to receive sounding triggers from a first beamformer 1010a and respond accordingly. For example, a sounding trigger may be directed to both the first beamformed receiver 1020a and the second beamformed receiver 1020b, and each beamformed receiver may respond with its own respective dedicated training signal. In these and other embodiments, a single sounding trigger may facilitate estimation of channel information for channels associated with multiple beamformers (e.g., first and second beamformers 1020a/1020b) of both the first beamformer 1010a and the second beamformer 1010 b.

In some embodiments, the dedicated training signal may include instructions to the beamforming receive 1020 regarding the manner in which the dedicated training signal is transmitted. For example, the instructions may indicate that each beamforming receiver is to transmit a dedicated training signal at a given point in time according to a schedule, or that the dedicated training signals are to be multiplexed in a particular manner. Examples of such implementations may be described in more detail with reference to fig. 11B and 11C, respectively. Additionally or alternatively, the detection trigger may include any of the information and/or instructions described herein with reference to fig. 4B.

Although fig. 10A and 10B illustrate two examples of potential arrangements of the beamformer 1010 and the beamformed receiving end 1020, it should be understood that any configuration and/or number of beamformers 1010 and beamformed receiving ends 1020 are within the scope of the present disclosure. For example, in a mesh network, there may be a large number of overlapping beamformers serving a large number of beamforming receiving ends.

11A-11D illustrate additional exemplary sequences of probing of requests according to various exemplary implementations. Sequence 1100a of fig. 11A shows an exemplary embodiment with first and second beamformers 1110a and 1110b and a first beamformed receive 1120 a. Sequence 1100B of fig. 11B illustrates an exemplary embodiment with first and second beamformers 1110a/1110B and first and second beamformed receive-ends 1120a/1120B, where the first and second beamformed receive-ends 1120a/1120B respond in separate time slots. Sequence 1100C of fig. 11C illustrates an exemplary embodiment with first and second beamformers 1110a/1110b and first and second beamformed receive-ends 1120a/1120b, where the first and second beamformed receive-ends 1120a/1120b respond in a multiplexed manner. Sequence 1100D of fig. 11D illustrates an exemplary embodiment with first and second beamformers 1110a/1110b and first and second beamformed receive 1120a/1120b, wherein the first and second beamformed receive 1120a/1120b respond in separate time periods and the second beamformer 1100b also transmits a second sounding trigger. Although the sequences 1100a-1100d show NDP poll and NDP signals as sounding trigger and dedicated training signals, respectively, it should be understood that these are used as examples and that any number of communications are within the scope of the present disclosure as sounding trigger and dedicated training signals.

Referring to sequence 1100a, a first beamformer 1110a may broadcast a sounding trigger, such as NDP poll 1151. The NDP poll 1151 may identify the first beamformer 1110a as the initiator of the NDP poll and may identify the first beamformer 1120a as the target recipient of the NDP poll 1151. In some embodiments, the NDP poll 1151 may include a training option for the first beamforming receive end 1120a when transmitting the dedicated training signal. For example, the NDP poll 1151 may include scheduling information for a time period in which the beamforming receiver 1120a will transmit the dedicated training signal or the additional dedicated training signal. As another example, the NDP poll 1151 may include repeated symbols to be included in the dedicated training signal, a portion of bandwidth to be used in transmitting the dedicated training signal, a plurality of bits to be included in the dedicated training signal, and so on. In some embodiments, the dedicated training signal does not include any user data that may be processed to estimate the reverse channel information.

As shown in fig. 11A, the second beamformer 1110b and the first beamformer receiver 1120a may receive the NDP poll as blocks 1152a and 1152b, respectively. In response to receiving the NDP poll 1151, the first beamforming receive end 1120a may broadcast a dedicated training signal, such as NDP 1153. The dedicated training signals may be received by the first and second beamformers 1110a/1110b as blocks 1154a/1154b, respectively. In some embodiments, the first and second beamformers 1110a/1110b may reserve a given portion of network resources for receiving NDPs, as shown at block 1154/1154 b. For example, the second beamformer 1110b may observe the scheduling included in the NDP poll 1152b and may reserve a corresponding given portion of the network resources within which the first beamformed receiver is scheduled to transmit the NDP 1153. In some embodiments, the portion of network resources may include a time slot, a portion of bandwidth, a frequency range, a Resource Unit (RU), and/or the like.

After receiving the NDP 1153, each of the first and second beamformers 1110a/1110b may determine respective channel characteristics of a forward channel between the first and second beamformers 1110a/1110b and the first beamformed receiver 1120 a. For example, the second beamformer 1110b may estimate reverse channel characteristics based on the NDP 1153 and may estimate forward channel characteristics using the estimate of the reverse channel characteristics. The second beamformer 1110b may use the estimates of the forward channel characteristics to determine a corresponding link matrix for adjusting forward channel precoding for subsequent transmission of user data by the second beamformer 1110b to the first beamformed receiver 1120 a.

In some implementations, the sequence 1100a may be particularly advantageous in cases where signal strength or other channel information between the first and second beamformers 1110a/1110b is important with respect to a single beamforming receive (e.g., the first beamforming receive 1120 a). For example, when performing WiFi motion detection, the relative signal strength and/or other channel information between the first beamformer 1120a and the first and second beamformers 1110a/1110b may be used to detect and determine the direction of motion, amount of motion, and so on. By using the requested sounding method of the present disclosure, overhead and/or network usage may be minimally increased to obtain accurate channel information. For example, only a single beamformer 1110a represents multiple beamformers (such as beamformers 1110a and 1110b) transmitting sounding triggers (e.g., NDP polls 1151) such that all beamformers of the multiple beamformers can estimate their respective channel characteristics with minimal network usage with the beamformed receive end 1120 a.

As shown in fig. 11B, the sequence 1100B may initiate the requested sounding process by the first beamformer 1110a transmitting the NDP poll 1161. The NDP poll 1161 may identify both the first beamforming receiver 1120a and the second beamforming receiver 1120b as the target receivers of the NDP poll 1161. In these and other embodiments, NDP poll 1161 may be similar to or comparable to NDP poll 1151 of fig. 11A. The NDP poll 1161 may be received by the second beamformer 1110b and the first and second beamformed receive ends 1120a/1120b as blocks 1162a, 1162b, and 1162c, respectively.

In the implementation shown in fig. 11B, the NDP poll 1161 may include scheduling information specific to each of the first and second beamformed receivers 1120 a/1120B. For example, the scheduling information may indicate that the first beamformed receiver 1120a will transmit the NDP 11163 within a first time slot and the second beamformed receiver 1120B will transmit the NDP 21165 within a second time slot (as illustrated by the continuous transmission of the NDP 11163 and the NDP 21165 in fig. 11B). NDP 11163 may be received by both the first beamformer 1110a and the second beamformer 1110b as blocks 1164a/1164b, respectively. NDP 21165 may be received by both the first beamformer 1110a and the second beamformer 1110b as blocks 1166a/1166b, respectively. After receiving the NDP 11163 and the NDP 21165, each of the first and second beamformed receivers 1110a/1110b may determine respective channel characteristics of the forward channel between the first and second beamformers 1110a/1110b and the first and second beamformed receivers 1120a/1120 b. In these and other embodiments, the beamforming receive ends 1120a/1120b may obtain their scheduling information and/or determine their time periods in a manner similar or equivalent to that described with reference to fig. 5D and/or fig. 5E.

The schedule may include any indication of the timing and/or frequency of transmission of the dedicated training signal, with sequence 1100b illustrating one example. As another example, the schedule may indicate that the first beamformee receiver 1120a will provide NDP in four initial consecutive time slots, after which the second beamformee receiver 1120b provides NDP in the next four consecutive time slots. As another example, the schedule may indicate that a first beamformee receiver 1120a will provide an NDP in one time slot, followed by a second beamformee receiver 1120b providing an NDP in the next time slot, followed by the first beamformee receiver 1120a, followed by the second beamformee receiver 1120 b. The scheduling may provide a balanced number of NDP transmissions across all target beamformed receivers, or may provide one beamformed receiver to transmit NDPs more frequently than another beamformed receiver.

As shown in fig. 11C, the sequence 1100C may initiate the requested sounding process by the first beamformer 1110a transmitting the NDP poll 1171. NDP poll 1171 may be similar or equivalent to NDP polls 1151 and/or 1161 of fig. 11A and 11B. The NDP poll 1171 may be received by the second beamformer 1110b and the first and second beamformed receivers 1120a/1120b as blocks 1172a, 1172b, and 1172c, respectively.

The NDP poll 1171 may include information indicating a bandwidth, frequency range, and/or a portion of the spatial stream within which the first and second beamformed receivers 1120a and 1120b are to transmit their respective NDPs 1173a and 1173 b. For example, the first and second beamformers 1110a/1110b may include uplink MU-MIMO capabilities as described with reference to fig. 5F such that different data may be received simultaneously from two or more MU-MIMO enabled beamforming receive ends (such as beamforming receive ends 1120a and 1120 b). Continuing with the example, the NDP poll 1171 may indicate a target spatial stream of the first beamformee 1120a and another target spatial stream of the second beamformee 1120b, such that the NDP 11173 a and the NDP 21173 b may be multiplexed and received simultaneously. In some embodiments, the NDP poll 1171 may operate as a temporal reference point for the first and second beamformed receivers 1120a/1120b such that the NDP 11173 a and NDP 21173 b may be transmitted in a coordinated manner.

In these and other implementations, both the first and second beamformers 1110a/1110b may receive the multiplexed NDP 1+2 as blocks 1174a, 1174b, respectively. The first and second beamformers 1110a/1110b may use dedicated training signals (e.g., NDP 11173 a and NDP 21173 b) to estimate forward channel characteristics.

As shown in fig. 11D, the sequence 1100D may initiate the requested sounding process by the first beamformer 1110a transmitting NDP poll-11181 a. NDP poll-11181A may be similar or equivalent to NDP polls 1151, 1161, and/or 1171 of FIGS. 11A-C. The NDP poll-11181 a may be received by the second beamformer 1110b and the first beamformed receive ends 1120a/1120b as blocks 1182a, 1182b, and 1182 c.

The NDP poll-11181 a may include scheduling information for the first beamformed receiver 1120a and the second beamformed receiver 1120B in a manner similar or equivalent to that shown in fig. 11B. Additionally or alternatively, NDP poll-11181 a may include information for other beamformers to listen to, such as the second beamformer 1110 b. For example, NDP poll-11181 a may establish a master-slave relationship between a first beamformer 1110a and a second beamformer 1110 b. In this relationship, the second beamformer 1110b may take certain actions or avoid certain actions based on instructions from the first beamformer 1110 a. In some embodiments, such messages may include a schedule indicating the frequency or trigger events on which the target beamformer will transmit additional sounding triggers. For example, as shown in fig. 11D, the second beamformer 1110b may transmit the second sounding trigger as an NDP poll-21181 b based on instructions included in the NDP poll-11181 a from the first beamformer 1110 a.

In some implementations, the first beamformer 1110a and the second beamformer 1110b may have a pre-existing relationship. For example, a developer/engineer may deploy both the first beamformer 1110a and the second beamformer 1110b in a mesh network or other network, where the first beamformer 1110a and the second beamformer 1110b may be aware of each other and/or communicate with each other. In these and other embodiments, a master-slave relationship may or may not be established prior to the transmission of NDP poll-11181 a. When aware of the second beamformer 1110b, the first beamformer 1110a may include explicit instructions for the second beamformer 1110b, such as informing the second beamformer 1110b that it is a slave to the first beamformer 1110a, a schedule for sending sounding triggers, and so on.

In some embodiments, the first beamformer 1110a may be unaware of the second beamformer 1110b prior to transmitting the NDP poll-11181 a. In these and other embodiments, NDP poll-11181 a may include instructions for any listening beamformer. For example, if the NDP poll-11181 a includes a schedule for another beamformer to send a second NDP poll at a given time, the first beamformer 1110a may wait until a timeout period after the given time has elapsed to observe whether another beamformer transmits an NDP poll. In such embodiments, even two unrelated beamformers may enjoy the benefit of reduced overhead using the claimed sounding method of the present disclosure.

For example, referring to fig. 11D, the first beamformer 1110a may transmit NDP poll-11181 a (received by the second beamformer 1110b and the first and second beamformed receive ends as blocks 1182a-c, respectively). In response, the first beamformed receiver 1120a may submit the NDPs 1-11183 a at a first time (received by the first beamformer 1110a and the second beamformer 1110b as blocks 1184a and 1184 b), and the second beamformed receiver 1120b may submit the NDPs 1-11185 a at a second time (received by the first beamformer 1110a and the second beamformer 1110b as blocks 1186a and 1186 b). The NDP poll-11181 a may include instructions for the second beamformer 1110b to transmit the NDP poll-21181 b at a given time (based on a pre-existing relationship, a relationship established via the NDP poll-11181 a, or based on including instructions for any listening beamformers). The first beamformer 1110a may receive the NDP poll-21181 b at a given time as block 1182d, and may therefore refrain from sending a second NDP poll as another beamformer (second beamformer 1110b) transmitting the NDP poll. In response to the NDP poll-21181 b (received by the first and second beamformers as 1182e and 1182 f), the first beamformer 1120a may submit the NDPs 1-21183 b at a third time (received by the first and second beamformers 1110a and 1110b as blocks 1184c and 1184 d), and the second beamformer 1120b may submit the NDPs 2-21185 b at a fourth time (received by the first and second beamformers 1110a and 1110b as blocks 1186c and 1186 d).

Using NDP 1-11184 a/1184b, the first beamformer 1110a and/or the second beamformer 1110b may estimate forward channel information for communication with the first beamformed receiver 1120 a. In addition, the forward channel information may be updated based on NDP 1-21184 c/1184 d. Using NDP 2-11186 a/1186b, the first beamformer 1110a and/or the second beamformer 1110b may estimate forward channel information for communication with the second beamformed receiver 1120 b. In addition, the forward channel information may be updated based on NDP 2-21186 c/1186 d.

Any of the sequences shown in fig. 11A-11D may be modified, added, or omitted. Furthermore, any of the sequences shown in fig. 5A-5G are equally applicable to embodiments where the second beamformer (or additional beamformers) is listening for a response and also estimating its own corresponding forward channel characteristics.

12-15 illustrate flow diagrams of an exemplary requested probing process according to an exemplary implementation. Fig. 12 shows an exemplary implementation of two beamformers performing the requested sounding process with a single beamformed receiver, where only the first beamformer transmits a sounding trigger. Fig. 13 illustrates an exemplary implementation in which the second beamformer (which does not transmit a sounding trigger) has no pre-existing relationship with the first beamformer (which transmits a sounding trigger). Fig. 14 illustrates an exemplary implementation in which the validity of the requested probing process is calibrated. Fig. 15 shows an exemplary implementation of two beamformers performing a requested sounding process with two beamformers, and where the first beamformer is the master on the second beamformer.

Returning to fig. 12, at block 1210, a sounding trigger may be broadcast by a first beamformer. For example, the wireless access point may send a probe trigger that identifies the wireless access point as one or more stations targeted to initiate the requested probe process. The probe trigger may or may not include instructions to the target station indicating when and/or how to send the response specific training signal. For example, the sounding trigger may indicate a target time slot and/or a target spatial stream in which the target station will transmit the dedicated training signal.

At block 1220, in response to the sounding trigger, a dedicated training signal may be broadcast by the beamformed receiving end. For example, the target station may respond with an NDP message. The NDP message may be sent according to instructions provided in the sounding trigger.

At block 1230, a dedicated training signal from a beamformed receive end may be received by a first beamformer. For example, the first beamformer may reserve a target time slot and/or a target spatial stream within which to instruct the beamforming receiver to transmit the dedicated training signal.

At block 1240, first channel characteristics for communication between the first beamformer and the beamformed receive end may be generated. For example, the first beamformer may use the dedicated training signals to estimate characteristics of a reverse channel from the beamforming receive end to the beamformer, and may use the characteristics of the reverse channel to estimate characteristics of a forward channel (e.g., a first channel) from the first beamformer to the beamforming receive end.

At block 1250, a sounding trigger broadcast by a first beamformer may be received at a second beamformer. The second beamformer may or may not have a pre-existing relationship with the first beamformer. The second beamformer may analyze and/or observe any instructions within the sounding trigger so that the second beamformer may know when and how any target beamformed receive end is to transmit the dedicated training signal. In addition, the second beamformer may analyze which beamforming receivers the sounding trigger targets, such that for beamforming receivers not applicable to the second beamformer, the second beamformer may not know and/or otherwise ignore dedicated training signals from such beamforming receivers.

In some embodiments, the sounding trigger may include information for the second beamformer. For example, the sounding trigger may include an instruction to establish a master-slave relationship between the first beamformer and the second beamformer.

At block 1260, the second beamformer may receive dedicated training from the beamformed receive end. For example, based on instructions in the sounding trigger received at block 1250, the second beamformer may reserve a time slot and/or spatial stream within which the beamformed receiver may be instructed to transmit the dedicated training signals.

At block 1270, second channel characteristics may be generated for communication between the second beamformer and the beamformed receive end. For example, the second beamformer may measure channel information of a dedicated training signal received via the reverse channel, calculate CSI of the reverse channel from the measured channel information, and derive forward CSI of the forward channel from the CSI of the reverse channel according to characteristics of the second beamformer (e.g., the number of transmit and receive chains, antennas, etc.). In these and other implementations, the second beamformer may use the estimate of the forward channel to determine a corresponding link matrix for adjusting forward channel precoding for subsequent transmission of user data to the beamformed receiving end.

At block 1280, a packet may be transmitted from the second beamformer to the precoded beamformed receiving end based on the second channel characteristics. For example, user data may be transmitted to the beamformed receiving end and precoded using the updated precoding of block 1270. In these and other embodiments, the first beamformer may also transmit packets to the beamformed receiving end using updated precoding of the requested sounding process according to the present disclosure. For example, the first beamformer may update its precoding based on the first channel characteristics generated at block 1240.

Returning to fig. 13, at block 1310, the opportunistic beamformer may opportunistically monitor probe triggers from the individual beamformers without coordination with the individual beamformers. For example, the opportunistic beamformer may be configured to monitor the detection triggers being transmitted by any other beamformer, and may analyze any such detection triggers received.

At block 1320, a sounding trigger broadcast by a separate beamformer may be observed. For example, a separate beamformer may transmit a detection trigger, and based on the monitoring, the detection trigger may be received and/or analyzed by an opportunistic beamformer. In some implementations, the opportunistic beamformer may observe the beamformers identified in the sounding trigger and may determine whether the identified beamformed receivers are in communication with or otherwise have some association with the opportunistic beamformer. Additionally or alternatively, the opportunistic beamformer may observe instructions to the beamforming receive end as to when and/or how to transmit the dedicated training signals.

At block 1330, a dedicated training signal may be received at an opportunistic beamformer from a beamformer, where the dedicated training signal may be sent in response to a sounding trigger of a separate beamformer. For example, based on instructions in the sounding trigger, the opportunistic beamformer may reserve a particular time window and/or spatial stream within which to transmit dedicated training signals.

At block 1340, channel characteristics for communicating with the beamformed receiving end may be generated based on the dedicated training signals. For example, the opportunistic beamformer may follow a process comparable or similar to the process described with reference to the second beamformer at block 1270.

Returning to fig. 14, at block 1410, after receiving a first dedicated training signal from a beamforming receiving end in response to an initial sounding trigger of an individual beamformer, a first channel estimate for communicating with the beamforming receiving end may be generated based on the first dedicated training signal. For example, a separate beamformer may send a sounding trigger for which the beamformee responds with a first dedicated training signal. The calibration beamformer may generate a first channel estimate of a forward channel between the calibration beamformer and the beamformed receive end based on the dedicated training signals in a manner similar or comparable to that described with reference to the second beamformer at block 1270.

At block 1420, a second dedicated training signal may be transmitted to the beamforming receive end. For example, the calibration beamformer may initiate the explicit sounding process by sending a second dedicated training signal to the beamforming receive end. In these and other embodiments, the second dedicated training signal may comprise a series of communications, such as NDPA frames, followed by NDPs.

At block 1430, feedback may be received from the beamforming receive end in response to the second dedicated training signal. For example, the beamforming receive end may perform some processing on the NDP received from the calibration beamformer (e.g., analyzing the training fields and computing the feedback matrix), and may send the feedback matrix in response.

At block 1440, the calibration beamformer may calibrate its beamforming for communicating with the beamformed receive end based on an analysis of the first channel estimate (based on the first dedicated training signal) and the second channel estimate (based on the received feedback). For example, the calibration beamformer may compare a first channel estimate based on a requested sounding procedure with a second channel estimate based on explicit sounding. The calibration beamformer may identify any differences and may use the differences between the two channel estimates to derive a correction factor or algorithm that may be applied to any additional channel estimates performed using the requested sounding process. Using such methods, the calibration beamformer can verify the accuracy of beamforming using the requested sounding process, and can provide corrections to improve such beamforming without using explicit sounding each time an update to precoding is needed. Rather, the requested probing process may be used with a single (or infrequent/periodic use) of explicit probing in order to calibrate the requested probing process.

Although an example of calibrating beamformers following an initial sounding trigger of a sounding process that does not send a request, it should be appreciated that beamformers sending sounding triggers may also apply the same calibration process represented by blocks 1420, 1430, and/or 1440.

Returning to fig. 15, at block 1505, a message may be transmitted from a first beamformer to a second beamformer to establish the first beamformer as a master. For example, the message may indicate one or more beamformers that will be subordinate to the first beamformer transmitting the message, the duration for which they will be subordinate, and so on. The message may also indicate a trigger event and/or schedule according to which the first beamformer and the second beamformer transmit sounding triggers.

At block 1510, a first sounding trigger may be broadcast from a first beamformer to a first beamformed receive end and a second beamformed receive end. For example, based on a first beamformer as a master, the first beamformer may transmit a first sounding trigger to initiate a requested sounding process with each of the first beamformer and a second beamformer. The first sounding trigger may identify each of the first beamformed receiver and the second beamformed receiver as a target of the sounding trigger. Additionally or alternatively, the first sounding trigger may identify each of the first beamformer and the second beamformer as a recipient seeking a dedicated training signal. In some embodiments, the message to establish the slave-master relationship of block 1505 may be included in the first probing trigger.

At block 1515, first and second dedicated training signals responsive to the first sounding trigger may be received at the first beamformer from the first and second beamforming receivers. For example, the dedicated training signals may be sent in consecutive time periods (such as shown in fig. 11B) or may be multiplexed (such as shown in fig. 11C).

At block 1520, first channel characteristics for communication between the first beamformer and the first beamformee (e.g., a forward channel from the first beamformer to the first beamformee) may be generated based on the first dedicated training signal. For example, the first beamformer may follow a process comparable or similar to the process described with reference to the second beamformer at block 1270.

At block 1525, second channel characteristics for communication between the first beamformer and the second beamformee (e.g., a forward channel from the first beamformer to the second beamformee) may be generated based on the second dedicated training signal. Block 1525 may be similar to or comparable to block 1520, but performed for the second channel characterization based on the second dedicated training signal.

At block 1530, a first detection trigger may be received by a second beamformer. For example, the first sounding trigger may inform the second beamformer that it is now slaved to the first beamformer. As another example, the first sounding trigger may include instructions regarding how and/or when the first beamforming receiver and the second beamforming receiver transmit respective dedicated training signals.

At block 1535, first and second dedicated training signals responsive to the first sounding trigger may also be received at the second beamformer from the first and second beamformed receive ends. For example, the second beamformer may reserve any time slots and/or spatial streams for the first dedicated training signal and the second dedicated training signal identified in the sounding trigger.

At block 1540, third channel characteristics for communication between the second beamformer and the first beamformee based on the first dedicated training signal (e.g., a forward channel from the second beamformer to the first beamformee) may be generated. Block 1540 may be similar to or comparable to block 1520, but is performed by the second beamformer for the third channel characteristic based on the first dedicated training signal.

At block 1545, fourth channel characteristics for communication between the second beamformer and the second beamformee (e.g., a forward channel from the second beamformer to the second beamformee) may be generated based on the second dedicated training signal. Block 1545 may be similar to or comparable to block 1520, but is performed for a fourth channel characteristic by the second beamformer based on the second dedicated training signal.

Some portions of the detailed description are presented in terms of algorithms and symbolic representations of operations within a computer. These algorithmic descriptions and symbolic representations are the means used by those skilled in the data processing arts to convey the substance of their innovation to others skilled in the art. An algorithm is a defined series of operations that produce a desired end state or result. In an exemplary implementation, the operations performed require a tangible number of physical manipulations to achieve a tangible result.

Unless specifically stated otherwise as apparent from the discussion, it is appreciated that throughout the description, discussions utilizing terms such as detecting, determining, analyzing, identifying, scanning, or the like, may include the action and processes of a computer system, or other information processing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other information storage, transmission or display devices.

Example implementations may also relate to an apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may comprise one or more general-purpose computers selectively activated or reconfigured by one or more computer programs.

Exemplary means may comprise a Wireless Access Point (WAP) or station and incorporate a Very Large Scale Integration (VLSI) processor and program code for support. The exemplary transceiver is coupled via an integrated modem to one of a cable, fiber optic, or digital subscriber backbone connection to the internet to support wireless communications, such as IEEE 802.11 compliant communications, over a Wireless Local Area Network (WLAN). The WiFi phase includes a baseband phase, as well as an Analog Front End (AFE) and Radio Frequency (RF) phases. In the baseband part, wireless communications transmitted to and received from each user/client/station are processed. The AFE and RF sections handle up-conversion on each transmit path of the wireless transmission initiated in baseband. The RF section also processes the down-conversion of signals received on the receive path and passes them to baseband for further processing.

The WAP and/or site may support multiple protocols and multi-language protocols capable of communicating with multiple protocols (e.g., internet of things protocols, including bluetooth low energy, Zigbee, threads, etc.) and communicatively coupled to one or more resources to access analytics or machine learning capabilities. In some implementations, the WAP and/or station is battery powered and mobile, or integrated into a larger mobile device such as an automobile or airplane.

An exemplary device may be a multiple-input multiple-output (MIMO) device that supports up to nxn discrete communication streams over N antennas. In an example, the MIMO device signal processing unit may be implemented as N × N. In various examples, the value of N may be 4, 6, 8, 12, 16, etc. Extended MIMO operation enables the use of up to 2N antennas communicating with another similarly equipped wireless system. It should be noted that an extended MIMO system may communicate with other wireless systems even if the system does not have the same number of antennas, but may not utilize some of the antennas of one of the stations, thereby reducing optimal performance.

In some implementations, the beamforming antenna configuration sounding discussed herein may be equally advantageously applied to WAPs or sites having any number of transmit chains, receive chains, or MIMO antennas, without departing from the disclosure, including but not limited to: 1 × 2, 1 × n, 2 × 3, 2 × 4, 2 × n, 3 × 4, 3 × n, 4 × 5, 4 × 8, 4 × n, 8 × 9, 8 × 16, 8 × n, and so forth. The components and processes disclosed herein may be implemented in a combination of software, circuitry, hardware, and firmware, integrated with existing transmit and receive path components of WAP without departing from the scope of the present disclosure.

An exemplary transmission path/chain includes the following discrete and shared components. The WiFi Media Access Control (WMAC) component comprises: a hardware queue for each downlink and uplink communication flow; encryption and decryption circuitry for encrypting and decrypting downlink traffic and uplink traffic; medium access circuitry for performing Clear Channel Assessment (CCA) and performing exponential random backoff and retransmission decisions; and packet processor circuitry for packet processing of the transmitted communication stream and the received communication stream. The WMAC component has access to a node table that lists each node/station on the WLAN, the station's capabilities, the corresponding encryption key, and the priority associated with its traffic.

Each probe or data packet for wireless transmission over the transmission path component to one or more stations is framed in a framer. Next, each stream is encoded and scrambled in an encoder and scrambler, and then demultiplexed into individual streams in a demultiplexer. The next stream is subjected to interleaving and mapping in a corresponding one of the interleaving mappers. Next, all transfers are space mapped using a Space Mapping Matrix (SMM) in the space mapper. The spatially mapped stream from the spatial mapper is input to an Inverse Discrete Fourier Transform (IDFT) component for conversion from the frequency domain to the time domain and subsequent transmission in the AFT and RF stages.

The IDFT is coupled to a corresponding one of the transmit paths/chain elements in the AFT RF stage for wireless transmission over an associated one of the MIMO antennas. In particular, each IDFT is coupled to an associated one of digital-to-analog converters (DACs) 550 for converting digital transmissions to analog, filters, up-converters, to a common Voltage Controlled Oscillator (VCO) for up-converting the transmission to the appropriate center frequency for the selected channel, and to power amplifiers for setting the transmission power level of the transmission on the MIMO antenna array.

The receive path/chain includes the following separate and shared components. During the AFE-RF phase, communications received on the MIMO antenna array of the WAP are RF processed, including downconversion. There are six receive paths, each including the following discrete and shared components: a Low Noise Amplifier (LNA) for amplifying the received signal under control of an Analog Gain Control (AGC) (not shown) for setting an amount by which the received signal is amplified; a down converter coupled to the VCO for down converting the received signal, a filter for band pass filtering the received signal, an analog to digital converter (ADC) for digitizing the down converted signal. In an exemplary implementation, an optional sampler 568 at the output of the ADC allows sampling of the received WiFi signal in the time domain for subsequent WiFi space diagnostics by the processor and non-volatile memory. The digital output from each ADC is passed to a corresponding one of the Discrete Fourier Transform (DFT) components in the baseband portion of the WiFi stage for conversion from the time domain to the frequency domain.

The receive processing in the baseband stage includes the following shared and discrete components, including: an equalizer for suppressing channel loss, the equalizer coupled to an output of the DFT. In an exemplary implementation, the WiFi signal received from the frequency domain with or without equalization at the output of the DFT is provided to a processor and non-volatile memory. The received WiFi streams at the output of the equalizer are subject to demapping and deinterleaving in a corresponding number of demappers and deinterleaving. Next, the received stream or streams are multiplexed in a multiplexer and decoded and descrambled in a decoder and descrambler section and then deframed in a deframer. The received communication is then passed to the WMAC component where it is decrypted with a decryption circuit and placed in the appropriate upstream hardware queue for uploading to the internet.

The non-transitory computer readable storage medium may refer to a tangible medium such as, but not limited to, optical disks, magnetic disks, read-only memories, random access memories, solid state devices and drives, or any other type of tangible or non-transitory medium suitable for storing electronic information. A computer readable signal medium may include a medium such as a carrier wave. The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. A computer program may refer to a pure software implementation involving instructions to perform operations of the desired implementation.

The computing device is communicatively coupled to an input/user interface and an output device/interface. One or both of the input/user interface and the output device/interface may be a wired or wireless interface, and may be detachable. The input/user interface may include any device, component, sensor, or interface, physical or virtual, that may be used to provide input (e.g., buttons, touch screen interfaces, keyboards, pointing/cursor controls, microphones, cameras, lettering, motion sensors, optical readers, etc.).

The term "communicatively connected" is intended to include any type of wired or wireless connection in which data may be communicated. The term "communicatively connected" is intended to include, but is not limited to, connections between devices and/or programs within a single computer, or between devices and/or individual computers over a network. The term "network" is intended to include, but is not limited to, packet-switched networks, such as Local Area Networks (LANs), Wide Area Networks (WANs), TCP/IP (Internet), and may use various transmission means, such as, but not limited to

Internet protocol version 6 over low power wireless area network (6LowPAN), Power Line Communication (PLC), ethernet (e.g., 10 megabytes (Mb), 100 megabytes (Mb), and/or 1 gigabyte (Gb) ethernet), or other communication protocols.

Furthermore, some example implementations of the present application may be performed solely in hardware, while other functions may be performed solely in software. Further, various functions described may be performed in a single unit or may be distributed across a plurality of components in any number of ways. When executed by software, the method may be performed by a processor, such as a general purpose computer, based on instructions stored on a computer-readable medium. The instructions may be stored on the media in a compressed and/or encrypted format, if desired.

The exemplary implementations may have various differences and advantages over the related art. In addition, other specific implementations of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the teachings herein. The various aspects and/or components of the exemplary implementations may be used alone or in any combination. It is intended that the specification and exemplary implementations be considered as examples only, with a true scope and spirit of the application being indicated by the following claims.

Claims (10)

1. A method, the method comprising:

receiving, by the second access point, a probe trigger broadcast by the first access point;

receiving, by the second access point, a first dedicated training signal from a first station in response to the probe trigger broadcast by the first access point; and

generating, by the second access point, channel characteristics for a channel based on the first dedicated training signal, the channel comprising a forward channel between the second access point and the first station.

2. The method of claim 1, further comprising transmitting a packet from the second access point to the first station over the channel, the packet being precoded using a precoding derived from the channel characteristics.

3. The method of claim 1, further comprising:

receiving, by the second access point, a second dedicated training signal from a second station in response to the probe trigger broadcast by the first access point; and

generating, by the second access point, second channel characteristics for a second channel based on the second dedicated training signal, the second channel comprising a second forward channel between the second access point and the second station.

4. The method of claim 3, wherein the first dedicated training signal and the second dedicated training signal are multiplexed and at least partially overlap in time based on information in the sounding trigger.

5. The method of claim 3, wherein the first and second dedicated training signals are received in a chronological order based on information in the sounding trigger.

6. The method of claim 1, further comprising receiving a message from the first access point to the second access point, the message establishing a master-slave relationship between the first access point and the second access point such that the first access point but not the second access point transmits the probing trigger.

7. The method of claim 6, wherein the message is included in the probing trigger.

8. The method of claim 1, wherein the probe trigger is received by the second access point while opportunistically monitoring for a trigger without coordination with the first access point.

9. An access point, comprising:

one or more processors; and

one or more non-transitory computer-readable media containing instructions that, when executed by the one or more processors, are configured to cause the access point to perform operations comprising:

opportunistically monitoring a probe trigger from an individual access point without coordinating with the individual wireless access point;

observing the sounding trigger from the individual access point;

receiving, from a first station, a first dedicated training signal generated in response to the probe trigger; and

generating first channel characteristics for a first channel based on the first dedicated training signal, the first channel comprising communications between the access point and the first station.

10. The access point of claim 9, wherein the operations further comprise:

receiving a second dedicated training signal from a second station in response to the probing trigger; and

generating second channel characteristics for a second channel based on the second dedicated training signal, the second channel comprising communications between the access point and the second station.

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