Beam search procedure for multiple spatial streams

Abstract

The present disclosure provides methods, components, devices, and systems for a beam search procedure for multiple spatial streams. Some aspects more specifically relate to a beamforming training procedure for multiple spatial streams. The beamforming training procedure can provide beam separation between beams during the training procedure to prevent selection of beams that result in inter-stream interference. In some examples, the multi-stream beamforming training procedure described herein can provide beam separation using antenna polarization. For example, different radio frequency (RF) chains can use different antenna polarizations. Additionally or alternatively, the multi-stream beamforming training procedure can provide beam separation by antenna orientation, with different RF chains using mutually exclusive beam search regions. Additionally or alternatively, a responding wireless communication device can select beamforming directions for spatial streams iteratively or one at a time, and an initiating wireless communication device can perform an additional beam search excluding directions within a beam width of previously selected beams.

Description

[0001] Cross-referencing

[0002] This patent application claims priority to U.S. Patent Application No. 18 / 768,429, filed July 10, 2024, entitled “BEAM SEARCH PROCEDURES FOR MULTIPLE SPATIAL STREAMS,” and U.S. Provisional Patent Application No. 63 / 619,940, filed January 11, 2024, entitled “BEAMSEARCH PROCEDURES FOR MULTIPLE SPATIAL STREAMS,” each of which is assigned to the assignee of this application, and the entire contents of each of which are expressly incorporated herein by reference. Technical Field

[0003] This disclosure relates generally to wireless communication, and more specifically to beam search procedures for multiple spatial streams.

[0004] Related technical descriptions

[0005] A Wireless Local Area Network (WLAN) can be formed by one or more wireless access points (APs) that provide a shared wireless communication medium for use by multiple client devices (also known as wireless stations (STAs)). The basic building block of a WLAN conforming to the IEEE 802.11 standard family is the Basic Service Set (BSS) managed by the AP. Each BSS is identified by a Basic Service Set Identifier (BSSID) advertised by the AP. The AP periodically broadcasts beacon frames to enable any STA within the AP's wireless range to establish or maintain a communication link with the WLAN.

[0006] In some WLANs, the STA can use the millimeter-wave RF spectrum band for communication to increase data signaling throughput. The STA can communicate using a lower-frequency anchor spectrum band (compared to the millimeter-wave RF spectrum band) used for control and BSS signaling, and use the millimeter-wave RF spectrum band as a data pipeline. In some examples, the STA can use multiple spatial flows to communicate with the AP in the WLAN via the millimeter-wave RF spectrum band. The STA can perform a multi-flow beamforming training process to identify the corresponding beamforming direction for each spatial flow. However, if the multi-flow beamforming training process selects similar beamforming directions for multiple spatial flows, inter-flow interference may occur. Summary of the Invention

[0007] The systems, methods, and apparatus disclosed herein each have some innovative aspects, and no single aspect is solely responsible for the desired properties disclosed herein.

[0008] One aspect of the subject matter described in this disclosure can be implemented in a method for wireless communication by a first wireless communication device. The method may include: receiving a beam search trigger for a second link in a second RF band via a first link in a first RF band; receiving, according to the beam search trigger, a set of multiple training signals via the second link through a set of multiple receive RF chains of the first wireless communication device from a set of multiple transmit RF chains of the second wireless communication device; selecting an RF chain pair for each spatial stream in a set of spatial streams based on the set of multiple training signals, wherein each RF chain pair includes a receive RF chain from the set of multiple receive RF chains and a transmit RF chain from the set of multiple transmit RF chains; and selecting a beamforming direction for each spatial stream in the set of spatial streams based on the set of multiple training signals.

[0009] Another aspect of the subject matter described in this disclosure can be implemented in a first wireless communication device for wireless communication. The first wireless communication device may include a processing system comprising processor circuitry and memory circuitry storing code. The processing system may be configured to cause the first wireless communication device to: receive a beam search trigger for a second link in a second RF band via a first link in a first RF band; receive, according to the beam search trigger, a set of multiple training signals via the second link through a set of multiple receive RF chains of the first wireless communication device from a set of multiple transmit RF chains of the second wireless communication device; select a pair of RF chains for each spatial stream in the set of spatial streams based on the set of multiple training signals, wherein each RF chain pair includes a receive RF chain in the set of multiple receive RF chains and a transmit RF chain in the set of multiple transmit RF chains; and select a beamforming direction for each spatial stream in the set of spatial streams based on the set of multiple training signals.

[0010] Another aspect of the subject matter described in this disclosure can be implemented in a first wireless communication device for wireless communication. The first wireless communication device may include: means for receiving a beam search trigger for a second link in a second RF band via a first link in a first RF band; means for receiving a set of multiple training signals from a set of multiple transmit RF chains of a second wireless communication device via the second link through a set of multiple receive RF chains of the first wireless communication device, based on the beam search trigger; means for selecting an RF chain pair for each spatial stream in the set of spatial streams based on the set of multiple training signals, wherein each RF chain pair includes a receive RF chain in the set of multiple receive RF chains and a transmit RF chain in the set of multiple transmit RF chains; and means for selecting a beamforming direction for each spatial stream in the set of spatial streams based on the set of multiple training signals.

[0011] Another aspect of the subject matter described in this disclosure can be implemented in a non-transitory computer-readable medium storing code for wireless communication. The code may include instructions executable by one or more processors to: receive a beam search trigger for a second link in a second RF band via a first link in a first RF band; receive, according to the beam search trigger, a set of multiple training signals via the second link through a set of multiple receive RF chains of the first wireless communication device from a set of multiple transmit RF chains of the second wireless communication device; select an RF chain pair for each spatial stream in the set of spatial streams based on the set of multiple training signals, wherein each RF chain pair includes a receive RF chain in the set of multiple receive RF chains and a transmit RF chain in the set of multiple transmit RF chains; and select a beamforming direction for each spatial stream in the set of spatial streams based on the set of multiple training signals.

[0012] Another aspect of the subject matter described in this disclosure can be implemented in a method for wireless communication by a first wireless communication device. The method may include: transmitting a beam search trigger for a second link in a second radiative spectrum via a first link in a first radiative spectrum; transmitting a set of multiple training signals via the second link to a set of multiple receive radiative chains of a second wireless communication device via a set of multiple transmit radiative chains of the first wireless communication device; and receiving a feedback message indicating a pair of radiative chains for each spatial stream in the set of spatial streams and a beamforming direction for each spatial stream in the set of spatial streams.

[0013] Another aspect of the subject matter described in this disclosure can be implemented in a first wireless communication device for wireless communication. The first wireless communication device may include a processing system comprising processor circuitry and memory circuitry storing code. The processing system may be configured to cause the first wireless communication device to: transmit a beam search trigger for a second link in a second radiative spectrum via a first link in a first radiative spectrum; transmit a set of multiple training signals via the second link through a set of multiple transmit RF chains of the first wireless communication device to a set of multiple receive RF chains of the second wireless communication device, according to the beam search trigger; and receive a feedback message indicating a pair of RF chains for each spatial stream in the set of spatial streams and a beamforming direction for each spatial stream in the set of spatial streams.

[0014] Another aspect of the subject matter described in this disclosure can be implemented in a first wireless communication device for wireless communication. The first wireless communication device may include: means for transmitting a beam search trigger for a second link in a second radiative spectrum via a first link in a first radiative spectrum; means for transmitting a set of multiple training signals via the second link through a set of multiple transmit RF chains of the first wireless communication device to a set of multiple receive RF chains of the second wireless communication device according to the beam search trigger; and means for receiving a feedback message indicating a pair of RF chains for each spatial stream in the set of spatial streams and a beamforming direction for each spatial stream in the set of spatial streams.

[0015] Another aspect of the subject matter described in this disclosure may be implemented in a non-transitory computer-readable medium storing code for wireless communication. The code may include instructions executable by one or more processors to: transmit a beam search trigger for a second link in a second radiative spectrum via a first link in a first radiative spectrum; transmit a set of multiple training signals via the second link to a set of multiple receive radiative chains of a second wireless communication device via a set of multiple transmit radiative chains of the first wireless communication device, according to the beam search trigger; and receive a feedback message indicating a pair of radiative chains for each spatial stream in the set of spatial streams and a beamforming direction for each spatial stream in the set of spatial streams.

[0016] Details of one or more specific embodiments of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, drawings, and claims. It should be noted that the relative dimensions in the following drawings may not be drawn to scale. Attached Figure Description

[0017] Figure 1 shows a schematic diagram of an example wireless communication network.

[0018] Figure 2 shows an example Protocol Data Unit (PDU) that can be used for communication between a wireless access point (AP) and one or more wireless stations (STA).

[0019] Figure 3 shows an example physical layer (PHY) protocol data unit (PPDU) that can be used for communication between a wireless AP and one or more wireless STAs.

[0020] Figure 4 shows a hierarchical format of an example PPDU that can be used for communication between a wireless AP and one or more wireless STAs.

[0021] Figure 5 shows an example of a signaling diagram that supports a beam search process for multiple spatial streams.

[0022] Figure 6 shows an example of multi-stream beamforming training that supports beam search processes for multiple spatial streams.

[0023] Figure 7 shows an example of multi-stream beamforming training that supports beam search processes for multiple spatial streams.

[0024] Figure 8 shows an example of the process flow that supports beam search for multiple spatial streams.

[0025] Figure 9 shows a block diagram of an example wireless communication device that supports a beam search process for multiple spatial streams.

[0026] Figure 10 A block diagram of an example wireless communication device supporting a beam search process for multiple spatial streams is shown.

[0027] Figure 11 and Figure 12 A flowchart illustrating an example process that can be executed by or at a first wireless communication device that supports beam search procedures for multiple spatial streams is shown.

[0028] The same reference numerals and names in different figures denote the same elements. Detailed Implementation

[0029] The following description refers to certain specific examples in order to illustrate the innovative aspects of this disclosure. However, those skilled in the art will readily recognize that the teachings herein can be applied in a variety of different ways. Some or all of the examples described can be applied in accordance with the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, the IEEE 802.15 standard, or Bluetooth as defined by the Bluetooth Special Interest Group (SIG). ®This can be implemented in any device, system, or network that transmits and receives radio frequency (RF) signals according to one or more of the standards or those published by the 3rd Generation Partnership Project (3GPP), such as Long Term Evolution (LTE), 3G, 4G, 5G (New Radio (NR)), or 6G. The described examples can be implemented in any suitable device, component, system, or network capable of transmitting and receiving RF signals according to one or more of the following technologies or techniques: Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiplexing (OFDM), Frequency Division Multiple Access (FDMA), Orthogonal FDMA (OFDMA), Single Carrier FDMA (SC-FDMA), Space Division Multiple Access (SDMA), Rate Split Multiple Access (RSMA), Multi-User Shared Access (MUSA), Single-User (SU) Multiple-Input Multiple-Output (MIMO), and Multi-User (MU)-MIMO (MU-MIMO). The described examples can also be implemented using other wireless communication protocols or RF signals suitable for use in one or more of the following: Wireless Personal Area Network (WPAN), Wireless Local Area Network (WLAN), Wireless Wide Area Network (WWAN), Wireless Metropolitan Area Network (WMAN), Non-Terrestrial Network (NTN), or Internet of Things (IoT) networks.

[0030] Wireless communication devices can establish communication links across multiple RF spectrum bands. For example, a radio station (STA) can communicate control and basic service set (BSS) information with an access point (AP) on a first communication link (such as in the anchor spectrum band), and the STA can communicate data signaling on a second communication link in a higher-frequency RF spectrum band. In some examples, the STA can use multiple spatial streams for the second communication link. The STA and AP can perform a multi-stream beamforming process to identify beam pairs and RF chain pairs for each spatial stream. For example, the STA can select an RF chain pair for each spatial stream, including the AP's transmit RF chain and the STA's receive RF chain. The STA can also select a beamforming direction for each spatial stream. Using multiple spatial streams for the second communication link can provide higher data rates and increased throughput compared to using a single spatial stream; however, if the beamforming directions selected for the spatial streams are too similar or overlap, using multiple spatial streams can lead to inter-stream interference or cross-stream interference.

[0031] Various aspects as a whole relate to multi-stream beamforming training on links in the high-frequency band. Some aspects more specifically relate to a multi-stream beamforming training process that provides sufficient beam separation for conveying multiple spatial streams using multiple corresponding beams. In some examples, the multi-stream beamforming training process may utilize different antenna polarizations and / or different antenna orientations. For example, different RF chains may use different antenna polarizations. A first RF transmission chain at the initiating wireless communication device (such as an AP) may transmit using a first polarization (such as horizontal polarization), and a second RF transmission chain at the initiating wireless communication device may transmit using a second polarization (such as vertical polarization). Alternatively, different RF chains may be connected to antennas with different orientations, thus resulting in mutually exclusive corresponding beam search areas. For example, the first transmission RF chain of the AP may be oriented to transmit training signals on a first set of directions, and the second transmission RF chain of the AP may be oriented to transmit training signals on a second set of directions that do not overlap with the first set of directions. Because of the use of opposite polarization or mutually exclusive beam search regions, the first and second transmit RF chains can be scanned concurrently (e.g., at least partially overlapping or simultaneously) in all possible transmit beam directions. The responding wireless communication device (such as a STA) can record measurements for multiple combinations of RF chain pairs. The responding wireless communication device can then select a first RF chain pair for a first spatial flow and a second RF chain pair for a second spatial flow, and can further select a corresponding beam direction for beamforming each of the first and second spatial flows. Additionally or alternatively, the responding wireless communication device can iteratively select beamforming directions for the spatial flows, and the initiating wireless communication device can perform additional beam searches excluding directions within a certain amount (such as beamwidth) of the previously selected beam. For example, the initiating wireless communication device can use the first transmit RF chain to transmit a first set of training signals in all beamforming directions. The responding wireless communication device can use the first receive RF chain to receive the first set of training signals and select a first beamforming direction for the first spatial flow between the first transmit RF chain and the first receive RF chain based on measurements of the first set of training signals. The responding wireless communication device can indicate a first beamforming direction of the first spatial flow to the initiating wireless communication device. The initiating wireless communication device can then use a second transmit RF chain on a subset of all beamforming directions to transmit a second set of training signals, this subset excluding beamforming directions within the beamwidth of the first beamforming direction. The responding wireless communication device can use a second receive RF chain to receive the second set of training signals and select a second beamforming direction for the second spatial flow between the second transmit RF chain and the second receive RF chain.Because the training signal is transmitted in a second set of beamforming directions that do not overlap with the first beamforming direction of the first spatial flow, the first beamforming direction and the second beamforming direction may not overlap or may not cause inter-flow interference between the first spatial flow and the second spatial flow.

[0032] Specific aspects of the subject matter described in this disclosure can be implemented to achieve one or more of the following potential advantages. In some examples, the described techniques reduce inter-stream interference when multiple spatial streams are used for a communication link by using orthogonal or separated beams during a multi-stream beam search process. Reducing inter-stream interference as described herein can increase the signal-to-interference-plus-noise ratio (SINR) and the number of effective channel paths, which can improve channel capacity due to improved beam selection during the multi-stream beam search process and the resulting beam separation. In some examples, since the initiating wireless communication device can simultaneously transmit training signals using orthogonal spatial beams from multiple transmit RF chains, performing a beam training process with beam separation can improve the beam training rate by enabling both the initiating and responding wireless communication devices to perform beam training for multiple spatial streams simultaneously and without inter-stream interference. In some examples, beam separation during the beam training process can prevent the STA from selecting overlapping beamforming directions for the beam, thereby reducing inter-stream interference and improving signal quality. For example, by using different polarizations for different spatial streams, signaling from the first spatial stream can be orthogonal to signaling from the second spatial stream, which can reduce the interference of signaling from the first spatial stream to signaling from the second spatial stream.

[0033] Figure 1 illustrates a schematic diagram of an example wireless communication network 100. Depending on some aspects, the wireless communication network 100 may be an example of a wireless local area network (WLAN) (such as a Wi-Fi network). For example, the wireless communication network 100 may be a network implementing at least one of the IEEE 802.11 wireless communication protocol standard families (such as those defined by the IEEE 802.11-2020 specification or its revisions, including but not limited to 802.11ay, 802.11ax, 802.11az, 802.11ba, 802.11bc, 802.11bd, 802.11be, 802.11bf, and 802.11bn). In some other examples, the wireless communication network 100 may be an example of a cellular radio access network (RAN), such as a 5G RAN or 6G RAN implementing one or more cellular protocols (such as those specified in one or more 3GPP standards). In some other examples, the wireless communication network 100 may include a WLAN that operates in a manner interoperable with or converged with one or more cellular RANs to provide greater or enhanced network coverage to wireless communication devices within the wireless communication network 100, or to enable these devices to connect to the core of the cellular network, such as accessing network management capabilities and functionality provided by the cellular network core. In some other examples, the wireless communication network 100 may include a WLAN that operates in a manner interoperable with or converged with one or more personal area networks (PANs), such as networks implementing Bluetooth or other wireless technologies, to provide greater or enhanced network coverage or to provide or implement other capabilities, functionality, applications, or services.

[0034] Wireless communication network 100 may include numerous wireless communication devices, such as at least one wireless access point (AP) 102 and any number of wireless stations (STA) 104. Although only one AP 102 is shown in Figure 1, wireless communication network 100 may include multiple APs 102. AP 102 may be or represent various different types of network entities, including but not limited to home networking APs, enterprise APs, single-band APs, dual-band synchronous (DBS) APs, tri-band synchronous (TBS) APs, standalone APs, non-standalone APs, software-enabled APs (software APs), and multi-link APs (also known as AP multi-link devices (MLDs)), as well as cellular (such as 3GPP, 4G LTE, 5G, or 6G) base stations or other cellular network nodes (such as Node B, evolved Node B (eNB), gNB, Transmitter Receiver Point (TRP)) or another type of equipment or apparatus included in a radio access network (RAN), including open RAN (O-RAN) network entities such as central units (CUs), distributed units (DUs), or radio units (RUs).

[0035] Each STA in STA 104 may also be referred to as a mobile station (MS), mobile device, mobile phone, wireless phone, access terminal (AT), user equipment (UE), subscriber station (SS), or subscriber unit, etc. STA 104 can represent a variety of devices such as mobile phones, other handheld or wearable communication devices, netbooks, laptops, tablets, laptops, Chromebooks, augmented reality (AR), virtual reality (VR), mixed reality (MR), or extended reality (XR) wireless headsets or other peripherals, wireless earbuds, other wearable devices, display devices (such as TVs, computer monitors, or video game consoles), video game controllers, navigation systems, music or other audio or stereo devices, remote control devices, printers, kitchen appliances (including smart refrigerators) or other home appliances, remote keys (such as those for passive keyless entry and start (PKES) systems), Internet of Things (IoT) devices, and vehicles, etc.

[0036] A single AP 102 and its associated set of STAs 104 may be referred to as a BSS, which is managed by the respective AP 102. Figure 1 additionally illustrates an example coverage area 108 of AP 102, which may represent the Basic Service Area (BSA) of the wireless communication network 100. The BSS can be identified by STAs 104 and other devices through a Service Set Identifier (SSID) and a Basic Service Set Identifier (BSSID), which may be the Media Access Control (MAC) address of AP 102. AP 102 may periodically broadcast beacon frames (“beacons”) including the BSSID to enable any STA 104 within the wireless range of AP 102 to “associate” or reassociate with AP 102 to establish a corresponding communication link 106 (also referred to hereinafter as a “Wi-Fi link”) with AP 102 or maintain a communication link 106 with that AP. For example, the beacon may include an identifier of the primary channel used by the corresponding AP 102 or an indication of that primary channel, as well as a timing synchronization function (TSF) for establishing or maintaining timing synchronization with the AP 102. The AP 102 may provide access to external networks to each STA 104 in the wireless communication network 100 via the corresponding communication link 106.

[0037] To establish a communication link 106 with AP 102, each STA 104 is configured to perform passive or active scanning operations (“scans”) on frequency channels in one or more frequency bands (such as 2.4 GHz, 5 GHz, 6 GHz, 45 GHz, or 60 GHz bands). To perform a passive scan, STA 104 listens for beacons transmitted by the corresponding AP 102 at periodic time intervals (referred to as the Target Beacon Transmission Time (TBTT)). To perform an active scan, STA 104 generates probe requests and transmits these requests sequentially on each channel to be scanned, and listens for probe responses from AP 102. Each STA 104 can identify, determine, detect, or select an AP 102 to associate with based on the scanning information obtained through passive or active scanning, and performs authentication and association operations to establish a communication link 106 with the selected AP 102. The selected AP 102 assigns an association identifier (AID) to STA 104 at the end of the association operation, and AP 102 uses the association identifier (AID) to track STA 104.

[0038] As wireless networks become increasingly prevalent, STA 104 may have the opportunity to choose from one of many BSSs within its range or from multiple APs 102 that together form an Extended Service Set (ESS) (comprising multiple connected BSSs). For example, wireless communication network 100 may be connected to a wired or wireless distribution system capable of connecting multiple APs 102 in such an ESS. Therefore, STA 104 may be covered by more than one AP 102 and may be associated with different APs 102 at different times for different transmissions. Additionally, after associating with an AP 102, STA 104 may periodically scan its surroundings to find a more suitable AP 102 to associate with. For example, STA 104 moving relative to its associated AP 102 may perform a “roaming” scan to find another AP 102 with more desirable network characteristics, such as a larger Received Signal Strength Indicator (RSSI) or reduced traffic load.

[0039] STA 104 can form a network that does not have AP 102 or any other equipment besides STA 104 itself. An example of such a network is an ad hoc network (or wireless ad hoc network). Ad hoc networks may also be referred to as mesh networks or peer-to-peer (P2P) networks. In some examples, ad hoc networks can be implemented within a larger network, such as wireless communication network 100. In such examples, while STA 104 may be able to communicate with each other via communication link 106 through AP 102, STA 104 can also communicate directly with each other via direct wireless communication link 110. Additionally, two STA 104 can communicate via direct wireless communication link 110, regardless of whether the two STA 104 are associated with and served by the same AP 102. In such ad hoc systems, one or more STAs among STA 104 can assume the role played by AP 102 in the BSS. Such STA 104 can be referred to as the group owner (GO) and can coordinate transmissions within the ad hoc network. Examples of direct wireless communication links 110 include Wi-Fi direct connections, connections established by using Wi-Fi Tunneling Direct Link Establishment (TDLS) links, and other P2P group connections.

[0040] In some networks, AP 102 or STA 104, or both, can support applications associated with high throughput or low latency requirements, or provide lossless audio to one or more other devices. For example, AP 102 or STA 104 can support applications and use cases associated with ultra-low latency (ULL), such as ULL gaming, or streaming lossless audio and video to one or more personal audio devices (such as peripherals) or AR / VR / MR / XR headsets. In scenarios where a user uses two or more peripherals, AP 102 or STA 104 can support extended personal audio networks that enable communication with these two or more peripherals. Additionally, AP 102 and STA 104 can support additional ULL applications with ULL and high throughput requirements, such as cloud-based applications (such as VR cloud gaming).

[0041] As indicated above, in some implementations, AP 102 and STA 104 may operate and communicate according to one or more of the IEEE 802.11 wireless communication protocol family of standards (via the corresponding communication link 106). These standards define WLAN radio and baseband protocols for the physical (PHY) layer and MAC layer. AP 102 and STA 104 transmit and receive wireless communications to and from each other in the form of PHY Protocol Data Units (PPDUs) (also referred to below as "Wi-Fi communication" or "wireless packets").

[0042] Each PPDU is a composite structure comprising a PHY preamble and a payload in the form of a PHY Service Data Unit (PSDU). The information provided in the preamble can be used by the receiving device to decode subsequent data in the PSDU. In instances where the PPDU is transmitted on a bound channel or a wideband channel, the preamble field may be copied and transmitted in each of the multiple component channels. The PHY preamble may include both a legacy portion (or "legacy preamble") and a non-legacy portion (or "non-legacy preamble"). The legacy preamble can be used for other purposes such as packet detection, automatic gain control, and channel estimation. The legacy preamble is also typically used to maintain compatibility with legacy equipment. The format, decoding, and information provided in the non-legacy portion of the preamble are associated with the specific IEEE 802.11 wireless communication protocol to be used to transmit the payload.

[0043] AP 102 and STA 104 in wireless communication network 100 can transmit PPDUs on unlicensed spectrum, which may be a portion of the spectrum including bands traditionally used by Wi-Fi technologies, such as the 2.4 GHz band, 5 GHz band, 6 GHz band, 45 GHz band, and 60 GHz band. Some examples of AP 102 and STA 104 described herein can also communicate in other bands that can support both licensed and unlicensed communication. For example, AP 102 or STA 104, or both, may also be able to communicate on licensed operating bands, where multiple operators may have corresponding licenses to operate in the same or overlapping frequency ranges. Such licensed operating bands may be mapped to or associated with the following frequency ranges: FR1 (410MHz–7.125GHz), FR2 (24.25GHz–52.6GHz), FR3 (7.125GHz–24.25GHz), FR4a or FR4–1 (52.6GHz–71GHz), FR4 (52.6GHz–114.25GHz), and FR5 (114.25GHz–300GHz).

[0044] Each of these frequency bands may include multiple subbands and frequency channels (also referred to as subchannels). For example, PPDUs conforming to revisions of the IEEE 802.11n, 802.11ac, 802.11ax, 802.11be, and 802.11bn standards may be transmitted on one or more of the 2.4 GHz, 5 GHz, or 6 GHz frequency bands, each of which is divided into multiple 20 MHz channels. Therefore, these PPDUs are transmitted on physical channels with a minimum bandwidth of 20 MHz, but larger channels can be formed through channel bonding. For example, PPDUs may be transmitted on physical channels with bandwidths of 40 MHz, 80 MHz, 160 MHz, 240 MHz, 320 MHz, 480 MHz, or 640 MHz by bonding multiple 20 MHz channels together.

[0045] AP 102 can determine or select the operational or operational bandwidth for STA 104 in its BSS, and select a series of channels within the band to provide that operational bandwidth. For example, AP 102 can select sixteen 20MHz channels that collectively span an operational bandwidth of 320MHz. Within the operational bandwidth, AP 102 typically selects a single primary 20MHz channel on which AP 102 and STA 104 in its BSS monitor contention-based access schemes. In some examples, AP 102 or STA 104 may be able to monitor only a single primary 20MHz channel for packet detection (e.g., for detecting the preamble of a PPDU). Conventionally, any transmission made by AP 102 or STA 104 within the BSS must involve transmission on the primary 20MHz channel. Therefore, in a conventional system, the transmitting device must contend for and win the TXOP on the primary channel to fully transmit anything. However, some APs 102 and STAs 104 that support Ultra-High Reliability (UHR) communication or communication according to the IEEE 802.11bn standard revision can be configured to operate, monitor, contend, and communicate using multiple primary 20MHz channels. This monitoring of multiple primary 20MHz channels can be sequential, such that in response to determining, detecting, or identifying that a first primary 20MHz channel is unavailable, the wireless communication device can switch to monitoring and contending using a second primary 20MHz channel. Additionally or alternatively, the wireless communication device can be configured to monitor multiple primary 20MHz channels in parallel. In some examples, the first primary 20MHz channel may be referred to as the main primary (M-primary) channel, and one or more additional secondary primary channels may each be referred to as the opportunistic primary (O-primary) channel. For example, if the wireless communication device measures, identifies, detects, or otherwise determines that the M-primary channel is busy or occupied (e.g., due to overlapping BSS (OBSS) transmissions), the wireless communication device can switch to monitoring and contending on the O-primary channel. In some examples, the M primary channel can be used for beacon transmission and to serve legacy client equipment, while the O primary channel can be used by non-legacy (e.g., UHR or IEEE 802.11bn compatible) equipment for opportunistic access to spectrum that may otherwise be underutilized.

[0046] Furthermore, as described herein, the terms "channel" and "subchannel" are used interchangeably, and each term can refer to a portion of the spectrum through which communication between two or more wireless communication devices can occur. For example, a channel or subchannel can refer to a discrete portion (such as a discrete amount, span, range, or subset) of the frequency of the operating bandwidth. A channel or subchannel can refer to a 20MHz portion, a 40MHz portion, an 80MHz portion, or a 160MHz portion, etc. In other words, a channel or subchannel may include one or more 20MHz channels. A primary channel or subchannel can be understood as a portion of the spectrum that includes the primary 20MHz used for beacon transmission and other (management) frame transmissions. A secondary channel or secondary subchannel can be understood as a portion of the spectrum excluding the primary 20MHz (or at least excluding the main primary (M-primary) channel). In some systems, a secondary channel or secondary subchannel may include an opportunistic primary (O-primary) channel. Wireless communication devices may use an M-master channel (such as M-master 20MHz) for beacon transmission and / or service to legacy clients, and may use an O-master channel (such as O-master 20MHz) for opportunistic access on one or more other channels (such as when the M-master channel is busy or occupied).

[0047] In some aspects, different portions of the spectrum (such as a 40MHz portion, an 80MHz portion, or a 160MHz portion) may be associated with multiple (20MHz) sub-channels and at least one anchor channel. In such aspects, the anchor channel may define, indicate, or identify the lowest (20MHz) sub-channel within a given portion of the spectrum. For example, a first anchor channel may define, indicate, or identify the lowest 20MHz sub-channel within a secondary 40MHz bandwidth, a second anchor channel may define, indicate, or identify the lowest 20MHz sub-channel within a secondary 80MHz bandwidth, and a third anchor channel may define, indicate, or identify the lowest 20MHz sub-channel within a secondary 160MHz bandwidth. In some aspects, wireless communication devices may use the anchor channel as a primary channel.

[0048] In some examples, the AP 102 or STA 104 of the wireless communication network 100 can achieve extremely high throughput (EHT) or other features conforming to current and future generations of the IEEE 802.11 wireless communication protocol family of standards, such as the IEEE 802.11be and 802.11bn revisions, to provide additional capabilities superior to other previous systems, such as high-efficiency (HE) systems or other legacy systems. For example, the IEEE 802.11be revision introduced a 320MHz channel, which is twice the width of the channel achievable by the IEEE 802.11ax revision. Therefore, the AP 102 or STA 104 can use the 320MHz channel to achieve twice the throughput and network capacity, as well as rate and range gains at high data rates due to the trade-off between linear bandwidth and logarithmic SNR. EHT and newer wireless communication protocols (such as those known as the IEEE 802.11bn standard revision or related protocols) support flexible operating bandwidth enhancements, such as broadened operating bandwidths or finer-grained operation relative to older operating bandwidths. For example, EHT systems can allow communication across operating bandwidths of 20 MHz, 40 MHz, 80 MHz, 160 MHz, 240 MHz, and 320 MHz. EHT systems can support various bandwidth modes, such as a continuous 240 MHz bandwidth mode, a continuous 320 MHz bandwidth mode, a non-contiguous 160+160 MHz bandwidth mode, or a non-contiguous 80+80+80+80 (or "4x80") MHz bandwidth mode.

[0049] In some examples where the wireless communication device (such as AP 102 or STA 104) operates in a continuous 320MHz bandwidth mode or a 160+160MHz bandwidth mode, the signal used for transmission may be generated by two different transmit chains of the wireless communication device, each with or associated with a 160MHz bandwidth (and each transmit chain coupled to a different power amplifier). In some other examples, two transmit chains can be used to support a 240MHz / 160+80MHz bandwidth mode by puncturing the 320MHz / 160+160MHz bandwidth mode with one or more 80MHz sub-channels. For example, the signal used for transmission may be generated by two different transmit chains of the wireless communication device, each with a 160MHz bandwidth, one of which outputs a signal with 80MHz sub-channels punctured within it. In some other examples where the wireless communication device can operate in a continuous 240MHz bandwidth mode or a non-continuous 160+80MHz bandwidth mode, the signal used for transmission may be generated by three different transmit chains of the wireless communication device, each with an 80MHz bandwidth. In some other examples, the signal used for transmission may be generated by four or more different transmission chains of a wireless communication device, each with a bandwidth of 80 MHz.

[0050] In discontinuous examples, the operating bandwidth can span one or more completely different sets of sub-channels. For example, a 320MHz bandwidth can be continuous and located in the same 6GHz band, or it can be discontinuous and located in different bands or different zones within a band (such as partially located in the 5GHz band and partially located in the 6GHz band).

[0051] In some examples, AP 102 or STA 104 may benefit from operability enhancements associated with EHT and the next-generation IEEE 802.11 wireless communication protocol family of standards. For example, AP 102 or STA 104 attempting to gain access to the wireless medium of wireless communication network 100 may perform techniques such as free channel assessment (CCA) operations based on EHT enhancements (such as increased bandwidth, puncturing, or refinement of carrier sensing and signal reporting mechanisms), which may include modifications to existing rules, structures, or signaling implemented for legacy systems.

[0052] The multi-stream beamforming training process described herein can provide some separation between beams to avoid inter-stream interference. For example, the multi-stream beamforming training process can use antenna polarization at different RF chains. A first RF transmit chain at the initiating wireless communication device (such as an AP) can transmit using horizontal polarization, and a second RF transmit chain at the initiating wireless communication device can transmit using vertical polarization. Similarly, a first RF receive chain at the responding wireless communication device (such as a STA) can receive using horizontal polarization, and a second RF receive chain at the responding wireless communication device can receive using vertical polarization. Additionally or alternatively, the multi-stream beamforming training process can provide beam separation through antenna orientation. For example, different Tx or Rx RF chains can use or be assigned mutually exclusive beam search areas. Additionally or alternatively, the responding wireless communication device can iteratively or sequentially select beamforming directions for the spatial streams, and the initiating wireless communication device can perform additional beam searches within the beamwidth excluding previously selected beams.

[0053] Figure 2 illustrates an example Protocol Data Unit (PDU) 200 capable of wireless communication between a wireless AP and one or more wireless STAs. For example, the AP and STA could be examples of AP 102 and STA 104 as described with reference to Figure 1. The PDU 200 can be configured as a PPDU. As shown, the PDU 200 includes a PHY preamble 202 and a PHY payload 204. For example, the preamble 202 may include a legacy portion, which itself includes a legacy short training field (L-STF) 206 consisting of two symbols, a legacy long training field (L-LTF) 208 consisting of two symbols, and a legacy signal field (L-SIG) 210 consisting of two symbols. The legacy portion of the preamble 202 can be configured according to the IEEE 802.11a wireless communication protocol standard. The preamble 202 may also include a non-legacy portion, which includes one or more non-legacy fields 212, for example, conforming to one or more of the IEEE 802.11 wireless communication protocol standard family.

[0054] L-STF 206 generally enables receiving devices (such as AP 102 or STA 104) to perform coarse timing and frequency tracking, as well as automatic gain control (AGC). L-LTF 208 generally enables receiving devices to perform fine timing and frequency tracking, and also to perform initial estimation of the radio channel. L-SIG 210 generally enables receiving devices to determine (such as acquire, select, identify, detect, detect, calculate, or operate) the duration of the PDU and use the determined duration to avoid transmission over the PDU. The legacy portion of the preamble can be modulated according to binary phase shift keying (BPSK) modulation schemes, including L-STF 206, L-LTF 208, and L-SIG 210. The payload 204 can be modulated according to a BPSK modulation scheme, a quadrature BPSK (Q-BPSK) modulation scheme, a quadrature amplitude modulation (QAM) modulation scheme, or another suitable modulation scheme. Payload 204 may include a PSDU containing a data field (DATA) 214, which in turn may carry higher-level data in the form of, for example, MAC Protocol Data Unit (MPDU) or Aggregated MPDU (A-MPDU).

[0055] The multi-stream beamforming training process enables various aspects of the example PDU 200, which can be used for communication between a wireless AP and one or more wireless STAs. The multi-stream beamforming training process described herein can provide some separation between beams to avoid inter-stream interference. For example, the multi-stream beamforming training process can utilize antenna polarization at different RF chains. A first RF transmit chain at the initiating wireless communication device (such as an AP) can transmit using horizontal polarization, and a second RF transmit chain at the initiating wireless communication device can transmit using vertical polarization. Similarly, a first RF receive chain at the responding wireless communication device (such as a STA) can receive using horizontal polarization, and a second RF receive chain at the responding wireless communication device can receive using vertical polarization. Additionally or alternatively, the multi-stream beamforming training process can provide beam separation through antenna orientation. For example, different Tx or Rx RF chains can use or be assigned mutually exclusive beam search areas. Additionally or alternatively, the responding wireless communication device may iteratively or sequentially select beamforming directions for the spatial flow, and the initiating wireless communication device may perform additional beam searches for directions within the beamwidth excluding previously selected beams.

[0056] Figure 3 illustrates an example Physical Layer (PHY) Protocol Data Unit (PPDU) 350 capable of being used for communication between a wireless AP and one or more wireless STAs. For example, the AP and STA could be examples of AP 102 and STA 104 as described with reference to Figure 1. As shown, the PPDU 350 includes a PHY preamble (which includes a legacy portion 352 and a non-legacy portion 354) and a payload 356 (which includes a data field 374). The legacy portion 352 of the preamble includes L-STF 358, L-LTF 360, and L-SIG 362. The non-legacy portion 354 of the preamble includes a repetition of L-SIG (RL-SIG) 364 and multiple wireless communication protocol version-related signal fields following RL-SIG 364. For example, the non-legacy portion 354 may include a general signal field 366 (referred to herein as "U-SIG 366") and an EHT signal field 368 (referred to herein as "EHT-SIG 368"). The presence of RL-SIG 364 and U-SIG366 indicates to an EHT-compliant or later version STA 104 that PPDU 350 is an EHT PPDU or any later (post-EHT) version PPDU conforming to a new wireless communication protocol (conforming to the future IEEE 802.11 wireless communication protocol standard). One or both of U-SIG366 and EHT-SIG 368 can be constructed as other wireless communication protocol versions above EHT that are associated with a revision of the IEEE standards family and carry version-related information for those protocol versions. For example, U-SIG 366 can be used by a receiving device (such as AP 102 or STA 104) to interpret bits in one or more of EHT-SIG 368 or data field 374. Similar to L-STF 358, L-LTF 360, and L-SIG 362, in instances involving the use of bound channels, the information in U-SIG366 and EHT-SIG 368 can be repeated and transmitted in each of the component 20MHz channels.

[0057] The non-legacy portion 354 also includes an additional short training field 370 (referred to herein as "EHT-STF 370," but which can be constructed for other wireless communication protocol versions above EHT and carries version-related information for those protocols) and one or more additional long training fields 372 (referred to herein as "EHT-LTF 372," but which can be constructed for other wireless communication protocol versions above EHT and carry version-related information for those protocols). EHT-STF 370 can be used for timing and frequency tracking and AGC, while EHT-LTF 372 can be used for more refined channel estimation.

[0058] EHT-SIG 368 can be used by AP 102 to identify one or more STAs 104 and notify those STAs that AP 102 has scheduled uplink (UL) or downlink (DL) resources for them. EHT-SIG 368 can be decoded by each compatible STA 104 served by AP 102. EHT-SIG 368 can generally be used by the receiving device to interpret the bits in data field 374. For example, EHT-SIG 368 may include resource element (RU) allocation information, spatial flow configuration information, and per-user (such as STA-specific) signaling information. Each EHT-SIG 368 may include a common field and at least one user-specific field. In the context of OFDMA, the common field may indicate the RU distribution across multiple STAs 104, indicate RU assignment in the frequency domain, indicate which RUs are allocated for MU-MIMO transmission and which RUs correspond to OFDMA transmission, and the number of users in the allocation, etc. The user-specific field is assigned to a specific STA 104 and carries STA-specific scheduling information, such as user-specific MCS values ​​and user-specific RU allocation information. This information enables the corresponding STA 104 to identify and decode the corresponding RU in the associated data field 374.

[0059] Multistream beamforming training processes enable various aspects of a PPDU 350 for communication between a wireless AP and one or more wireless STAs. The multistream beamforming training processes described herein can provide some separation between beams to avoid interstream interference. For example, multistream beamforming training processes can utilize antenna polarization at different RF chains. A first RF transmit chain at the initiating wireless communication device (such as an AP) can transmit using horizontal polarization, and a second RF transmit chain at the initiating wireless communication device can transmit using vertical polarization. Similarly, a first RF receive chain at the responding wireless communication device (such as a STA) can receive using horizontal polarization, and a second RF receive chain at the responding wireless communication device can receive using vertical polarization. Additionally or alternatively, multistream beamforming training processes can provide beam separation through antenna orientation. For example, different Tx and Rx RF chains can use or be assigned mutually exclusive beam search areas. Additionally or alternatively, the responding wireless communication device may iteratively or sequentially select beamforming directions for the spatial flow, and the initiating wireless communication device may perform additional beam searches for directions within the beamwidth excluding previously selected beams.

[0060] Figure 4 illustrates a layered format of an example PPDU capable of being used for communication between a wireless AP and one or more wireless STAs. For example, the AP and STA could be examples of AP 102 and STA 104 as described with reference to Figure 1. As described, each PPDU 400 includes a PHY preamble 402 and a PSDU 404. Each PSDU 404 may represent (or “carry”) one or more MAC Protocol Data Units (MPDUs) 416. For example, each PSDU 404 may carry an aggregated MPDU (A-MPDU) 406, which comprises an aggregation of multiple A-MPDU subframes 408. Each A-MPDU subframe 408 may include an MPDU frame 410, which includes a MAC delimiter 412 and a MAC header 414 preceding an accompanying MPDU 416, which includes the data portion (“payload” or “frame body”) of the MPDU frame 410. Each MPDU frame 410 may also include a Frame Check Sequence (FCS) field 418 for error detection (such as the FCS field 418 may include Cyclic Redundancy Check (CRC)) and padding bits 420. MPDU 416 may carry one or more MAC Service Data Units (MSDUs) 430. For example, MPDU 416 may carry an aggregated MSDU (A-MSDU) 422, which comprises multiple A-MSDU subframes 424. Each A-MSDU subframe 424 may be associated with an MSDU frame 426 (such as an example of an MSDU frame or also referred to as an MSDU frame) and may contain a corresponding MSDU 430 preceded by a subframe header 428, and in some examples, followed by padding bits 432.

[0061] Returning to reference MPDU frame 410, MAC delimiter 412 can be used as a marker for the start of associated MPDU 416 and to indicate the length of associated MPDU 416. MAC header 414 may include multiple fields containing information defining or indicating the characteristics or attributes of the data encapsulated within the frame body. MAC header 414 includes a duration field indicating the duration from the end of the PPDU to at least the end of an acknowledgment (ACK) or block ACK (BA) to be sent by the receiving wireless communication device to the PPDU. The use of the duration field is to preserve the wireless medium for the indicated duration and to enable the receiving device to establish its Network Allocation Vector (NAV). MAC header 414 also includes one or more fields indicating the address of the data encapsulated within the frame body. For example, MAC header 414 may include a combination of source address, transmitter address, receiver address, or destination address. MAC header 414 may also include a frame control field containing control information. The frame control field may specify the frame type, such as a data frame, control frame, or management frame.

[0062] In some wireless communication systems, wireless communication between AP 102 and its associated STA 104 can be secure. For example, AP 102 or STA 104 can establish a security key to protect its wireless communication with another device, and this security key can be used to encrypt data and manage the content of frames. In some examples, control frames and fields within the MAC header of data frames or management frames, or both, can also be protected via encryption or via integrity checks (e.g., by generating a Message Integrity Check (MIC) for one or more relevant fields).

[0063] Access to a shared wireless medium is typically managed by a Distributed Coordination Function (DCF). With DCF, there is generally no centralized master device allocating time and frequency resources for the shared wireless medium. Instead, a wireless communication device (such as an AP102 or STA104) can wait for a specific time before being granted permission to transmit data and subsequently contend for access to the wireless medium. DCF is implemented using time intervals, including time slot times (or “time slot intervals”) and inter-frame gaps (IFS). IFS provides priority access for control frames used for appropriate network operation. Transmission can begin at time slot boundaries. Different variations of IFS exist, including Short IFS (SIFS), Distributed IFS (DIFS), Extended IFS (EIFS), and Arbitrated IFS (AIFS). Values ​​for time slot times and IFS can be provided by appropriate standard specifications, such as one or more of the IEEE 802.11 wireless communication protocol family.

[0064] In some examples, wireless communication devices (such as AP 102 or STA 104) can implement DCF using Carrier-Sensed Multiple Access (CSMA) with Collision Avoidance (CA) (CSMA / CA) technology. According to this technology, before transmitting data, the wireless communication device can perform an idle channel assessment (CCA) and determine (such as identifying, detecting, probing, calculating, or computed) whether the relevant wireless channel is idle. CCA includes both physical (PHY-level) carrier sensing and virtual (MAC-level) carrier sensing. Physical carrier sensing is accomplished by measuring the received signal strength of a valid frame, comparing this strength to a threshold to determine (such as identifying, detecting, probing, calculating, or computed) whether the channel is busy. For example, if the received signal strength of the detected preamble is higher than a threshold, the medium is considered busy. Physical carrier sensing also includes energy detection. Energy detection involves measuring the total energy received by the wireless communication device, regardless of whether the received signal represents a valid frame. If the detected total energy is higher than a threshold, the medium is considered busy.

[0065] Virtual carrier sensing is implemented using a Network Allocation Vector (NAV), which effectively serves as the duration before a wireless communication device can contend for access, even in the absence of detected symbols or even when the detected energy is below a relevant threshold. The NAV is reset each time a valid frame not addressed to the wireless communication device is received. When the NAV reaches 0, the wireless communication device performs physical carrier sensing. If the channel remains idle for an appropriate IFS (Instantaneous Transfer Opportunity), the wireless communication device initiates a backoff timer, which represents the duration for which the device senses the medium is idle before allowing transmission. If the channel remains idle until the backoff timer expires, the wireless communication device becomes the owner (or "owner") of a Transmission Opportunity (TXOP) and can begin transmission. TXOP is the duration for which the wireless communication device can transmit frames on the channel after it has "won" contention for the wireless medium. The duration of TXOP can be indicated in the U-SIG field of the PPDU. Conversely, if one or more carrier sensing mechanisms in the carrier sensing mechanism indicate that the channel is busy, the MAC controller within the wireless communication device will not allow transmission.

[0066] Each time a wireless communication device generates a new PPDU for transmission in a new TXOP, it randomly selects a new backoff timer duration. The available distribution of numbers that can be randomly selected for the backoff timer is called the contention window (CW). Different CW and TXOP durations exist for each of the following four access classes (AC): Voice (AC_VO), Video (AC_VI), Background (AC_BK), and Best Effort (AC_BE). This allows for prioritizing specific types of traffic within the network.

[0067] In some other examples, wireless communication devices (such as AP 102 or STA 104) may contend for access to the WLAN's wireless medium according to an Enhanced Distributed Channel Access (EDCA) procedure. Random channel access mechanisms (such as EDCA) can provide a greater probability of high-priority traffic gaining medium access than low-priority traffic. Wireless communication devices using EDCA can classify data into different access categories. Each AC can be associated with a different priority level and can be assigned a different range of random backoff (RBO), making higher-priority data more likely to win TXOPs (e.g., by assigning a lower RBO to higher-priority data and vice versa). While EDCA increases the likelihood that low-latency data traffic will gain access to the shared wireless medium during a given contention period, the unpredictable outcome of medium access contention operations may prevent low-latency applications from achieving specific levels of throughput or meeting specific latency requirements.

[0068] Some APs and STAs (such as AP 102 and STA 104 as described with reference to Figure 1) can implement space reuse techniques. For example, AP 102 and STA 104 configured to communicate using protocols defined in the IEEE 802.11ax or 802.11be standard revisions can be configured with BSS colors. AP 102 associated with different BSSs can be associated with different BSS colors. The BSS color is a numerical identifier (such as a 6-bit field carried by the SIG field) of the corresponding BSS of AP 102. Each STA 104 can learn its own BSS color when associated with the corresponding AP 102. BSS color information is communicated at both the PHY sublayer and the MAC sublayer. If AP 102 or STA 104 detects, acquires, selects, or identifies a radio packet from another wireless communication device during access contention, AP 102 or STA 104 may apply different contention parameters, such as those determined, identified, detected, or calculated by the BSS color indication in the preamble of the radio packet, depending on whether the radio packet was sent by or received by another wireless communication device within its BSS (such as another AP 102 or STA 104) or from or from a wireless communication device in an overlapping BSS (OBSS). For example, if the BSS color associated with the radio packet is the same as the BSS color of AP 102 or STA 104, AP 102 or STA 104 may use a first RSSI detection threshold when performing CCA on the wireless channel. However, if the BSS color associated with a radio packet is different from the BSS color of AP 102 or STA 104, AP 102 or STA 104 may use a second RSSI detection threshold, which is greater than the first RSSI detection threshold, instead of the first RSSI detection threshold when performing CCA on the radio channel. In this way, the criteria for winning contention are relaxed when interference transmission is associated with the OBSS.

[0069] Some APs and STAs (such as AP 102 and STA 104 described with reference to Figure 1) implement techniques for spatial reuse involving coordinated communication schemes. According to such techniques, AP 102 may contend for access to a radio medium to gain control of that medium for use in the TXOP. The AP that wins the contention (also referred to below as the “sharing AP”) may select one or more other APs (also referred to below as the “shared AP”) to share the TXOP resources. The sharing AP and the shared AP may be located close to each other such that at least some of their radio coverage areas at least partially overlap. Some examples may specifically involve coordinated AP TDMA or OFDMA techniques for sharing time or frequency resources of the TXOP. To share the time or frequency resources of the TXOP, the sharing AP may divide the TXOP into multiple time segments or frequency segments, each time segment or frequency segment including a corresponding time or frequency resource representing a portion of the TXOP. The sharing AP may allocate the time or frequency segment to itself or to one or more of the shared APs. For example, each shared AP can use a portion of the TXOPs assigned by the shared AP to perform uplink or downlink communication with its associated STA.

[0070] In some examples of such TDMA technologies, each of the multiple sections of the TXOP includes a set of time resources that do not overlap with any time resources of any other section of the TXOP. In such examples, scheduling information may include indications of the time resources associated with each section of the TXOP among the multiple time resources. For example, scheduling information may include indications of time segments of the TXOP (such as indications of one or more time slots or sets of symbol periods associated with each section of the TXOP), such as for use in multi-user TDMA.

[0071] In some examples of OFDMA technology, each of the multiple sections of a TXOP includes a set of frequency resources that do not overlap with any frequency resources of any other section. In such examples, scheduling information may include indications of the frequency resources associated with each section of the TXOP. For example, scheduling information may include indications of bandwidth portions of a radio channel (such as indications of one or more sub-channels or resource elements associated with each section of the TXOP), such as for use in multi-user OFDMA.

[0072] In this manner, the acquisition of TXOPs by a shared AP enables communication between one or more additional shared APs and their respective BSSs with appropriate power control and link adaptation. For example, the sharing AP can limit the transmit power of a selected shared AP so that interference from the selected AP does not prevent the STA associated with the TXOP owner from successfully decoding packets transmitted by the shared AP. Such techniques can be used to reduce latency because other APs can transmit and receive data according to conventional CSMA / CA or Enhanced Distributed Channel Access (EDCA) techniques without waiting to win contention for the TXOP. Additionally, by enabling a group of APs 102 associated with different BSSs to participate in a coordinated AP transmission session, during which the group of APs can share at least a portion of a single TXOP acquired by any of the participating APs, such techniques can increase throughput on the BSSs associated with the participating APs and also improve throughput fairness. Furthermore, through the appropriate selection of shared APs and the scheduling of their respective time or frequency resources, media utilization can be maximized or otherwise increased, while packet loss caused by OBSS interference is minimized or otherwise reduced. Various implementations can achieve these and other advantages without requiring the sharing AP or the AP being shared to know about the STA 104 associated with other BSSs, without requiring pre-assigned or dedicated master APs or pre-assigned AP groups, and without requiring backhaul coordination between APs participating in TXOP.

[0073] In some examples where the signal strength or interference level associated with the selected AP is relatively low (e.g., less than a given value), or when the decoding error rate of the selected AP is relatively low (e.g., less than a threshold), the start time of communication between different BSSs can be synchronized. Conversely, when the signal strength or interference level associated with the selected AP is relatively high (e.g., greater than a given value), or when the decoding error rate of the selected AP is relatively high (e.g., greater than a threshold), the start time can be offset from each other by a time period associated with decoding the preamble of the radio packet and determining whether the radio packet is an intra-BSS packet or an OBSS packet based on the decoded preamble. For example, the time period between the transmission of an intra-BSS packet and the transmission of an OBSS packet can allow the corresponding AP (or its associated STA) to decode the preamble of the radio packet and obtain the BSS color value carried in the radio packet to determine whether the radio packet is an intra-BSS packet or an OBSS packet. In this way, each of the participating APs and its associated STAs can be able to receive and decode intra-BSS packets in the presence of OBSS interference.

[0074] In some examples, a shared AP may perform polling of a set of unmanaged or non-co-managed APs that support coordinated reuse to identify candidates for future space reuse opportunities. For example, a shared AP may send one or more space reuse polling frames to determine one or more space reuse criteria and select one or more other APs as part of the shared APs. Based on the polling, the shared AP may receive responses from one or more of the polled APs. In some specific examples, the shared AP may send a Coordinating AP TXOP Indication (CTI) frame to other APs, indicating the time and frequency of resources for a shareable TXOP. The shared AP may select one or more candidate APs upon receiving a Coordinating AP TXOP Request (CTR) frame from the corresponding candidate AP, indicating that the corresponding AP expects to participate in the TXOP. The polling response or CTR frame may include power indications, such as received (RX) power or RSSI measured by the corresponding AP. In some other examples, the shared AP may directly measure potential interference with services (such as UL transmission) supported at one or more APs and select the shared APs based on the measured potential interference. Shared APs typically select an AP to participate in coordinated space reuse, allowing it to still protect its own outgoing traffic and transmissions from STAs in its BSS (these transmissions may be referred to as primary transmissions). As described above, resources can be allocated to the selected AP during TXOP.

[0075] Retransmission protocols, such as Hybrid Automatic Repeat Request (HARQ) , can also provide performance gains. HARQ protocols can support various HARQ signaling between transmitting and receiving wireless communication devices (such as AP 102 and STA 104 as described with reference to Figure 1), as well as signaling between the PHY and MAC layers, to improve retransmission operations in WLANs. HARQ uses a combination of error detection and error correction. For example, HARQ transmission may include adding error detection bits to the data to be transmitted using error detection (ED) codes, such as Cyclic Redundancy Check (CRC) . These error detection bits can be used by the receiving device to determine whether it has correctly decoded the received HARQ transmission. In some examples, forward error correction (FEC) codes, such as low-density parity check (LDPC) decoding schemes that systematically encode information bits to produce parity bits, can be used to encode the original data (information bits) to be transmitted. The transmitting device may send both the original information bits and the parity bits to the receiving device in a HARQ transmission. The receiving device can use parity bits to correct errors in the information bits, thereby avoiding retransmission.

[0076] Implementing the HARQ protocol in a WLAN improves the reliability of data transmitted from a transmitting device to a receiving device. The HARQ protocol supports the establishment of a HARQ session between two devices. Once a HARQ session is established, if the receiving device cannot correctly decode a first HARQ transmission received from the transmitting device (and cannot correct errors), the receiving device can send a HARQ feedback message (such as a negative acknowledgment (NACK)) to the transmitting device, indicating that at least a portion of the first HARQ transmission was not correctly decoded. This type of HARQ feedback message may differ from the traditional block ACK feedback message type associated with regular ARQ. In response to receiving a HARQ feedback message, the transmitting device can send a second HARQ transmission to the receiving device to convey at least a portion that further assists the receiving device in decoding the first HARQ transmission. For example, the transmitting device may include some or all of the original information bits, some or all of the original parity bits, and other different parity bits in the second HARQ transmission. The combined HARQ transmissions can be processed for decoding and error correction, making it possible to obtain the complete signal associated with the HARQ transmission.

[0077] In some examples, the receiving device can control whether to continue the HARQ process or revert to a non-HARQ retransmission scheme (such as the Automatic Repeat Request (ARQ) protocol). By allowing the device to dynamically switch between ARQ and HARQ protocols during frame exchange, such switching reduces feedback overhead and increases retransmission flexibility. Some implementations also allow the multiplexing of ARQ-based and HARQ-based communications.

[0078] APs and STAs with multiple antennas (such as AP 102 and STA 104 as described with reference to Figure 1) can support various diversity schemes. For example, spatial diversity can be used by one or both of the transmitting devices (such as AP 102 or STA 104) or the receiving devices (such as AP 102 or STA 104) to improve transmission robustness. For example, to implement a transmit diversity scheme, the transmitting devices can redundantly transmit the same data on two or more antennas.

[0079] The AP 102 and STA 104, which include multiple antennas, also support Space-Time Block Decoding (STBC). Using STBC, the transmitting device also transmits multiple copies of the data stream across multiple antennas to increase the likelihood of correctly decoding the data by utilizing various received versions of the data. More specifically, the data stream to be transmitted is encoded in blocks, which are distributed across spaced antennas and over time. Generally, when the number of transmitting antennas... Exceeding the number of spatial flows STBC can be used at this time. A spatial flow can be mapped to a number of... The spacetime stream, which is mapped to One sending chain.

[0080] The AP 102 and STA 104, which include multiple antennas, also support spatial multiplexing, which can be used to improve the spectral efficiency of transmission and the resulting throughput. To achieve spatial multiplexing, the transmitting device divides the data stream into numerous... These are separate, independent spatial streams. These spatial streams are then encoded individually and transmitted via multiple... The transmitting antennas transmit in parallel.

[0081] The AP 102 and STA 104, which include multiple antennas, also support beamforming. Beamforming generally refers to directing transmitted energy in the direction of the target receiver. Beamforming can be used in single-user (SU) environments (e.g., to improve the signal-to-noise ratio (SNR)) or multi-user (MU) environments (e.g., to enable MU-MIMO transmission (also known as spatial division multiple access (SDMA))). In the MU-MIMO context, beamforming may additionally or alternatively involve canceling energy in the direction of other receiving devices. To perform SU beamforming or MU-MIMO, the transmitting device (called a beamformer) transmits a signal from each of the multiple antennas. The beamformer configures the amplitude and phase shift between the signals transmitted from the different antennas such that these signals are constructively added along a specific direction toward the intended receiver (called a beamformer receiver), or destructively added in other directions toward other devices, to mitigate interference in the MU-MIMO context. The way beamformers configure amplitude and phase shift depends on the channel state information (CSI) associated with the wireless channel on which the beamformer is designed to communicate with the beamforming receiver.

[0082] To obtain the Channel Sounding Indicator (CSI) required for beamforming, the beamformer can perform a channel sounding process with the beamforming receiver. For example, the beamformer can send one or more sounding signals (such as in the form of empty data packets (NDPs)) to the beamforming receiver. An NDP is a PPDU without any data field. The beamforming receiver can then target all pairs of transmit and receive antennas associated with the sounding signal. × Measurements are performed on each of the sub-channels. The beamforming receiver generates a feedback matrix associated with the channel measurements and typically compresses this feedback matrix before sending the feedback to the beamformer. The beamformer can generate a pre-decoding (or “guide”) matrix for the beamforming receiver associated with this feedback and uses this guide matrix to pre-decode the data stream to configure amplitude and phase shifts for subsequent transmissions to that beamforming receiver. The beamformer can use the guide matrix to determine (such as identification, detection, probing, computation, or arithmetic) how to transmit signals on each of the beamformer's antennas to perform beamforming. For example, the guide matrix can indicate the phase shift or power level that will be used to transmit a corresponding signal on each of the beamformer's antennas.

[0083] When beamforming is performed, the transmitted beamforming array gain is equal to... and The ratio is logarithmically proportional. Therefore, when performing beamforming to increase gain, the number of transmit antennas is increased within other constraints. Generally, this is as expected. More precise transmission or nulling can also be achieved by increasing the number of transmit antennas. This is particularly advantageous in MU transmission contexts where reducing inter-user interference is especially important.

[0084] To increase the spatial multiplexing capability of AP 102, AP 102 may need to support an increased number of spatial streams (e.g., up to 16 spatial streams). However, supporting additional spatial streams can lead to increased CSI feedback overhead. Implicit CSI acquisition techniques can avoid CSI feedback overhead by leveraging the assumption that the UL and DL channels have reciprocal impulse responses (i.e., channel reciprocity exists). For example, implicit channel probing procedures (such as implicit beamforming report (BFR) techniques, such as where STA 104 transmits NDP probe packets in the UL while AP 102 is measuring the channel) can be used to reduce CSI feedback overhead, since no BFR is transmitted. Once AP 102 receives the NDP, the AP can implicitly evaluate the channel for each STA in STA 104 and use the channel evaluation to configure the bootstrapping matrix. To mitigate hardware mismatches that may compromise channel reciprocity on the UL and DL (e.g., baseband to RF chain and RF to baseband chain are not reciprocal), AP 102 can implement calibration methods to compensate for mismatches between the UL and DL channels. For example, AP 102 can select a reference antenna, transmit pilot signals from each of the AP's antennas, and estimate the baseband to RF gain relative to the reference antenna for each of the non-reference antennas.

[0085] In some examples, multiple APs 102 can simultaneously transmit signaling or communication to a single STA 104 using a distributed MU-MIMO scheme. Examples of such distributed MU-MIMO transmissions include coordinated beamforming (CBF) and joint transmission (JT). With CBF, a signal (such as a data stream) for a given STA 104 can be transmitted by only a single AP 102. However, the coverage areas of adjacent APs may overlap, and a signal transmitted by a given AP 102 may arrive as an OBSS signal at a STA in an OBSS associated with an adjacent AP. CBF allows multiple adjacent APs to transmit simultaneously while minimizing or avoiding interference, potentially creating more opportunities for spatial reuse. More specifically, using CBF, AP 102 can beamform a signal onto a STA 104 within its BSS while simultaneously creating nulls in the direction of the STA in the OBSS, ensuring that any signal received at the OBSS STA has sufficiently low power to limit interference at the STA. To achieve this, an inter-BSS coordination set can be defined among adjacent APs, containing identifiers of all APs and STAs participating in the CBF transmission.

[0086] Using JT, a signal for a given STA 104 can be transmitted by multiple coordinating APs 102. For multiple APs 102 to transmit data concurrently to STA 104, all APs 102 may require copies of the data to be sent to STA 104. Therefore, APs 102 may need to exchange data with each other to send to STA 104. Using JT, the combination of antennas of multiple APs 102 transmitting to one or more STAs 104 can be considered as a large antenna array (which can be represented as a virtual antenna array) for beamforming and signal transmission. Combined with MU-MIMO technology, the multiple antennas of multiple APs 102 can be able to transmit data via multiple spatial streams. Therefore, each STA 104 can receive data via one or more of the multiple spatial streams.

[0087] In some specific implementations, AP 102 and STA 104 can support various multi-user communications; that is, concurrent transmissions from one device to each of multiple devices (such as multiple simultaneous downlink communications from AP 102 to the corresponding STA 104), or concurrent transmissions from multiple devices to a single device (such as multiple simultaneous uplink transmissions from the corresponding STA 104 to AP 102). As an example, in addition to MU-MIMO, AP 102 and STA 104 can also support OFDMA. In some respects, OFDMA is a multi-user version of OFDM.

[0088] In the OFDMA scheme, the available spectrum of a radio channel can be divided into multiple Resource Units (RUs), each comprising multiple frequency subcarriers (also referred to as "tones"). Different RUs can be allocated by AP 102 at specific times or assigned to different STAs 104. The size and distribution of RUs are referred to as RU allocation. In some examples, RUs can be allocated in 2MHz intervals, and therefore, a minimum RU can include 26 tones consisting of 24 data tones and 2 pilot tones. Thus, in a 20MHz channel, up to 9 RUs (such as 2MHz, 26-tone RUs) can be allocated (because some tones are reserved for other purposes). Similarly, in a 160MHz channel, up to 74 RUs can be allocated. Other tone RUs, such as 52-tone, 106-tone, 242-tone, 484-tone, and 996-tone RUs, can also be allocated. Adjacent RUs can be separated by empty subcarriers (such as DC subcarriers) to reduce interference between adjacent RUs, reduce receiver DC offset, and avoid leakage of the transmit center frequency.

[0089] For UL MU transmissions, AP 102 can send trigger frames to initiate and synchronize ULOFDMA or UL MU-MIMO transmissions from multiple STAs 104 to AP 102. Such trigger frames thus enable multiple STAs 104 to concurrently transmit UL services to AP 102 in time. The trigger frame can address one or more STAs 104 via a corresponding Association Identifier (AID), and can assign one or more RUs to each AID (and thus to each STA 104), which can be used to transmit UL services to AP 102. AP can also specify one or more Random Access (RA) RUs that unscheduled STAs 104 can contend for.

[0090] Some APs and STAs (such as AP 102 and STA 104, as described with reference to Figure 1) are capable of multi-link operation (MLO). For example, AP 102 and STA 104 may support MLO as defined in one or both of the IEEE 802.11be and 802.11bn standard revisions. Devices with MLO capability may be referred to as multi-link devices (MLDs). In some examples, MLO supports the establishment of multiple different communication links between MLDs (such as a first link in the 2.4 GHz band, a second link in the 5 GHz band, and a third link in the 6 GHz band). Each communication link may support one or more sets of channels or logical entities. For example, an AP MLD can set a corresponding operating bandwidth, one or more corresponding primary channels, and various BSS configuration parameters for each communication link in the communication links. An MLD may include a single upper MAC entity and may include, for example, three independent lower MAC entities and three associated independent PHY entities for the corresponding links in the 2.4 GHz, 5 GHz, and 6 GHz bands. This architecture can implement a single association process and security context. AP MLD may include multiple APs 102, each of which is configured to communicate with a corresponding STA among multiple STAs 104 that are not AP MLDs (also referred to as "STA MLDs") on a corresponding communication link.

[0091] To support MLO technology, AP MLDs and STA MLDs can exchange MLO capability information (such as supported aggregation types or supported frequency bands, and other information). In some examples, information exchange can occur via beacon frames, probe request frames, probe response frames, association request frames, association response frames, another management frame, dedicated action frames, or Operation Mode Indicators (OMIs), etc. In some examples, an AP MLD can designate a specific channel of a link within a frequency band as an anchor channel, on which it periodically transmits beacons and other control or management frames. In such examples, the AP MLD can also transmit shorter beacons (such as beacons containing less information) on other links for discovery or other purposes.

[0092] MLDs can dynamically and, in some instances concurrently, exchange packets on one or more communication links. MLDs can also independently contend for access on each communication link, which reduces latency by allowing the MLD to transmit its packets on the first communication link that becomes available. For example, "alternating multilink" can refer to MLO mode, in which an MLD can concurrently listen on two or more different high-performance links and associated channels. In alternating multilink operation mode, an MLD can alternately use two links to transmit portions of its traffic. Specifically, an MLD with buffered traffic can use the first link it wins contention for and obtains a TXOP to transmit traffic. While in some examples such an MLD can only transmit or receive on one communication link at any given time, having access opportunities via two different links allows the MLD to avoid congestion, reduce latency, and maintain throughput.

[0093] Multi-link aggregation (MLA) (also known as carrier aggregation (CA)) is another MLO mode in which an MLD can simultaneously send traffic to or receive traffic from another MLD via multiple communication links, thereby increasing the utilization of available resources to achieve higher throughput. That is, for at least some duration, transmission or portions of transmission can occur simultaneously and in parallel through two or more communication links. In some examples, the parallel communication links can support synchronous transmission. In some other examples, or during some other durations, transmissions via communication links can be parallel, but not synchronous or concurrent. Additionally, in some examples or durations, two or more communication links can be used for communication between MLDs in the same direction (such as all uplinks or all downlinks), while in some other examples or durations, two or more communication links can be used for communication in different directions (e.g., one or more communication links can support uplink communication, and one or more communication links can support downlink communication). In such examples, at least one MLD can operate in full-duplex mode.

[0094] MLA can be packet-based or stream-based. For packet-based aggregation, frames of a single service stream (such as all services associated with a given service identifier (TID)) can be transmitted concurrently across multiple communication links. For stream-based aggregation, each service stream (such as all services associated with a given TID) can be transmitted using a single corresponding communication link among multiple communication links. As an example, a single STA MLD can access a web browser while streaming video in parallel. According to the example above, services associated with web browser access can be conveyed via a first communication link, while services associated with the video stream can be conveyed in parallel via a second communication link (so that at least some of the data can be transmitted concurrently on the first channel with the data transmitted on the second channel). In some other examples, MLA can be implemented as a hybrid of stream-based and packet-based aggregation. For example, MLA can employ stream-based aggregation when multiple service streams are created, and packet-based aggregation in other cases. Switching between MLA techniques or modes can be additionally or alternatively associated with other metrics (such as time of day, network traffic load, or battery level of wireless communication devices, and other factors or considerations).

[0095] Other MLO techniques can be associated with traffic steering and QoS characterization. They can achieve latency reduction and other QoS enhancements by mapping traffic flows with different latency or other requirements to different links. For example, traffic with low latency requirements can be mapped to a communication link operating in the 6 GHz band, and more latency-tolerant flows can be mapped to communication links operating in the 2.4 GHz or 5 GHz bands. This operation (called TID-to-Link Mapping (TTLM)) allows two MLDs to negotiate mapping specific traffic flows in the DL direction or UL direction, or both directions, to one or more sets of communication links established between them. In some examples, the AP MLD can advertise a global TTLM applicable to all associated non-AP MLDs. A communication link to which no TID is mapped in either direction is called a disabled link. An enabled link has at least one TID mapped to it in at least one direction.

[0096] In some examples, an MLD may include multiple radio components, and each communication link associated with the MLD may be associated with a corresponding radio component of the MLD. Each radio component may include one or more of its own transmit / receive (Tx / Rx) chains, including its own physical antenna or one or more shared antennas or coupled thereto, and includes signal processing components and other components. An MLD with multiple radio components that can be used concurrently for MLO may be referred to as a multi-link multi-radio component (MLMR) MLD. Some MLMR MLDs may also be able to operate in an enhanced MLMR (eMLMR) mode, in which the MLD may be able to dynamically switch radio resources (such as antennas or RF front-ends) between multiple communication links (e.g., from using radio resources for one communication link to using radio resources for another communication link) to achieve higher transmit and receive speeds using higher capacity on a given communication link. In this eMLMR operating mode, the MLD may be able to move Tx / Rx radio resources from one communication link to another, thereby increasing the spatial streaming capability of another communication link. For example, if a non-APMLD includes four or more STAs, the STAs associated with the eMLMR link can "pool" their antennas so that each of these STAs can use the antennas of the other STAs when transmitting or receiving on one of the eMLMR links.

[0097] Other MLDs may have more limited capabilities and may not include multiple radio components. An MLD with only a single radio component shared across multiple communication links can be called a Multi-Link Single Radio Component (MLSR) MLD. When at least one MLD operates as an MLSR MLD, control frames can be exchanged between MLDs before initiating data or management frame exchanges between them. Because an MLD operating in MLSR mode is limited to a single radio component, it cannot use multiple communication links simultaneously, but can only listen (e.g., monitor), transmit, or receive on a single communication link at any given time. An MLSR MLD can alternatively switch between different frequency bands in a TDM manner. In contrast, some MLSR MLDs may also be able to operate in an enhanced MLSR (eMLSR) mode, in which the MLD can concurrently listen for specific types of packets, such as Buffer Status Report Polling (BSRP) frames or Multi-User (MU) Request Transmit (RTS) (MU-RTS) frames, on multiple links. Although an MLD operating in eMLSR mode can still only transmit or receive on one link at any given time, it can dynamically switch between frequency bands, resulting in improvements in both latency and throughput. For example, when a STA of a non-AP MLD can detect a BSRP frame on its corresponding communication link, the non-AP MLD can tune all its antennas to the communication link that detected the BSRP frame. In contrast, a non-AP MLD operating in MLSR mode can only listen on one communication link at any given time and can only transmit or receive on that one communication link.

[0098] A multi-channel radio (MLD) capable of simultaneously transmitting and receiving on multiple communication links can be called a simultaneous transmit and receive (STR) device. In an STR-capable MLD, the radio component associated with a communication link can independently transmit or receive frames on that link without interfering with, or being interfered with by, the operation of another radio component associated with a different communication link of the MLD. For example, an MLD with suitable filters can simultaneously transmit in the 2.4 GHz band and receive in the 5 GHz band, or vice versa, or simultaneously transmit in the 5 GHz band and receive in the 6 GHz band, or vice versa, and is therefore considered an STR device for the corresponding paired communication links. Such an STR-capable MLD can typically be an AP MLD or a higher-end STA MLD with more high-performance filters. An MLD that cannot simultaneously transmit and receive on multiple communication links can be called a non-STR (NSTR) device. When transmission occurs on another communication link of an NSTR device, the radio component associated with a given communication link in the NSTR device may experience interference. For example, an MLD with a standard filter may not be able to transmit on the 5 GHz band and receive on the 6 GHz band simultaneously, or vice versa, and therefore can be considered an NSTR device for both communication links.

[0099] In some wireless communication systems, an MLD can include multiple non-co-located entities. For example, an AP MLD can include non-co-located AP devices, while a STA MLD can include non-co-located STA devices. In the example where an AP MLD includes multiple non-co-located AP devices, a single Mobility Domain (SMD) entity can refer to the logical entity that controls the associated non-co-located APs. Non-AP STAs (such as non-MLD non-AP STAs or non-AP MLDs including one or more associated non-AP STAs) can be associated with an SMD entity via one of their constituent APs and can roam seamlessly between APs associated with the SMD entity (e.g., without needing to re-associate). The SMD entity can also maintain other contexts (such as security and block ACK) for its associated non-AP STAs.

[0100] The aforementioned and related MLO techniques can provide several benefits to the wireless communication network 100. For example, MLO can improve user-aware throughput (UPT) (e.g., by rapidly refreshing the per-user transmit queue). Similarly, MLO can improve throughput by improving the utilization of available channels and can increase spectrum utilization (e.g., by increasing the bandwidth-time product). Furthermore, MLO can enable smooth transitions between multi-band radio components (e.g., where each radio component can be associated with a given RF band) or implement a framework for separating control and data channels. Other benefits of MLO include reducing the modem's "on" time, which can benefit wireless communication devices in terms of power consumption. Another benefit of MLO is increased multiplexing opportunities in the case of a single BSS. For example, MLA can increase the number of users per multiplexed transmit serviced by a multi-link AP MLD.

[0101] Multistream beamforming training processes can implement various aspects of a layered format of an example PPDU capable of being used for communication between a wireless AP and one or more wireless STAs. The multistream beamforming training process described herein can provide some separation between beams to avoid interstream interference. For example, the multistream beamforming training process can use antenna polarization at different RF chains. A first RF transmission chain at the initiating wireless communication device (such as an AP) can transmit using horizontal polarization, and a second RF transmission chain at the initiating wireless communication device can transmit using vertical polarization. Additionally or alternatively, the multistream beamforming training process can provide beam separation through antenna orientation. For example, different RF chains can use or be assigned mutually exclusive beam search areas. Additionally or alternatively, the responding wireless communication device can iteratively or sequentially select beamforming directions for the spatial streams, and the initiating wireless communication device can perform additional beam searches within the beamwidth excluding previously selected beams.

[0102] Figure 5 shows an example of a signaling diagram 500 that supports a beam search process for multiple spatial streams.

[0103] STA 104 can communicate using multiple communication links. For example, STA 104 can communicate with AP 102 using first link 502 and second link 504. First link 502 can be an example of an anchor link. In some examples, first link 502 can be in a sub-7 GHz RF band. STA 104 and AP 102 can communicate control information and BSS management information via first link 502. In some examples, first link 502 can support a 320 MHz channel.

[0104] The second link 504 can be in a higher frequency RF band. For example, the second link 504 can be in a millimeter-wave band (such as the 45 GHz or 60 GHz RF band). The second link 504 can be integrated with or used in conjunction with the first link 502 to provide control information through the first link and data signaling through the second link 504. For example, due to the higher frequency of the second link, the second link 504 can have a larger data throughput than the first link 502, but with reduced range and lower reliability. In some examples, the second link 504 can act as the data pipe for STA 104, while the first link 502 can be used for control signaling.

[0105] In some examples, a single AP 102 can provide a first link 502 and a second link 504. For example, a first AP 102 can provide a first link 502, and a second AP 102 can provide a second link 504. The first AP 102 and the second AP 102 can be in communication, connection, or synchronization, or any combination thereof, such as through multi-AP coordination. For example, the first AP 102 and the second AP 102 can communicate via wired or wireless backhaul.

[0106] In some examples, STA 104 may receive a beam search trigger 506 for a second link 504 via a first link 502. For example, AP 102 may send the beam search trigger 506 to STA 104 via the first link 502. The beam search trigger 506 may trigger STA 104 to perform a beam search or beam training process on the second link 504. In examples where a single AP 102 provides both the first and second links, the first AP 102 may transmit an instruction for the beam search trigger 506 to both the second AP 102 and STA 104. In some examples, the trigger frame (beam search trigger 506) may synchronize AP 102 and STA 104 for a beam training process. In some examples, the terms "beam search process," "beam training process," "beamforming training process," and "beam search" and "beamforming training" may be used interchangeably.

[0107] STA 104 can receive a beam search trigger 506 for control information from the first link 502 and switch to the second link 504. STA 104 can pre-correct timing and frequency offsets used in the beam search process. In some examples, switching to the second link 504 or correcting timing and frequency information used in the beam search process, or both, can correspond to a link search delay 508 between receiving the beam search trigger 506 and monitoring or receiving the training signal 510 used in the beam search process. STA 104 can wait for a training signal or beam training sequence from AP 102-a via the second link 504.

[0108] For single-stream data transmission, AP 102 can send a set of training sequences to STA 104. In some examples, AP 102 and STA 104 can perform a beam search scan to obtain data from the transmitter codebook. and receiver codebook The best beam pair is selected from the combinations. For example, the AP 102 can be used across the transmitter codebook. All beams transmit training signals, and the STA 104 can use the receiver codebook. One configuration is used to receive and measure training signals. STA 104 can use the next receiver codebook configuration, and AP 102 can again transmit training signals across all beams of the transmitter codebook. For example, the total number of candidate beams can be Or, all combinations of transmitter and receiver codebooks. This type of beam search process can be called 2D scanning.

[0109] In some examples, AP 102 and STA 104 can perform the first stage of the beam search process to select the optimal transmit beam from the transmitter codebook. For example, AP 102 can use all transmit beams in the transmitter codebook to transmit a training signal to STA 104, and STA 104 can use an omnidirectional or quasi-omnidirectional receive beam to receive and measure the training signal. The first stage of the beam search process can be referred to as transmitter sector-level sweep (SLS).

[0110] Using the optimal transmit beam, AP 102 and STA 104 can perform the second stage of the beam search process to select the optimal receive beam from the receiver codebook. For example, AP 102 can use the selected transmit beam to transmit a training signal, and STA 104 can scan the receive beams of the receiver codebook. This second stage of the beam search process can be referred to as receiver SLS. This two-stage beam training scheme can have relatively low training overhead. Alternatively, it can perform a beam sweep number equal to the sum of the number of beams in the receiver codebook and the number of beams in the transmitter codebook.

[0111] STA 104 and AP 102 can support an enhanced two-stage beam search process, in which STA 104 selects multiple beams in the first stage of the beam search process. For example, during the first stage or transmitter SLS, AP 102 can use each transmit beam in the transmitter codebook to transmit a training signal to STA 104, and STA 104 can use omnidirectional or quasi-omnidirectional receive beams to receive the training signal. STA 104 can select multiple beams from the transmitter codebook based on measurements of the training signal. The selected beams can correspond to the beams with the highest number of measured thresholds, such as three or four beams with the highest Reference Signal Received Power (RSRP) or SINR measurement. In some examples, STA 104 can transmit feedback indicating the selected transmit beams, such as SLS feedback. During the second stage or receiver SLS, STA 104 can select the optimal transmit-receive beam pair from multiple good transmit beams and all receive beams.

[0112] In some examples, STA 104 may send an SLS feedback message 512. The SLS feedback message 512 may indicate the RF chain pair (in cases where more than one chain or spatial stream is used), the beamforming direction of the spatial stream, the optimal transmit beam, the optimal receive beam, or any combination thereof. STA 104 may send the SLS feedback message 512 to AP 102 via the second link 504, or via the first link 502. In some examples, the second link 504 may support uplink signaling, and STA 104 may send a training signal 514 to AP 102 via the second link 504 after an SIFS from the SLS feedback message 512.

[0113] In some examples of signaling diagram 500, STA 104 can support multiple spatial streams on the second link 504 to increase the peak data rate on the second link 504. For example, STA 104 can communicate with AP 102 via the second link 504 through the first spatial stream and the second spatial stream.

[0114] STA 104 and AP 102 can perform a multi-stream beamforming process to select RF chain pairs for each spatial stream and to select a beamforming direction for each spatial stream. Each spatial stream can be formed between the transmit RF chain of AP 102 and the receive RF chain of STA 104. For example, STA and AP 102 use two spatial streams to communicate via a second link 504; AP 102 can have two transmit RF chains (such as ANT_TX1 and ANT_TX2), and STA 104 can have two receive RF chains (such as ANT_RX1 and ANT_RX2). The multi-stream beamforming process can select between pairing ANT_TX1 with ANT_RX1 and pairing ANT_TX2 with ANT_RX2, or pairing ANT_TX1 with ANT_RX2 and pairing ANT_TX2 with ANT_RX1. The multi-stream beamforming process can also identify the beamforming direction for each spatial stream. In some examples, the multistream beam training process can implement aspects of an enhanced two-stage beam search process to identify RF chain pairs of a spatial stream or to identify the beamforming direction of a spatial stream, or both.

[0115] Using multiple spatial streams can lead to inter-stream interference, where signaling from the first spatial stream interferes with the signaling of the second spatial stream. For example, if the beamforming direction of the first spatial stream overlaps with that of the second spatial stream, these spatial streams may have inter-stream interference. If AP 102 uses the first spatial stream for transmission and the second spatial stream uses the same time and frequency resources, the waveforms of the first and second spatial streams may conflict. Inter-stream interference can result in lower SINR. Choosing similar beamforming directions at the same time and frequency can lead to fewer effective channel paths, thus reducing channel capacity.

[0116] The beam search process for multiple spatial streams described herein can provide beam separation while scanning for optimal RF chain pairs and optimal beamforming orientations. In some examples, the multi-stream beamforming training process can achieve beam separation through antenna polarization. For example, different RF chains or RF chain pairs can use different polarizations such that the signaling of the first spatial stream is orthogonal to the signaling of the second spatial stream. Some additional examples of providing beam separation through polarization are described in more detail with reference to Figure 6. In some examples, the multi-stream beamforming training process can achieve beam separation through antenna orientation. For example, the transmit RF chain at AP102 can be assigned or assigned mutually exclusive beam search areas.

[0117] In some examples, the multistream beamforming training process may include iterative or sequential beam selection for each RF chain. For example, during the first step, the first RF chain may perform a single-beam training process to identify the first beam of the first spatial stream. The single-beam training process may be referred to as a single-input single-output (SISO) beam search. In some examples, an enhanced two-stage beam search process may be an example of a single-beam training process or a SISO beam search.

[0118] For sequential beam search, after selecting the first beam, the second RF chain can perform a single-beam training process to select the second beam. However, the single-beam training process for the second beam can exclude any directions overlapping with the first beam. For example, AP 102 and STA 104 can perform SISO beam search on the angle of interest within the beamwidth excluding the first beam. Sequential beam search can support up to... One beam, including the RF chain Beam search in beam exclusion to SISO beam search is applied to the angle of interest within the beamwidth. In some examples, the STA104 can send a feedback message indicating the selected beam or beamforming direction after each iteration or all iterations of the sequential beam search.

[0119] In some examples, STA 104 and AP 102 can use a variety of different techniques to provide beam separation for a single MIMO beamforming training process. For example, STA 104 and AP 102 can perform a multi-stream beamforming training process using antenna polarization and antenna orientation. Additionally or alternatively, polarization-separated MIMO beamsearch techniques can be implemented in conjunction with sequential beamsearch techniques used for MIMO beamforming training.

[0120] Figure 6 illustrates an example of a multi-stream beamforming training 600 that supports a beam search process for multiple spatial streams.

[0121] The initiating wireless communication device of the multi-stream beamforming training 600 may be equipped with multiple RF chains, including at least a first transmit RF chain 602 and a second transmit RF chain 604. AP 102 may be an example of the initiating wireless communication device. In some examples, AP 102 may provide a first link (anchor link) and a second link in a high-frequency band. The responding wireless communication device of the multi-stream beamforming training 600 may also be equipped with multiple RF chains, including at least a first receive RF chain 606 and a second receive RF chain 608. STA 104 may be an example of the responding wireless communication device.

[0122] Multistream beamforming training 600 can implement techniques for providing beam separation between beams during the multistream beamforming training process. For example, beam separation can be achieved through antenna polarization during the multistream beamforming training process. Different RF chains can be used or assigned to different antenna polarizations. For example, a first transmit RF chain 602 can transmit using horizontal polarization, and a second transmit RF chain 604 can transmit using vertical polarization.

[0123] The first transmit RF chain 602 and the second transmit RF chain 604 can use different training sequences to scan simultaneously in multiple transmit beam directions. For example, the first transmit RF chain 602 and the second transmit RF chain 604 can scan simultaneously in all possible transmit beam directions. In some examples, the first transmit RF chain 602 and the second transmit RF chain 604 can use different training sequences and different polarizations. After the first transmit RF chain 602 and the second transmit RF chain 604 have scanned in all possible transmit beam directions, the first receive RF chain 606 and the second receive RF chain 608 can be scanned. In some examples, scanning the transmit RF chain can correspond to the first stage of an enhanced two-stage beam search process (such as exhaustively scanning all transmit beam directions), and scanning the receive RF chain can correspond to the second stage of an enhanced two-stage beam search process. For example, the first receive RF chain 606 and the second receive RF chain 608 can scan a subset of the transmit beam directions in all possible receive beam directions.

[0124] The responder wireless communication device can record measurements for all possible combinations of the RF chain pair. For example, the responder wireless communication device can generate a MIMO matrix comprising four sets of measurements for four possible combinations of the RF chain pair. Each element in the MIMO matrix can correspond to a set of measurements obtained from a SISO beamforming process between the initiator's transmit RF chain and the responder's receive RF chain. For example, the first element in the MIMO matrix could be the RSRP for the SISO beam search of the RF chain pair, which includes a first transmit RF chain 602 and a first receive RF chain 606.

[0125] The MIMO matrix can include comprehensive measurements of RF chain pairs. For example, the second element of the MIMO matrix can be used to include an RF chain pair comprising a first transmit RF chain 602 and a second receive RF chain 608. The third element of the MIMO matrix can be used to include an RF chain pair comprising a second transmit RF chain 604 and a first receive RF chain 606. The fourth element of the MIMO matrix can be used to include an RF chain pair comprising a second transmit RF chain 604 and a second receive RF chain 608.

[0126] In other examples, such as when the initiator and responder are establishing additional spatial streams (e.g., more than two), the responder can generate a MIMO matrix that includes measurements for all possible RF chain pairs. For instance, if there are four transmit RF chains and four receive RF chains, and the initiator and responder are establishing four spatial streams, the responder can generate a MIMO matrix that includes measurements for sixteen different RF chain pairs, or for all possible RF chain pairs between the initiator's transmit RF chain and the responder's receive RF chain. The responder can identify the highest received power and corresponding optimal beam pair for each element of the MIMO matrix.

[0127] The responder can select an RF chain pair for each spatial stream and choose the corresponding optimal beam direction for each spatial stream. For example, when using a multi-stream beamforming training process that provides beam separation through antenna polarization, the initiator and responder can select two RF chain pairs for two spatial streams. In a first option, the first transmit RF chain 602 can transmit to the first receive RF chain 606, and the second transmit RF chain 604 can transmit to the second receive RF chain 608. In a second option, the first transmit RF chain 602 can transmit to the second receive RF chain 608, and the second transmit RF chain 604 can transmit to the first receive RF chain 606. The responder can determine whether the first or second option has a higher sum of power measurements. In some examples, the power measurements can be, for example, SINR measurements or received power measurements.

[0128] The responder can select either the first option or the second option RF chain pair as the RF chain pair for the spatial stream based on measurements. For example, the responder can select the first option for the RF chain pair, where the first transmit RF chain 602 and the first receive RF chain 606 can be used for the first spatial stream, and the second transmit RF chain 604 and the second receive RF chain 608 can be used for the second spatial stream.

[0129] The responder can select a beamforming direction for each spatial stream. For example, the responder can select a first beamforming direction for a first spatial stream and a second beamforming direction for a second spatial stream. The responder can identify a first beamforming direction for a first transmit beam 610 formed by a first transmit RF chain 602 and a second beamforming direction for a first receive beam 612 formed by a first receive RF chain 606. The responder can identify a third beamforming direction for a second transmit beam 614 formed by a second transmit RF chain 604 and a fourth beamforming direction for a second receive beam 616 formed by a second receive RF chain 608. The responder can select the beamforming direction based on measurements of the training signal in all possible transmit beam directions.

[0130] Figure 7 shows an example of a multi-stream beamforming training 700 that supports beam search processes for multiple spatial streams.

[0131] The initiating wireless communication device of the multi-stream beamforming training 700 may be equipped with multiple RF chains, including at least a first transmit RF chain 702 and a second transmit RF chain 704. AP 102 may be an example of the initiating wireless communication device. The responding wireless communication device may also be equipped with multiple RF chains (such as a first receive RF chain and a second receive RF chain) that can be used to receive training signals during the multi-stream beamforming training 700. STA 104 may be an example of the responding wireless communication device.

[0132] Multistream beamforming training 700 can implement techniques for providing beam separation between beams during a multistream beamforming training process. For example, beam separation can be achieved through antenna orientation during multistream beamforming training. Different RF chains can be used or assigned beamforming directions within mutually exclusive beam search regions. A first transmit RF chain 702 can be used for beam search within a first region, and a second transmit RF chain 704 can be used for beam search within a second region mutually exclusive with the first region. For example, the angle of interest for multistream beamforming training 700 can span... The first transmitting RF chain can be assigned from... The angle region of interest, and the second transmitting RF chain can be assigned from the angle region of interest. The angle region of interest.

[0133] The first transmitting RF chain 702 and the second transmitting RF chain 704 can simultaneously scan on respective assigned subsets of the transmitting beam direction. For example, the first transmitting RF chain 702 can scan on the first beam search area, and simultaneously, the second transmitting RF chain 704 can scan on the second beam search area. For example, the first transmitting RF chain 702 can use beam 706 to transmit the first training signal, use beam 708 to transmit the second training signal, and so on up to using beam 710 to transmit the second training signal. The second transmission RF chain 704 can use beam 712 to transmit the first training signal, use beam 714 to transmit the second training signal, and so on, until beam 716 is used to transmit the third training signal. One training signal. In some other examples, beams of different orders or different beam search areas can be used.

[0134] After the first transmit RF chain 702 and the second transmit RF chain 704 have scanned on an assigned subset of the transmit beam direction, the responder wireless communication device can perform a beam scan against its receive RF chain. The responder wireless communication device can record measurements for all possible combinations of the RF chain pairs. For example, the responder wireless communication device can generate a MIMO matrix including measurements for all possible combinations of the RF chain pairs, as described in more detail with reference to Figure 6. Each element in the MIMO matrix can correspond to a set of measurements obtained from the SISO beamforming process between the initiator's transmit RF chain and the responder's receive RF chain. The responder can select an RF chain pair for each spatial flow and choose the corresponding optimal beam direction for each spatial flow based on the measurements.

[0135] Orientation-separated beam search can support more than two spatial streams. For example, the angle of interest (such as the 180-degree phase angle allowed for the initiating and responding antennas) can be divided into four sub-regions. The four transmit RF chains of the initiating wireless communication device can be assigned beamforming directions within 45-degree segments for beam search.

[0136] Figure 8 illustrates an example of a process flow 800 supporting a beam search process for multiple spatial streams. Process flow 800 can implement various aspects of the wireless communication network 100. For example, process flow 800 can exemplify operations between wireless communication device 802 and wireless communication device 804. Wireless communication device 802 can be an example of STA 104, and wireless communication device 804 can be an example of AP 102. In the following description of process flow 800, operations between wireless communication device 802 and wireless communication device 804 may be transmitted in a different order than the example order shown, or operations performed by wireless communication device 802 and wireless communication device 804 may be performed in a different order or at different times. Some operations may also be omitted from process flow 800, and other operations may be added to process flow 800.

[0137] At 806, wireless communication device 802 can receive a beam search trigger. For example, wireless communication device 802 can receive a beam search trigger for a second link in a second RF band via a first link in a first RF band. In some examples, wireless communication device 804 can send a beam search trigger to wireless communication device 802. For example, wireless communication device 804 can provide a first link (anchor link) in a first RF band and a second link in a second RF band (high-frequency band).

[0138] At point 808, wireless communication device 804 can send training signals to wireless communication device 802. For example, wireless communication device 802 can receive multiple training signals from multiple transmit radio frequency links of wireless communication device 804 via a second link through multiple receive radio frequency links, triggered by beam search.

[0139] The wireless communication device 804 can transmit training signals for use in a beam search process with some separation between beams. For example, the beam search process can be based on antenna polarization, antenna orientation, or selection of non-overlapping beams (such as using sequential beam search), or any combination thereof with separation between beams.

[0140] For example, beam searching can be performed using antenna polarization for beam splitting. Wireless communication device 802 can receive a first set of training signals from a first transmit RF link with first polarization via a second link through a first receive RF chain with first polarization. Wireless communication device 802 can receive a second set of training signals from a second transmit RF link with second polarization via the first receive RF chain, simultaneously with the first set of training signals. Wireless communication device 802 can receive the first set and the second set of training signals in each beamforming direction of a set of beamforming directions (such as all possible beamforming directions) triggered by beam searching.

[0141] The wireless communication device 802 can receive a first set of training signals from a first transmit RF link with a first polarization via a second receive RF link with a second polarization through a second link, and simultaneously receive a second set of training signals from the second transmit RF link with a second polarization. The wireless communication device 802 can receive the first set of training signals and the second set of training signals in each beamforming direction of the set of beamforming directions, triggered by beam search.

[0142] In some examples, the beam search process can use antenna orientation for beam splitting. Wireless communication device 802, triggered by beam search, can receive a first set of training signals from a first transmitting RF link and a second set of training signals from a second transmitting RF link via a second link through a first receiving RF link. Wireless communication device 804 can transmit the first set of training signals on a first subset of the beamforming direction, and wireless communication device 804 can transmit the second set of training signals on a second subset of the beamforming direction that does not overlap with the first subset of the beamforming direction. Wireless communication device 802, triggered by beam search, can receive the first set of training signals from a first transmitting RF link and the second set of training signals from a second transmitting RF link via a second receiving RF link in the set of receiving RF links.

[0143] At 810, the wireless communication device 802 can select RF chain pairs for the spatial streams. For example, the wireless communication device 802 can select a set of RF chain pairs for a set of spatial streams based on a training signal. The wireless communication device 802 can select an RF chain pair for each spatial stream in the set of spatial streams based on the training signal. In some examples, each RF chain pair in the set of RF chain pairs may include a receive RF chain in a set of receive RF chains and a transmit RF chain in a set of transmit RF chains.

[0144] At 812, wireless communication device 802 can select a set of beamforming directions for a set of spatial flows based on the training signal. Wireless communication device 802 can select a beamforming direction for each spatial flow in the set of spatial flows based on the training signal. In some examples, at 814, wireless communication device 802 can send a feedback message (such as an SLS feedback message) to wireless communication device 804. The feedback message can indicate a set of RF chain pairs or a set of beamforming directions, or both.

[0145] Figure 9 shows a block diagram of an example wireless communication device 900 supporting a beam search process for multiple spatial streams. In some examples, the wireless communication device 900 is configured to perform a reference... Figure 11 The process described is 1100. Wireless communication device 900 may include one or more chips, SoCs, chipsets, packages, components, or devices that individually or collectively constitute or include a processing system. The processing system may interface with other components of wireless communication device 900 and typically processes information (such as inputs or signals) received from and outputs information (such as outputs or signals) to such other components. In some aspects, an example chip may include a processing system, a first interface for outputting or transmitting information, and a second interface for receiving or acquiring information. For example, the first interface may refer to an interface between the chip's processing system and a transmitting component, enabling wireless communication device 900 to transmit information output from the chip. In such an example, the second interface may refer to an interface between the chip's processing system and a receiving component, enabling wireless communication device 900 to receive information, which is then delivered to the processing system. In some such examples, the first interface may also, for example, acquire information from the transmitting component, and the second interface may also, for example, output information to the receiving component.

[0146] The processing system of the wireless communication device 900 includes processor (or “processing”) circuitry in the form of one or more processors, microprocessors, processing units (such as a central processing unit (CPU), graphics processing unit (GPU), neural processing unit (NPU) (also referred to as a neural network processor or deep learning processor (DLP)) or digital signal processor (DSP)), processing blocks, application-specific integrated circuits (ASICs), programmable logic devices (PLDs) (such as field-programmable gate arrays (FPGAs)), or other discrete gate or transistor logic components or circuits (all of which are generally referred to herein individually as “processors” or collectively as “processors” or “processor circuitry”). One or more of these processors may be individually or collectively configured to perform the various functions or operations described herein. The processing system may also include memory circuitry in the form of one or more memory devices, memory blocks, memory elements, or other discrete gate or transistor logic components or circuitry, each of which may include tangible storage media such as random access memory (RAM) or ROM or combinations thereof (all of which are generally referred to herein individually as “memory” or collectively as “memory” or “memory circuitry”). One or more of these memories may be coupled to one or more processors and may store processor-executable code, individually or collectively, which, when executed by one or more processors, configures one or more processors to perform the various functions or operations described herein. Additionally or alternatively, in some examples, one or more processors may be pre-configured to perform the various functions or operations described herein without software configuration. The processing system may also include or be coupled to one or more modems (such as Wi-Fi (e.g., IEEE compliant) modems or cellular (e.g., 3GPP 4G LTE, 5G, or 6G compliant) modems). In some embodiments, one or more processors of the processing system include or implement one or more modems. The processing system may also include or be coupled to multiple radio components (collectively, “radio components”), multiple RF chains, or multiple transceivers, each of which may in turn be coupled to one or more antennas. In some embodiments, one or more processors of the processing system include or implement one or more of the radio components, RF chains, or transceivers.

[0147] In some examples, wireless communication device 900 may be configured for or be configured for use in a STA (such as STA 104 as described with reference to Figure 1). In some other examples, wireless communication device 900 may be a STA including such a processing system and other components including multiple antennas. Wireless communication device 900 is capable of transmitting and receiving wireless communications in, for example, the form of wireless packets. For example, wireless communication device 900 may be configured to or be configured to transmit and receive packets in the form of physical layer PPDUs and MPDUs conforming to one or more of the IEEE 802.11 series of wireless communication protocol standards. In some other examples, wireless communication device 900 may be configured to or be configured to transmit and receive signals and communications conforming to one or more 3GPP specifications, including those for 5G NR or 6G. In some examples, wireless communication device 900 also includes one or more application processors or may be coupled to one or more application processors, which may also be coupled to one or more other memories. In some examples, wireless communication device 900 also includes a user interface (UI) (such as a touchscreen or keypad) and a display that may be integrated with the UI to form a touchscreen display coupled to the processing system. In some examples, the wireless communication device 900 may also include one or more sensors, such as one or more inertial sensors, accelerometers, temperature sensors, pressure sensors, or altitude sensors coupled to the processing system.

[0148] Wireless communication device 900 includes a beam search triggering component 925, a training signal receiving component 930, an RF chain pair selection component 935, and a beamforming direction selection component 940. A portion of one or more of the beam search triggering component 925, the training signal receiving component 930, the RF chain pair selection component 935, and the beamforming direction selection component 940 may be implemented at least partially in hardware or firmware. For example, one or more of the beam search triggering component 925, the training signal receiving component 930, the RF chain pair selection component 935, and the beamforming direction selection component 940 may be implemented at least partially by at least a processor or a modem. In some examples, a portion of one or more of the beam search triggering component 925, the training signal receiving component 930, the RF chain pair selection component 935, and the beamforming direction selection component 940 may be implemented at least partially by a processor and software in the form of processor-executable code stored in memory.

[0149] According to the examples disclosed herein, wireless communication device 900 may support wireless communication. Beam search triggering component 925 can be configured or configured to receive beam search triggering for a second link in a second RF band via a first link in a first RF band. Training signal receiving component 930 can be configured or configured to receive a set of multiple training signals from a set of multiple transmit RF chains of a second wireless communication device via a set of multiple receive RF chains of a first wireless communication device, based on the beam search triggering. RF chain pair selection component 935 can be configured or configured to select an RF chain pair for each spatial stream in the set of spatial streams based on the set of multiple training signals, wherein each RF chain pair includes a receive RF chain from the set of multiple receive RF chains and a transmit RF chain from the set of multiple transmit RF chains. Beamforming direction selection component 940 can be configured or configured to select a beamforming direction for each spatial stream in the set of multiple training signals.

[0150] In some examples, to support the reception of a set of multiple training signals, the training signal receiving component 930 can be configured or be configured to receive a first set of multiple training signals from a first transmit RF link having a first polarization via a second link through a first receive RF link in a set of multiple receive RF links, the first receive RF link having a first polarization, and simultaneously receive a second set of multiple training signals from a second transmit RF link having a second polarization, the first set of multiple training signals and the second set of multiple training signals being received in each of a set of multiple beamforming directions according to beam search triggering. In some examples, to support the reception of a set of multiple training signals, the training signal receiving component 930 can be configured or be configured to receive a first set of multiple training signals from a first transmit radio link having a first polarization via a second receive radio link in a set of multiple receive radio links, the second receive radio link having a second polarization, and simultaneously receive a second set of multiple training signals from a second transmit radio link having a second polarization, the first set of multiple training signals and the second set of multiple training signals being received in each of a set of multiple beamforming directions according to beam search triggering.

[0151] In some examples, in order to support the selection of a set of radio frequency chain pairs, the radio frequency chain pair selection component 935 can be configured or configured to select a first radio frequency chain pair for a first spatial stream and a second radio frequency chain pair for a second spatial stream based on a first set of multiple training signals and a second set of multiple training signals received.

[0152] In some examples, in order to support the selection of a set of beamforming directions, the beamforming direction selection component 940 can be configured or configured to select a first beamforming direction for a first spatial flow and a second beamforming direction for a second spatial flow from a set of multiple beamforming directions, based on a first set of multiple training signals received via a first radio frequency chain pair and a second set of multiple training signals received via a second radio frequency chain pair.

[0153] In some examples, the radio frequency chain pair selection component 935 can be configured or configured to measure, based on a first set of received training signals and a second set of received training signals, a first received power of a first radio frequency chain pair including a first transmit radio frequency chain and a first receive radio frequency chain, a second received power of a second radio frequency chain pair including a second transmit radio frequency chain and a second receive radio frequency chain, a third received power of a third radio frequency chain pair including a first transmit radio frequency chain and a second receive radio frequency chain, and a fourth received power of a fourth radio frequency chain pair including a second transmit radio frequency chain and a first receive radio frequency chain.

[0154] In some examples, the first RF chain pair and the second RF chain pair are selected based on the fact that the first sum of the first and second received power is greater than the second sum of the third and fourth received power.

[0155] In some examples, to support receiving a set of multiple training signals, the training signal receiving component 930 can be configured or configured to be triggered by beam search, receiving a first set of multiple training signals from a first transmitting radio frequency link via a second link through a first receiving radio frequency link in a set of multiple receiving radio frequency links, and receiving a second set of multiple training signals from a second transmitting radio frequency link. The first set of multiple training signals is transmitted on a first subset of the beamforming direction, and the second set of multiple training signals is transmitted on a second subset of the beamforming direction that does not overlap with the first subset of the beamforming direction. In some examples, to support receiving a set of multiple training signals, the training signal receiving component 930 can be configured or configured to be triggered by beam search, receiving a first set of multiple training signals from a first transmitting radio frequency link via a second link through a second receiving radio frequency link in a set of multiple receiving radio frequency links, and receiving a second set of multiple training signals from a second transmitting radio frequency link. The first set of multiple training signals is transmitted on a first subset of the beamforming direction, and the second set of multiple training signals is transmitted on a second subset of the beamforming direction.

[0156] In some examples, in order to support the selection of a set of radio frequency chain pairs, the radio frequency chain pair selection component 935 can be configured or configured to select a first radio frequency chain pair for a first spatial stream and a second radio frequency chain pair for a second spatial stream based on a first set of multiple training signals and a second set of multiple training signals received.

[0157] In some examples, in order to support the selection of a set of beamforming directions, the beamforming direction selection component 940 can be configured or configured to select a first beamforming direction for a first spatial flow from a first subset of beamforming directions or a second subset of beamforming directions, and select a second beamforming direction for a second spatial flow from a first subset of beamforming directions or a second subset of beamforming directions, based on a first set of multiple training signals received via a first RF chain pair and a second set of multiple training signals received via a second RF chain pair.

[0158] In some examples, a first set of multiple training signals is polarized according to a first polarization, and a second set of multiple training signals is polarized according to a second polarization.

[0159] In some examples, to support receiving a set of multiple training signals, the training signal receiving component 930 can be configured or configured to receive a first set of multiple training signals over a set of multiple beamforming directions via a second link through a first receiving radio frequency chain, triggered by a beam search, wherein the set of selected radio frequency chain pairs includes... In some examples, to support receiving a set of multiple training signals, the beamforming direction selection component 940 can be configured or configured to select a first beamforming direction for a first beam of a first spatial stream from the set of multiple beamforming directions based on the first set of multiple training signals received.

[0160] In some examples, to support receiving a set of multiple training signals, the training signal receiving component 930 can be configured or configured to receive a second set of multiple training signals via a second link through a second receiving radio frequency chain on a set of multiple beamforming directions, excluding a subset of beamforming directions within the beamwidth of the first beam, triggered by a beam search; and wherein the set of selected radio frequency chain pairs includes... In some examples, to support receiving a set of multiple training signals, the beamforming direction selection component 940 can be configured or configured to select a second beamforming direction for the second beam of the second spatial flow from the set of multiple beamforming directions based on the received second set of multiple training signals.

[0161] In some examples, the beamforming direction selection component 940 can be configured to, or be configured to, send a feedback message via a first link or a second link, indicating a set of RF link pairs and a set of beamforming directions.

[0162] In some examples, the RF chain pair selection component 935 can be configured or is configured to measure the received power of all combinations of RF chain pairs between a set of multiple receive RF chains and a set of multiple transmit RF chains, wherein the set of RF chain pairs has the highest combined received power among all combinations of RF chain pairs having the same number of RF chain pairs as the set of RF chain pairs.

[0163] Figure 10 A block diagram of an example wireless communication device 1000 supporting a beam search process for multiple spatial streams is shown. In some examples, the wireless communication device 1000 is configured to perform a reference... Figure 12 The process described is 1200. Wireless communication device 1000 may include one or more chips, SoCs, chipsets, packages, components, or devices that individually or collectively constitute or include a processing system. The processing system may interface with other components of wireless communication device 1000 and typically processes information (such as inputs or signals) received from and outputs information (such as outputs or signals) to such other components. In some aspects, an example chip may include a processing system, a first interface for outputting or transmitting information, and a second interface for receiving or acquiring information. For example, the first interface may refer to an interface between the chip's processing system and a transmitting component, enabling wireless communication device 1000 to transmit information output from the chip. In such an example, the second interface may refer to an interface between the chip's processing system and a receiving component, enabling wireless communication device 1000 to receive information, which is then delivered to the processing system. In some such examples, the first interface may also, for example, acquire information from the transmitting component, and the second interface may also, for example, output information to the receiving component.

[0164] The processing system of the wireless communication device 1000 includes processor (or “processing”) circuitry in the form of one or more processors, microprocessors, processing units (such as a central processing unit (CPU), graphics processing unit (GPU), neural processing unit (NPU) (also referred to as a neural network processor or deep learning processor (DLP)) or digital signal processor (DSP)), processing blocks, application-specific integrated circuits (ASICs), programmable logic devices (PLDs) (such as field-programmable gate arrays (FPGAs)), or other discrete gate or transistor logic components or circuits (all of which are generally referred to herein individually as “processors” or collectively as “processors” or “processor circuitry”). One or more of these processors may be individually or collectively configured to perform the various functions or operations described herein. The processing system may also include memory circuitry in the form of one or more memory devices, memory blocks, memory elements, or other discrete gate or transistor logic components or circuitry, each of which may include tangible storage media such as random access memory (RAM) or ROM or combinations thereof (all of which are generally referred to herein individually as “memory” or collectively as “memory” or “memory circuitry”). One or more of these memories may be coupled to one or more processors and may store processor-executable code, individually or collectively, which, when executed by one or more processors, configures one or more processors to perform the various functions or operations described herein. Additionally or alternatively, in some examples, one or more processors may be pre-configured to perform the various functions or operations described herein without software configuration. The processing system may also include or be coupled to one or more modems (such as Wi-Fi (e.g., IEEE compliant) modems or cellular (e.g., 3GPP 4G LTE, 5G, or 6G compliant) modems). In some embodiments, one or more processors of the processing system include or implement one or more modems. The processing system may also include or be coupled to multiple radio components (collectively, “radio components”), multiple RF chains, or multiple transceivers, each of which may in turn be coupled to one or more antennas. In some embodiments, one or more processors of the processing system include or implement one or more of the radio components, RF chains, or transceivers.

[0165] In some examples, the wireless communication device 1000 may be configured for or be configured for use in an AP such as AP 102 as described with reference to FIG1. ​​In some other examples, the wireless communication device 1000 may be an AP including such a processing system as well as other components including multiple antennas. The wireless communication device 1000 is capable of transmitting and receiving wireless communications, for example, in the form of wireless packets. For example, the wireless communication device 1000 may be configured to or be configured to transmit and receive packets in the form of physical layer PPDUs and MPDUs conforming to one or more of the IEEE 802.11 series of wireless communication protocol standards. In some other examples, the wireless communication device 1000 may be configured to or be configured to transmit and receive signals and communications conforming to one or more 3GPP specifications, including those for 5G NR or 6G. In some examples, the wireless communication device 1000 also includes one or more application processors or may be coupled to one or more application processors, which may also be coupled to one or more other memories. In some examples, the wireless communication device 1000 also includes at least one external network interface coupled to a processing system, which enables communication with a core network or backhaul network that allows the wireless communication device 1000 to access external networks, including the Internet.

[0166] The wireless communication device 1000 includes a beam search triggering component 1025, a training signal component 1030, and a beamforming feedback component 1035. A portion of one or more of the beam search triggering component 1025, the training signal component 1030, and the beamforming feedback component 1035 may be implemented at least partially in hardware or firmware. For example, one or more of the beam search triggering component 1025, the training signal component 1030, and the beamforming feedback component 1035 may be implemented at least partially by at least a processor or a modem. In some examples, a portion of one or more of the beam search triggering component 1025, the training signal component 1030, and the beamforming feedback component 1035 may be implemented at least partially by a processor and software in the form of processor-executable code stored in memory.

[0167] According to the examples disclosed herein, wireless communication device 1000 may support wireless communication. Beam search triggering component 1025 can be configured or configured to transmit a beam search trigger for a second link in a second radiative spectrum via a first link in a first radiative spectrum. Training signal component 1030 can be configured or configured to transmit a set of multiple training signals via the second link to a set of multiple receive radiative chains of a second wireless communication device, according to the beam search trigger. Beamforming feedback receiving component 1035 can be configured or configured to receive a feedback message indicating the radiative chain pair of each spatial stream in the set of spatial streams and the beamforming direction of each spatial stream in the set of spatial streams.

[0168] In some examples, to support the transmission of a set of multiple training signals, the training signal component 1030 can be configured or configured to transmit a first set of multiple training signals over a set of multiple beamforming directions via a first transmit RF chain having a first polarization, triggered by a beam search. In some examples, to support the transmission of a set of multiple training signals, the training signal component 1030 can be configured or configured to transmit a second set of multiple training signals over a set of multiple beamforming directions via a second transmit RF chain having a second polarization, triggered by a beam search.

[0169] In some examples, to support the transmission of a set of multiple training signals, the training signal component 1030 can be configured or configured to transmit a first set of multiple training signals on a first subset of the beamforming direction via a first transmit radio frequency chain, triggered by a beam search. In some examples, to support the transmission of a set of multiple training signals, the training signal component 1030 can be configured or configured to transmit a second set of multiple training signals on a second subset of the beamforming direction that does not overlap with the first subset of the beamforming direction, triggered by a second transmit radio frequency chain.

[0170] In some examples, to support the transmission of a set of multiple training signals, the training signal component 1030 can be configured or configured to transmit a first set of multiple training signals over a set of multiple beamforming directions via a first transmit radio frequency chain, triggered by a beam search, wherein a feedback message indicates a first beam direction of a first spatial flow, the first beam direction being associated with a first beam having a first beamwidth. In some examples, to support the reception of a set of multiple training signals, the training signal component 1030 can be configured or configured to transmit a second set of multiple training signals over a set of multiple beamforming directions, excluding a subset of the beamforming directions within the first beamwidth of the first beam, via a second transmit radio frequency chain, triggered by a beam search and a feedback message.

[0171] Figure 11 A flowchart illustrating an example process 1100 that can be executed by or at a first wireless communication device supporting a beam search process for multiple spatial streams is shown. Operation of process 1100 can be implemented by a first wireless communication device or its components as described herein. For example, process 1100 can be executed by a wireless communication device (such as wireless communication device 900 described with reference to FIG. 9) operating as or within a wireless STA. In some examples, process 1100 can be executed by a wireless STA (such as one of the STAs 104 described with reference to FIG. 1).

[0172] In some examples, in block 1105, a first wireless communication device may receive a beam search trigger for a second link in a second radiative spectrum band via a first link in a first radiative spectrum band. Operation of block 1105 may be performed according to examples disclosed herein. In some specific implementations, aspects of operation of block 1105 may be performed by a beam search triggering component 925 as described with reference to FIG9.

[0173] In some examples, in block 1110, the first wireless communication device can receive a set of multiple training signals from a set of multiple transmit radio frequency chains of the second wireless communication device via a second link, triggered by a beam search, through a set of multiple receive radio frequency chains of the first wireless communication device. The operation of block 1110 can be performed according to the examples disclosed herein. In some specific implementations, aspects of the operation of block 1110 can be performed by the training signal receiving component 930 as described with reference to FIG. 9.

[0174] In some examples, in block 1115, the first wireless communication device can select a radio frequency chain pair for each spatial stream in a set of spatial streams based on a set of multiple training signals, wherein each radio frequency chain pair includes a receive radio frequency chain in a set of multiple receive radio frequency chains and a transmit radio frequency chain in a set of multiple transmit radio frequency chains. The operation of block 1115 can be performed according to the examples disclosed herein. In some specific implementations, aspects of the operation of block 1115 can be performed by radio frequency chain pair selection component 935 as described with reference to FIG. 9.

[0175] In some examples, in block 1120, the first wireless communication device can select a beamforming direction for each spatial stream in a set of spatial streams based on a set of multiple training signals. The operation of block 1120 can be performed according to examples disclosed herein. In some specific implementations, aspects of the operation of block 1120 can be performed by a beamforming direction selection component 940 as described with reference to FIG. 9.

[0176] Figure 12A flowchart illustrating an example process 1200 that can be executed by or at a first wireless communication device supporting a beam search process for multiple spatial streams is shown. Operation of process 1200 can be implemented by a first wireless communication device or its components as described herein. For example, process 1200 can be implemented by a wireless communication device operating as a wireless access point (AP) or within that wireless AP (such as reference 1200). Figure 10 The process 1200 is performed by the wireless communication device 1000 described herein. In some examples, the process 1200 may be performed by a wireless AP (such as one of the APs 102 described with reference to Figure 1).

[0177] In some examples, in block 1205, the first wireless communication device may transmit a beam search trigger for a second link in a second radiative spectrum via a first link in a first radiative spectrum. Operation of block 1205 may be performed according to examples as disclosed herein. In some specific implementations, aspects of the operation of block 1205 may be as described in references... Figure 10 The described beam search triggering component 1025 is used to perform this.

[0178] In some examples, in block 1210, the first wireless communication device can, based on beam search triggering, transmit a set of multiple training signals via a second link through a set of multiple transmit radio frequency chains of the first wireless communication device to a set of multiple receive radio frequency chains of the second wireless communication device. The operation of block 1210 can be performed according to the examples disclosed herein. In some specific implementations, aspects of the operation of block 1210 can be derived from references... Figure 10 The training signal component 1030 described herein is used to perform this action.

[0179] In some examples, in block 1215, the first wireless communication device may receive a feedback message indicating the radio frequency chain pair of each spatial stream in the set of spatial streams and the beamforming direction of each spatial stream in the set of spatial streams. Operation of block 1215 may be performed according to examples as disclosed herein. In some specific implementations, aspects of the operation of block 1215 may be provided by reference to [reference needed]. Figure 10 The beamforming feedback component 1035 described herein is used to perform this action.

[0180] Specific implementation examples are described in the following numbered clauses: The following provides an overview of the various aspects of this disclosure: Aspect 1: A method for wireless communication by a first wireless communication device, the method comprising: receiving a beam search trigger for a second link in a second RF band via a first link in a first RF band; receiving a plurality of training signals via the second link from a plurality of transmit RF links of a second wireless communication device via a plurality of receive RF links of the first wireless communication device according to the beam search trigger; selecting a pair of RF links for each spatial stream in a set of spatial streams according to the plurality of training signals, wherein each pair of RF links includes a receive RF link in the plurality of receive RF links and a transmit RF link in the plurality of transmit RF links; and selecting a beamforming direction for each spatial stream in the set of spatial streams according to the plurality of training signals.

[0181] Aspect 2: According to the method of Aspect 1, receiving the plurality of training signals includes: receiving a first plurality of training signals via the second link through a first receiving radio frequency chain of the plurality of receiving radio frequency chains having a first polarization, the first receiving radio frequency chain having the first polarization, and simultaneously receiving a second plurality of training signals from a second transmitting radio frequency chain having a second polarization, the first plurality of training signals and the second plurality of training signals being received in each of the plurality of beamforming directions according to the beam search trigger; and receiving the first plurality of training signals via the second link through a second receiving radio frequency chain of the plurality of receiving radio frequency chains having the first polarization, the second receiving radio frequency chain having the second polarization, and simultaneously receiving the second plurality of training signals from the second transmitting radio frequency chain having the second polarization, the first plurality of training signals and the second plurality of training signals being received in each of the plurality of beamforming directions according to the beam search trigger.

[0182] Aspect 3: According to the method of aspect 2, selecting the radio frequency chain pair for each spatial stream includes: selecting a first radio frequency chain pair for a first spatial stream and selecting a second radio frequency chain pair for a second spatial stream based on receiving the first plurality of training signals and the second plurality of training signals.

[0183] Aspect 4: The method according to any one of Aspects 2 to 3, wherein selecting the beamforming direction for each spatial flow comprises: selecting a first beamforming direction for a first spatial flow and selecting a second beamforming direction for a second spatial flow from the plurality of beamforming directions based on receiving the first plurality of training signals via the first radio frequency chain pair and receiving the second plurality of training signals via the second radio frequency chain pair.

[0184] Aspect 5: The method according to any one of Aspects 2 to 4, the method further comprising: measuring, based on receiving the first plurality of training signals and the second plurality of training signals, a first received power of a first radio frequency chain pair including the first transmit radio frequency chain and the first receive radio frequency chain, a second received power of a second radio frequency chain pair including the second transmit radio frequency chain and the second receive radio frequency chain, a third received power of a third radio frequency chain pair including the first transmit radio frequency chain and the second receive radio frequency chain, and a fourth received power of a fourth radio frequency chain pair including the second transmit radio frequency chain and the first receive radio frequency chain.

[0185] Aspect 6: According to the method of aspect 5, wherein the first radio frequency chain pair and the second radio frequency chain pair are selected based on the fact that a first sum of the first received power and the second received power is greater than a second sum of the third received power and the fourth received power.

[0186] Aspect 7: The method according to any one of Aspects 1 to 6, wherein receiving the plurality of training signals comprises: receiving a first plurality of training signals from a first transmit radio frequency link and receiving a second plurality of training signals from a second transmit radio frequency link via a first receive radio frequency link of the plurality of receive radio frequency links, the first plurality of training signals being transmitted on a first subset in the beamforming direction, and the second plurality of training signals being transmitted on a second subset in the beamforming direction that does not overlap with the first subset in the beamforming direction; and receiving the first plurality of training signals from the first transmit radio frequency link and receiving the second plurality of training signals from the second transmit radio frequency link via a second receive frequency link of the plurality of receive radio frequency links, the first plurality of training signals being transmitted on the first subset in the beamforming direction, and the second plurality of training signals being transmitted on the second subset in the beamforming direction, according to the beam search trigger.

[0187] Aspect 8: According to the method of aspect 7, selecting the radio frequency chain pair for each spatial stream includes: selecting a first radio frequency chain pair for a first spatial stream and selecting a second radio frequency chain pair for a second spatial stream based on receiving the first plurality of training signals and the second plurality of training signals.

[0188] Aspect 9: The method according to any one of Aspects 7 to 8, wherein selecting the beamforming direction for each spatial flow comprises: receiving the first plurality of training signals via the first radio frequency chain pair and receiving the second plurality of training signals via the second radio frequency chain pair, selecting a first beamforming direction for a first spatial flow from a first subset of beamforming directions or a second subset of beamforming directions, and selecting a second beamforming direction for a second spatial flow from the first subset of beamforming directions or the second subset of beamforming directions.

[0189] Aspect 10: The method according to any one of Aspects 7 to 9, wherein the first plurality of training signals are polarized according to a first polarization, and the second plurality of training signals are polarized according to a second polarization.

[0190] Aspect 11: The method according to any one of Aspects 1 to 10, wherein receiving the plurality of training signals comprises: receiving a first plurality of training signals via a second link through a first receiving radio frequency chain in a plurality of beamforming directions according to the beam search trigger, and wherein selecting the radio frequency chain pair for each spatial flow comprises: selecting a first beamforming direction for a first beam of a first spatial flow from the plurality of beamforming directions according to receiving the first plurality of training signals.

[0191] Aspect 12: According to the method of aspect 11, receiving the plurality of training signals includes: receiving a second plurality of training signals via the second link through a second receiving radio frequency chain in a subset of the plurality of beamforming directions excluding the beamwidth of the first beam, based on the beam search trigger; and wherein selecting the radio frequency chain pair for each spatial flow includes: selecting a second beamforming direction from the plurality of beamforming directions for a second beam of a second spatial flow based on receiving the second plurality of training signals.

[0192] Aspect 13: The method according to any one of Aspects 1 to 12, the method further comprising: transmitting a feedback message via the first link or the second link, the feedback message indicating the radio frequency chain pair of each spatial stream and the beamforming direction of each spatial stream.

[0193] Aspect 14: The method according to any one of Aspects 1 to 13, the method further comprising: measuring the received power of all combinations of radio frequency chain pairs between the plurality of receiving radio frequency chains and the plurality of transmitting radio frequency chains, wherein the selected radio frequency chain pair has the highest combined received power among all combinations of radio frequency chain pairs having the same number of radio frequency chain pairs as the selected radio frequency chain pair.

[0194] Aspect 15: A method for wireless communication by a first wireless communication device, the method comprising: transmitting a beam search trigger for a second link in a second radiative spectrum via a first link in a first radiative spectrum; transmitting a plurality of training signals via the second link to a plurality of receiving radiative chains of a second wireless communication device via a plurality of transmitting radiative chains of the first wireless communication device according to the beam search trigger; and receiving a feedback message indicating a pair of radiative chains for each spatial stream in a set of spatial streams and a beamforming direction for each spatial stream in the set of spatial streams.

[0195] Aspect 16: According to the method of aspect 15, transmitting the plurality of training signals includes: transmitting a first plurality of training signals in a plurality of beamforming directions via a first transmit radio frequency chain having a first polarization according to the beam search trigger; and transmitting a second plurality of training signals in the plurality of beamforming directions via a second transmit radio frequency chain having a second polarization according to the beam search trigger.

[0196] Aspect 17: The method according to any one of Aspects 15 to 16, wherein transmitting the plurality of training signals comprises: transmitting a first plurality of training signals on a first subset in the beamforming direction via a first transmit radio frequency chain according to the beam search trigger; and transmitting a second plurality of training signals on a second subset in the beamforming direction that does not overlap with the first subset in the beamforming direction via a second transmit radio frequency chain according to the beam search trigger.

[0197] Aspect 18: The method according to any one of Aspects 15 to 17, wherein transmitting the plurality of training signals comprises: transmitting a first plurality of training signals via a first transmit radio frequency chain in a plurality of beamforming directions according to the beam search trigger, wherein the feedback message indicates a first beam direction of a first spatial flow, the first beam direction being associated with a first beam having a first beamwidth; and transmitting a second plurality of training signals via a second transmit radio frequency chain in the plurality of beamforming directions, a subset of beamforming directions excluding the first beam within the first beamwidth, according to the beam search trigger and the feedback message.

[0198] Aspect 19: A first wireless communication device for wireless communication, the first wireless communication device comprising: one or more memories storing processor-executable code; and one or more processors coupled to the one or more memories and capable of operating individually or jointly to execute the code to cause the first wireless communication device to perform a method according to any one of Aspects 1 to 14.

[0199] Aspect 20: A first wireless communication device for wireless communication, the first wireless communication device comprising at least one component for performing the method according to any one of aspects 1 to 14.

[0200] Aspect 21: A non-transitory computer-readable medium storing code for wireless communication, said code including instructions executable by one or more processors to perform the method according to any one of aspects 1 to 14.

[0201] Aspect 22: A first wireless communication device for wireless communication, the first wireless communication device comprising: one or more memories storing processor-executable code; and one or more processors coupled to the one or more memories and capable of operating individually or jointly to execute the code to cause the first wireless communication device to perform a method according to any one of aspects 15 to 18.

[0202] Aspect 23: A first wireless communication device for wireless communication, the first wireless communication device comprising at least one component for performing the method according to any one of aspects 15 to 18.

[0203] Aspect 24: A non-transitory computer-readable medium storing code for wireless communication, said code comprising instructions executable by one or more processors to perform the method according to any one of Aspects 15 to 18. As used herein, the term “determine” covers a wide variety of actions, and therefore, “determine” can include calculation, operation, processing, deduction, estimation, investigation, lookup (such as via searching in a table, database, or other data structure), inference, detection, or measurement, among other possibilities. Furthermore, “determine” can include receiving (such as receiving information), accessing (such as accessing data stored in memory), or transmitting (such as transmitting information), among other possibilities. Additionally, “determine” can include parsing, selecting, obtaining, choosing, establishing, and other similar actions.

[0204] As used herein, the phrase “at least one of” or “one or more of” refers to any combination of these items, including a single member. For example, “at least one of a, b, or c” is intended to cover: a, b, c, ab, ac, bc, and abc. As used herein, “or” is intended to be interpreted in an inclusive sense unless otherwise expressly indicated. For example, “a or b” may include only a, only b, or a combination of a and b. Furthermore, as used herein, the phrase referring to “one” element means one or more of such elements that act individually or collectively to perform the stated function. Additionally, “set” means one or more items, and “subset” means less than the entire set, but not empty.

[0205] As used herein, unless otherwise expressly indicated, “based on” is intended to be interpreted in an inclusive sense. For example, unless otherwise explicitly indicated, “based on” may be used interchangeably with “at least partially based on,” “associated with,” “associated with,” or “according to.” Specifically, unless the phrase in the context means “based on only one” or an equivalent, whether it is “based on one” or “at least partially based on one”, it may be based solely on “one” or based on a combination of “one” and one or more other factors, conditions, or information.

[0206] The various exemplary components, logic units, logic blocks, modules, circuits, operations, and algorithmic processes described in conjunction with the examples disclosed herein can be implemented as electronic hardware, firmware, software, or a combination of hardware, firmware, or software, including the structures disclosed in this specification and their structural equivalents. This interchangeability of hardware, firmware, and software has been generally described in terms of its functionality and exemplified in the various exemplary components, blocks, modules, circuits, and processes described above. Whether this functionality is implemented in hardware, firmware, or software depends on the specific application and the design constraints imposed on the overall system.

[0207] Various modifications to the examples described in this disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other examples without departing from the spirit or scope of this disclosure. Therefore, the claims are not intended to be limited to the examples shown herein, but are to be granted the widest scope consistent with this disclosure, the principles disclosed herein, and the novel features.

[0208] Additionally, the various features described in this specification in the context of individual examples may also be implemented in combination in a single specific embodiment. Conversely, the various features described in the context of a single specific embodiment may also be implemented individually or in any suitable sub-combination in multiple examples. Thus, although features may be described above as functioning in a particular combination, and even initially claimed in this way, one or more features from the claimed combination may be removed from the combination in some cases, and the claimed combination may involve sub-combinations or variations of sub-combinations.

[0209] Similarly, although operations are depicted in a specific order in the diagrams, this should not be construed as requiring such operations to be performed in the specific order shown or in sequential order, or to perform all illustrated operations to achieve the desired result. Furthermore, the accompanying figures may schematically depict one or more example processes in the form of flowcharts or flow diagrams. However, other operations not depicted may be incorporated into the schematically illustrated example processes. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the illustrated operations. In some environments, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the examples described above should not be construed as requiring such separation in all examples, but rather should be understood as meaning that the described program components and systems can generally be integrated together in a single software product or encapsulated in multiple software products.

Claims

1. A first wireless communication device, the first wireless communication device comprising: A processing system, comprising processor circuitry and memory circuitry for storing code, is configured to cause the first wireless communication device to: Beam search triggering is achieved by receiving a beam through a first link in a first RF band and targeting a second link in a second RF band. According to the beam search trigger, multiple training signals are received from multiple transmit radio links of the second wireless communication device via the second link through multiple receive radio links of the first wireless communication device. Radio frequency chain pairs are selected for each spatial stream in the set of spatial streams based on the plurality of training signals, wherein each radio frequency chain pair includes a receive radio frequency chain in the plurality of receive radio frequency chains and a transmit radio frequency chain in the plurality of transmit radio frequency chains; as well as Beamforming direction is selected for each spatial flow in the set of spatial flows based on the plurality of training signals.

2. The first wireless communication device according to claim 1, wherein, in order to receive the plurality of training signals, the processing system is configured to cause the first wireless communication device to: The second link receives a first plurality of training signals from a first transmit RF link having a first polarization via a first receive RF link of the plurality of receive RF links, and simultaneously receives a second plurality of training signals from a second transmit RF link having a second polarization different from the first polarization, wherein the first receive RF link has the first polarization, and the first plurality of training signals and the second plurality of training signals are received in each of the plurality of beamforming directions according to the beam search trigger; and The first plurality of training signals are received from the first transmit radio link having the first polarization via the second receive radio link in the plurality of receive radio links, and the second plurality of training signals are received simultaneously from the second transmit radio link having the second polarization, the second receive radio link having the second polarization, the first plurality of training signals and the second plurality of training signals being received in each of the plurality of beamforming directions according to the beam search trigger.

3. The first wireless communication device according to claim 2, wherein, in order to select the radio frequency chain pair for each spatial stream, the processing system is configured to cause the first wireless communication device to: Based on the received first plurality of training signals and second plurality of training signals, a first radio frequency chain pair is selected for the first spatial stream and a second radio frequency chain pair is selected for the second spatial stream.

4. The first wireless communication device according to claim 2, wherein, in order to select the beamforming direction for each spatial flow, the processing system is configured to cause the first wireless communication device to: Based on receiving the first plurality of training signals via a first radio frequency chain pair and receiving the second plurality of training signals via a second radio frequency chain pair, a first beamforming direction is selected for a first spatial flow from the plurality of beamforming directions, and a second beamforming direction is selected for a second spatial flow from the plurality of beamforming directions.

5. The first wireless communication device according to claim 2, wherein the processing system is further configured to cause the first wireless communication device to: The first received power of a first radio frequency chain pair including the first transmit radio frequency chain and the first receive radio frequency chain, the second received power of a second radio frequency chain pair including the second transmit radio frequency chain and the second receive radio frequency chain, the third received power of a third radio frequency chain pair including the first transmit radio frequency chain and the second receive radio frequency chain, and the fourth received power of a fourth radio frequency chain pair including the second transmit radio frequency chain and the first receive radio frequency chain are measured based on the received first plurality of training signals and the second plurality of training signals.

6. The first wireless communication device according to claim 5, wherein the first radio frequency chain pair and the second radio frequency chain pair are selected based on the fact that a first sum of the first received power and the second received power is greater than a second sum of the third received power and the fourth received power.

7. The first wireless communication device according to claim 1, wherein, in order to receive the plurality of training signals, the processing system is configured to cause the first wireless communication device to: According to the beam search trigger, a first plurality of training signals are received from a first transmit RF link and a second plurality of training signals are received from a second transmit RF link via the second link through a first receive RF link of the plurality of receive RF links. The first plurality of training signals are transmitted on a first subset of the beamforming direction, and the second plurality of training signals are transmitted on a second subset of the beamforming direction that does not overlap with the first subset of the beamforming direction; and According to the beam search trigger, the first plurality of training signals are received from the first transmit RF link and the second plurality of training signals are received from the second transmit RF link via the second receive RF link of the plurality of receive RF links, wherein the first plurality of training signals are transmitted on the first subset in the beamforming direction and the second plurality of training signals are transmitted on the second subset in the beamforming direction.

8. The first wireless communication device of claim 7, wherein, in order to select the radio frequency chain pair for each spatial stream, the processing system is configured to cause the first wireless communication device to: Based on the received first plurality of training signals and second plurality of training signals, a first radio frequency chain pair is selected for the first spatial stream and a second radio frequency chain pair is selected for the second spatial stream.

9. The first wireless communication device of claim 7, wherein, in order to select the beamforming direction for each spatial flow, the processing system is configured to cause the first wireless communication device to: Based on receiving the first plurality of training signals via a first radio frequency chain pair and receiving the second plurality of training signals via a second radio frequency chain pair, a first beamforming direction is selected for a first spatial flow from the first subset or the second subset of the beamforming direction, and a second beamforming direction is selected for a second spatial flow from the first subset or the second subset of the beamforming direction.

10. The first wireless communication device of claim 7, wherein the first plurality of training signals are polarized according to a first polarization, and the second plurality of training signals are polarized according to a second polarization.

11. The first wireless communication device of claim 1, wherein, in order to receive the plurality of training signals, the processing system is configured to cause the first wireless communication device to: Based on the beam search trigger, a first plurality of training signals are received via the second link through the first receiving radio frequency chain in multiple beamforming directions, and wherein, in order to select the radio frequency chain pair for each spatial stream, the processing system is configured to cause the first wireless communication device to: Based on receiving the first plurality of training signals, a first beamforming direction is selected from the plurality of beamforming directions for a first beam of a first spatial flow; and Based on the beam search trigger, a second plurality of training signals are received via the second link through a second receiving radio frequency chain in a plurality of beamforming directions, excluding the beamwidth of the first beam, within the plurality of beamforming directions; and wherein, in order to select the radio frequency chain pair for each spatial stream, the processing system is configured to cause the first wireless communication device to: Based on the received second plurality of training signals, a second beamforming direction is selected from the plurality of beamforming directions for the second beam of the second spatial flow.

12. The first wireless communication device according to claim 1, wherein the processing system is further configured to cause the first wireless communication device to: A feedback message is sent via the first link or the second link, the feedback message indicating the radio frequency chain pair of each spatial stream and the beamforming direction of each spatial stream.

13. The first wireless communication device according to claim 1, wherein the processing system is further configured to cause the first wireless communication device to: Measure the received power of all combinations of RF chain pairs between the plurality of receive RF chains and the plurality of transmit RF chains, wherein the selected RF chain pair has the highest combined received power among all combinations of RF chain pairs having the same number of RF chain pairs as the selected RF chain pair.

14. A first wireless communication device, the first wireless communication device comprising: A processing system, comprising processor circuitry and memory circuitry for storing code, is configured to cause the first wireless communication device to: Beam search triggering is transmitted via the first link in the first RF band to the second link in the second RF band; According to the beam search trigger, multiple training signals are sent to multiple receiving radio chains of the second wireless communication device via the second link through multiple transmitting radio chains of the first wireless communication device. as well as Receive feedback messages, the feedback messages indicating the radio frequency chain pair of each spatial stream in the set of spatial streams and the beamforming direction of each spatial stream in the set of spatial streams.

15. The first wireless communication device of claim 14, wherein, in order to transmit the plurality of training signals, the processing system is configured to cause the first wireless communication device to: Based on the beam search trigger, a first plurality of training signals are transmitted in a plurality of beamforming directions via a first transmit RF chain having a first polarization; and According to the beam search trigger, a second plurality of training signals are transmitted via a second transmit radio frequency chain with a second polarization in the plurality of beamforming directions.

16. The first wireless communication device of claim 14, wherein, in order to transmit the plurality of training signals, the processing system is configured to cause the first wireless communication device to: Based on the beam search trigger, a first plurality of training signals are transmitted via a first transmit radio frequency chain on a first subset of the beamforming direction; and Based on the beam search trigger, a second plurality of training signals are transmitted via a second transmit radio frequency chain on a second subset that does not overlap with the first subset in the beamforming direction.

17. The first wireless communication device of claim 14, wherein, in order to transmit the plurality of training signals, the processing system is configured to cause the first wireless communication device to: Based on the beam search trigger, a first plurality of training signals are transmitted via a first transmit RF chain in a plurality of beamforming directions, wherein the feedback message indicates a first beam direction of a first spatial flow, the first beam direction being associated with a first beam having a first beamwidth; and Based on the beam search trigger and the feedback message, a second plurality of training signals are transmitted via a second transmit radio frequency chain in a plurality of beamforming directions, a subset of beamforming directions within the first beamwidth excluding the first beam.

18. A method for wireless communication by a first wireless communication device, the method comprising: Beam search triggering is achieved by receiving a beam through a first link in a first RF band and targeting a second link in a second RF band. According to the beam search trigger, multiple training signals are received from multiple transmit radio links of the second wireless communication device via the second link through multiple receive radio links of the first wireless communication device. Radio frequency chain pairs are selected for each spatial stream in the set of spatial streams based on the plurality of training signals, wherein each radio frequency chain pair includes a receive radio frequency chain in the plurality of receive radio frequency chains and a transmit radio frequency chain in the plurality of transmit radio frequency chains; as well as Beamforming direction is selected for each spatial flow in the set of spatial flows based on the plurality of training signals.

19. The method of claim 18, wherein receiving the plurality of training signals comprises: The first plurality of training signals are received from a first transmit radio link having a first polarization via the second link through the first receive radio link of the plurality of receive radio links, and simultaneously from a second transmit radio link having a second polarization different from the first polarization, the first receive radio link having the first polarization, the first plurality of training signals and the second plurality of training signals being received in each of the plurality of beamforming directions according to the beam search trigger; as well as The first plurality of training signals are received from the first transmit radio link having the first polarization via the second receive radio link in the plurality of receive radio links, and the second plurality of training signals are received simultaneously from the second transmit radio link having the second polarization, the second receive radio link having the second polarization, the first plurality of training signals and the second plurality of training signals being received in each of the plurality of beamforming directions according to the beam search trigger.

20. The method of claim 19, wherein selecting the radio frequency chain pair for each spatial flow comprises: Based on the received first plurality of training signals and second plurality of training signals, a first radio frequency chain pair is selected for the first spatial stream and a second radio frequency chain pair is selected for the second spatial stream.

21. The method of claim 19, wherein selecting the beamforming direction for each spatial flow comprises: Based on receiving the first plurality of training signals via a first radio frequency chain pair and receiving the second plurality of training signals via a second radio frequency chain pair, a first beamforming direction is selected for a first spatial flow from the plurality of beamforming directions, and a second beamforming direction is selected for a second spatial flow from the plurality of beamforming directions.

22. The method according to claim 19, further comprising: The first received power of a first radio frequency chain pair including the first transmit radio frequency chain and the first receive radio frequency chain, the second received power of a second radio frequency chain pair including the second transmit radio frequency chain and the second receive radio frequency chain, the third received power of a third radio frequency chain pair including the first transmit radio frequency chain and the second receive radio frequency chain, and the fourth received power of a fourth radio frequency chain pair including the second transmit radio frequency chain and the first receive radio frequency chain are measured based on the received first plurality of training signals and the second plurality of training signals.

23. The method of claim 22, wherein the first radio frequency chain pair and the second radio frequency chain pair are selected based on the fact that a first sum of the first received power and the second received power is greater than a second sum of the third received power and the fourth received power.

24. The method of claim 18, wherein receiving the plurality of training signals comprises: According to the beam search trigger, the second link receives a first plurality of training signals from the first transmit RF link and a second plurality of training signals from the second transmit RF link via the first receive RF link of the plurality of receive RF links. The first plurality of training signals are transmitted on a first subset in the beamforming direction, and the second plurality of training signals are transmitted on a second subset in the beamforming direction that does not overlap with the first subset in the beamforming direction. as well as According to the beam search trigger, the first plurality of training signals are received from the first transmit RF link and the second plurality of training signals are received from the second transmit RF link via the second receive RF link of the plurality of receive RF links, wherein the first plurality of training signals are transmitted on the first subset in the beamforming direction and the second plurality of training signals are transmitted on the second subset in the beamforming direction.

25. The method of claim 24, wherein selecting the radio frequency chain pair for each spatial flow comprises: Based on the received first plurality of training signals and second plurality of training signals, a first radio frequency chain pair is selected for the first spatial stream and a second radio frequency chain pair is selected for the second spatial stream.

26. The method of claim 24, wherein selecting the beamforming direction for each spatial flow comprises: Based on receiving the first plurality of training signals via a first radio frequency chain pair and receiving the second plurality of training signals via a second radio frequency chain pair, a first beamforming direction is selected for a first spatial flow from the first subset or the second subset of the beamforming direction, and a second beamforming direction is selected for a second spatial flow from the first subset or the second subset of the beamforming direction.

27. The method of claim 24, wherein the first plurality of training signals are polarized according to a first polarization, and the second plurality of training signals are polarized according to a second polarization.

28. The method of claim 18, wherein receiving the plurality of training signals comprises: Based on the beam search trigger, a first plurality of training signals are received via the second link through a first receiving RF chain in multiple beamforming directions, wherein selecting the RF chain pair for each spatial stream includes: Based on receiving the first plurality of training signals, a first beamforming direction is selected from the plurality of beamforming directions for a first beam of a first spatial flow; and Based on the beam search trigger, a second plurality of training signals are received via the second link through a second receiving RF chain in a plurality of beamforming directions, excluding the beamwidth of the first beam; and wherein selecting the RF chain pair for each spatial stream includes: Based on the received second plurality of training signals, a second beamforming direction is selected from the plurality of beamforming directions for the second beam of the second spatial flow.

29. The method according to claim 18, further comprising: A feedback message is sent via the first link or the second link, the feedback message indicating the radio frequency chain pair of each spatial stream and the beamforming direction of each spatial stream.

30. The method according to claim 18, further comprising: Measure the received power of all combinations of RF chain pairs between the plurality of receive RF chains and the plurality of transmit RF chains, wherein the selected RF chain pair has the highest combined received power among all combinations of RF chain pairs having the same number of RF chain pairs as the selected RF chain pair.

31. A method for wireless communication by a first wireless communication device, the method comprising: Beam search triggering is transmitted via the first link in the first RF band to the second link in the second RF band; According to the beam search trigger, multiple training signals are sent to multiple receiving radio chains of the second wireless communication device via the second link through multiple transmitting radio chains of the first wireless communication device. as well as Receive feedback messages, the feedback messages indicating the radio frequency chain pair of each spatial stream in the set of spatial streams and the beamforming direction of each spatial stream in the set of spatial streams.

32. The method of claim 31, wherein sending the plurality of training signals comprises: According to the beam search trigger, a first plurality of training signals are transmitted in a plurality of beamforming directions via a first transmit radio frequency chain having a first polarization; as well as According to the beam search trigger, a second plurality of training signals are transmitted via a second transmit radio frequency chain with a second polarization in the plurality of beamforming directions.

33. The method of claim 31, wherein sending the plurality of training signals comprises: According to the beam search trigger, a first plurality of training signals are transmitted via a first transmit radio frequency chain on a first subset of the beamforming direction; as well as Based on the beam search trigger, a second plurality of training signals are transmitted via a second transmit radio frequency chain on a second subset that does not overlap with the first subset in the beamforming direction.

34. The method of claim 31, wherein sending the plurality of training signals comprises: According to the beam search trigger, a first plurality of training signals are transmitted in a plurality of beamforming directions via a first transmit radio frequency chain, wherein the feedback message indicates a first beam direction of a first spatial flow, the first beam direction being associated with a first beam having a first beamwidth; as well as Based on the beam search trigger and the feedback message, a second plurality of training signals are transmitted via a second transmit radio frequency chain in a plurality of beamforming directions, a subset of beamforming directions within the first beamwidth excluding the first beam.

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