Patent Description:
These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (such as time, frequency, and power). A wireless network, for example a wireless local area network (WLAN) or Wi-Fi (i.e., Institute of Electrical and Electronics Engineers (IEEE) <NUM>) network may include an access point (AP) that may communicate with one or more stations (STAs) or mobile devices. The AP may be coupled to a network, such as the Internet, and may enable a mobile device to communicate via the network (or communicate with other devices coupled to the AP). A wireless device may communicate with a network device bi-directionally. For example, in a WLAN, a STA may communicate with an associated AP via downlink and uplink transmissions. The downlink (or forward link) may refer to the communication link from the AP to the STA, and the uplink (or reverse link) may refer to the communication link from the STA to the AP.

<CIT> discloses methods and systems for performing channel estimation between a beamformer and a beamformee. A beamformer can determine that a beamformee is configured to perform channel estimation for up to a preconfigured number of transmit spatial streams from the beamformer. The preconfigured number of transmit spatial streams can be less than a plurality of transmit spatial streams of the beamformer. The beamformer can determine a plurality of subsets of transmit spatial streams from the plurality of transmit spatial streams. The beamformer can send a plurality of sounding frames to the beamformee for channel estimation based at least on the determined plurality of subsets of transmit spatial streams.

<CIT> provides a sounding method of a receiving device. The receiving device receives an NDPA frame and then receives an NDP frame, from a transmitting device. After receiving the NDP frame, the receiving device transmits to the transmitting device a channel feedback frame including feedback information according to a feedback type indicated by the feedback type information.

There is still a need for an improved way of managing multiple space-time streams.

The present invention provides a solution according to the subject matter of the independent claims.

The systems, methods, and devices of this disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein.

One innovative aspect of the subject matter described in this disclosure can be implemented in a method of wireless communication, as defined in claim <NUM>.

Another innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus for wireless communication, as defined claim <NUM>.

Another innovative aspect of the subject matter described in this disclosure can be implemented in a computer program for wireless communication, as defined in claim <NUM>.

In some implementations, the first subset of the NDP information can correspond to a first NDP and the second subset of the NDP information can correspond to a second NDP different from the first NDP. In some other implementations, the first subset of the NDP information and the second subset of the NDP information can both correspond to a same NDP, where the first subset of the NDP information may be transmitted in a first subset of the set of tones and the second subset of the NDP information may be transmitted in a second subset of the set of tones.

In some implementations, transmitting the first subset of the NDP information and transmitting the second subset of the NDP information may further involve transmitting the first subset of the NDP information and the second subset of the NDP information to a station (STA), where the threshold number of streams may be based on a capability of the STA. In some implementations, the capability of the STA includes at least one of a total number of space-time-streams the STA can process for a single NDP and a number of LTFs the STA can process for the single NDP.

In some implementations, both the first subset of antennas and the second subset of antennas can include at least one shared antenna. In some implementations, the method, apparatuses, and non-transitory computer-readable medium can include operations, features, means, or instructions for mitigating a phase offset between the first subset of the NDP information and the second subset of the NDP information based on the at least one shared antenna serving as a phase reference.

The following description is directed to certain implementations for the purposes of describing the innovative aspects of this disclosure. However, a person having ordinary skill in the art will readily recognize that the teachings herein can be applied in a multitude of different ways. The described implementations may be implemented in any device, system or network that is capable of transmitting and receiving RF signals according to any of the IEEE <NUM> standards, or any of the IEEE <NUM> standards, the Bluetooth® standard, code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), Global System for Mobile communications (GSM), GSM/General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), Terrestrial Trunked Radio (TETRA), Wideband-CDMA (W-CDMA), Evolution Data Optimized (EV-DO), 1xEV-DO, EV-DO Rev A, EV-DO Rev B, High Speed Packet Access (HSPA), High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Evolved High Speed Packet Access (HSPA+), Long Term Evolution (LTE), AMPS, or other known signals that are used to communicate within a wireless, cellular or internet of things (IOT) network, such as a system utilizing <NUM>, <NUM> or <NUM>, or further implementations thereof, technology.

Techniques are disclosed for wireless devices to support a high volume of space-time-streams (for example, greater than eight space-time-streams). In a wireless communications system, an access point (AP) may perform spatial multiplexing to improve throughput to one or more mobile stations (STAs). According to these techniques, the AP may identify a number of space-time-streams, which may alternatively be referred to as spatial streams or, simply, streams, for spatial multiplexing, and may transmit a packet to one or more STAs using the identified streams. The packet may include at least a long training field (LTF) section for the purposes of channel estimation, the LTF section including one or more orthogonal frequency division multiplexing (OFDM) symbols. Additionally, the AP may perform a modulation process prior to transmitting the packet in order to improve separation of the space-time-streams at a receiving STA.

An AP may perform modulation during the LTF section using one or more P matrices, which may be examples of square orthogonal matrices. A first dimension of each P matrix may correspond to LTF symbols or indices, while the second dimension may correspond to space-time-streams. In some implementations, an AP may select a P-matrix for modulation with dimensions smaller than the number of space-time-streams being transmitted. The AP may perform the modulation process on the LTF section using the selected P-matrix.

In some implementations, the AP may modulate the LTF section with the smaller P-matrix using tone-interleaving. For example, the AP may modulate the LTF section over a subset of the space-time-streams in a first set of tones using the P-matrix. The AP may additionally modulate the LTF section over a second subset of the space-time-streams in a second set of tones (for example, either using the same P-matrix or a different P-matrix). In other implementations, the AP may modulate space-time-streams over the LTF symbols with the smaller P-matrix and use a second orthogonal matrix for modulating the space-time-streams over frequency to ensure orthogonality. For example, the AP may modulate the LTF section across OFDM symbols using the selected P-matrix, and may select the same or a different orthogonal matrix for modulating across blocks of frequency tones. In some other implementations, rather than selecting a smaller P-matrix, the AP may be configured to select a P-matrix equal in size to the number of space-time-streams (for example, the AP may use a <NUM> × <NUM> P-matrix for modulating sixteen LTF symbols over sixteen space-time-streams).

Additionally, or alternatively, the AP may manage STAs with lesser sounding capabilities than the number of space-time-streams. For example, some types of STAs may not be configured to process spatial multiplexing with a high volume of space-time-streams (such as sixteen streams) during the sounding process. In some implementations, and AP may employ dual/tone-interleaved NDP approaches or frequency-domain orthogonal matrix modulation approaches. In some implementations, an AP transmitting a packet, such as a null data packet (NDP), with a high volume of space-time-streams to such a STA may transmit some of the NDP information in a first NDP using a first set of antennas and some of the NDP information in a second NDP using a second set of antennas. In some other implementations, the AP may transmit a single NDP, but may transmit the NDP in a first set of tones using a first set of antennas and in a second set of tones using a second set of antennas. These two sets of tones may be interleaved in the frequency domain. Antennas, as referred to above, may be examples of physical antennas, antenna ports, or virtual antennas. In yet other implementations, the AP may modulate the LTF section of the NDP in the time domain using a first orthogonal matrix and in the frequency domain using a second orthogonal matrix.

In some wireless communications systems, the AP may transmit packets both to the types of STAs not configured to process spatial multiplexing with a high volume of space-time-streams and to the types of STAs configured to process spatial multiplexing with a high volume of space-time-streams. In some implementations, STAs capable of processing up to eight space-time-streams or eight LTFs in sounding may be referred to as "legacy" STAs, while STAs capable of processing up to sixteen space-time-streams or sixteen LTFs in sounding-that is, a high volume of space-time-streams or LTFs-may be referred to as extremely high throughput (EHT) STAs or Next Generation STAs. In such systems, the AP may perform aggregation of space-time-streams into super streams, and may reduce the number of LTFs corresponding to a high number of streams by implementing a number of super-stream techniques. For example, in some implementations, the AP may share a channel estimation resource (e.g., a row of a P-matrix) during modulation between different streams across tones. Such streams that share a channel estimation resource may constitute a super-stream. STAs not configured for the high volume of space-time-streams may receive each super stream as if it is a single space-time-stream, while STAs configured for the high volume of space-time-streams may separately receive each space-time-stream contained within a super stream. In some implementations, the AP may utilize downlink multi-user, multiple-input, multiple-output (DL MU-MIMO) techniques to transmit a high volume of spatial streams to STAs with lesser reception capabilities. In some other implementations, super streams may be implemented for uplink transmissions as well. STAs configured to support the high volume of space-time-streams may transmit to an AP in one or more super streams, where each super stream includes multiple space-time-streams transmitted in the uplink. STAs not configured to support the high volume of space-time-streams may transmit simultaneously (for example, using single space-time-streams), and may not identify the presence of the multiple streams within each uplink super stream.

Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. Specifically, the proposed techniques allow for an AP to transmit packets to one or more STAs using a high volume of space-time-streams (for example, greater than eight space-time-streams). Transmitting using a high volume of space-time-streams increases spatial multiplexing, resulting in an improved spectral efficiency. An AP configured to perform the proposed techniques may therefore increase the number of bits it can transmit in given time and frequency intervals, increasing network throughputs and reducing latency in the Next Generation Wi-Fi system. Additionally, the proposed techniques allow for an AP using the high volume of space-time-streams to transmit simultaneously to STAs with different capabilities. For example, the AP may utilize its full spatial multiplexing capability, even in systems including STAs not configured to support the high volume of spatial streams (for example, by implementing super streams). This may improve the usage rate of the space-time-streams and allow the AP to efficiently utilize the channel, regardless of the configurations of the receiving STAs. Another potential advantage of the proposed techniques is the ability for an AP or STA to use a P-matrix of a smaller dimension than the number of space-time-streams in a downlink or uplink packet, which may lead to easier implementations (e.g., implementations that are less complex with respect to processing or memory resources).

<FIG> shows an example of a wireless communications system <NUM> that supports high volumes of space-time-streams. The system may be an example of a wireless local area network (WLAN) (such as a Next Generation, Next Big Thing (NBT), Ultra-High Throughput (UHT) or EHT Wi-Fi network) configured in accordance with various aspects of the present disclosure. As described herein, the terms Next Generation, NBT, UHT, and EHT may be considered synonymous and may each correspond to a Wi-Fi network supporting a high volume of space-time-streams (with one non-limiting example including sixteen streams). The wireless communications system <NUM> may include an AP <NUM> and multiple associated STAs <NUM>, which may represent devices such as mobile stations, personal digital assistant (PDAs), other handheld devices, netbooks, notebook computers, tablet computers, laptops, display devices (such as TVs, computer monitors, etc.), printers, etc. The AP <NUM> and the associated STAs <NUM> may represent a basic service set (BSS) or an extended service set (ESS). The various STAs <NUM> in the network may communicate with one another through the AP <NUM> or directly via device-to-device (D2D) communication. Also shown is a coverage area <NUM> of the AP <NUM>, which may represent a basic service area (BSA) of the wireless communications system <NUM>. An extended network station (not shown) associated with the wireless communications system <NUM> may be connected to a wired or wireless distribution system that may allow multiple APs <NUM> to be connected in an ESS. In some implementations, an AP <NUM> may transmit to one or more STAs <NUM> using a high volume of space-time-streams (for example, greater than eight space-time-streams, which also may be referred to as spatial streams or, simply, streams). The AP <NUM> may perform modulation and transmission to manage this high volume of space-time-streams, as well as to support both STAs <NUM> that support high volumes of streams and STAs <NUM> that do not support high volumes of streams.

Although not shown in <FIG>, a STA <NUM> may be located at the intersection of more than one coverage area <NUM> and may associate with more than one AP <NUM>. A single AP <NUM> and an associated set of STAs <NUM> may be referred to as a BSS. An ESS is a set of connected BSSs. A distribution system (not shown) may be used to connect APs <NUM> in an ESS. In some implementations, the coverage area <NUM> of an AP <NUM> may be divided into sectors (also not shown). The wireless communications system <NUM> may include APs <NUM> of different types (such as metropolitan area APs, home network APs, etc.) with varying and overlapping coverage areas <NUM>. The AP <NUM> may communicate with one or more STAs <NUM> within the coverage area <NUM> corresponding to the AP <NUM>. For example, the AP <NUM> may communicate with a STA <NUM> over a communication link <NUM>, where transmissions from the AP <NUM> to the STA <NUM> may be referred to as downlink transmissions and transmissions from the STA <NUM> to the AP <NUM> may be referred to as uplink transmissions. Additionally, two STAs <NUM> also may communicate directly via a direct wireless link <NUM> regardless of whether both STAs <NUM> are in the same coverage area <NUM>. Examples of direct wireless links <NUM> may include Wi-Fi Direct connections, Wi-Fi Tunneled Direct Link Setup (TDLS) links, and other group connections. STAs <NUM> and APs <NUM> may communicate according to the WLAN radio and baseband protocol for physical and MAC layers from IEEE <NUM> and versions including, but not limited to, <NUM>. 11b, <NUM>, <NUM>. 11a, <NUM>. 11n, <NUM>. 11ac, <NUM>. 11ad, <NUM>. 11ah, <NUM>. 11ax, and subsequent versions. In some other implementations, peer-to-peer connections or ad hoc networks may be implemented within the wireless communications system <NUM>.

In some implementations, a STA <NUM> (or an AP <NUM>) may be detectable by a central AP <NUM>, but not by other STAs <NUM> in the coverage area <NUM> of the central AP <NUM>. For example, one STA <NUM> may be at one end of the coverage area <NUM> of the central AP <NUM> while another STA <NUM> may be at the other end. Thus, both STAs <NUM> may communicate with the AP <NUM>, but may not receive the transmissions of the other. This may result in colliding transmissions for the two STAs <NUM> in a contention-based environment (such as an environment or system supporting carrier-sense multiple access with collision avoidance (CSMA/CA)) because the STAs <NUM> may not refrain from transmitting on top of each other. A STA <NUM> whose transmissions are not identifiable, but that is within the same coverage area <NUM> may be known as a hidden node. CSMA/CA may be supplemented by the exchange of a request-to-send (RTS) packet transmitted by a sending STA <NUM> (or AP <NUM>) and a clear-to-send (CTS) packet transmitted by the receiving STA <NUM> (or AP <NUM>). This may alert other devices within range of the sender and receiver not to transmit for the duration of the primary transmission. Thus, RTS/CTS may help mitigate a hidden node problem.

The various systems and methods described may provide means to support a high volume of space-time-streams present in Wi-Fi communications. In some wireless communications systems <NUM>, an AP <NUM> may transmit a packet containing an LTF section using a given number of streams, where a STA <NUM> may receive and further decode the packet. For improved spectral efficiency, the AP <NUM> may transmit using up to sixteen streams (and, correspondingly using up to sixteen LTFs), which may be referred to as a high volume of space-time-streams. In some implementations, the AP <NUM> may modulate the LTF section using a square orthogonal matrix with dimensions smaller than the number of streams or LTF indices. For example, the AP <NUM> may store an <NUM> × <NUM> matrix in memory for packet modulation and may use this <NUM> × <NUM> matrix for modulating when transmitting with any number of space-time-streams. Using a smaller P-matrix for modulation may allow the AP <NUM> to store fewer matrices in memory, and may support backwards compatibility with STAs <NUM> or other APs <NUM> that do not support a high volume of space-time-streams.

In some implementations, a STA <NUM> receiving the packet may be unable to process a large number of space-time-streams (for example, greater than eight space-time-streams) due to one or more capabilities of the STA <NUM>. In these implementations, the AP <NUM> may modulate the LTF section using an orthogonal matrix with dimensions less than the number of tone-interleaved streams, or by utilizing separate matrices to modulate the LTF over for example, time and frequency resources. Additionally, or alternatively, the AP <NUM> may identify subsets of antennas to sound in separate attempts, where each group of antennas may transmit the packet across different subsets of tones. The AP <NUM> may further combine the number of space-time-streams to create a super stream to support reception at various different types of STAs <NUM>. For example, implementing super streams may allow for the AP <NUM> to obtain the spectral efficiency benefits provided by a high volume of space-time-streams even in a wireless communications system <NUM> where some STAs <NUM> are incapable of processing this high volume of space-time-streams.

<FIG> shows an example of a wireless communications system <NUM> that supports high volumes of space-time-streams. The wireless communications system <NUM> may be an example of a Next Generation or EHT Wi-Fi system, and may include an AP <NUM>-a, a STA <NUM>-a, and a coverage area <NUM>-a, which may be examples of the corresponding components described with respect to <FIG>. The AP <NUM>-a may transmit a packet <NUM> on the downlink <NUM> to the STA <NUM>-a using a number of space-time-streams. The packet may include an LTF section <NUM>.

Some configurations of wireless communications systems (for example, "legacy" systems) may support up to eight space-time-streams or spatial streams for simultaneous communication, which may represent the total number of streams across all users or STAs <NUM>-a served by a same AP <NUM>. However, some Next Generation or EHT Wi-Fi systems, such as a wireless communications system <NUM>, may support configurations to manage a higher volume of space-time-streams (that is, higher than the legacy systems). For example, the wireless communications system <NUM> may include support for a number of space-time-streams larger than eight (such as sixteen space-time-streams). The AP <NUM>-a, the STA <NUM>-a, or both may include capabilities for processing up to sixteen space-time-streams at a same instant in time (for example, during a same transmission time interval (TTI)).

To communicate information contained in the packet <NUM> to the STA <NUM>-a, the AP <NUM>-a may employ methods to modulate the LTF section <NUM> prior to transmission. The modulation process for the LTF section <NUM> may be part of a larger modulation procedure for the entire packet <NUM>. The LTF section <NUM> may span one or more OFDM symbols and may include information used for initial channel estimation at the STA <NUM>-a. For example, the LTF section <NUM> may include a number of long training symbols (i.e., LTF symbols) and a cyclic prefix. A STA <NUM>-a receiving the LTF section <NUM> may use the repeated long training symbols for frequency offset estimation, channel estimation, etc. The AP <NUM>-a may select an orthogonal matrix (for example, a P-matrix) to modulate the LTF section <NUM> over a number of space-time-streams. This modulation process may involve spreading each space-time-stream over the time and frequency resources allocated for the LTF section <NUM>-a. One example of a <NUM> × <NUM> P-matrix may be an orthogonal discrete Fourier transform (DFT) matrix used in signal processing methods: <MAT> In the above example, the constant w may be defined as w = exp (- j<NUM>π/<NUM>). The dimensions of the P-matrix may be based on the number of LTF indices and the number of space-time-streams. For example, each column of the matrix may correspond to an LTF index, and each row of the matrix may correspond to a space-time-stream. The DFT P-matrix may multiply the frequency-domain LTF sequence for the LTF section <NUM> to obtain LTF sequences spread across the time-domain for each of the space-time-streams. A STA <NUM>-a receiving the LTF symbols (for example, for all of the spatial streams) may separate the different spatial streams based on the orthogonality of the P-matrix used for modulation.

An AP <NUM>-a configured to use higher volumes of space-time-streams may store P-matrices to manage these higher numbers of streams. For example, an AP <NUM>-a in a Next Generation or EHT Wi-Fi system may store a variety of orthogonal matrices (for example, a <NUM> × <NUM> matrix, a <NUM> × <NUM> matrix, a <NUM> × <NUM> matrix, a <NUM> × <NUM> matrix, etc.) for handling larger numbers of space-time-streams. These larger P-Matrices extended for higher dimensions may be commonly defined across EHT wireless communications systems <NUM>. In some implementations, these matrices may be composed of smaller P-matrices as sub-components. In one example, a <NUM> × <NUM> P-matrix may be constructed using constituent <NUM> × <NUM> orthogonal P-matrices, such that: <MAT> In another example, a <NUM> × <NUM> matrix may be constructed using <NUM> × <NUM> orthogonal P-matrices as building blocks: <MAT> Additional higher-dimensional matrices (for example, matrices larger than <NUM> × <NUM>) may be constructed using similar methods. For example, an AP <NUM>-a may store a <NUM> × <NUM> matrix, a <NUM> × <NUM> matrix, or both constructed by performing element-by-element multiplication on existing (that is, smaller) matrices or on arrays. One example of code for constructing such a <NUM> × <NUM> P-matrix includes: <MAT> <MAT> <MAT> <MAT> where the "first row" array can include any values and the P-matrix may maintain orthogonality (although an array of all "<NUM>" may result in a spectral line) and ". *" corresponds to the element-by-element multiplication operation. In this example, the code may result in a <NUM> × <NUM> orthogonal P-matrix based on the dimensions of the first row and the number of rows specific by the variable P. Other mathematical operations may be performed on smaller P-matrices or arrays to produce new matrices with desired dimensions for storage at the APs <NUM>, the STAs <NUM>, or both. Each constituent matrix may be an example of an orthogonal DFT matrix or may contain different characteristic entries to avoid creating spectral lines or channel interferences.

The number of high volume matrices-for example, matrices with dimensions greater than <NUM> × <NUM>-stored by the AP <NUM>-a may be limited by an LTF overhead wastage threshold. For example, if the AP <NUM>-a stores one P-matrix larger than <NUM> × <NUM>, such as a <NUM> × <NUM> matrix, the AP <NUM>-a transmits a full set of sixteen LTF symbols for any number of space-time-streams greater than eight streams. In this example, if the AP <NUM>-a transmits using ten space-time-streams, the AP <NUM>-a may experience an LTF overhead wastage of six LTFs, as a full set of sixteen LTF symbols is used for ten space-time-streams in order to support modulation by the <NUM> × <NUM> orthogonal matrix. Alternatively, if the AP <NUM>-a stores a <NUM> × <NUM> matrix in addition to the <NUM> × <NUM> matrix, the AP <NUM>-a may use additional memory resources for storing the additional matrix, but may reduce the LTF overhead wastage by transmitting ten LTFs when transmitting using ten space-time-streams. In this way, the AP <NUM>-a may experience a tradeoff between the number of P-matrices stored in memory and the LTF overhead wastage, where a greater number of stored P-matrices results in less LTF overhead wastage but greater memory usage. As such, in some implementations, AP <NUM>-a may store multiple P-matrices, including both small P-matrices (that is, P-matrices with dimensions <NUM> × <NUM> or smaller) and large P-matrices (that is, P-matrices with dimensions larger than <NUM> × <NUM>). For example, an AP <NUM>-a may store P-matrices including P<NUM>×<NUM>, P4x4, P<NUM>×<NUM>, P<NUM>×<NUM>, P<NUM>×<NUM>, P<NUM>×<NUM>, P<NUM>×<NUM>, and P<NUM>×<NUM>.

In some implementations, an AP <NUM>-a may use a P-matrix for modulation such that each dimension of the P-matrix is less than the total number of space-time-streams. For example, rather than store high volume P-matrices with dimensions greater than <NUM> × <NUM>, the AP <NUM>-a may use smaller P-matrices, such as an <NUM> × <NUM> orthogonal P-matrix, to modulate LTFs for high volume space-time-stream transmissions. The AP <NUM>-a may modulate the LTF section <NUM> over the space-time-streams using the selected P-matrix and may transmit the modulated LTF <NUM> over a set of tones corresponding to the space-time-streams. To handle modulation of the LTF section <NUM> with a P-matrix that has dimensions smaller than the number of space-time-streams, the AP <NUM>-a may use one or more modulation techniques as described below with reference to <FIG> and <FIG>.

<FIG> shows an example of techniques for performing LTF modulation in a wireless communications system <NUM> that supports high volumes of space-time-streams. The wireless communications system <NUM> may be an example of a Next Generation or EHT Wi-Fi system, and may include an AP <NUM>-b, a STA <NUM>-b, and a coverage area <NUM>-b, which may be examples of the corresponding components described with respect to <FIG> and <FIG>. The AP <NUM>-b may transmit a packet on the downlink <NUM> to the STA <NUM>-b using a number of space-time-streams. The AP <NUM>-b may use a first LTF modulation technique <NUM>-a, a second LTF modulation technique <NUM>-b, or a combination thereof to modulate an LTF section of the packet for transmission. In the first LTF modulation technique <NUM>-a, the AP <NUM>-b may use a first P-matrix <NUM>-a to modulate a first group of space-time-streams across the LTF symbols over a first set of frequency tones <NUM> and may use a second P-matrix <NUM>-b to modulate a second group of space-time-streams across the LTF symbols over a second set of frequency tones <NUM>. The first and second sets of frequency tones <NUM> may be interleaved. In the second LTF modulation technique <NUM>-b, the AP <NUM>-b may modulate the space-time-streams across symbols in the time domain using a first P-matrix <NUM>-a and may modulate the space-time-streams across frequency tones <NUM> in the frequency domain using a third P-matrix <NUM>-c.

In some implementations, an AP <NUM>-b and a STA <NUM>-b may utilize a smaller P-matrix <NUM> for estimating a channel with a larger number of space-time-streams (for example, an AP <NUM>-b may modulate an LTF section with sixteen space-time-streams using a P-matrix <NUM> with dimensionality less than <NUM> × <NUM>). In a first LTF modulation technique <NUM>-a, the AP <NUM>-b may modulate and transmit different groups of streams on different frequency tones <NUM>. In one implementation, the first LTF modulation technique <NUM>-a may be an example of a tone-interleaving process, where the AP <NUM>-b may switch between or select certain tones for certain space-time-streams to support a higher number of space time streams in a network. The AP <NUM>-b may modulate stream groups using multiple orthogonal P-matrices <NUM>, such as P-matrix <NUM>-a and P-matrix <NUM>-b, which in some implementations may be examples of the same matrix. In the first LTF modulation technique <NUM>-a, AP <NUM>-b may separate the total number of space-time-streams (for example, sixteen streams) into stream sets each containing a number of streams less than or equal to the size of the P-matrix <NUM> for modulation (for example, a first set of streams <NUM>-<NUM> and second set of streams <NUM>-<NUM> if P-matrices <NUM>-a and <NUM>-b are at least <NUM> × <NUM>). The AP <NUM>-b may identify a number of frequency tones <NUM> for transmission of the packet and may use a tone interleaving technique to transmit the sixteen streams with less than sixteen corresponding LTFs (for example, eight LTFs and an <NUM> × <NUM> P-matrix may be used for sixteen space-time-streams). In an example, the AP <NUM>-b modulates streams <NUM>-<NUM> using the P-matrix <NUM>-a over the odd frequency tones <NUM> and modulates streams <NUM>-<NUM> using the P-matrix <NUM>-b over the even tones and transmits these subsets of space-time-streams on the alternating frequency tones <NUM>.

A receiving STA <NUM>-b may receive the packet with the modulated LTFs, and may use interpolation to determine the channel for every stream on every frequency tone <NUM>. For example, the STA <NUM>-b may use interpolation or another estimation technique to estimate the channel for streams <NUM>-<NUM> on the even tones and for streams <NUM>-<NUM> on the odd tones. In some implementations, the interpolation process may involve the STA <NUM>-b averaging values for corresponding alternate tones to determine a value for an intermediate frequency tone <NUM>. For example, for the first space-time-stream, the STA <NUM>-b may average two odd frequency tones <NUM> to estimate the channel associated with the even frequency tone <NUM> between the two odd frequency tones <NUM>.

In a second LTF modulation technique <NUM>-b, modulating an LTF section in both time and frequency may provide separation between space-time-streams on adjacent tones without tone interleaving. An AP <NUM>-b may apply an orthogonal code over time resources using a P-matrix <NUM>-a. Additionally, the AP <NUM>-b may apply an orthogonal code over frequency resources (for example, frequency tones <NUM>) using a P-matrix <NUM>-c to separate spatial streams over tone blocks. While P-matrices <NUM>-a and <NUM>-c may each have smaller dimensions than the number of space-time-streams, in combination the P-matrices <NUM> may modulate the larger number of streams (for example, sixteen streams). P-matrix <NUM>-a and P-matrix <NUM>-c may be the same matrix or may be different matrices. In one example, the AP <NUM>-b may use a P-matrix <NUM>-a of one size (for example, an <NUM> × <NUM> P-matrix) to modulate across OFDM symbols and a P-matrix <NUM>-c of another size different than P-matrix <NUM>-a (for example, a <NUM> × <NUM> P-matrix) to modulate across frequency tones <NUM>. That is, the AP <NUM>-b may spread the space-time-streams over blocks of tones using the P-matrix <NUM>-c to separate the streams across the full set of frequency resources and may modulate the space-time-streams across the time resources (for example, the LTF symbols) using the P-matrix <NUM>-a. The AP <NUM>-b may differentiate a larger number of streams than the number of LTFs by modulating the LTFs across both OFDM symbols and across blocks of frequency tones <NUM> using two P-matrices <NUM>. In some implementations, the product of the dimensions of the selected P-matrices <NUM>-a and <NUM>-c may be greater than or equal to the number of space-time-streams, which may allow for differentiating the full set of space-time-streams during the second LTF modulation technique <NUM>-b.

In some implementations, the AP <NUM>-b may utilize LTF compression techniques in addition to LTF modulation techniques <NUM>. For example, the AP <NUM>-b may use shorter or compressed LTFs (for example, 1x or 2x LTFs) in a packet for transmission. The AP <NUM>-b may transmit these short LTFs across a smaller number of tones. As compared to transmitting an uncompressed LTF, the AP <NUM>-b may transmit 2x LTFs on one half the tones of the uncompressed LTF and may transmit 1x LTFs on one quarter of the tones of the uncompressed LTF. In further examples, the AP <NUM>-b may use other sizes of compressed LTFs in packet transmissions over other specified tones. A STA <NUM>-b receiving a compressed LTF may perform additional interpolation as compared to a STA <NUM>-b receiving an uncompressed LTF to estimate the channel across the full set of frequency tones <NUM>. In some implementations, the amount of interpolation performed by the STA <NUM>-b may increase as the LTF compression factor increases. In one specific example, the AP <NUM>-b may implement the first LTF modulation technique <NUM>-a for modulating 2x LTFs using sixteen space-time-streams across half a set of frequency tones <NUM>, where subsets of the streams are interleaved in this half set of frequency tones <NUM>. In this example, a receiving STA <NUM>-b may interpolate to estimate the channel for the interleaved frequency tones <NUM> for each space-time-stream based on the first LTF modulation technique <NUM>-a. Additionally, the receiving STA <NUM>-b may interpolate to estimate the channel for the other half set of frequency tones <NUM> based on the LTF compression.

In some wireless communications systems <NUM>, a STA <NUM>-b may transmit a packet with an LTF section on the uplink to the AP <NUM>-b. For example, the STA <NUM>-b may transmit the packet in a multi-user (MU) multiple-input, multiple-output (MIMO) system. In some implementations of this uplink MU-MIMO LTF design, the LTF section may be long (for example, longer than an LTF threshold length), which may impact the reliability and accuracy of carrier phase tracking. Phase tracking may occur on a per-STA <NUM> or per-AP <NUM> basis. In transmissions involving long LTF sections, a STA <NUM>-b may implement a method involving tone-interleaved LTFs or other LTF modulation techniques <NUM> similar to those described above with respect to downlink <NUM> transmissions from the AP <NUM>-b.

In some implementations, the wireless communications system <NUM> may implement a number of cyclic shift delays (CSDs) for signal transmission and per-stream orthogonality. CSDs may reduce correlation and improve diversity between space-time-streams and may result in improved automatic gain control (AGC) settings at a receiving device. An AP <NUM>-b may use a CSD table to determine signal timing, where each table value corresponds to a time interval TCS,VHT(n) (for example, a certain number of nanoseconds (ns)) that the AP <NUM>-b may delay a transmission for the corresponding space-time-stream. The AP <NUM>-b may store such a CSD table in memory and may identify values from the CSD table for transmissions (for example, physical layer convergence protocol (PLCP) protocol data unit (PPDU) transmissions) using multiple spatial streams. The CSD values in the table may be determined such that the spatial streams are de-coupled and have timing diversity better than some threshold timing diversity (for example, at least <NUM> ns). A CSD value may relate to the number of total space-time-streams present in a system or may be constant for a given space-time-stream index no matter the number of space-time-streams in the system. Multiple CSD tables may be constructed for various numbers of space-time-streams based on measurements, simulations, optimizations, or other techniques. An example of a CSD table constructed for transmission of up to eight total space-time-streams is given below:.

Table <NUM> may be an example of a CSD table for a legacy system, with support for up to eight space-time-streams. Similar tables may exist for systems supporting a larger number of space-time-streams (for example, up to sixteen space-time-streams in an EHT system). In such examples, the CSDs for the first eight streams may be based on Table <NUM> or may include values different than those given in Table <NUM>. In some implementations, a CSD reference table may follow a nested structure, where for each incremental total number of space-time-streams, the cyclic shifts for each stream may be the same as for the previous total number of space-time-streams, with one additional cyclic shift value for the additional stream. Additionally, the CSD table may contain alternating large and small values for the space-time-streams (where "large" and "small" are in comparison to the other CSD values), which may serve to maintain cyclic shift separation between adjacent streams.

One example CSD table supporting sixteen space-time-streams is given below. This example follows a nested structure, so the cyclic shift values for the first eight spatial streams are given by Table <NUM>. Additionally, this example follows steps-or cyclic shift diversity thresholds-of <NUM> ns and a maximum cyclic shift value of <NUM> ns. The cyclic shift values for the additional streams may be determined such that the CSDs are a certain threshold away from the existing stream CSDs and the other additional stream CSDs. In an example, a new stream cyclic shift value may be an average calculated from values of other cyclic shift values. The additional values for the CSD table supporting a high volume of space-time-streams may be calculated using any averaging or numerical optimization methods or simulations to maximize performance of the spatial streams. In a system supporting sixteen space-time-streams, a nested CSD table may include the following table entries corresponding to the cyclic shifts for space-time-streams <NUM>-<NUM>:.

These CSD table values are given as examples. It is to be understood that many other permutations of the new CSD table entries are possible and depending on the implementation, performance benefits may vary.

Additionally, or alternatively, the AP <NUM>-b and the STA <NUM>-b supporting a high volume of space-time-streams (for example, up to sixteen streams) may communicate using modified signals as compared to legacy systems (for example, systems supporting up to eight space-time-streams). For example, the AP <NUM>-b may allocate additional bits to the High Efficiency Signal A Field (HE-SIG-A) to support the additional space-time-streams. The AP <NUM>-b may further introduce additional rows for a spatial configuration field encoding for the High Efficiency Signal B Field (HE-SIG-B). In some implementations, the AP <NUM>-b may maintain support for a lower number of users in a MU-MIMO system despite the additional space-time-streams. For example, the AP <NUM>-b may support transmitting to up to eight users (that is, different STAs <NUM>) using sixteen spatial streams for MU-MIMO transmissions.

<FIG> shows an example of techniques for transmitting an NDP in a wireless communications system <NUM> that supports high volumes of space-time-streams. The wireless communications system <NUM> may be an example of a Next Generation or EHT Wi-Fi system, and may include an AP <NUM>-c, a STA <NUM>-c, and a STA <NUM>-d, which may be examples of the corresponding devices described with respect to <FIG>. The AP <NUM>-c may transmit a null data packet announcement (NDPA) <NUM>, one or more NDPs <NUM>, and a trigger frame <NUM>. Each STA <NUM> may transmit a beam forming (BF) report <NUM>. For example, STA <NUM>-c may transmit BF report <NUM>-a and STA <NUM>-d may transmit BF report <NUM>-b. The AP <NUM>-c may include a total number of antennas or antenna ports for transmitting NDPs <NUM> on space-time-streams. However, some STAs <NUM> may not be configured to receive the number of streams that the AP <NUM>-c is transmitting. To manage this, the AP <NUM>-c may transmit the one or more NDPs <NUM> using a first technique <NUM>-a, a second technique <NUM>-b, or a third technique <NUM>-c. In the first technique <NUM>-a, the AP <NUM>-c may transmit a first NDP <NUM>-a using a first group of antennas <NUM>-a and a second NDP <NUM>-b using a second group of antennas <NUM>-b. In the second technique <NUM>-b, the AP <NUM>-c may transmit a single NDP <NUM>, where the AP <NUM>-c may transmit the single NDP <NUM> on a first set of streams in a first set of tones using a first group of antennas <NUM>-a and on a second set of streams in a second set of tones using a second group of antennas <NUM>-b. As discussed above, the antennas may refer to physical antennas or logical antenna ports. In the third technique <NUM>-c, the AP <NUM>-c may modulate the NDP <NUM> across LTF symbols using a first P-matrix <NUM>-a and may modulate across pairs or groups of adjacent frequency tones using a second P-matrix <NUM>-b. Each of the first technique <NUM>-a, the second technique <NUM>-b, and the third technique <NUM>-c may support STAs <NUM> that may not process the full number of LTFs or streams in sounding.

In some implementations, NDPs <NUM> may remain unchanged for systems supporting high volumes of space-time-streams as compared to systems supporting lower volumes of space-time-streams, such as eight space-time-streams. In some other implementations, the NDP <NUM> format may change based on the numbers of space-time-streams used for transmission. The increased volume of space-time streams may have implications for other signaling processes, such as the production of BF reports <NUM>. In some implementations, a BF report <NUM> may include additional components or additional supported angles based on the larger number of spatial streams. These new angles may be used for rotation for other feedback configurations (for example, for higher dimensioned matrices) and may be sent or indicated in BF feedback by a STA <NUM> or AP <NUM>. Additionally, or alternatively, other fields may be modified due to the high volume of supported space-time-streams, such as a number of columns (nc) subfield, which may include an additional bit to indicate the larger number of supported streams.

In the wireless communications system <NUM>, the AP <NUM>-c may manage a number of STAs <NUM> with different sounding capabilities. For example, one set of STAs, including STA <NUM>-c, may not be configured to process spatial multiplexing with a high volume of space-time-streams or corresponding LTFs (for example, sixteen space-time-streams or sixteen LTFs), while another set of STAs <NUM>, including STA <NUM>-b (which may be an example of an EHT Wi-Fi device) may support processing the full number of space-time-streams or LTFs. An AP <NUM>-c may employ a number of techniques <NUM> to support communication with STAs <NUM> capable of processing up to eight spatial streams while efficiently communicating with STAs <NUM> capable of processing up to sixteen spatial streams. In this way, the AP <NUM>-c may accommodate STAs <NUM> with lesser sounding capabilities while communicating using improved spatial multiplexing and spectral efficiency with STAs <NUM> supporting greater sounding capabilities.

In a first technique <NUM>-a, the AP <NUM>-c may contain a set of antennas-that is, physical antennas or logical antenna ports-to transmit information to a STA <NUM>-c. The AP <NUM>-c may perform a sounding process to transmit a sequence of NDPs <NUM>-a and <NUM>-b, where each NDP <NUM> contains a number of LTFs within the sounding capability of the STA <NUM>-c. During the sounding process, the AP <NUM>-c may sound a first group of antennas <NUM>-a of the total set of antennas to transmit the first NDP <NUM>-a in a first attempt and may sound a second group of antennas <NUM>-b of the total set of antennas to transmit a second NDP <NUM>-b in a second attempt. This first group of antennas <NUM>-a and second group of antennas <NUM>-b may overlap (for example, share at least one same antenna between the two groups) or may be mutually exclusive. For example, if the AP <NUM>-c utilizes sixteen space-time-streams (and, corresponding, sixteen LTFs), and the STA <NUM>-c is capable of processing eight space-time-streams or LTFs, the AP <NUM>-c may transmit two NDPs <NUM> each containing eight of the sixteen LTFs. In such implementations, the receiving STA <NUM>-c may stitch the two channel components together to determine the sixteen LTFs. In some implementations, the different groups of antennas <NUM>-a and <NUM>-b may have different automatic gain control (AGC) states as processed by STA <NUM>-c, for example, due to transmitting the NDPs <NUM> in different attempts. The STA <NUM>-c may calibrate out or otherwise mitigate any differences in the AGC states in order to stitch the channel components. Additionally, or alternatively, the AP <NUM>-c may freeze the phase for transmission of the different NDPs <NUM> to remove or mitigate any phase offset across the groups of antennas <NUM> transmitting the NDPs <NUM> at different times. This also may improve reception and stitching of the two channel components at the receiving STA <NUM>-c.

In a second technique <NUM>-b, the AP <NUM>-c may perform tone-interleaving using a single NDP <NUM> over different sets of tones to support sounding a higher number of streams than the number of LTFs (for example, sixteen streams with eight LTFs). The AP <NUM>-c may modulate a transmission using an orthogonal P-matrix or multiple P-matrices. The AP <NUM>-c may transmit the NDP <NUM> on a first set of tones using a first subset of antennas <NUM>-a and may further transmit the NDP <NUM> on a second set of tones using a second subset of antennas <NUM>-b. In some implementations, the first and second set of tones may be half of the total number of tones used for transmission and may be interleaved in the frequency domain. In some implementations, the first subset of antennas <NUM>-a and the second subset of antennas <NUM>-b may contain one or more shared antennas for improved reception and stitching at the receiving STA <NUM>-c. For example, antennas shared between the first and second subsets of antennas <NUM> may serve as phase references for the receiving STA <NUM>-c.

In a third technique <NUM>-c, the AP <NUM>-c may use an orthogonal code (for example, an orthogonal cover code (OCC) or some other orthogonal code, such as a P-matrix) for frequency domain modulation in addition to an orthogonal P-matrix <NUM>-a used for time domain modulation. In one implementation, the AP <NUM>-c may use one P-matrix <NUM>-a of one size (for example, an <NUM> × <NUM> P-matrix) for modulation across LTF symbols in the time domain and may use a second P-matrix <NUM>-b of another size (for example, a <NUM> × <NUM> P-matrix) for modulation across adjacent tones in the frequency domain. This may allow a STA <NUM>-c capable of receiving <NUM> space-time-streams or LTFs to differentiate sixteen space-time-streams.

<FIG> shows an example of space-time-stream and super stream transmissions in a wireless communications system <NUM> that supports managing high volumes of space-time-streams. The wireless communications system <NUM> may be an example of a Next Generation or EHT Wi-Fi system, and may include an AP <NUM>-d and a STA <NUM>-e, which may be examples of the devices described with respect to <FIG>. The AP <NUM>-d may transmit one or more packets (such as an NDP) to the STA <NUM>-e in space-time-streams <NUM>. The AP <NUM>-d may combine some space-time-streams <NUM> to form super streams <NUM>. If the STA <NUM>-e is configured for a high volume of streams (for example, greater than eight streams), the STA <NUM>-e may detect and receive all of the space-time-streams <NUM>. If the STA <NUM>-e is not configured for a high volume of streams, the STA <NUM>-e may detect the super streams <NUM> as if they are space-time-streams <NUM>, so that, as illustrated, the STA <NUM>-e may detect and receive eight space-time-streams <NUM>, rather than the full ten transmitted space-time-streams <NUM>.

The AP <NUM>-d may transmit a high volume of space-time-streams (for example, greater than eight space-time-streams) in a wireless communications system <NUM> containing STAs <NUM> that are not equipped to support a high volume of streams based on one or more capabilities of the STAs <NUM>. In some implementations, the AP <NUM>-d may transmit a high volume of streams by implementing super-streaming techniques, which may group or combine a number of space-time-streams <NUM> into super streams <NUM> to accommodate the legacy STAs <NUM> capable of receiving up to a threshold number of streams (for example, eight space-time-streams) while still transmitting with more streams than the threshold number of streams. In some other implementations, super-streaming techniques may include reducing the number of LTFs corresponding to a high volume of space time streams. If a STA <NUM>-e is configured to support a high volume of streams, the STA <NUM>-e may detect and receive each of the multiple space-time-streams <NUM> within super stream <NUM> separately, or as individual streams. In some other implementations, where the STA <NUM>-e is unable to support a high volume of streams, the STA <NUM>-e may detect and receive a super stream <NUM> as a single space-time-stream <NUM>. In some implementations, an AP <NUM>-d transmitting, for example, sixteen space-time-streams <NUM> may transmit eight super streams <NUM>, where each super stream <NUM> contains two single space-time-streams <NUM>. This may result in some STAs <NUM> receiving sixteen streams for a single transmission while other STAs receive a different number of streams due to the different capabilities of the STAs <NUM>. In some other implementations, an AP <NUM>-d may transmit ten space-time-streams <NUM> including two super streams <NUM>, where each super stream <NUM> contains two of the space-time-streams <NUM>. This may result in a subset of the STAs <NUM> in the wireless communications system <NUM> detecting ten streams (the ten space-time-streams <NUM>) while a different subset of STAs <NUM> may detect eight streams (the two super streams <NUM> and the six uncombined space-time-streams <NUM>).

In some implementations, STAs <NUM> and APs <NUM> may implement super streams <NUM> in uplink and downlink transmissions, such as MU-MIMO LTF transmissions. In some implementations, an AP <NUM> may transmit a packet in a downlink MU-MIMO system to a STA <NUM>, which may not be configured to support a high volume of space-time streams. In one implementation, some STAs <NUM> served by an AP <NUM> may support up to sixteen total space time streams, while another STA <NUM> served by AP <NUM> may support reception of eight total space time streams. In order to transmit for example, twelve space time streams in a downlink MU-MIMO transmission, AP <NUM> may transmit four singular space time streams along with four super streams each consisting of two singular space-time streams. In this example, STAs <NUM> supporting a high volume of space time streams may receive the transmission as containing twelve total space time streams, while the STA <NUM> with lesser reception capabilities may receive the transmission as containing eight total space time streams.

The STAs <NUM> may use a P-matrix for LTF modulation and transmission across tones. The AP <NUM>-d may allocate a row of the P-matrix (e.g., a channel estimation resource) to a STA <NUM>-e, where the STA <NUM>-e is configured for a lower volume of streams. For STAs <NUM> supporting a higher volume of streams, the AP <NUM>-d may allocate some rows of the P-matrix such that the rows shift during modulation between different streams across tones. For example, an EHT STA <NUM> may rotate a row of the P-matrix between space-time-streams from tone-to-tone, generating two streams from a single row of the P-matrix. The AP <NUM>-d receiving the two streams may perform interpolation to estimate the channel for the in-between tones. For example, if the EHT STA <NUM> modulates streams <NUM>-<NUM> on a first tone and streams <NUM>-<NUM> on a second tone, the AP <NUM>-d may interpolate LTF values for streams <NUM>-<NUM> on the first tone and interpolate LTF values for streams <NUM>-<NUM> on the second tone. In another example, APs <NUM>-d may share the same row of the P-matrix.

<FIG> shows a block diagram of an example system <NUM> including an AP <NUM> that supports high volumes of space-time-streams. The AP <NUM> may be an example of a wireless device configured to operate in a Next Generation or EHT Wi-Fi system. The AP <NUM> may include components for bi-directional voice and data communications including components for transmitting and receiving communications, such as a processor <NUM>, a memory <NUM>, software <NUM>, a transceiver <NUM>, an antenna <NUM>, and an input/output (I/O) controller <NUM>. These components may be in electronic communication via one or more buses, such as a bus <NUM>. The transceiver <NUM> may include a space-time-stream packet module <NUM> configured to implement one or more of the techniques described with respect to <FIG>, in cooperation with the processor <NUM>, a memory <NUM>, software <NUM>, antenna <NUM>, and I/O controller <NUM>.

The space-time-stream packet module <NUM> may perform a number of operations for managing high volumes of space-time-streams. For example, the space-time-stream packet module <NUM> may handle transmitting packets to different types of STAs <NUM>, where some STAs <NUM> in the system <NUM> are capable of processing up to eight space-time-streams and other STAs <NUM> in the system <NUM> are capable of processing more than eight space-time-streams. For example, the first type of STAs <NUM> may be referred to as "legacy" STAs, and the second type of STAs <NUM> may be referred to as "EHT" STAs and may process up to sixteen space-time-streams (i.e., a "high volume" of space-time-streams). In some implementations, in addition or alternative to having a limit on space-time-stream processing capabilities, a STA <NUM> may have similar limits on processing LTFs in sounding. For example, legacy STAs may support processing up to eight LTFs in sounding, while EHT STAs may support processing up to sixteen LTFs in sounding.

In a first example, the space-time-stream packet module <NUM> may identify a number of space-time-streams for transmission of NDP information in a set of tones, where the number of space-time-streams is greater than a threshold number of streams. This threshold number of streams may be based on the different capabilities of STAs <NUM> in the system <NUM>. For example, the threshold number of streams may be equal to eight streams, where a subset of the STAs <NUM> support processing more than the threshold number of streams and another subset of STAs <NUM> support processing less than or equal to the threshold number of streams. The space-time-stream packet module <NUM>, via the transceiver <NUM> and antennas <NUM>, may transmit a first subset of the NDP information using a first subset of the antennas <NUM>, such as half of the antennas <NUM>, and may transmit a second subset of the NDP information using a second subset of the antennas <NUM>, such as the other half of the antennas <NUM>.

In a second example, the space-time-stream packet module <NUM> may identify the number of space-time-streams for transmission of a packet, where the number of space-time-streams is greater than the threshold number of streams. This packet may include an LTF section spanning one or more OFDM symbols. The space-time-stream packet module <NUM> may select an orthogonal matrix for modulation of the LTF section. In some implementations, the orthogonal matrix may be selected from a lookup table in the memory <NUM>. A size of the first dimension and the second dimension of the matrix may be less than the identified number of space-time-streams. The space-time-stream packet module <NUM> may modulate the LTF section over the space-time-streams using the selected orthogonal matrix-that is, the space-time-stream packet module <NUM> may spread the space-time-streams over the OFDM symbols of the LTF section using the selected orthogonal matrix. The space-time-stream packet module <NUM> may use tone-interleaving with interpolation or separate matrices in time and frequency to fully spread the signal using a matrix with dimensions smaller than the number of space-time-streams. The space-time-stream packet module <NUM>, via the transceiver <NUM> and antenna(s) <NUM>, may transmit the packet including the modulated LTF section over a set of tones using the space-time-streams.

In a third example, the space-time-stream packet module <NUM> may identify the number of space-time-streams for transmission of a packet, where the number of space-time-streams is greater than the threshold number of streams. The space-time-stream packet module <NUM> may combine some of the space-time-streams to form one or more super streams and obtain a total number of streams equal to or less than the threshold number of streams. For example, if the space-time-stream packet module <NUM> identifies ten streams, but the threshold number of streams is eight, the space-time-stream packet module <NUM> may form two super streams composed of two space-time-streams each. The space-time-stream packet module <NUM>, via the transceiver <NUM> and antenna(s) <NUM>, may transmit the packet over a set of tones using the super streams and space-time-streams. Legacy STAs <NUM> may receive each super stream as a single space-time-stream, while EHT STAs <NUM> may receive each super stream as its component space-time-streams. Accordingly, in the example given above, a legacy STA <NUM> may identify eight streams while an EHT STA <NUM> may identify ten streams for the same transmission based on these super streams.

In a fourth example, the space-time-stream packet module <NUM> may identify the number of space-time-streams for transmission of NDP information in a set of tones. This NDP information may include an LTF section spanning one or more OFDM symbols. The space-time-stream packet module <NUM> may determine that the number of space-time-streams is greater than the threshold number of space-time-streams and may group the set of tones into tone blocks. The space-time-stream packet module <NUM> may modulate an NDP containing the NDP information across the OFDM symbols of the LTF section using a first orthogonal matrix and across each of the tone blocks using a second orthogonal matrix. In some implementations, these matrices may be selected from a lookup table in the memory <NUM>. The space-time-stream packet module <NUM>, via the transceiver <NUM> and antenna(s) <NUM>, may transmit the modulated NDP over the set of tones using the space-time-streams. The space-time-stream packet module <NUM> may operate as described above in a single example, or in any combination of the examples.

The processor <NUM> may include an intelligent hardware device, such as a general-purpose processor, a digital signal processor (DSP), a central processing unit (CPU), a microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or some combination of these components. The processor <NUM> may be configured to execute computer-readable instructions stored in a memory to perform various functions, such as the functions described with respect to the space-time-stream packet module <NUM>.

The memory <NUM> may include random access memory (RAM) and read-only memory (ROM). The memory <NUM> may store computer-readable, computer-executable code or software <NUM> including instructions that, when executed, cause the processor to perform various functions described herein. In some implementations, the memory <NUM> may contain, among other things, a basic input/output system (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices.

The transceiver <NUM> may communicate bi-directionally, via one or more antennas <NUM> or antenna ports, wired, or wireless links as described above. The transceiver <NUM> also may include a modem to modulate the packets and provide the modulated packets to the antennas <NUM> for transmission, and to demodulate packets received from the antennas <NUM>. The antennas <NUM> may transmit packets, such as NDPs, to STAs <NUM> or other APs <NUM> within the system <NUM>.

The I/O controller <NUM> may manage input and output signals for the AP <NUM>. The I/O controller <NUM> also may manage peripherals not integrated into the AP <NUM>. In some implementations, the I/O controller <NUM> may represent a physical connection or port to an external peripheral. In some other implementations, the I/O controller <NUM> may be implemented as part of a processor <NUM>. A user may interact with the AP <NUM> via the I/O controller <NUM> or via hardware components controlled by the I/O controller <NUM>.

The AP <NUM> may include alternative or additional components to those described above. For example, the AP <NUM> may include a network communications manager, an inter-station communications manager, or any combination of these or any other AP <NUM> components.

<FIG> shows a flowchart illustrating an example method <NUM> for managing high volumes of space-time-streams in Next Generation Wi-Fi systems. The operations of the method <NUM> may be implemented by an AP <NUM> or its components as described herein. For example, the operations of method <NUM> may be implemented by a space-time-stream packet module <NUM> as described with reference to <FIG>.

At block <NUM> the AP <NUM> may identify a number of space-time-streams for transmission of a packet, the packet including an LTF section that contains one or more OFDM symbols. At block <NUM> the AP <NUM> may select an orthogonal matrix for modulation of the LTF section, where a size of a first and a second dimension of the orthogonal matrix is less than the number of space-time-streams. In some implementations, the size of the matrix may be based on a number of LTF indices, on a number of space-time-streams, or on a maximum supported matrix size. For example, the matrix may be an example of an <NUM> × <NUM> orthogonal matrix stored in the memory of the AP <NUM>. At block <NUM> the AP <NUM> may modulate the LTF section over the space-time-streams using the selected orthogonal matrix. For example, the AP <NUM>, using a modulator, may spread the space-time-streams over the OFDM symbols of the LTF section using the selected orthogonal matrix. In some implementations, the AP <NUM> may additionally perform interpolation or frequency spreading to fully modulate the LTF section. At block <NUM> the AP <NUM> may transmit, via one or more antennas and using a transmitter or transceiver, the packet including the modulated LTF section over a set of tones using the space-time-streams.

<FIG> shows a flowchart illustrating an example method <NUM> for managing high volumes of space-time-streams in Next Generation Wi-Fi systems. The operations of the method <NUM> may be implemented by an AP <NUM> or its components as described herein. For example, the operations of the method <NUM> may be implemented by a space-time-stream packet module <NUM> as described with reference to <FIG>.

At block <NUM> the AP <NUM> may identify a number of space-time-streams for transmission of NDP information in a set of tones, the NDP information including an LTF section that contains OFDM symbols. At block <NUM> the AP <NUM> may determine that the number of space-time-streams is greater than a threshold number of streams. In some implementations, the determination may be implicit, and may be based on the system in which the AP <NUM> operates. For example, if the AP <NUM> operates within a system supporting both legacy and EHT STAs <NUM>-that is, STAs <NUM> that support processing for different numbers of space-time-streams, LTFs, or both-the AP <NUM> may implicitly perform the following functions. At block <NUM> the AP <NUM> may transmit, using a transmitter or transceiver, a first subset of the NDP information corresponding to a first subset of antennas, where a number of the first subset of antennas is less than or equal to the threshold number of streams. At block <NUM> the AP <NUM> may transmit, using the transmitter or transceiver, a second subset of the NDP information corresponding to a second subset of the antennas, where a number of the second subset of antennas is less than or equal to the threshold number of streams.

<FIG> shows a flowchart illustrating an example method <NUM> for managing high volumes of space-time-streams in Next Generation Wi-Fi systems. The operations of the method <NUM> may be implemented by an AP <NUM> or its components as described herein. For example, the operations of the method <NUM> may be may be implemented by a space-time-stream packet module <NUM> as described with reference to <FIG>.

At block <NUM> the AP <NUM> may identify a number of space-time-streams for transmission of NDP information in a set of tones, the NDP information including an LTF section that contains one or more OFDM symbols. At block <NUM> the AP <NUM> may determine (implicitly or explicitly) that the number of the space-time-streams is greater than a threshold number of streams. The threshold number of streams may be based on the capabilities of STAs <NUM> in the system. At block <NUM> the AP <NUM> may group the set of tones into a number of tone blocks. At block <NUM> the AP <NUM> may modulate an NDP including the NDP information across the one or more OFDM symbols of the LTF section using a first orthogonal matrix and across each of the number of tone blocks using a second orthogonal matrix. These orthogonal matrices may be stored in the memory of the AP <NUM>. In one example, the first orthogonal matrix is an <NUM> × <NUM> orthogonal matrix and the second orthogonal matrix is a <NUM> × <NUM> orthogonal matrix. At block <NUM> the AP <NUM> may transmit the modulated NDP over the set of tones using the number of space-time-streams. The AP <NUM> may perform this transmission using a transmitter or transceiver and one or more antennas or antenna ports.

At block <NUM> the AP <NUM> may identify a number of space-time-streams for transmission of a packet. At block <NUM> the AP <NUM> may determine (implicitly or explicitly) that the number of the space-time-streams is greater than a threshold number of space-time-streams. In some implementations, this determination may be based on the capabilities of different STAs <NUM> serviced by the AP <NUM>. At block <NUM> the AP <NUM> may combine a number of the space-time-streams to form one or more super streams, where a total number of the one or more super streams and any remaining uncombined space-time-streams is less than or equal to the threshold number of streams. For example, if the AP <NUM> determines to transmit the packet using sixteen space-time-streams, but a subset of the STAs <NUM> (legacy STAs) receiving the space-time-streams support up to eight space-time-streams, the AP <NUM> may instead transmit the packet using eight super streams, where each super stream contains two space-time-streams. At block <NUM> the AP <NUM> may transmit the packet over a set of tones using the one or more super streams and the remaining uncombined space-time-streams. For example, the AP <NUM> may transmit the super streams and space-time-streams using a transmitter or transceiver and any number of antennas or antenna ports. A legacy STA <NUM> supporting eight streams receiving the packet may identify eight streams (for example, the eight super streams), while an EHT STA <NUM> supporting sixteen streams receiving the packet may identify sixteen streams (for example, the sixteen space-time-streams making up the super streams).

The hardware and data processing apparatus used to implement the various illustrative logics, logical blocks, modules and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose single- or multi-chip processor, a DSP, an ASIC, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, or, any conventional processor, controller, microcontroller, or state machine. A processor also may be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a number of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some implementations, particular processes and methods may be performed by circuitry that is specific to a given function.

By way of example, and not limitation, such computer-readable media may include RAM, ROM, electrically erasable programmable ROM (EEPROM), compact disc ROM (CD-ROM) or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to store desired program code in the form of instructions or data structures and that may be accessed by a computer. Combinations of the above also may be included within the scope of computer-readable media.

Various modifications to the implementations described in this disclosure may be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other implementations without departing from the scope of the appended claims.

Certain features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some implementations be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

Claim 1:
A method for wireless communication, performed by an access point, AP, and comprising:
identifying (<NUM>) a number of space-time-streams for transmission of null data packet, NDP, information in a set of tones to a station, STA, (<NUM>), the NDP information comprising a long training field, LTF, section (<NUM>) that comprises orthogonal frequency division multiplexing, OFDM, symbols;
determining (<NUM>) that the number of space-time-streams is greater than a threshold number of streams, wherein the threshold number of streams is based on a capability of the STA (<NUM>);
transmitting (<NUM>), to the STA (<NUM>), a first subset of the NDP information corresponding to a first subset of antennas (<NUM>-a), wherein a number of the first subset of antennas (<NUM>-a) is less than or equal to the threshold number of streams; transmitting (<NUM>), to the STA (<NUM>), a second subset of the NDP information corresponding to a second subset of antennas (<NUM>-b), wherein a number of the second subset of antennas (<NUM>-b) is less than or equal to the threshold number of streams; and
transmitting, to an additional STA which supports the identified number of space-time streams, the NDP information via the identified number of space-time-streams using a superset of antennas comprising the first subset of antennas (<NUM>-a) and the second subset of antennas (<NUM>-b).