Managing high volumes of space-time-streams in next generation extremely high throughput (EHT) Wi-Fi systems

This disclosure provides systems, methods, and apparatuses, including computer programs encoded on computer storage media, for managing high volumes of space-time-streams in Wi-Fi systems. An access point (AP) may transmit packets including long training field (LTF) sections using a number of space-time-streams greater than eight. Mobile stations (STAs) in the system may or may not be capable of processing this number of streams. The AP may modulate an LTF section using a matrix with dimensions smaller than the number of streams by using tone-interleaving or by performing modulation with separate matrices in time and frequency. In some other implementations, the AP may split the antennas for transmission into groups, each group transmitting either different packets in a subset of streams or a same packet in a subset of tones. In further implementations, the AP may combine multiple space-time-streams into a super stream that supports reception at different types of STAs.

TECHNICAL FIELD

This disclosure relates to wireless communications, and more specifically to a next generation extremely high throughput (EHT) Wi-Fi system supporting a high volume of space-time-streams, such as sixteen space-time-streams.

DESCRIPTION OF THE RELATED TECHNOLOGY

Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. 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) 802.11) 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.

SUMMARY

One innovative aspect of the subject matter described in this disclosure can be implemented in a method of wireless communication. The method can include identifying a number of space-time-streams for transmission of null data packet (NDP) information in a set of tones, the NDP information containing a long training field (LTF) section that includes orthogonal frequency division multiplexing (OFDM) symbols, and determining that the number of space-time-streams is greater than a threshold number of streams. The method can further include transmitting 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, and transmitting 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.

Another innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus for wireless communication. The apparatus can include means for identifying a number of space-time-streams for transmission of NDP information in a set of tones, the NDP information containing an LTF section that includes OFDM symbols, and means for determining that the number of space-time-streams is greater than a threshold number of streams. The apparatus can further include means for transmitting 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, and means for transmitting 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.

Another innovative aspect of the subject matter described in this disclosure can be implemented in another apparatus for wireless communication. The apparatus can include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions can be operable to cause the processor to identify a number of space-time-streams for transmission of NDP information in a set of tones, the NDP information containing an LTF section that includes OFDM symbols, and determine that the number of space-time-streams is greater than a threshold number of streams. The instructions can be further operable to cause the processor to transmit 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, and transmit 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.

Another innovative aspect of the subject matter described in this disclosure can be implemented in a non-transitory computer-readable medium for wireless communication. The non-transitory computer-readable medium can include instructions operable to cause a processor to identify a number of space-time-streams for transmission of NDP information in a set of tones, the NDP information containing an LTF section that includes OFDM symbols, and determine that the number of space-time-streams is greater than a threshold number of streams. The instructions can be further operable to cause the processor to transmit 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, and transmit 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.

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.

Another innovative aspect of the subject matter described in this disclosure can be implemented in a method for wireless communication. The method can include identifying a number of space-time-streams for transmission of a packet, the packet containing an LTF section that includes one or more OFDM symbols. The method can further include selecting an orthogonal matrix for modulation of the LTF section, where the size of a first and a second dimension of the orthogonal matrix is less than the number of space-time-streams used for transmission. Additionally, the method can include modulating the LTF section over the space-time-streams using the selected orthogonal matrix, and transmitting the packet including the modulated LTF section over a set of tones using the identified space-time-streams.

Another innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus for wireless communication. The apparatus can include means for identifying a number of space-time-streams for transmission of a packet, the packet containing an LTF section that includes one or more OFDM symbols. The apparatus can further include means for selecting 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. Additionally, the apparatus can include means for modulating the LTF section over the space-time-streams using the selected orthogonal matrix and means for transmitting the packet including the modulated LTF section over a set of tones using the identified space-time-streams.

Another innovative aspect of the subject matter described in this disclosure can be implemented in another apparatus for wireless communication. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions can be operable to cause the processor to identify a number of space-time-streams for transmission of a packet, the packet containing an LTF section that includes one or more OFDM symbols. The instructions can be further operable to cause the processor to 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. Additionally, the instructions can be operable to cause the processor to modulate the LTF section over the space-time-streams using the selected orthogonal matrix, and transmit the packet including the modulated LTF section over a set of tones using the identified space-time-streams.

Another innovative aspect of the subject matter described in this disclosure can be implemented in a non-transitory computer-readable medium for wireless communication. The non-transitory computer-readable medium can include instructions operable to cause a processor to identify a number of space-time-streams for transmission of a packet, the packet containing an LTF section that includes one or more OFDM symbols. The instructions can further be operable to cause the processor to 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. Additionally, the instructions can be operable to cause the processor to modulate the LTF section over the space-time-streams using the selected orthogonal matrix, and transmit the packet including the modulated LTF section over a set of tones using the identified space-time-streams.

In some implementations, modulating the LTF section over the space-time-streams using the selected orthogonal matrix may include operations, features, means, or instructions for spreading the space-time-streams over the one or more OFDM symbols of the LTF section using the selected orthogonal matrix.

In some implementations, modulating the LTF section over the space-time-streams using the selected orthogonal matrix may include operations, features, means, or instructions for modulating, for a first subset of the set of tones, the LTF section over a first subset of the space-time-streams using the selected orthogonal matrix and modulating, for a second subset of the set of tones, the LTF section over a second subset of the space-time-streams using a second orthogonal matrix. In some implementations, modulating the LTF section over the first subset of the space-time-streams using the selected orthogonal matrix and modulating the LTF section over the second subset of the space-time-streams using the second orthogonal matrix may include operations, features, means, or instructions for spreading the first subset of the space-time-streams over the one or more OFDM symbols of the LTF section for the first subset of the set of tones using the selected orthogonal matrix and spreading the second subset of the space-time-streams over the one or more OFDM symbols of the LTF section for the second subset of the set of tones using the second orthogonal matrix. Additionally, in some implementations, the first subset of the space-time-streams and the second subset of the space-time-streams are spread such that a STA receiving the packet interpolates the spread first subset of the space-time-streams and the spread second subset of the space-time-streams to determine the first subset of the space-time-streams over the one or more OFDM symbols of the LTF section for the second subset of the set of tones and the second subset of the space-time-streams over the one or more OFDM symbols of the LTF section for the first subset of the set of tones.

In some implementations, both the first subset of the space-time-streams and the second subset of the space-time-streams include at least one shared space-time-stream. Additionally, or alternatively, in some implementations, the selected orthogonal matrix and the second orthogonal matrix may be the same.

In some implementations, the method, apparatuses, and non-transitory computer-readable medium can include operations, features, means, or instructions for grouping the set of tones into a set of tone blocks, selecting a third orthogonal matrix for modulation of the space-time-streams within each of the set of tone blocks, and modulating, for each of the set of tone blocks, the space-time-streams using the selected third orthogonal matrix to obtain orthogonal signals in neighboring tones of the set of tones. In some implementations, modulating the space-time-streams using the selected third orthogonal matrix can include operations, features, means, or instructions for spreading the space-time-streams over the set of tones using the selected third orthogonal matrix. In some implementations, a first dimension of the selected third orthogonal matrix multiplied by the first dimension of the selected orthogonal matrix may be greater than or equal to the number of space-time-streams, where the first dimension of the selected third orthogonal matrix may be less than the number of space-time-streams.

In some implementations, the LTF section can include a compressed LTF section and the set of tones can include a number of tones that is less than a number of tones corresponding to an uncompressed LTF section.

Another innovative aspect of the subject matter described in this disclosure can be implemented in a method of wireless communication. The method can include identifying a number of space-time-streams for transmission of a packet and determining that the number of the space-time-streams is greater than a threshold number of space-time-streams. The method can further include combining 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, and transmitting the packet over a set of tones using the one or more super streams and the remaining uncombined space-time-streams.

Another innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus for wireless communication. The apparatus can include means for identifying a number of space-time-streams for transmission of a packet and means for determining that the number of the space-time-streams is greater than a threshold number of space-time-streams. The apparatus can further include means for combining 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, and means for transmitting the packet over a set of tones using the one or more super streams and the remaining uncombined space-time-streams.

Another innovative aspect of the subject matter described in this disclosure can be implemented in another apparatus for wireless communication. The apparatus can include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions can be operable to cause the processor to identify a number of space-time-streams for transmission of a packet and determine that the number of the space-time-streams is greater than a threshold number of space-time-streams. The instructions can be further operable to cause the processor to 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, and transmit the packet over a set of tones using the one or more super streams and the remaining uncombined space-time-streams.

Another innovative aspect of the subject matter described in this disclosure can be implemented in a non-transitory computer-readable medium for wireless communication. The non-transitory computer-readable medium can include instructions operable to cause a processor to identify a number of space-time-streams for transmission of a packet and determine that the number of the space-time-streams is greater than a threshold number of space-time-streams. The instructions can be further operable to cause the processor to 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, and transmit the packet over a set of tones using the one or more super streams and the remaining uncombined space-time-streams.

In some implementations, each of the one or more super streams may be designed such that a first type of STAs receive the super stream as a single space-time-stream and a second type of STAs receive the super stream as a set of separate space-time-streams. In these implementations, the first type of STAs can include STAs capable of receiving a total number of space-time-streams equal to or less than the threshold number of space-time-streams and the second type of STAs can include STAs capable of receiving a total number of space-time-streams greater than the threshold number of space-time-streams.

In some implementations, the packet can include an LTF section. In these implementations, the method, apparatuses, and non-transitory computer-readable medium can include operations, features, means, or instructions for selecting an orthogonal matrix for modulation of the LTF section, where each row of the selected orthogonal matrix corresponds to a super stream, an uncombined space-time-stream, or a set of combined space-time-streams.

In some implementations, a first row of the selected orthogonal matrix can correspond to a set of combined space-time-streams. In these implementations, the method, apparatuses, and non-transitory computer-readable medium can include operations, features, means, or instructions for spreading a first space-time-stream of the set of combined space-time-streams over the LTF section for a first subset of the set of tones using the first row of the selected orthogonal matrix and spreading a second space-time-stream of the set of combined space-time-streams over the LTF section for a second subset of the set of tones using the first row of the selected orthogonal matrix.

Another innovative aspect of the subject matter described in this disclosure can be implemented in a method of wireless communication. The method can include identifying a number of space-time-streams for transmission of NDP information in a set of tones, the NDP information containing an LTF section that includes one or more OFDM symbols, and determining that the number of the space-time-streams is greater than a threshold number of streams. The method can further include grouping the set of tones into a number of tone blocks, modulating 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 tone blocks using a second orthogonal matrix, and transmitting the modulated NDP over the set of tones using the identified space-time-streams.

Another innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus for wireless communication. The apparatus can include means for identifying a number of space-time-streams for transmission of NDP information in a set of tones, the NDP information containing an LTF section that includes one or more OFDM symbols, and means for determining that the number of the space-time-streams is greater than a threshold number of streams. The apparatus can include further means for grouping the set of tones into a number of tone blocks, means for modulating 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 tone blocks using a second orthogonal matrix, and means for transmitting the modulated NDP over the set of tones using the identified space-time-streams.

Another innovative aspect of the subject matter described in this disclosure can be implemented in another apparatus for wireless communication. The apparatus can include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions can be operable to cause the processor to identify a number of space-time-streams for transmission of NDP information in a set of tones, the NDP information containing an LTF section that includes one or more OFDM symbols, and determine that the number of the space-time-streams is greater than a threshold number of streams. The instructions can be further operable to cause the processor to group the set of tones into a number of tone blocks, 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 tone blocks using a second orthogonal matrix, and transmit the modulated NDP over the set of tones using the identified space-time-streams.

Another innovative aspect of the subject matter described in this disclosure can be implemented in a non-transitory computer-readable medium for wireless communication. The non-transitory computer-readable medium can include instructions operable to cause a processor to identify a number of space-time-streams for transmission of NDP information in a set of tones, the NDP information containing an LTF section that includes one or more OFDM symbols, and determine that the number of the space-time-streams is greater than a threshold number of streams. The instructions can be further operable to cause the processor to group the set of tones into a number of tone blocks, 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 tone blocks using a second orthogonal matrix, and transmit the modulated NDP over the set of tones using the identified space-time-streams.

DETAILED DESCRIPTION

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 16×16 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. 1shows an example of a wireless communications system100that 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 system100may include an AP105and multiple associated STAs115, 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 AP105and the associated STAs115may represent a basic service set (BSS) or an extended service set (ESS). The various STAs115in the network may communicate with one another through the AP105or directly via device-to-device (D2D) communication. Also shown is a coverage area110of the AP105, which may represent a basic service area (BSA) of the wireless communications system100. An extended network station (not shown) associated with the wireless communications system100may be connected to a wired or wireless distribution system that may allow multiple APs105to be connected in an ESS. In some implementations, an AP105may transmit to one or more STAs115using 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 AP105may perform modulation and transmission to manage this high volume of space-time-streams, as well as to support both STAs115that support high volumes of streams and STAs115that do not support high volumes of streams.

Although not shown inFIG. 1, a STA115may be located at the intersection of more than one coverage area110and may associate with more than one AP105. A single AP105and an associated set of STAs115may be referred to as a BSS. An ESS is a set of connected BSSs. A distribution system (not shown) may be used to connect APs105in an ESS. In some implementations, the coverage area110of an AP105may be divided into sectors (also not shown). The wireless communications system100may include APs105of different types (such as metropolitan area APs, home network APs, etc.) with varying and overlapping coverage areas110. The AP105may communicate with one or more STAs115within the coverage area110corresponding to the AP105. For example, the AP105may communicate with a STA115over a communication link120, where transmissions from the AP105to the STA115may be referred to as downlink transmissions and transmissions from the STA115to the AP105may be referred to as uplink transmissions. Additionally, two STAs115also may communicate directly via a direct wireless link125regardless of whether both STAs115are in the same coverage area110. Examples of direct wireless links125may include Wi-Fi Direct connections, Wi-Fi Tunneled Direct Link Setup (TDLS) links, and other group connections. STAs115and APs105may communicate according to the WLAN radio and baseband protocol for physical and MAC layers from IEEE 802.11 and versions including, but not limited to, 802.11b, 802.11g, 802.11a, 802.11n, 802.11ac, 802.11ad, 802.11ah, 802.11ax, and subsequent versions. In some other implementations, peer-to-peer connections or ad hoc networks may be implemented within the wireless communications system100.

In some implementations, a STA115(or an AP105) may be detectable by a central AP105, but not by other STAs115in the coverage area110of the central AP105. For example, one STA115may be at one end of the coverage area110of the central AP105while another STA115may be at the other end. Thus, both STAs115may communicate with the AP105, but may not receive the transmissions of the other. This may result in colliding transmissions for the two STAs115in a contention-based environment (such as an environment or system supporting carrier-sense multiple access with collision avoidance (CSMA/CA)) because the STAs115may not refrain from transmitting on top of each other. A STA115whose transmissions are not identifiable, but that is within the same coverage area110may 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 STA115(or AP105) and a clear-to-send (CTS) packet transmitted by the receiving STA115(or AP105). 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 systems100, an AP105may transmit a packet containing an LTF section using a given number of streams, where a STA115may receive and further decode the packet. For improved spectral efficiency, the AP105may 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 AP105may modulate the LTF section using a square orthogonal matrix with dimensions smaller than the number of streams or LTF indices. For example, the AP105may store an 8×8 matrix in memory for packet modulation and may use this 8×8 matrix for modulating when transmitting with any number of space-time-streams. Using a smaller P-matrix for modulation may allow the AP105to store fewer matrices in memory, and may support backwards compatibility with STAs115or other APs105that do not support a high volume of space-time-streams.

In some implementations, a STA115receiving 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 STA115. In these implementations, the AP105may 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 AP105may identify subsets of antennas to sound in separate attempts, where each group of antennas may transmit the packet across different subsets of tones. The AP105may further combine the number of space-time-streams to create a super stream to support reception at various different types of STAs115. For example, implementing super streams may allow for the AP105to obtain the spectral efficiency benefits provided by a high volume of space-time-streams even in a wireless communications system100where some STAs115are incapable of processing this high volume of space-time-streams.

FIG. 2shows an example of a wireless communications system200that supports high volumes of space-time-streams. The wireless communications system200may be an example of a Next Generation or EHT Wi-Fi system, and may include an AP105-a, a STA115-a, and a coverage area110-a, which may be examples of the corresponding components described with respect toFIG. 1. The AP105-amay transmit a packet210on the downlink205to the STA115-ausing a number of space-time-streams. The packet may include an LTF section215.

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 STAs115-aserved by a same AP105. However, some Next Generation or EHT Wi-Fi systems, such as a wireless communications system200, may support configurations to manage a higher volume of space-time-streams (that is, higher than the legacy systems). For example, the wireless communications system200may include support for a number of space-time-streams larger than eight (such as sixteen space-time-streams). The AP105-a, the STA115-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 packet210to the STA115-a, the AP105-amay employ methods to modulate the LTF section215prior to transmission. The modulation process for the LTF section215may be part of a larger modulation procedure for the entire packet210. The LTF section215may span one or more OFDM symbols and may include information used for initial channel estimation at the STA115-a. For example, the LTF section215may include a number of long training symbols (i.e., LTF symbols) and a cyclic prefix. A STA115-areceiving the LTF section215may use the repeated long training symbols for frequency offset estimation, channel estimation, etc. The AP105-amay select an orthogonal matrix (for example, a P-matrix) to modulate the LTF section215over 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 section105-a. One example of a 6×6 P-matrix may be an orthogonal discrete Fourier transform (DFT) matrix used in signal processing methods:

In the above example, the constant w may be defined as w=exp(−j2π/6). 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 section215to obtain LTF sequences spread across the time-domain for each of the space-time-streams. A STA115-areceiving 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 AP105-aconfigured to use higher volumes of space-time-streams may store P-matrices to manage these higher numbers of streams. For example, an AP105-ain a Next Generation or EHT Wi-Fi system may store a variety of orthogonal matrices (for example, a 10×10 matrix, a 12×12 matrix, a 14×14 matrix, a 16×16 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 systems200. In some implementations, these matrices may be composed of smaller P-matrices as sub-components. In one example, a 12×12 P-matrix may be constructed using constituent 6×6 orthogonal P-matrices, such that:

P12×12=[P6×6P6×6P6×6-P6×6].
In another example, a 16×16 matrix may be constructed using 8×8 orthogonal P-matrices as building blocks:

P12×12=[P8×8P8×8P8×8-P8×8].
Additional higher-dimensional matrices (for example, matrices larger than 8×8) may be constructed using similar methods. For example, an AP105-amay store a 10×10 matrix, a 14×14 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 10×10 P-matrix includes:

z=exp⁡(jmath*2*pi/10);first_row=[1-1111-1111-1];vector⁡[1zz^2z^3z^4z^5z^6z^7z^8z^9];P=[first_row;first_row.*vector;first_row.*(vector.^2);first_row.*(vector.^3);first_row.*(vector.^4);first_row.*(vector.^5);first_row.*(vector.^6);first_row.*(vector.^7);first_row.*(vector.^8);first_row.*(vector.^9);],
where the “first row” array can include any values and the P-matrix may maintain orthogonality (although an array of all “is” may result in a spectral line) and “.*” corresponds to the element-by-element multiplication operation. In this example, the code may result in a 10×10 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 APs105, the STAs115, 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 8×8—stored by the AP105-amay be limited by an LTF overhead wastage threshold. For example, if the AP105-astores one P-matrix larger than 8×8, such as a 16×16 matrix, the AP105-atransmits a full set of sixteen LTF symbols for any number of space-time-streams greater than eight streams. In this example, if the AP105-atransmits using ten space-time-streams, the AP105-amay 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 16×16 orthogonal matrix. Alternatively, if the AP105-astores a 10×10 matrix in addition to the 16×16 matrix, the AP105-amay 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 AP105-amay 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, AP105-amay store multiple P-matrices, including both small P-matrices (that is, P-matrices with dimensions 8×8 or smaller) and large P-matrices (that is, P-matrices with dimensions larger than 8×8). For example, an AP105-amay store P-matrices including P2×2, P4×4, P6×6, P8×8, P10×10, P12×12, P14×14, and P16×16.

In some implementations, an AP105-amay 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 8×8, the AP105-amay use smaller P-matrices, such as an 8×8 orthogonal P-matrix, to modulate LTFs for high volume space-time-stream transmissions. The AP105-amay modulate the LTF section215over the space-time-streams using the selected P-matrix and may transmit the modulated LTF215over a set of tones corresponding to the space-time-streams. To handle modulation of the LTF section215with a P-matrix that has dimensions smaller than the number of space-time-streams, the AP105-amay use one or more modulation techniques as described below with reference toFIGS. 3 and 4.

FIG. 3shows an example of techniques for performing LTF modulation in a wireless communications system300that supports high volumes of space-time-streams. The wireless communications system300may be an example of a Next Generation or EHT Wi-Fi system, and may include an AP105-b, a STA115-b, and a coverage area110-b, which may be examples of the corresponding components described with respect toFIGS. 1 and 2. The AP105-bmay transmit a packet on the downlink305to the STA115-busing a number of space-time-streams. The AP105-bmay use a first LTF modulation technique310-a, a second LTF modulation technique310-b, or a combination thereof to modulate an LTF section of the packet for transmission. In the first LTF modulation technique310-a, the AP105-bmay use a first P-matrix315-ato modulate a first group of space-time-streams across the LTF symbols over a first set of frequency tones320and may use a second P-matrix315-bto modulate a second group of space-time-streams across the LTF symbols over a second set of frequency tones320. The first and second sets of frequency tones320may be interleaved. In the second LTF modulation technique310-b, the AP105-bmay modulate the space-time-streams across symbols in the time domain using a first P-matrix315-aand may modulate the space-time-streams across frequency tones320in the frequency domain using a third P-matrix315-c.

In some implementations, an AP105-band a STA115-bmay utilize a smaller P-matrix315for estimating a channel with a larger number of space-time-streams (for example, an AP105-bmay modulate an LTF section with sixteen space-time-streams using a P-matrix315with dimensionality less than 16×16). In a first LTF modulation technique310-a, the AP105-bmay modulate and transmit different groups of streams on different frequency tones320. In one implementation, the first LTF modulation technique310-amay be an example of a tone-interleaving process, where the AP105-bmay switch between or select certain tones for certain space-time-streams to support a higher number of space time streams in a network. The AP105-bmay modulate stream groups using multiple orthogonal P-matrices315, such as P-matrix315-aand P-matrix315-b, which in some implementations may be examples of the same matrix. In the first LTF modulation technique310-a, AP105-bmay 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-matrix315for modulation (for example, a first set of streams1-8and second set of streams9-16if P-matrices315-aand315-bare at least 8×8). The AP105-bmay identify a number of frequency tones320for 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 8×8 P-matrix may be used for sixteen space-time-streams). In an example, the AP105-bmodulates streams1-8using the P-matrix315-aover the odd frequency tones320and modulates streams9-16using the P-matrix315-bover the even tones and transmits these subsets of space-time-streams on the alternating frequency tones320.

A receiving STA115-bmay receive the packet with the modulated LTFs, and may use interpolation to determine the channel for every stream on every frequency tone320. For example, the STA115-bmay use interpolation or another estimation technique to estimate the channel for streams1-8on the even tones and for streams9-16on the odd tones. In some implementations, the interpolation process may involve the STA115-baveraging values for corresponding alternate tones to determine a value for an intermediate frequency tone320. For example, for the first space-time-stream, the STA115-bmay average two odd frequency tones320to estimate the channel associated with the even frequency tone320between the two odd frequency tones320.

In a second LTF modulation technique310-b, modulating an LTF section in both time and frequency may provide separation between space-time-streams on adjacent tones without tone interleaving. An AP105-bmay apply an orthogonal code over time resources using a P-matrix315-a. Additionally, the AP105-bmay apply an orthogonal code over frequency resources (for example, frequency tones320) using a P-matrix315-cto separate spatial streams over tone blocks. While P-matrices315-aand315-cmay each have smaller dimensions than the number of space-time-streams, in combination the P-matrices315may modulate the larger number of streams (for example, sixteen streams). P-matrix315-aand P-matrix315-cmay be the same matrix or may be different matrices. In one example, the AP105-bmay use a P-matrix315-aof one size (for example, an 8×8 P-matrix) to modulate across OFDM symbols and a P-matrix315-cof another size different than P-matrix315-a(for example, a 2×2 P-matrix) to modulate across frequency tones320. That is, the AP105-bmay spread the space-time-streams over blocks of tones using the P-matrix315-cto 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-matrix315-a. The AP105-bmay differentiate a larger number of streams than the number of LTFs by modulating the LTFs across both OFDM symbols and across blocks of frequency tones320using two P-matrices315. In some implementations, the product of the dimensions of the selected P-matrices315-aand315-cmay 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 technique310-b.

In some implementations, the AP105-bmay utilize LTF compression techniques in addition to LTF modulation techniques310. For example, the AP105-bmay use shorter or compressed LTFs (for example, 1× or 2× LTFs) in a packet for transmission. The AP105-bmay transmit these short LTFs across a smaller number of tones. As compared to transmitting an uncompressed LTF, the AP105-bmay transmit 2× LTFs on one half the tones of the uncompressed LTF and may transmit 1× LTFs on one quarter of the tones of the uncompressed LTF. In further examples, the AP105-bmay use other sizes of compressed LTFs in packet transmissions over other specified tones. A STA115-breceiving a compressed LTF may perform additional interpolation as compared to a STA115-breceiving an uncompressed LTF to estimate the channel across the full set of frequency tones320. In some implementations, the amount of interpolation performed by the STA115-bmay increase as the LTF compression factor increases. In one specific example, the AP105-bmay implement the first LTF modulation technique310-afor modulating 2× LTFs using sixteen space-time-streams across half a set of frequency tones320, where subsets of the streams are interleaved in this half set of frequency tones320. In this example, a receiving STA115-bmay interpolate to estimate the channel for the interleaved frequency tones320for each space-time-stream based on the first LTF modulation technique310-a. Additionally, the receiving STA115-bmay interpolate to estimate the channel for the other half set of frequency tones320based on the LTF compression.

In some wireless communications systems300, a STA115-bmay transmit a packet with an LTF section on the uplink to the AP105-b. For example, the STA115-bmay 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-STA115or per-AP105basis. In transmissions involving long LTF sections, a STA115-bmay implement a method involving tone-interleaved LTFs or other LTF modulation techniques310similar to those described above with respect to downlink305transmissions from the AP105-b.

In some implementations, the wireless communications system300may 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 AP105-bmay 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 AP105-bmay delay a transmission for the corresponding space-time-stream. The AP105-bmay 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 50 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 1TCS,VHT(n)values for the modulated fields of a PPDUTotalnumber ofspace-time-streamsCyclic Shift for space-time-stream n (ns)(NSTS,total)1234567810———————20−400——————30−400−200—————40−400−200−600————50−400−200−600−350———60−400−200−600−350−650——70−400−200−600−350−650−100—80−400−200−600−350−650−100−750
Table 1 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 1 or may include values different than those given in Table 1. 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 1. Additionally, this example follows steps—or cyclic shift diversity thresholds—of 50 ns and a maximum cyclic shift value of 800 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-streams9-16:

TABLE 2Additional TCS,VHT(n)values for Space-Time-Streams 9-16Space-Time-Stream n910111213141516Cyclic Shift−250−550−300−450−50−700−150−500(in ns)
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 AP105-band the STA115-bsupporting 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 AP105-bmay allocate additional bits to the High Efficiency Signal A Field (HE-SIG-A) to support the additional space-time-streams. The AP105-bmay further introduce additional rows for a spatial configuration field encoding for the High Efficiency Signal B Field (HE-SIG-B). In some implementations, the AP105-bmay maintain support for a lower number of users in a MU-MIMO system despite the additional space-time-streams. For example, the AP105-bmay support transmitting to up to eight users (that is, different STAs115) using sixteen spatial streams for MU-MIMO transmissions.

FIG. 4shows an example of techniques for transmitting an NDP in a wireless communications system400that supports high volumes of space-time-streams. The wireless communications system400may be an example of a Next Generation or EHT Wi-Fi system, and may include an AP105-c, a STA115-c, and a STA115-d, which may be examples of the corresponding devices described with respect toFIGS. 1-3. The AP105-cmay transmit a null data packet announcement (NDPA)405, one or more NDPs410, and a trigger frame415. Each STA115may transmit a beam forming (BF) report420. For example, STA115-cmay transmit BF report420-aand STA115-dmay transmit BF report420-b. The AP105-cmay include a total number of antennas or antenna ports for transmitting NDPs410on space-time-streams. However, some STAs115may not be configured to receive the number of streams that the AP105-cis transmitting. To manage this, the AP105-cmay transmit the one or more NDPs410using a first technique430-a, a second technique430-b, or a third technique430-c. In the first technique430-a, the AP105-cmay transmit a first NDP410-ausing a first group of antennas425-aand a second NDP410-busing a second group of antennas425-b. In the second technique430-b, the AP105-cmay transmit a single NDP410, where the AP105-cmay transmit the single NDP410on a first set of streams in a first set of tones using a first group of antennas425-aand on a second set of streams in a second set of tones using a second group of antennas425-b. As discussed above, the antennas may refer to physical antennas or logical antenna ports. In the third technique430-c, the AP105-cmay modulate the NDP410across LTF symbols using a first P-matrix435-aand may modulate across pairs or groups of adjacent frequency tones using a second P-matrix435-b. Each of the first technique430-a, the second technique430-b, and the third technique430-cmay support STAs115that may not process the full number of LTFs or streams in sounding.

In some implementations, NDPs410may 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 NDP410format 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 reports420. In some implementations, a BF report420may 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 STA115or AP105. 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) sub-field, which may include an additional bit to indicate the larger number of supported streams.

In the wireless communications system400, the AP105-cmay manage a number of STAs115with different sounding capabilities. For example, one set of STAs, including STA115-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 STAs115, including STA115-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 AP105-cmay employ a number of techniques430to support communication with STAs115capable of processing up to eight spatial streams while efficiently communicating with STAs115capable of processing up to sixteen spatial streams. In this way, the AP105-cmay accommodate STAs115with lesser sounding capabilities while communicating using improved spatial multiplexing and spectral efficiency with STAs115supporting greater sounding capabilities.

In a first technique430-a, the AP105-cmay contain a set of antennas—that is, physical antennas or logical antenna ports—to transmit information to a STA115-c. The AP105-cmay perform a sounding process to transmit a sequence of NDPs410-aand410-b, where each NDP410contains a number of LTFs within the sounding capability of the STA115-c. During the sounding process, the AP105-cmay sound a first group of antennas425-aof the total set of antennas to transmit the first NDP410-ain a first attempt and may sound a second group of antennas425-bof the total set of antennas to transmit a second NDP410-bin a second attempt. This first group of antennas425-aand second group of antennas425-bmay overlap (for example, share at least one same antenna between the two groups) or may be mutually exclusive. For example, if the AP105-cutilizes sixteen space-time-streams (and, corresponding, sixteen LTFs), and the STA115-cis capable of processing eight space-time-streams or LTFs, the AP105-cmay transmit two NDPs410each containing eight of the sixteen LTFs. In such implementations, the receiving STA115-cmay stitch the two channel components together to determine the sixteen LTFs. In some implementations, the different groups of antennas425-aand425-bmay have different automatic gain control (AGC) states as processed by STA115-c, for example, due to transmitting the NDPs410in different attempts. The STA115-cmay calibrate out or otherwise mitigate any differences in the AGC states in order to stitch the channel components. Additionally, or alternatively, the AP105-cmay freeze the phase for transmission of the different NDPs410to remove or mitigate any phase offset across the groups of antennas425transmitting the NDPs410at different times. This also may improve reception and stitching of the two channel components at the receiving STA115-c.

In a second technique430-b, the AP105-cmay perform tone-interleaving using a single NDP410over 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 AP105-cmay modulate a transmission using an orthogonal P-matrix or multiple P-matrices. The AP105-cmay transmit the NDP410on a first set of tones using a first subset of antennas425-aand may further transmit the NDP410on a second set of tones using a second subset of antennas425-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 antennas425-aand the second subset of antennas425-bmay contain one or more shared antennas for improved reception and stitching at the receiving STA115-c. For example, antennas shared between the first and second subsets of antennas425may serve as phase references for the receiving STA115-c.

In a third technique430-c, the AP105-cmay 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-matrix435-aused for time domain modulation. In one implementation, the AP105-cmay use one P-matrix435-aof one size (for example, an 8×8 P-matrix) for modulation across LTF symbols in the time domain and may use a second P-matrix435-bof another size (for example, a 2×2 P-matrix) for modulation across adjacent tones in the frequency domain. This may allow a STA115-ccapable of receiving8space-time-streams or LTFs to differentiate sixteen space-time-streams.

FIG. 5shows an example of space-time-stream and super stream transmissions in a wireless communications system500that supports managing high volumes of space-time-streams. The wireless communications system500may be an example of a Next Generation or EHT Wi-Fi system, and may include an AP105-dand a STA115-e, which may be examples of the devices described with respect toFIGS. 1-4. The AP105-dmay transmit one or more packets (such as an NDP) to the STA115-ein space-time-streams505. The AP105-dmay combine some space-time-streams505to form super streams510. If the STA115-eis configured for a high volume of streams (for example, greater than eight streams), the STA115-emay detect and receive all of the space-time-streams505. If the STA115-eis not configured for a high volume of streams, the STA115-emay detect the super streams510as if they are space-time-streams505, so that, as illustrated, the STA115-emay detect and receive eight space-time-streams505, rather than the full ten transmitted space-time-streams505.

The AP105-dmay transmit a high volume of space-time-streams (for example, greater than eight space-time-streams) in a wireless communications system500containing STAs115that are not equipped to support a high volume of streams based on one or more capabilities of the STAs115. In some implementations, the AP105-dmay transmit a high volume of streams by implementing super-streaming techniques, which may group or combine a number of space-time-streams505into super streams510to accommodate the legacy STAs115capable 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 STA115-eis configured to support a high volume of streams, the STA115-emay detect and receive each of the multiple space-time-streams505within super stream510separately, or as individual streams. In some other implementations, where the STA115-eis unable to support a high volume of streams, the STA115-emay detect and receive a super stream510as a single space-time-stream505. In some implementations, an AP105-dtransmitting, for example, sixteen space-time-streams505may transmit eight super streams510, where each super stream510contains two single space-time-streams505. This may result in some STAs115receiving sixteen streams for a single transmission while other STAs receive a different number of streams due to the different capabilities of the STAs115. In some other implementations, an AP105-dmay transmit ten space-time-streams505including two super streams510, where each super stream510contains two of the space-time-streams505. This may result in a subset of the STAs115in the wireless communications system500detecting ten streams (the ten space-time-streams505) while a different subset of STAs115may detect eight streams (the two super streams510and the six uncombined space-time-streams505).

In some implementations, STAs115and APs105may implement super streams510in uplink and downlink transmissions, such as MU-MIMO LTF transmissions. In some implementations, an AP105may transmit a packet in a downlink MU-MIMO system to a STA115, which may not be configured to support a high volume of space-time streams. In one implementation, some STAs115served by an AP105may support up to sixteen total space time streams, while another STA115served by AP105may support reception of eight total space time streams. In order to transmit for example, twelve space time streams in a downlink MU-MIMO transmission, AP105may transmit four singular space time streams along with four super streams each consisting of two singular space-time streams. In this example, STAs115supporting a high volume of space time streams may receive the transmission as containing twelve total space time streams, while the STA115with lesser reception capabilities may receive the transmission as containing eight total space time streams.

The STAs115may use a P-matrix for LTF modulation and transmission across tones. The AP105-dmay allocate a row of the P-matrix (e.g., a channel estimation resource) to a STA115-e, where the STA115-eis configured for a lower volume of streams. For STAs115supporting a higher volume of streams, the AP105-dmay allocate some rows of the P-matrix such that the rows shift during modulation between different streams across tones. For example, an EHT STA115may 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 AP105-dreceiving the two streams may perform interpolation to estimate the channel for the in-between tones. For example, if the EHT STA115modulates streams1-6on a first tone and streams7-12on a second tone, the AP105-dmay interpolate LTF values for streams7-12on the first tone and interpolate LTF values for streams1-6on the second tone. In another example, APs105-dmay share the same row of the P-matrix.

FIG. 6shows a block diagram of an example system600including an AP605that supports high volumes of space-time-streams. The AP605may be an example of a wireless device configured to operate in a Next Generation or EHT Wi-Fi system. The AP605may include components for bi-directional voice and data communications including components for transmitting and receiving communications, such as a processor620, a memory625, software630, a transceiver635, an antenna640, and an input/output (I/O) controller645. These components may be in electronic communication via one or more buses, such as a bus610. The transceiver635may include a space-time-stream packet module615configured to implement one or more of the techniques described with respect toFIGS. 1-5, in cooperation with the processor620, a memory625, software630, antenna640, and I/O controller645.

The space-time-stream packet module615may perform a number of operations for managing high volumes of space-time-streams. For example, the space-time-stream packet module615may handle transmitting packets to different types of STAs115, where some STAs115in the system600are capable of processing up to eight space-time-streams and other STAs115in the system600are capable of processing more than eight space-time-streams. For example, the first type of STAs115may be referred to as “legacy” STAs, and the second type of STAs115may 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 STA115may 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 module615may 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 STAs115in the system600. For example, the threshold number of streams may be equal to eight streams, where a subset of the STAs115support processing more than the threshold number of streams and another subset of STAs115support processing less than or equal to the threshold number of streams. The space-time-stream packet module615, via the transceiver635and antennas640, may transmit a first subset of the NDP information using a first subset of the antennas640, such as half of the antennas640, and may transmit a second subset of the NDP information using a second subset of the antennas640, such as the other half of the antennas640.

In a second example, the space-time-stream packet module615may 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 module615may 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 memory625. 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 module615may modulate the LTF section over the space-time-streams using the selected orthogonal matrix—that is, the space-time-stream packet module615may spread the space-time-streams over the OFDM symbols of the LTF section using the selected orthogonal matrix. The space-time-stream packet module615may 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 module615, via the transceiver635and antenna(s)640, 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 module615may 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 module615may 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 module615identifies ten streams, but the threshold number of streams is eight, the space-time-stream packet module615may form two super streams composed of two space-time-streams each. The space-time-stream packet module615, via the transceiver635and antenna(s)640, may transmit the packet over a set of tones using the super streams and space-time-streams. Legacy STAs115may receive each super stream as a single space-time-stream, while EHT STAs115may receive each super stream as its component space-time-streams. Accordingly, in the example given above, a legacy STA115may identify eight streams while an EHT STA115may identify ten streams for the same transmission based on these super streams.

In a fourth example, the space-time-stream packet module615may 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 module615may 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 module615may 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 memory625. The space-time-stream packet module615, via the transceiver635and antenna(s)640, may transmit the modulated NDP over the set of tones using the space-time-streams. The space-time-stream packet module615may operate as described above in a single example, or in any combination of the examples.

The processor620may 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 processor620may 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 module615.

The memory625may include random access memory (RAM) and read-only memory (ROM). The memory625may store computer-readable, computer-executable code or software630including instructions that, when executed, cause the processor to perform various functions described herein. In some implementations, the memory625may 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 transceiver635may communicate bi-directionally, via one or more antennas640or antenna ports, wired, or wireless links as described above. For example, the transceiver635may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver635also may include a modem to modulate the packets and provide the modulated packets to the antennas640for transmission, and to demodulate packets received from the antennas640. The antennas640may transmit packets, such as NDPs, to STAs115or other APs105within the system600.

The I/O controller645may manage input and output signals for the AP605. The I/O controller645also may manage peripherals not integrated into the AP605. In some implementations, the I/O controller645may represent a physical connection or port to an external peripheral. In some other implementations, the I/O controller645may be implemented as part of a processor620. A user may interact with the AP605via the I/O controller645or via hardware components controlled by the I/O controller645.

The AP605may include alternative or additional components to those described above. For example, the AP605may include a network communications manager, an inter-station communications manager, or any combination of these or any other AP605components.

FIG. 7shows a flowchart illustrating an example method700for managing high volumes of space-time-streams in Next Generation Wi-Fi systems. The operations of the method700may be implemented by an AP105or its components as described herein. For example, the operations of method700may be implemented by a space-time-stream packet module615as described with reference toFIG. 6.

At block705the AP105may 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 block710the AP105may 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 8×8 orthogonal matrix stored in the memory of the AP105. At block715the AP105may modulate the LTF section over the space-time-streams using the selected orthogonal matrix. For example, the AP105, 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 AP105may additionally perform interpolation or frequency spreading to fully modulate the LTF section. At block720the AP105may 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. 8shows a flowchart illustrating an example method800for managing high volumes of space-time-streams in Next Generation Wi-Fi systems. The operations of the method800may be implemented by an AP105or its components as described herein. For example, the operations of the method800may be implemented by a space-time-stream packet module615as described with reference toFIG. 6.

At block805the AP105may 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 block810the AP105may 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 AP105operates. For example, if the AP105operates within a system supporting both legacy and EHT STAs115—that is, STAs115that support processing for different numbers of space-time-streams, LTFs, or both—the AP105may implicitly perform the following functions. At block815the AP105may 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 block820the AP105may 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. 9shows a flowchart illustrating an example method900for managing high volumes of space-time-streams in Next Generation Wi-Fi systems. The operations of the method900may be implemented by an AP105or its components as described herein. For example, the operations of the method900may be may be implemented by a space-time-stream packet module615as described with reference toFIG. 6.

At block905the AP105may 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 block910the AP105may 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 STAs115in the system. At block915the AP105may group the set of tones into a number of tone blocks. At block920the AP105may 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 AP105. In one example, the first orthogonal matrix is an 8×8 orthogonal matrix and the second orthogonal matrix is a 2×2 orthogonal matrix. At block925the AP105may transmit the modulated NDP over the set of tones using the number of space-time-streams. The AP105may perform this transmission using a transmitter or transceiver and one or more antennas or antenna ports.

FIG. 10shows a flowchart illustrating an example method1000for managing high volumes of space-time-streams in Next Generation Wi-Fi systems. The operations of the method1000may be implemented by an AP105or its components as described herein. For example, the operations of the method1000may be implemented by a space-time-stream packet module615as described with reference toFIG. 6.

At block1005the AP105may identify a number of space-time-streams for transmission of a packet. At block1010the AP105may 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 STAs115serviced by the AP105. At block1015the AP105may 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 AP105determines to transmit the packet using sixteen space-time-streams, but a subset of the STAs115(legacy STAs) receiving the space-time-streams support up to eight space-time-streams, the AP105may instead transmit the packet using eight super streams, where each super stream contains two space-time-streams. At block1020the AP105may 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 AP105may transmit the super streams and space-time-streams using a transmitter or transceiver and any number of antennas or antenna ports. A legacy STA115supporting eight streams receiving the packet may identify eight streams (for example, the eight super streams), while an EHT STA115supporting sixteen streams receiving the packet may identify sixteen streams (for example, the sixteen space-time-streams making up the super streams).