WIRELESS UPLINK MULTI-USER MIMO TRANSMISSION

Abstract

An access point (AP) for wireless communication may include computing hardware and storage hardware in communication with the computing hardware, the storage hardware storing instructions that, when executed on the computing hardware, cause the computing hardware to perform operations including identifying one or more transmitting stations having one or more spatial data streams at the AP; sending a sounding request from the AP to the one or more transmitting stations; performing multi-user, multi-input, multi-output (MU-MIMO) channel estimation at the AP based on the response to the sounding request; calculating one or more precoding coefficients for the one or more transmitting stations based on the MU-MIMO channel estimate at the AP;and transmitting the one or more precoding coefficients and a transmission trigger from the AP to the one or more transmitting stations;

Description

RELATED REGISTRATION

[0001] This application claims the benefit of US Provisional Application No. 63 / 383,255, filed November 10, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0002] This disclosure relates to aspects of wireless communications, and in particular to uplink multi-user (MU) multiple-input, multiple-output (MU-MIMO) transmission in wireless local area networks (WLANs). BACKGROUND

[0003] Unless otherwise stated herein, the materials described herein are not prior art within the meaning of the claims of the present application and are not acknowledged as prior art by inclusion in this section.

[0004] Wi-Fi® communications may be configured to operate in multiple frequency bands, including the 2.4 gigahertz (GHz), 5 GHz, and 6 GHz frequency bands. Some Wi-Fi® communications may be configured to use the same or similar frequencies as other Wi-Fi® communications. Under certain circumstances, interference may occur between different Wi-Fi® communications.

[0005] The subject matter claimed in the present disclosure is not limited to examples that solve any disadvantages or operate only in environments such as those described above. Rather, this background is intended to illustrate only one exemplary technology area in which some of the examples described in the present disclosure may be applied. SUMMARY

[0006] An access point (AP) for wireless communication may include computing hardware and storage hardware that communicates with the computing hardware. The storage hardware may store instructions that, when executed on the computing hardware, may cause the computing hardware to perform operations. The operations may include identifying a plurality of transmitting stations with a plurality of spatial streams at the AP. The operations may include sending a sounding request from the AP to the plurality of transmitting stations. The operations may include performing a channel estimation for a multi-user multiple-input, multiple-output (MU-MIMO) transmission at the AP based on a sounding request response.The operations may include calculating one or more precoding coefficients for the plurality of transmitting stations based on the MU-MIMO channel estimation at the AP. The operations may include transmitting the one or more precoding coefficients and a transmission trigger (a. transmit trigger) from the AP to the plurality of transmitting stations.

[0007] A wireless communication transmitting station (STA) may include computing hardware and storage hardware that communicates with the computing hardware. The storage hardware may store instructions that, when executed on the computing hardware, may cause the computing hardware to perform operations. The operations may include receiving a sounding request at the STA from an access point (AP). The operations may include sending a sounding packet in response to the sounding request from the STA to the AP. The operations may include receiving one or more precoding coefficients at the STA from the AP. The operations may include receiving a transmission trigger at the STA from the AP. The operations may include performing multiple-input multiple-output (MIMO) precoding at the STA using the one or more precoding coefficients.

[0008] A method for uplink multi-user multi-input multi-output (UL MU-MIMO) may include performing multi-input multi-output (MIMO) channel estimation in an uplink direction (UL) for a plurality of transmitting stations (STAs) at an access point (AP). The method may include calculating one or more precoding coefficients based on the MIMO channel estimation at the AP. The method may include transmitting the one or more precoding coefficients from the AP to the plurality of STAs.

[0009] The objects and advantages of the embodiments are realized and attained by at least the elements, features and combinations particularly pointed out in the claims

[0010] Both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Exemplary embodiments are described and explained in more detail with reference to the accompanying drawings in which they are shown: Fig. Figure 1 shows an example of a wireless local area network (WLAN) with an access point (AP) and several stations (STA) equipped with multiple antennas. Fig. Figure 2A shows an example packet sequence for uplink multiple input and multiple output (UL MU-MIMO) precoding. Fig. Figure 2B shows an example packet sequence for UL-MU-MIMO precoding with implicit channel estimation. Fig. Figure 2C shows an example packet sequence for UL MU-MIMO precoding derived from a downstream channel estimation Fig. Figure 3 shows an example block diagram of a UL MU-MIMO precoding STA. Fig. Figure 4 shows an example block diagram of a UL MU-MIMO precoding AP. Fig. Figure 5 shows an example of the phase optimization process. Fig. Figure 6 shows an exemplary packet sequence for a consecutive UL MU-MIMO pre-coded transmission. Fig. Figure 7 shows an example process flow for an access point that can receive UL MU-MIMO transmissions. Fig. Figure 8 shows an example process flow of a STA that can send UL MU-MIMO transmissions. Fig. Figure 9 shows an example of the process flow of a UL MU-MIMO transmission method. Fig. Figure 10 shows an example of a communication system that can be used for UL MU-MIMO transmissions. Fig. 11 shows a schematic representation of a computing machine in the exemplary form of a computer in which a set of instructions may be executed that cause the computing machine to perform one or more of the methods discussed herein. Fig. Figure 12 shows performance results comparing precoding without UL MU-MIMO and precoding with UL MU-MIMO. DETAILED DESCRIPTION

[0012] Multi-user, multiple-input, multiple-output (MU-MIMO) transmission can increase spectral efficiency in wireless local area networks (WLANs) by allowing multiple stations to be served simultaneously and on the same frequency while spatially separating them. If the transmitter is equipped with multiple antennas, spatial separation can be achieved through precoding at the transmitter side, which can be more efficient than multiple-input, multiple-output (MIMO) equalization at the receiver.

[0013] While MU-MIMO precoding can be used for downlink transmission from the AP to the stations, MIMO precoding has not been used for uplink transmission from the stations to the AP. Stations can be equipped with more than one antenna, which can enable MU-MIMO precoding for uplink transmission.

[0014] In uplink MU-MIMO transmission, compared to downlink MU-MIMO, the calculation of the precoder matrix for the stations can be performed jointly, with the channels between the stations' transmit antennas and the AP's receive antennas known. Therefore, the precoding calculation can be performed centrally at the AP, and the precoders can be applied at the stations. A single protocol can be used for communicating the precoder matrices from the AP to the stations.

[0015] Furthermore, upstream channel estimation can be performed in addition to downstream channel estimation, using sounding packets transmitted synchronously by the stations upstream. Compared to downstream MU-MIMO, upstream MU-MIMO can account for clock and phase drifts between the different transmitting stations.

[0016] In WLAN systems, MU-MIMO transmission can be used for downlink transmission. For uplink transmission, multiple antennas can be used to transmit phase-shifted copies of a transmitted signal across the antennas, for example, to transmit with higher power or greater linearity than a single antenna. Unlike downlink transmission, uplink transmission has not yet utilized centrally coordinated MIMO precoding.

[0017] In some examples, the station's multiple antennas may be used to perform MIMO precoding for the uplink transmission. To enable uplink multi-user MIMO transmission, some techniques may include one or more of the following: (i) MIMO channel estimation in the uplink direction from the stations to the AP (which may be implicit, using an uplink data transmission, or explicit, using a dedicated uplink sounding packet), (ii) calculation of MU MIMO uplink precoding coefficients for the transmitting stations (which may be performed centrally at the AP), (iii) communication of the precoders from the AP to the transmitting stations (e.g., using a protocol to exchange the precoding coefficients), or (iv) precoding at the station for an uplink MU MIMO transmission.

[0018] The disclosed systems and methods can increase uplink transmission capacity without additional cost and / or complexity when the proposed transmission scheme is low in use. Furthermore, higher uplink rates can reduce power consumption and latency when packets require less transmission time.

[0019] As in Fig. 1, a wireless local area network (WLAN) 100 may include one or more access points (APs) 110 and one or more station (STAs) 120a, 120b, 120c. The one or more STAs 120a, 120b, 120c may include one or more antennas 122a, 124a, 122b, 124b, 122c, 124c, or the like. One or more of the STAs 120a, 120b, 120c may include one or more antennas: (i) station 120a may include the one or more antennas 122a, 124a, (ii) station 120b may include the one or more antennas 122b, 124b, or (iii) station 120c may include the one or more antennas 122c, 124c.

[0020] UL MU-MIMO (Multi-User Multiple Input Multiple Output) precoding uses different functionality for uplink transmission (i.e., communication from the station to the access point) than for downlink transmission (i.e., communication from the access point to the station). The functionality used for UL MU-MIMO precoding also differs from that used for UL MU-MIMO transmission without precoding.

[0021] The functionality for UL MU-MIMO at the access point 110 may comprise one or more operations, including: (i) preparing channel estimation (sounding) packets, (ii) performing channel sounding operations, (iii) performing channel estimation operations, (iv) performing precoder matrix calculation operations, (v) transmitting precoder matrices to the one or more stations 120a, 120b, 120c, or (vi) receiving uplink transmissions from the one or more stations 120a, 120b, 120c.

[0022] In one example, a wireless communication AP 110 may include computing hardware and memory hardware that communicates with the computing hardware. The memory hardware may store instructions that, when executed on the computing hardware, cause the computing hardware to perform operations.

[0023] The operations may include identifying one or more transmitting stations (e.g., STA1 120a, STA2 120b, STA3 120c) at the AP 110. The one or more transmitting stations may comprise one or more spatial streams. That is, a transmitting station (e.g., STA1 120a, STA2 120b, STA3 120c) may be operated to transmit one or more spatial streams that do not exceed the number of transmit antennas for the transmitting station while enabling full channel estimation without using one or more sounding packets. The AP 110 may be capable of determining spatial streams associated with the transmitting stations (e.g., STA1 120a, STA2 120b, STA3 120c). The AP 110 may be capable of determining the transmitting stations and the spatial streams for the transmitting stations for UL MU-MIMO transmission.

[0024] The operations may include sending a sounding request from the AP 110 to the one or more transmitting stations (e.g., STA1 120a, STA2 120b, STA3 120c). The AP 110 may specify sounding settings and send the sounding request to the transmitting stations (e.g., STA1 120a, STA2 120b, STA3 120c) for which a UL MU-MIMO transmission is to be received.

[0025] The operations may include performing a MU-MIMO channel estimation at the AP 110 based on the response to the sounding request. The AP 110 may evaluate the sounding packets that may be received after the sounding request and perform a MU-MIMO channel estimation based on the sounding packets.

[0026] The operations may include calculating MIMO transmission settings (e.g., modulation and coding scheme, data streams, transmit power, bandwidth, operating frequency band, or similar) at the AP 110.

[0027] The operations may include calculating one or more precoding coefficients for the one or more transmitting stations (e.g., STA1 120a, STA2 120b, STA3 120c) based on the MU-MIMO channel estimation at the AP 110. The one or more precoding coefficients may be located in a precoding vector or a precoding matrix. The operations may further include calculating a MIMO equalizer at the AP 110.

[0028] The operations may include transmitting the one or more precoding coefficients from the AP 110 to the one or more transmitting stations (e.g., STA1 120a, STA2 120b, STA3 120c). The AP 110 may transmit a trigger to the one or more transmitting stations to initiate an uplink MU-MIMO transmission.

[0029] The operations may include receiving the uplink MU-MIMO transmissions from one or more transmitting stations (e.g., STA1 120a, STA2 120b, STA3 120c) at the AP 110. The MIMO equalizer may be updated and the data received from the transmitting stations may be decoded.

[0030] At one or more transmitting stations (e.g. STA1 120a, STA2 120b, STA3 120c) the transmitting operations corresponding to the receiving operations at the AP 110 can be performed. The operations may include one or more of the following steps: (i) receiving the sounding request from the AP 110 at the one or more transmitting stations (e.g., STA1 120a, STA2 120b, STA3 120c), (ii) sending the sounding packet from the one or more transmitting stations (e.g., STA1 120a, STA2 120b, STA3 120c) to the AP 110 in response to the sounding request received from the AP 110, (iii) receiving the one or more precoding coefficients and the UL MU-MIMO transmission trigger at the one or more transmitting stations (e.g., STA1 120a, STA2 120b, STA3 120c) from the AP 110, and (iv) communicating the UL MU-MIMO transmission from the one or more STAs to the AP 110.

[0031] In one example, a transmitting station (STA) (e.g., STA1 120a, STA2 120b, STA3 120c) operable for wireless communication may include computing hardware and storage hardware in communication with the computing hardware. The storage hardware may store instructions that, when executed on the computing hardware, may cause the computing hardware to perform operations.

[0032] The operations may include receiving a sounding request from an access point (AP) 110 at the STA (e.g., STA1 120a, STA2 120b, STA3 120c). The operations may include sending a sounding packet from the STA (e.g., STA1 120a, STA2 120b, STA3 120c) to the AP 110 in response to the sounding request. The operations may include receiving one or more precoding coefficients from the AP 110 at the STA (e.g., STA1 120a, STA2 120b, STA3 120c). The operations may include receiving a transmission trigger at the STA (e.g., STA1 120a, STA2 120b, STA3 120c) from the AP 110. The operations may include encoding a data packet. The operations may include performing MU-MIMO precoding at the STA (e.g., STA1 120a, STA2 120b, STA3 120c) using the one or more precoding coefficients.

[0033] The aforementioned operations on the AP 110 and the one or more transmitting stations (e.g., STA1 120a, STA2 120b, STA3 120c) may be performed on one or more of the transmitting stations when the transmitting stations transmit simultaneously.

[0034] The use of one or more precoding coefficients for the UL MU-MIMO data transmission from one or more transmitting stations (e.g., STA1 120a, STA2 120b, STA3 120c) to the AP 110 may enable an increase in upstream capacity, an increase in data rate, a reduction in power consumption, or a reduction in latency compared to a base upstream capacity, a base data rate, a reduction in power consumption, or a base latency when the one or more precoding coefficients are not used.

[0035] In one example, the use of the one or more precoding coefficients may increase the upstream capacity (e.g., measured in Mbps) compared to a base upstream capacity (e.g., measured in Mbps) when the one or more precoding coefficients are not used by one or more of the following values: more than 10%, more than 20%, more than 50%, more than 100%, more than 200%, or the like.

[0036] In one example, the use of the one or more precoding coefficients may increase the data rate (e.g., measured in Mbps) by one or more of the following amounts compared to a base data rate (e.g., measured in Mbps) when the one or more precoding coefficients are not used: more than 10%, more than 20%, more than 50%, more than 100%, more than 200%, or the like.

[0037] In one example, the use of the one or more precoding coefficients may reduce power consumption (e.g., measured in watt-hours Wh) by one or more of the following amounts: more than 10%, more than 20%, more than 50%, more than 80%, more than 90%, or the like, compared to a baseline power consumption (e.g., measured in watt-hours Wh) when the one or more precoding coefficients are not used.

[0038] In one example, using the one or more precoding coefficients may reduce the latency (e.g., measured in seconds) by one or more of the following: more than 10%, more than 20%, more than 50%, more than 80%, more than 90%, or the like, compared to a latency (e.g., measured in seconds) when not using the one or more precoding coefficients. The latency may be the uplink transmission latency. Transmission method and channel estimation

[0039] As in Fig. 2A to 2C, the operations performed at the AP 210 and the operations performed at one or more transmitting stations 220a, 220b, 220n may have various dependencies.

[0040] A dedicated upstream sounding packet can be used to perform MU-MIMO channel estimation. Compared to a downstream sounding packet, the transmission of a sounding packet from one or more stations can be triggered by the AP 210. The sounding packet can contain a formable orthogonal sequence to be applied to one or more antennas of the one or more transmitting stations 220a, 220b, 220c. The one or more transmitting stations 220a, 220b, 220c can transmit a different orthogonal sequence to separate the channels at the AP 210.

[0041] As in Fig. As shown in Figure 2A, functionality 200a may be provided to an AP 210 that may perform MU-MIMO channel estimation based on one or more uplink sounding packets received from one or more transmitting stations 220a, 220b, 220n. The AP may send a trigger frame containing a UL sounding packet request to the one or more transmitting stations 220a, 220b, 220n, as shown in operation 211.

[0042] After a delay 213a for the one or more transmitting stations 220a, 220b, 220n to receive the UL sounding packet request, the one or more transmitting stations 220a, 220b, 220n may transmit one or more UL sounding data packets, which may be null packets (NDPs). The one or more UL sounding packets may include one or more of UL sounding NDP 1 222a, UL sounding NDP 2 222b, or UL sounding NDP 3 222c, which may be transmitted by the one or more transmitting stations 220a, 220b, 220n.

[0043] After a processing time 213b for the AP 210 to receive the UL sounding packets from the one or more transmitting stations 220a, 220b, 220n, the AP 210 may use the channel estimate based on the UL sounding packets to calculate the one or more precoding coefficients, as shown in operation 214. The AP may trigger the UL transmission using a trigger frame UL and send the precoding coefficient data (e.g., the one or more precoding coefficients) to the one or more transmitting stations 220a, 220b, 220n, as shown in operation 216.

[0044] After a delay 217a in which the one or more transmitting stations 220a, 220b, 220n receive the trigger frame UL and the precoding coefficient data, the one or more transmitting stations 220a, 220b, 220n may transmit the one or more precoded data packets (e.g., precoded packet 1 226a, precoded packet 2 226b, or precoded packet 3 226n) to the AP 210.

[0045] The implicit estimation can be used for channel estimation if the number of columns of the implicit channel estimation matrix is ​​equal to the transmitted spatial data streamsL = Σ users u L u Thus, a full channel estimation can be used if the number of transmit antennas of the one or more transmit stations 220a, 220b, 220n is not higher than the number of receive antennas of the AP 210, which may be the limit of the transmitted spatial streams L.

[0046] As in Fig. As shown in Figure 2B, functionality 200b may be provided to an AP 210 that may perform implicit channel estimation using MU-MIMO channel estimation based on one or more uplink data transmissions received from the one or more transmitting stations 220a, 220b, 220n. The AP 210 may transmit a trigger frame to the one or more transmitting stations 220a, 220b, 220n, as shown in operation 212.

[0047] After a delay 213a for the one or more transmitting stations 220a, 220b, 220n to receive the trigger frame, the one or more transmitting stations 220a, 220b, 220n may transmit one or more unencoded packets, which may be unencoded UL MU-MIMO packets. The one or more unencoded packets may include one or more unencoded packets 223a, unencoded packets 223b, or unencoded packets 223n, which may be transmitted from the one or more transmitting stations 220a, 220b, 220n to the AP 210.

[0048] After a processing time 213b for the AP 210 to receive the uncoded packets from the one or more transmitting stations 220a, 220b, 220n, the AP 210 may use the channel estimate based on the uncoded packets to calculate the one or more precoding coefficients, as shown in operation 214. The AP may trigger the UL transmission using a trigger frame UL and send the precoding coefficient data (e.g., the one or more precoding coefficients) to the one or more transmitting stations 220a, 220b, 220n, as shown in operation 216.

[0049] After a delay 217a in which the one or more transmitting stations 220a, 220b, 220n receive the trigger frame UL and the precoding coefficient data, the one or more transmitting stations 220a, 220b, 220n may transmit the one or more precoded data packets (e.g., precoded packet 1 226a, precoded packet 2 226b, or precoded packet 3 226n) to the AP 210.

[0050] As in Fig. As illustrated in Figure 2C, functionality 200c may be provided for an AP 210 that may include a maximum number of spatial streams that may be received by one or more transmitting stations 220a, 220b, 220n. If the number of transmit antennas (tx antennas) of the one or more transmitting stations 220a, 220b, 220n transmitting simultaneously is higher than the maximum number of spatial streams that may be received by the AP 210, the implicit channel estimation may be incomplete.

[0051] A downlink MU-MIMO probing scheme can be used as input for the upstream precoder calculation. The dependency between uplink and downlink channels can be approximately Hup(k)=Hdown(k), H The compressed feedback report for downlink beamforming and precoding may not contain the complete channel matrices H (down). The compressed feedback report may contain the signal-to-noise ratio (SNR) and the V matrices from a singular value decomposition U(k)S(k)V(k), H=Hdown(k). To implement uplink MIMO precoding optimization from downlink channel estimation, the V matrices may not provide sufficient information, and a full channel matrix (e.g., H down ) may be reported back by the one or more transmitting stations 220a, 220b, 220n in the compressed feedback report.

[0052] As in Fig. 2C, functionality 200c may provide an AP 210 that may perform downlink channel estimation based on one or more compressed feedbacks (e.g., compressed feedback 1 224a, compressed feedback 2 224b, or compressed feedback n 224n) received from one or more transmitting stations 220a, 220b, 220n.

[0053] The AP 210 may transmit a data packet 213 containing null data to the one or more transmitting stations 220a, 220b, 220n. After a delay 213a until the one or more transmitting stations 220a, 220b, 220n receive the null data packet, the one or more transmitting stations 220a, 220b, 220n may transmit the one or more compressed acknowledgements (e.g., compressed acknowledgement 1 224a, compressed acknowledgement 2 224b, or compressed acknowledgement n 224n) to the AP 210.

[0054] After a processing time 213b for the AP 210 to receive the compressed feedback reports (e.g., compressed feedback 1 224a, compressed feedback 2 224b, or compressed feedback n 224n) from the one or more transmitting stations 220a, 220b, 220n, the AP 210 may use the channel estimate based on the compressed feedback reports (e.g., compressed feedback 1 224a, compressed feedback 2 224b, or compressed feedback n 224n) to calculate the one or more precoding coefficients, as shown in operation 214. The AP may initiate the UL transmission using a trigger frame UL and transmit the precoding coefficient data (e.g., the one or more precoding coefficients) to the one or more transmitting stations 220a, 220b, 220n, as shown by operation 216.

[0055] After a delay 217a in which the one or more transmitting stations 220a, 220b, 220n receive the trigger frame UL and the precoding coefficient data, the one or more transmitting stations 220a, 220b, 220n may transmit the one or more precoded data packets (e.g., precoded packet 1 226a, precoded packet 2 226b, or precoded packet 3 226n) to the AP 210.

[0056] Channel estimation can be performed after identifying the MIMO settings. For one or more carriers, the complete uplink channel matrix N tx -columns, which may be the sum of the transmitting antennas of one or more transmitting stations 220a, 220b, 220n, such as N tx = Σ users u N tx,u , and N rx Lines that can be the number of receiving antennas on the AP 210.

[0057] In one example, the AP may transmit to the one or more transmitting stations compressed precoding matrices containing one or more precoding coefficients, one or more frequency correction values, one or more phase correction values, or one or more time correction values.

[0058] The AP 210 may provide additional functions for performing channel estimation. The AP may estimate the clock frequency differences between the one or more transmitting stations 220a, 220b, 220n and send a frequency correction to the one or more transmitting stations 220a, 220b, 220n to increase the timing accuracy between the one or more transmitting stations 220a, 220b, 220n compared to a base time when the frequency correction is not used.

[0059] If the transmission time of the one or more transmitting stations 220a, 220b, 220n varies within the cyclic prefix, the AP 210 may estimate the timing differences between one or more transmitting stations 220a, 220b, 220n and transmit a timing correction for improved alignment between the one or more transmitting stations 220a, 220b, 220n compared to a base timing when the timing correction is not used.

[0060] The AP can determine a trade-off between the probing overhead and the channel estimation accuracy. The AP can set a channel estimation accuracy threshold and a probing overhead threshold. The AP can perform various operations to increase the channel estimation accuracy beyond the channel estimation accuracy threshold and / or reduce the probing overhead below the probing overhead threshold.

[0061] Probing can be performed on one or more carriers, which can increase the accuracy of the channel estimation. In some cases where the probing effort is to be reduced, probing can be performed, for example, every second, every fourth carrier, or similarly, to maintain the threshold for the accuracy of the channel estimation. In some cases, the temporal symbol length of the probing symbol can be, for example, 1 / 2, 1 / 4, 1 / 8, or similar, of the regular symbol time. MIMO precoding and equalization during uplink transmission

[0062] As in Fig. 3, a block diagram 300 for the one or more transmit stations operable for uplink MU-MIMO precoding may include one or more of the following operations: (i) a forward error correction (FEC) coding operation 310, (ii) a quadrature amplitude modulation (QAM) modulator operation 320, (iii) a precoding operation 330, or (iv) an inverse fast Fourier transform in the time domain (IFFT / TD) digital-to-analog conversion operation 340a, 340b. The one or more transmit stations may include more than one antenna, e.g., two transmit antennas. The one or more transmit stations may transmit one or more spatial data streams up to the number of transmit antennas.

[0063] At one or more transmitting stations, the uplink transmission may include an FEC coding operation 310 and a QAM modulator operation 320. After the FEC coding operation 310 and the QAM modulator operation 320, a non-precoded transmit signal vector xu(k) for the station u and the subcarrier k of the orthogonal frequency division multiplexing (OFDM) multicarrier transmission. The non-precoded transmission signal can contain one element per spatial transmission stream l = 1, ..., L u The transmission signal vectors of the one or more transmitting stations can be combined to form a transmission signal vector x(k)=[x1(k)⋮xU(k)] be summarized.

[0064] For the one or more transmitting stations, precoding can be carried out using a precoder matrix P u (k) for one or more carriers. For N tx,uTransmitting antennas, the matrix can have the size N tx,u × L u The precoding matrices of the stations can be added to the precoding matrix P(k)=[P1(k)000⋱000PU(k)] be summarized.

[0065] After pre-coding, the transmission from one transmitting station (e.g. station n) of the one or more transmitting stations yu(k)=Pu(k)xu(k) Thus, the entire transmission signal of the one or more transmission signals y (k) = P (k) x (k) be.

[0066] As in Fig. 4, a block diagram 450 for the AP may include one or more of the following elements: (i) one or more IFFT / TD operations 460a, 460b, 460c, 460d, (ii) an equalizer operation 470, (iii) a detector operation 480, or (iv) an FEC decode operation 490.

[0067] The transmission signal from one or more transmitting stations can be received at the AP and can be transmitted by ŷ (k) = H (k) y (k) + n (k) provided, where the receiver noise n (k) can be the received signal ŷ (k) size N rx × 1 and the channel matrix H (k) size N rx × N tx can be, where N tx = Σ u N tx,u . Receiver noise is not part of the AP, but has been included because thermal noise cannot be prevented.

[0068] The AP can equalize the equalization matrix G (k) of size L × N rx apply, where L = L u L u . The receive operation for carrier k can be described by x(k)^=G(k)yu(k)^ The transmitted bits can be recovered using the detector operation 480 and the FEC decoding operation 490.

[0069] Many of the hardware components available at the AP can also be available at one or more transmitting stations, and vice versa, e.g., to support point-to-point MIMO transmission. The equalizer G can be calculated at the AP, while the precoder P can be calculated at one or more transmitting stations.

[0070] In the downlink direction (e.g., communication from the AP to the one or more transmitting stations), the precoding calculation may be based on a compressed feedback report that may not contain the full precoding matrix. The compressed feedback report may contain compressed scaled amplitude and phase information. In the uplink direction (e.g., communication from the one or more transmitting stations to the AP), the channel estimation and / or the precoding calculation may be performed at the AP, so that no communication of the channel estimation over the channel is used. The full channel matrix and the noise estimate may be available for the precoding calculation.

[0071] In one example, the AP may calculate the one or more precoding coefficients using one or more of the following methods: minimum mean square error (MMSE), phase optimization, or power adaptation.

[0072] In one example, a weighted minimum mean square error (W-MMSE) calculation may be performed for the precoder. In one example, the precoder may be calculated based on the equalizer using uplink-downlink duality, or the equalizer may be calculated based on the precoder using uplink-downlink duality.

[0073] The equalizer can be G(k)=(H(k)P(k))H((H(k)P(k))(H(k)P(k))H+Cn(k))−1. The optimal precoder matrices can be derived using uplink-downlink duality. The dual uplink channel can be Hup(k)=(G(k)H(k)σ−1)H The dual uplink equalizer for the spatial stream l can be gup, lT=βlxu,lhup, lH(∑dhup,dhup,dHxu,d+Q)−1 provided, with the dual uplink noise of Q=(μ1I000⋱000μUI) can be provided.

[0074] The optimal precoder matrices can be updated with respect to the transmit power constraint per station u: ∑k=1Ktr(Pu(k)Pu(k),H)≤psum,u. The variables µ u can be updated as follows: μu,t+1=μu,t+α(∑carriers ktrace(Pu(k)Pu(k),H)−psum,u).

[0075] The dual uplink equalizer matrix Gup(k)=[gup,1T⋮gup,LT] can be a dense matrix, while a block diagonal structure according to P(k)=[P1(k)000⋱000PU(k)] can be used. The conversion from the dense matrix to the block-diagonal structure can be achieved by setting the off-diagonal elements to zero in one or more uplink-downlink duality iterations.

[0076] In the dual uplink, the transmission power can be optimized according to the following criteria xup,l=max(wl / log21+∑d≠1xup,dwd / log21+xup,dhu,dHAd−1hu,d|hup,dHAd−1hu,l|2−1hup,lHAl−1hup,l,0) where A l as Al=Q+∑d≠lhup,dhup,dHxup,d is defined. With multiple updates of x up,l and A l the uplink power allocation can converge quickly. Using the conversion matrix Z, which is defined as zld={gup,lT μ conj(gup,l)+∑j≠lxup,j|gup,lThup,j|2for l=d−xup,d|gup,dThup,l|2for d≠l the uplink power allocation can be calculated with x = Z -1 x upinto a downlink power allocation. The precoding matrix can be defined as follows: P=GuHdiag([x1,…,xL])

[0077] Depending on the modulation and coding scheme (MCS) used for the one or more transmitting stations, the SNR on a particular carrier and spatial data stream can be limited to a maximum SNR max be limited to avoid high transmission power for a specific carrier and spatial data stream. Avoiding high transmission power can be achieved by adjusting the weights w l,t+1 according to wl,t+1=min(wl,tα+SNRmaxα+SNRl,1) can be achieved.

[0078] After several iterations of precoder and equalizer updating with updated weights w and µ, the equalizer and / or precoder converge to the MMSE solution.

[0079] In one example, the AP may calculate the one or more precoding coefficients using a phase optimization calculation, as in Fig. 5. If a single spatial data stream is used per station and the one or more transmitting stations comprise two or more antennas per station, an optimization method based on phase optimization can be used. The individual precoder of one or more stations can be pu(k)=[1ejφu1(k)⋮ejφuNtx−(k)] be provided.

[0080] The AP can perform phase optimization using a sequential one-dimensional search, as in Fig. 5. The optimal phase values φun(k) can be found by sequential one-dimensional search. The search can be performed for one or more user precoders for the antenna n=2,...,N txand performed for one or more supports k. If the optimization requires multiple iterations to converge, multiple iterations i=1,...,Nit can be performed for one or more supports k.

[0081] The phase optimization process may comprise various operations, including one or more of the following: (i) initializing a carrier at k = 1, a user at u = 1, an antenna at n = 1, and an iteration at i = 1, as shown in operation 502, (ii) setting a precoder for a carrier at k = 1, a user at u = 1, and an antenna at n = 1 to the value 1, as shown in operation 504, (iii) increasing the number of antennas by 1, as shown in operation 506, (iv) calculating optimal phase values ​​phiopt(k,u,n) for a maximum signal-to-noise ratio of user u from carrier k, as shown in operation 508, (v) calculating the precoding coefficients as a function of the carrier, the user, and the antenna using: P(k,u,n) = exp(j phiopt (k, u, n)), as shown by operation 510, (vi) as shown by operation 512, determining whether the last antenna has been reached, and, if the last antenna has been reached,Proceed to operation 514, or, if the last antenna has not been reached, return to operation 508, (vii) as shown by operation 516, increment the user number by 1 and set the antenna number to 2 when the last antenna has been reached, (viii) as shown by operation 516, determine when the user number is greater than the number of users, and, if the user number is greater than the number of users, proceed to operation 518, or, if the user number is not greater than the number of users, proceed back to operation 508, (ix) as shown by operation 518, increment the iteration number by 1, set the user number to 1 and set the antenna number to 2, (x) as shown by operation 520, determine when the iteration number is greater than the maximum number of iterations, and, if the iteration number is greater than the maximum number of iterations is, continue with operation 522, or,if the iteration number is greater than the maximum number of iterations, proceeding to operation 508, (xi) as shown by operation 522, incrementing the carrier number by 1 and setting the user number to 1, setting the antenna number to 1, and setting the iteration number to 1, or (xii) as shown by operation 524, determining when the number of carriers is greater than the maximum number of carriers, and if the number of carriers is greater than the maximum number of carriers, then proceeding to complete the phase optimization process, or, if the number of carriers is not greater than the maximum number of carriers, then proceeding to operation 508.

[0082] Phase optimization may be followed by gain optimization (power adjustment). In one example, the AP may calculate the one or more precoding coefficients using power adjustment. The power adjustment may be performed at the AP for the one or more transmitting stations, and the gains may be reported to the stations. For power adjustment on the AP side, one gain value may be reported per spatial stream and carrier.

[0083] Alternatively or additionally, the gain optimization may be performed by the one or more transmitting stations, and the receive SNR may be reported to the one or more transmitting stations for gain optimization. The one or more transmitting stations may receive a signal-to-noise ratio (SNR) for a spatial data stream from the AP at the STA. The one or more transmitting stations may perform gain optimization at the STA using the SNR. If the power optimization is performed at the STA side, the SNR per spatial data stream and carrier may be reported by the AP.

[0084] Reducing the precoding message can be achieved through periodic messaging. That is, the message can be sent once every nth instance, e.g., per second, per fourth carrier, or similar. Precoding coefficient communication

[0085] In UL MU-MIMO, the precoding coefficients to be used by the one or more transmitting stations can be transmitted to the one or more transmitting stations. The precoding coefficients can include the amplitude and / or phase of the precoding coefficients.

[0086] To achieve high quality and low transmission overhead, an efficient transmission scheme can be used. Various transmission parameters can be transmitted from the AP to the one or more transmitting stations. An AP can send various transmission parameters from the AP to the one or more transmitting stations, including one or more of the following parameters: a power normalization value, a clock frequency, a clock phase, a clock start time correction value, a number of spatial streams, a number of transmitting antennas, antenna indices of transmitting antennas, a number of bits for a coefficient amplitude, a number of bits for a coefficient phase, amplitude values ​​for precoding coefficients, phase values ​​for precoding coefficients, real values ​​for precoding coefficients, or imaginary values ​​for precoding coefficients.

[0087] The power normalization value can be the total power. Alternatively or additionally, the power normalization value can be the maximum coefficient amplitude, e.g., in the form of the square root of the power, so that the transmitted amplitude values ​​can be normalized to one.

[0088] The clock frequency, the clock phase or the start time of the clock can be estimated by the AP between one or more transmitting stations, whereby a correction value can be sent in the form of one or more relative phases, a frequency correction value or similar.

[0089] Various techniques can be used to reduce signaling overhead without compromising transmission quality. The quantization of the one or more precoding coefficients can be based on a modulation and coding scheme (MCS). Alternatively or additionally, the AP can send transmission parameters to the one or more transmitting stations, including a first set of transmission parameters and a second set of transmission parameters. The first set of transmission parameters can be sent with high-bit resolution if the transmission uses a high MCS compared to a basic MCS, and the second set of transmission parameters can be sent with low-bit resolution if the transmission uses a low MCS compared to a basic MCS. More bits can be used for the high-bit resolution than for the low-bit resolution.

[0090] Other techniques that can be used to reduce signaling overhead without sacrificing transmission quality include using predetermined values ​​for stations. An AP may assign a predetermined phase value for a station from the one or more transmitting stations. To reduce the magnitude, the phase of the first coefficient may be set to 1 for one or more stations on one or more carriers without degrading performance. Alternatively or additionally, the AP may report the one or more precoding coefficients to the one or more transmitting stations based on a difference between consecutive carriers. Reporting using a difference between consecutive carriers may reduce the number of bits to be used.Alternatively or additionally, the AP may report the one or more precoding coefficients to the one or more transmitting stations using subcarrier grouping. That is, to reduce the size of the packet containing the precoder matrices, the precoder may be reported on a periodic basis, e.g., per nth basis, which may be per second subcarrier, per fourth subcarrier, or the like.

[0091] As shown by the functionality 600 in Fig. 6, for multiple consecutive transmissions to the same stations, an NDP transmission may not be used because the packet header of the precoded uplink packets can be used to estimate the channel for calculating and / or updating the precoding matrix.

[0092] An AP 610 may receive one or more MU-MIMO pre-coded transmissions (e.g., pre-coded packet 1 626a, pre-coded packet 2 626b, pre-coded packet 3 626n, pre-coded packet 1 636a, pre-coded packet 2 636b, pre-coded packet 3 636n) at the AP 610 from one or more transmitting stations 620a, 620b, 620n. The AP 610 may update the one or more precoding coefficients at the AP 610 based on the one or more MU-MIMO precoded transmissions (e.g., precoded packet 1 626a, precoded packet 2 626b, precoded packet 3 626n, precoded packet 1 636a, precoded packet 2 636b, precoded packet 3 636n) to generate one or more updated precoding coefficients. The AP may transmit the updated precoding coefficients from the AP to the one or more transmitting stations.

[0093] The one or more transmitting stations 620a, 620b, 620n may transmit one or more MU-MIMO precoded transmissions (e.g., precoded packet 1 626a, precoded packet 2 626b, precoded packet 3 626n, precoded packet 1 636a, precoded packet 2 636b, precoded packet 3 636n) from the STA 620a, 620b, 620n to the AP 610 and receive at the STA 620a, 620b, 620n updated precoding coefficients from the AP 610 based on the MU-MIMO precoded transmissions (e.g., precoded packet 1 626a, precoded packet 2 626b, precoded packet 3 626n, precoded packet 1 636a, precoded packet 2 636b, precoded packet 3 636n).

[0094] The AP 610 may send a trigger frame to the one or more transmitting stations 620a, 620b, 620n and request UL sounding packets, as shown in operation 611. After a delay 613a, the one or more transmitting stations 620a, 620b, 620n may send one or more UL sounding NDPs (UL sounding NDP 1 622a, UL sounding NDP 2 622b, UL sounding NDP 3 622n) to the AP 610. After a processing time 613b, the access point may use the channel estimate to calculate the precoder and generate precoding coefficients, as shown in operation 614. The access point 610 may initiate a UL frame and transmit precoded data to the one or more transmitting stations 620a, 620b, 620n, as shown in operation 616. After a delay 617a, the one or more transmitting stations may transmit one or more precoded MU-MIMO transmissions (e.g., precoded packet 1 626a, precoded packet 2 626b, precoded packet 3 626n) to the access point.

[0095] Using these one or more precoded MU-MIMO transmissions (e.g., precoded packet 1 626a, precoded packet 2 626b, precoded packet 3 626n) received from the one or more transmitting stations 620a, 620b, 620n after a processing time 617b, the access point may use the channel estimate (based on the one or more precoded MU-MIMO transmissions) for the precoding calculation and calculate precoding coefficients, as shown in operation 618. The access point 610 may trigger a frame UL from the one or more transmitting stations 620a, 620b, 620n and transmit precoded data to the one or more transmitting stations 620a, 620b, 620n, as shown in operation 619. After a delay 619b, the one or more transmitting stations 620a, 620b, 620n may transmit additional pre-coded MU-MIMO transmissions (e.g.Precoded packet 1 636a, precoded packet 2 636b, precoded packet 3 636n) to the access point. Therefore, using the one or more precoded MU MIMO transmissions (e.g., precoded packet 1 636a, precoded packet 2 636b, precoded packet 3 636n) in calculating the precoding matrix and / or in calculating the precoding coefficients may reduce overhead and / or processing time. In one example, to reduce overhead, a precoding update may be performed as the difference ΔP = P. t - P t-1 which may use a smaller number of bits compared to a base case where the complete precoding matrix is ​​transmitted.

[0096] Fig. 7 illustrates the process flow of an exemplary method 700 of UL MU-MIMO transmission according to at least one example described in the present disclosure. The method 700 may be implemented in accordance with at least one example described in the present disclosure.

[0097] The method 700 may be performed by processing logic that may include hardware (circuitry, dedicated logic, etc.), software (such as executing on a computer system or dedicated computing machine), or a combination of both, wherein the processing logic is implemented in the processing device (e.g., processor) 1102 of Fig. 11, the communication system 1000 of Fig. 10 or any other device, combination of devices or systems.

[0098] The method 700 may begin in block 705, where the processing logic may include identifying one or more transmitting stations with one or more spatial data streams at the AP.

[0099] In block 710, the processing logic may include sending a sounding request from the AP to the one or more transmitting stations.

[0100] In block 715, the processing logic includes performing a multi-user multi-input multi-output (MU-MIMO) channel estimation at the AP based on a sounding request-response.

[0101] In block 720, the processing logic may include calculating one or more precoding coefficients for the one or more transmitting stations based on the MU-MIMO channel estimation at the AP.

[0102] In block 725, the processing logic may include sending the one or more precoding coefficients and a transmission trigger from the AP to the one or more transmitting stations.

[0103] Changes, additions, or omissions may be made to the method 700 without departing from the scope of the present disclosure. Thus, in some examples, the method 700 may include any number of other components that may not be explicitly shown or described.

[0104] Fig. 8 illustrates the process flow of an exemplary method 800 that may be used for UL MU-MIMO transmission according to at least one example described in the present disclosure. The method 800 may be implemented in accordance with at least one example described in the present disclosure.

[0105] The method 800 may be performed by processing logic that may include hardware (circuitry, dedicated logic, etc.), software (such as executing on a computer system or dedicated computing machine), or a combination of both, wherein the processing logic is implemented in the processing device (e.g., processor) 1102 of Fig. 11, the communication system 1000 of Fig. 10 or any other device, combination of devices or systems.

[0106] The method 800 may begin in block 805, where processing logic may include receiving a sounding request from an access point (AP) at the STA.

[0107] In block 810, the processing logic may include sending a sounding packet in response to the sounding request from the STA to the AP.

[0108] In block 815, the processing logic may include receiving one or more precoding coefficients at the STA from the AP.

[0109] In block 820, the processing logic may include receiving a transmission trigger at the STA from the AP.

[0110] In block 825, the processing logic may include performing multiple input, multiple output (MIMO) precoding at the STA using the precoding matrix.

[0111] Changes, additions, or omissions may be made to the method 800 without affecting the scope of the present disclosure. Thus, in some examples, the method 800 may include any number of other components not explicitly shown or described.

[0112] Fig. 9 illustrates the process flow of an exemplary method 900 that may be used for UL MU-MIMO transmission according to at least one example described in the present disclosure. The method 900 may be implemented in accordance with at least one example described in the present disclosure.

[0113] The method 900 may be performed by processing logic that may include hardware (circuitry, dedicated logic, etc.), software (such as executing on a computer system or dedicated computing machine), or a combination of both, wherein the processing logic is implemented in the processing device (e.g., processor) 1102 of Fig. 11, the communication system 1000 of Fig. 10 or any other device, combination of devices or systems.

[0114] The method 900 may begin at block 905, where processing logic may include performing uplink (UL) multiple input multiple output (MIMO) channel estimation for one or more transmit stations (STAs) at an access point (AP).

[0115] In block 910, the processing logic may include calculating one or more precoding coefficients at the AP based on the MIMO channel estimate.

[0116] In block 915, the processing logic may include transmitting the one or more precoding coefficients from the AP to the one or more STAs.

[0117] The method may include performing MIMO channel estimation at the AP based on one or more uplink sounding packets or an uplink data transmission. The method may include calculating one or more precoding coefficients at the AP using one or more of the following methods: minimum mean square error (MMSE), phase optimization, or power adaptation.

[0118] Changes, additions, or omissions may be made to the method 900 without departing from the scope of the present disclosure. Thus, in some examples, the method 900 may include any number of other components not explicitly shown or described.

[0119] For simplicity, the methods and / or process flows described herein are illustrated and described as a number of acts. However, the acts according to this disclosure may be performed in different orders and / or concurrently, as well as with other acts not illustrated and described herein. Further, not all illustrated acts may be used to perform the methods according to the disclosed subject matter. Moreover, those skilled in the art will understand and appreciate that the methods may alternatively be represented as a number of interconnected states via a state diagram or events. Furthermore, the methods disclosed in this specification may be stored on an article of manufacture, such as a non-transitory computer-readable medium, to facilitate the transport and transfer of such methods to computers.The term "article of manufacture," as used herein, is intended to encompass a computer program accessible from any computer-readable device or storage medium. Although depicted as individual blocks, various blocks may be divided into additional blocks, combined into fewer blocks, or eliminated, depending on the desired implementation.

[0120] Fig. 10 shows a block diagram of an exemplary communication system 1000 configured to reduce AP interference, in accordance with at least one example described in the present disclosure. The communication system 1000 may include a digital transmitter 1002, a radio frequency circuit 1004, a device 1014, a digital receiver 1006, and a processing device 1008. The digital transmitter 1002 and the processing device may be configured to receive a baseband signal over a link 1010. A transceiver 1016 may include the digital transmitter 1002 and the radio frequency circuit 1004.

[0121] In some examples, communication system 1000 may include a system of devices that may be configured to communicate with each other via a wired or cabled connection. For example, a cabled connection in communication system 1000 may include one or more Ethernet cables, one or more fiber optic cables, and / or other similar cabled communication media. Alternatively or additionally, communication system 1000 may include a system of devices that may be configured to communicate via one or more wireless connections. For example, communication system 1000 may include one or more devices configured to transmit and / or receive radio waves, microwaves, ultrasonic waves, optical waves, electromagnetic induction, and / or similar wireless communications.Alternatively or additionally, the communication system 1000 may also include combinations of wireless and / or wired connections. In these and other examples, the communication system 1000 may include one or more devices that may be configured to receive a baseband signal, perform one or more operations on the baseband signal to generate a modified baseband signal, and transmit the modified baseband signal, e.g., to one or more loads.

[0122] In some examples, communication system 1000 may include one or more communication channels that may communicatively couple systems and / or devices included in communication system 1000. For example, transceiver 1016 may be communicatively coupled to device 1014.

[0123] In some examples, transceiver 1016 may be configured to receive a baseband signal. For example, as described herein, transceiver 1016 may be configured to generate a baseband signal and / or receive a baseband signal from another device. In some examples, transceiver 1016 may be configured to transmit the baseband signal. For example, after receiving the baseband signal, transceiver 1016 may be configured to transmit the baseband signal to a separate device, such as device 1014. Alternatively or additionally, transceiver 1016 may be configured to modify, condition, and / or transform the baseband signal prior to transmitting the baseband signal. For example, transceiver 1016 may include a quadrature upconverter and / or a digital-to-analog converter (DAC), which may be configured to modify the baseband signal.Alternatively or additionally, the transceiver 1016 may include a direct radio frequency sampling converter that may be configured to modify the baseband signal.

[0124] In some examples, digital transmitter 1002 may be configured to receive a baseband signal via connection 1010. In some examples, digital transmitter 1002 may be configured to upconvert the baseband signal. For example, digital transmitter 1002 may include a quadrature upconverter applied to the baseband signal. In some examples, digital transmitter 1002 may include an integrated digital-to-analog converter (DAC). The DAC may convert the baseband signal to an analog signal or a continuous-time signal. In some examples, the DAC architecture may include a direct RF sampling DAC. In some examples, the DAC may be a separate element from digital transmitter 1002.

[0125] In some examples, transceiver 1016 may include one or more subcomponents that may be used in preparing the baseband signal and / or transmitting the baseband signal. For example, transceiver 1016 may include an RF front end (e.g., in a wireless environment) that includes a power amplifier (PA), a digital transmitter (e.g., 1002), a digital front end, an IEEE 1588v2 (Institute of Electrical and Electronics Engineers) device, an LTE physical layer (L-PHY), an S-plane device (S-plane), an M-plane device (management plane), an Ethernet Media Access Control (MAC) / Personal Communications Service (PCS), a resource controller / scheduler, and the like. In some examples, a radio device (e.g., a radio frequency circuit 1004) of the transceiver 1016 may be synchronized to the resource controller via the S-plane device, which may contribute to highly accurate timing with respect to a reference clock.

[0126] In some examples, transceiver 1016 may be configured to receive the baseband signal for transmission. For example, transceiver 1016 may receive the baseband signal from a separate device, such as a signal generator. The baseband signal may, for example, originate from a converter that converts a variable into an electrical signal, such as an audio signal output from a microphone that captures a speaker's voice. Alternatively or additionally, transceiver 1016 may be configured to generate a baseband signal for transmission. In these and other examples, transceiver 1016 may be configured to transmit the baseband signal to another device, such as device 1014.

[0127] In some examples, device 1014 may be configured to receive a transmission from transceiver 1016. For example, transceiver 1016 may be configured to transmit a baseband signal to device 1014.

[0128] In some examples, the radio-frequency circuit 1004 may be configured to transmit the digital signal received from the digital transmitter 1002. In some examples, the radio-frequency circuit 1004 may be configured to transmit the digital signal to the device 1014 and / or the digital receiver 1006. In some examples, the digital receiver 1006 may be configured to receive a digital signal from the RF circuit and / or transmit a digital signal to the processing device 1008.

[0129] In some examples, the processing device 1008 may be a stand-alone device or system, as illustrated. Alternatively or additionally, the processing device 1008 may be a component of another device and / or system. For example, in some examples, the processing device 1008 may be integrated with the transceiver 1016. In cases where the processing device 1008 is a stand-alone device or system, the processing device 1008 may be configured to communicate with additional devices and / or systems remote from the processing device 1008, such as the transceiver 1016 and / or the device 1014. For example, the processing device 1008 may be configured to send and / or receive transmissions from the transceiver 1016 and / or the device 1014.In some examples, the processing device 1008 may be combined with other elements of the communication system 1000.

[0130] Fig.11 shows a schematic representation of a computing machine in the exemplary form of a computer 1100, in which a set of instructions may be executed to cause the computing machine to perform one or more of the methods discussed herein. The computing system may be configured to implement or control one or more operations related to reducing AP interference. The computer 1100 may be a rackmount server, a router computer, a server computer, a mainframe computer, a laptop computer, a tablet computer, a desktop computer, or any computer having at least one processor, etc., in which a set of instructions may be executed to cause the computing machine to perform one or more of the methods discussed herein. In alternative examples, the computing machine may be connected (e.g., via a LAN) to other computing machines on a local area network (LAN), an intranet, an extranet, or the Internet.B. networked). The computer may operate as a server in a client-server network environment. Although only a single computing machine is depicted, the term "computing machine" may also encompass any collection of computing machines that individually or collectively execute a set (or multiple sets) of instructions to perform one or more of the methods discussed herein.

[0131] The example computer 1100 includes a processing device (e.g., a processor) 1102, a main memory 1104 (e.g., read-only memory (ROM), flash memory, dynamic random access memory (DRAM) such as synchronous DRAM (SDRAM)), a static memory 1106 (e.g., flash memory, static random access memory (SRAM)), and a data storage device 1116 that communicate via a bus 1108.

[0132] Processing device 1102 is one or more general-purpose processing devices, such as a microprocessor, a central processing unit, or the like. In particular, processing device 1102 may include a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, or a processor implementing other instruction sets, or processors implementing a combination of instruction sets. Processing device 1102 may also include one or more special-purpose processing devices, such as an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a digital signal processor (DSP), a network processor, or the like. Processing device 1102 is configured to execute instructions 1126 to perform the operations and steps discussed herein.

[0133] Computer 1100 may also include a network interface 1122 that can communicate with a network 1118. Computer 1100 may also include a display device 1110 (e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT)), an alphanumeric input device 1112 (e.g., a keyboard), a cursor control device 1114 (e.g., a mouse), and a signal generating device 1120 (e.g., a speaker). In at least one example, display device 1110, alphanumeric input device 1112, and cursor control device 1114 may be combined into a single component or device (e.g., an LCD touchscreen).

[0134] The data storage device 1116 may include a computer-readable storage medium 1124 having stored thereon one or more sets of instructions 1126 embodying one or more of the methods or functions described herein. The instructions 1126 may also reside entirely or at least partially in the main memory 1104 and / or the processing device 1102 while being executed by the computer 1100, with the main memory 1104 and the processing device 1102 also representing computer-readable media. The instructions may further be transmitted or received over a network 1118 via the network interface device 1122.

[0135] While the computer-readable storage medium 1124 is illustrated as a single medium in one example, the term "computer-readable storage medium" may include a single medium or multiple media (e.g., a centralized or distributed database and / or associated caches and servers) that store the one or more sets of instructions. The term "computer-readable storage medium" may also include any medium capable of storing, encoding, or carrying a set of instructions for execution by the computing machine, and that causes the computing machine to perform one or more of the methods of the present disclosure. Accordingly, the term "computer-readable storage medium" may include, but is not limited to, solid-state storage, optical media, and magnetic media. EXAMPLES

[0136] The following are examples of the features according to embodiments of the present disclosure. EXAMPLE 1: Comparison between no UL MU-MIMO precoding and UL MU-MIMO precoding for the data rate

[0137] Uplink MU-MIMO precoding (a. Precoding) results in a significant performance improvement (e.g., measured by the PHY rate in Mbps) compared to a case where UL MU-MIMO precoding is not used. The performance difference was measured on a B-channel model with four transmit stations (two antennas and one spatial data stream per antenna) and an AP with four receive antennas (RX).

[0138] For example, at a channel SNR / dB of approximately 20, the case without UL-MU-MIMO precoding provides a PHY rate of approximately 2000 Mbps, while the case with UL-MU-MIMO provides a PHY rate of approximately 4000 Mbps. This performance difference is constant across the channel SNR / dB before reaching a plateau at a channel SNR / dB of approximately 40 and above. Therefore, UL-MU-MIMO precoding enables a performance improvement compared to the baseline case, where UL-MU-MIMO precoding is not used.

[0139] In some examples, the various components, modules, computing engines, and services described herein may be implemented as objects or processes executing on a computer system (e.g., as separate threads). While some of the systems and methods described herein are generally described as being implemented in software (stored on and / or executed by hardware), specific hardware implementations, or a combination of software and specific hardware implementations, are also possible and contemplated.

[0140] The terms used herein, and particularly in the appended claims (e.g., in the body of the appended claims), are generally to be understood as "open" terms (e.g., the term "including" is to be understood as "including, but not limited to," the term "including" is to be understood as "including at least," the term "comprises" is to be understood as "comprises, but not limited to," etc.).

[0141] If a specific number of introduced claim mentions is intended, this intention will be expressly mentioned in the claim; if such a mention is absent, there is no intention. For ease of understanding, in the following appended claims, the introductory expressions “at least one” and “one or more” may be used to introduce claim mentions. However, the use of such expressions should not be construed to mean that the introduction of a claim list by the indefinite articles “a” or “an” limits a particular claim containing such an introduced claim list to embodiments containing only one such list, even if the same claim contains the introductory expressions “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., "a" and / or "an" should be interpreted to mean "at least one" or "one or more"; the same applies to the use of certain articles used to introduce claims.

[0142] Even if a specific number of claims is expressly mentioned, it should be understood that at least that number is meant (e.g., the mere mention of "two mentions" without further modifiers means at least two mentions or two or more mentions). Where a convention analogous to "at least one of A, B, and C, etc." or "one or more of A, B, and C, etc." is used, this construction is generally intended to include A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B, and C together, etc. For example, the use of the term "and / or" should be understood in this sense.

[0143] Furthermore, any disjunctive word or phrase containing two or more alternative terms, whether in the description, claims, or drawings, should be understood to include the possibility of including either term, exactly one term, or both terms. For example, the phrase "A or B" should be understood to include the possibilities "A" or "B" or "A and B."

[0144] Furthermore, the terms "first," "second," "third," etc., are not necessarily used here to denote a specific order or number of elements. In general, the terms "first," "second," "third," etc., are used as generic labels to distinguish between different elements. Unless it is demonstrated that the terms "first," "second," "third," etc., denote a specific order, these terms should not be understood to denote a specific order. Unless it is demonstrated that the terms "first," "second," "third," etc., denote a specific number of elements, these terms should not be understood to denote a specific number of elements. For example, a first widget can be described as a first page, and a second widget can be described as a second page.The use of the term "second page" in reference to the second widget may serve to distinguish that page of the second widget from the "first page" of the first widget, and is not intended to imply that the second widget has two pages.

[0145] All examples and conditional expressions provided herein are intended for educational purposes to facilitate the reader's understanding of the disclosure and the concepts the inventor contributed to advancing the prior art, and are to be construed as not limiting to the specifically recited examples and conditions. Although the embodiments of the present disclosure have been described in detail, it is to be understood that various changes, substitutions, and alterations may be made without departing from the spirit and scope of the present disclosure. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 383,255

[0001]

Claims

[1] An access point (AP) for wireless communication, comprising: data processing hardware; and Storage hardware in communication with the computing hardware, the storage hardware storing instructions that, when executed on the computing hardware, cause the computing hardware to perform operations including: Identifying a plurality of transmitting stations with a plurality of spatial data streams at the AP; Sending a sounding request from the AP to the plurality of transmitting stations; Performing multiple-user multiple-input multiple-output (MU-MIMO) channel estimation at the AP based on a sounding request-response; Calculating one or more precoding coefficients for the plurality of transmitting stations based on the MU-MIMO channel estimation at the AP; and Sending the one or more precoding coefficients and a transmission trigger from the AP to the plurality of transmitting stations. [2] The AP of claim 1, wherein the storage hardware is further operable to cause the computing hardware to perform operations comprising: Performing MU-MIMO channel estimation at the AP based on one or more uplink sounding packets or an uplink data transmission. [3] The AP of claim 1, wherein the storage hardware is further operable to cause the computing hardware to perform operations comprising: Calculating the one or more precoding coefficients at the AP using one or more of the following methods: minimum mean square error (MMSE), phase optimization, or power adaptation. [4] The AP of claim 1, wherein the storage hardware is further operable to cause the computing hardware to perform operations comprising: Assigning a predetermined phase value for a transmitting station to the AP from the plurality of transmitting stations. [5] The AP of claim 1, wherein the storage hardware is further operable to cause the computing hardware to perform operations comprising: Reporting the one or more precoding coefficients based on a difference between consecutive carriers from the AP to the plurality of transmitting stations; or Reporting the one or more precoding coefficients using subcarrier grouping from the AP to the plurality of transmitting stations. [6] The AP of claim 1, wherein the storage hardware is further operable to cause the computing hardware to perform operations comprising: Reporting the one or more precoding coefficients using the signal-to-noise ratio (SNR) for one or more carriers or one or more spatial data streams from the AP to the plurality of transmitting stations. [7] The AP of claim 1, wherein the storage hardware is further operable to cause the computing hardware to perform operations comprising: Sending transmission parameters comprising one or more of the following elements from the AP to the plurality of transmitting stations: a performance normalization value, a clock frequency, a clock phase, a clock start time correction value, a number of spatial data streams, a number of transmitting antennas, Antenna indices of transmitting antennas, a number of bits for a coefficient amplitude, a number of bits for a coefficient phase, Amplitude values ​​for precoding coefficients, Phase values ​​for precoding coefficients, real values ​​for precoding coefficients, or imaginary values ​​for precoding coefficients. [8] The AP of claim 1, wherein the storage hardware is further operable to cause the computing hardware to perform operations comprising: reducing a quantization of the one or more precoding coefficients based on a modulation and coding scheme (MCS); and Sending transmission parameters comprising a first set of transmission parameters and a second set of transmission parameters from the AP to the plurality of transmitting stations, wherein the first set of transmission parameters is sent using a high-bit resolution and the second set of transmission parameters is sent using a low-bit resolution, wherein the high-bit resolution is higher than the low-bit resolution. [9] The AP of claim 1, wherein the storage hardware is further operable to cause the computing hardware to perform operations comprising: Transmitting compressed precoding matrices from the AP to the plurality of transmitting stations, comprising: the one or more precoding coefficients, one or more frequency correction values, one or more phase correction values, or one or more time correction values. [10] The AP of claim 1, wherein the storage hardware is further operable to cause the computing hardware to perform operations comprising: Receiving one or more MU-MIMO pre-coded transmissions at the AP from the plurality of transmitting stations; Updating the one or more precoding coefficients at the AP based on the one or more MU-MIMO precoded transmissions to generate one or more updated precoding coefficients; and Sending the updated precoding coefficients from the AP to the plurality of transmitting stations. [11] The AP of claim 1, wherein the use of the one or more precoding coefficients can enable an increase in upstream capacity, an increase in data rate, a decrease in power consumption, or a decrease in latency compared to a baseline scenario when the one or more precoding coefficients are not used. [12] A wireless communications transmitting station (STA) comprising: data processing hardware; and Storage hardware in communication with the computing hardware, the storage hardware storing instructions that, when executed on the computing hardware, cause the computing hardware to perform operations including: Receiving a sounding request at the STA from an access point (AP); Sending a sounding packet from the STA to the AP in response to the sounding request; Receiving one or more precoding coefficients from the AP at the STA; Receiving a transmission trigger at the STA from the AP; and Performing multiple-user multiple-input multiple-output (MU-MIMO) precoding at the STA using the one or more precoding coefficients. [13] The STA of claim 12, wherein the storage hardware is further operable to cause the computing hardware to perform operations comprising: Performing phase optimization in the STA using a sequential one-dimensional search. [14] The STA of claim 12, wherein the storage hardware is further operable to cause the computing hardware to perform operations comprising: Receiving a signal-to-noise ratio (SNR) for a spatial data stream at the STA from the AP; and Performing gain optimization on the STA using the SNR. [15] The STA of claim 12, wherein the storage hardware is further operable to cause the computing hardware to perform operations comprising: Receiving transmission parameters from the AP at the STA, which include one or more of the following elements: a performance normalization value, a clock frequency, a clock phase, a clock start time correction value, a number of spatial data streams, a number of transmitting antennas, Antenna indices of transmitting antennas, a number of bits for the coefficient amplitude, a number of bits for the coefficient phase, Amplitude values ​​for precoding coefficients, Phase values ​​for precoding coefficients, real values ​​for precoding coefficients, or imaginary values ​​for precoding coefficients. [16] The STA of claim 12, wherein the storage hardware is further operable to cause the computing hardware to perform operations comprising: Receiving compressed precoding matrices from the AP at the STA comprising: the one or more precoding coefficients, one or more frequency correction values, one or more phase correction values, or one or more time correction values. [17] The STA of claim 12, wherein the storage hardware is further operable to cause the computing hardware to perform operations comprising: Sending one or more MU-MIMO pre-coded transmissions from the STA to the AP; and Receiving updated precoding coefficients based on the MU-MIMO precoded transmissions from the AP to the STA. [18] A method for uplink multi-user multiple input multiple output (UL MU-MIMO) comprising: Performing multi-input multi-output (MIMO) channel estimation in an uplink (UL) direction for a plurality of transmitting stations (STAs) at an access point (AP); Calculating one or more precoding coefficients based on the MIMO channel estimate at the AP; and Sending the one or more precoding coefficients from the AP to the plurality of STAs. [19] The method of claim 18, further comprising: Performing MIMO channel estimation at the AP based on one or more uplink sounding packets or an uplink data transmission. [20] The method of claim 18, further comprising: Calculating the one or more precoding coefficients at the AP using one or more of the following methods: minimum mean square error (MMSE), phase optimization, or power adaptation.

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