Spectrum sharing wireless system

Abstract

Methods, systems, and devices for spectrum sharing wireless systems are described in which multiple user devices share time and frequency resources for uplink and / or downlink transmissions. One example wireless communication system includes a network station and a plurality of user devices, in which data transmissions on the same time and frequency resources are shared among the plurality of user devices in the downlink and / or uplink using spatial user device separation dynamically computed by the network station, and in which the network station derives the spatial user device separation based on uplink channel measurements.

Description

[0001] Cross-reference to related applications

[0002] This document claims priority and benefit to U.S. Provisional Application No. 62 / 705,182, filed on June 15, 2020, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure relates to wireless communications. Background Technology

[0004] As the number of wireless user devices and the amount of wireless data these devices can generate or consume grow rapidly, current wireless communication networks are quickly exhausting their bandwidth to accommodate this high growth in data traffic and to provide users with high-quality service.

[0005] The telecommunications industry is making various efforts to develop next-generation wireless technologies that can keep pace with the performance demands on wireless devices and networks. Many of these efforts involve scenarios where a large number of user devices can be served by the network. Summary of the Invention

[0006] This document discloses techniques useful for embodiments of wireless systems that share spectrum (e.g., time and frequency resources) among multiple user equipment.

[0007] In one example aspect, a system for wireless communication is disclosed. The system includes: a network station; and a plurality of user equipments, wherein spatial user equipment separation is dynamically calculated by the network station, and data transmission on the same time and frequency resources is shared among the plurality of user equipments in the downlink and / or uplink, and wherein the network station derives the spatial user equipment separation based on uplink channel measurements.

[0008] In another example aspect, a wireless communication method is disclosed. The method is implemented by a network station in a wireless system comprising a network station and multiple user equipments, the method comprising: transmitting transmission symbols from the network station to at least one user equipment by processing via a first precoder and a pre-compensation stage, wherein the pre-compensation stage is selected such that transmission symbols receivable at the at least one user equipment appear as if the transmission symbols were processed by a second precoder different from the first precoder.

[0009] In yet another example, a wireless communication method is disclosed. The method includes: a first wireless device determining a first precoder specific to a second wireless device for precoding a transmission, wherein the first precoder is determined to match a second precoder in a specific angular sector, and wherein the first precoder is determined based on channel measurements of transmissions from the second wireless device to the first wireless device.

[0010] In yet another example, a wireless communication method is disclosed. The method includes: determining a user equipment-specific precoder for application to signal transmission from a network station to the user equipment; and transmitting a data symbol stream to the user equipment by precoding using the user equipment-specific precoder, wherein the user equipment-specific precoder is unknown to the user equipment, and wherein the symbol stream has no reference signal for receiver-side channel equalization.

[0011] In yet another example, a wireless communication method is disclosed. The method includes: determining a first precoder by a network station based on measurements of one or more uplink signals received on an uplink channel; determining a second precoder by scaling the first precoder using a scaling factor; and performing downlink transmission on a downlink channel using the second precoder, wherein the downlink channel and the uplink channel are frequency-division duplex.

[0012] In yet another example, a wireless communication method is disclosed. The method includes: determining a spatial covariance matrix by a network station operating in a frequency division duplex wireless system based on measurements of uplink signals received from a user equipment on an uplink channel; and performing downlink transmission on a downlink channel by precoding using a precoder corresponding to a scaled version of the spatial covariance matrix.

[0013] In another example, a wireless communication method is disclosed. The method includes: determining the angle of arrival (AOA) corresponding to the plurality of user equipments based on transmissions received from a plurality of user equipments; grouping the plurality of user equipments into a device group based on the AOAs of the plurality of user equipments; and scheduling subsequent transmissions in the wireless system such that the same time and frequency resources are used for transmissions to or from user equipments in the same group, wherein subsequent transmissions to or from the plurality of user equipments use a pre-encoder or post-encoder determined entirely based on the transmissions received from the plurality of user equipments.

[0014] In another example, a wireless communication method is disclosed. The method is implemented by a network station of a wireless system and includes: receiving signals comprising uplink transmissions from a plurality of user equipments, wherein the uplink transmissions share the same time and frequency resource elements; and segmenting the received signals into parallel, independent data streams by dynamically applying a user equipment-specific post-encoder to the received signals, wherein the user equipment-specific post-encoder is an angle filter determined entirely from uplink measurements and designed to angle-filter desired user transmissions in each parallel, independent data stream and reject other interfering transmissions.

[0015] In another example, a wireless communication method is disclosed. The method, implemented by a network station of a wireless system, includes: applying a user-equipment-specific precoder to parallel, independent data streams corresponding to multiple user equipments; combining the results of the application to generate a signal for transmission achieved by sharing the same time and frequency resources; and transmitting the signal to the multiple user equipments on a downlink channel, wherein the user-equipment-specific precoder is an angle filter determined entirely from uplink measurements and designed to minimize interference to other users.

[0016] In yet another example, a wireless communication method is disclosed. The method includes: determining precoding by a network station for transmission to a plurality of user equipments in a wireless coverage area of ​​the network station, wherein the transmission to the plurality of user equipments includes the use of a multi-carrier modulation scheme, and wherein for each user equipment, the corresponding precoding is identical on all carriers of the multi-carrier modulation scheme; and generating one or more transmission waveforms for transmission to one or more of the plurality of user equipments by processing according to the precoding.

[0017] In yet another example, a wireless communication device that implements the above method is disclosed.

[0018] In yet another example, the method may be embodied as processor-executable code and may be stored on a computer-readable program medium.

[0019] These and other features are described in this document. Attached Figure Description

[0020] The accompanying drawings described herein are provided to provide a further understanding and form part of this application. The exemplary embodiments and illustrations in the drawings are intended to illustrate the technology and not to limit its scope.

[0021] Figure 1A An example of a mobile wireless network is shown.

[0022] Figure 1B An example of a fixed wireless access network is shown.

[0023] Figure 1C Another example of a fixed wireless access network is shown.

[0024] Figure 1D A simplified example of a wireless network is shown.

[0025] Figure 2 An example of a wireless system including a base station with L antennas and multiple users is shown.

[0026] Figure 3An example of a subframe structure that can be used to compute second-order statistics for training is shown.

[0027] Figure 4 An example of prediction training for channel estimation is shown.

[0028] Figure 5 An example of a prediction used for channel estimation is shown.

[0029] Figure 6 An example of a reciprocal wireless channel is shown.

[0030] Figure 7 This is a block diagram illustrating an example of a prediction setup in an FDD system.

[0031] Figure 8 An example transmission pattern using precoding is shown in a communication network.

[0032] Figure 9 An example of a public precoder is shown.

[0033] Figure 10 An example of a user-specific precoder is shown.

[0034] Figure 11A and Figure 11B A table representation of examples of shared downlink and uplink physical channels is shown, respectively.

[0035] Figure 12 An example of two-dimensional scheduling is shown.

[0036] Figure 13 An example of the pre-compensation operation is shown.

[0037] Figure 14 This is a block diagram illustrating an example of a network-side device.

[0038] Figure 15A and Figure 15B Examples of scaling operations with scaling factors of 0.5 and 2.0 are shown respectively.

[0039] Figure 16 An example of a dual-polarized link is shown.

[0040] Figure 17 An example with two antenna arrays is shown, each with L dual-polarized antennas.

[0041] Figures 18 to 26 This is a flowchart of an example method for wireless communication.

[0042] Figure 27 An example of a wireless transceiver device is shown. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this disclosure more apparent, various embodiments are described in detail below with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0044] Chapter headings are used in this document, including appendices, to improve readability and to never limit the discussion to the corresponding chapter. The terms "hub" and "user equipment / device" are used to refer to transmitting and receiving devices, and can take the form of base stations, relay nodes, access points, small cell access points, user equipment, etc.

[0045] In the description, the examples of fixed wireless access (FWA) systems are for illustrative purposes only, and the disclosed techniques can be applied to other wireless networks.

[0046] Although some descriptions here refer to FWA systems with orthogonal time-frequency space (OTFS) as modulation / multiplexing formats, the developed techniques are also suitable for other modulation / multiplexing formats, particularly orthogonal frequency division multiplexing (OFDM) or OFDM access (OFDMA).

[0047] 1. Introduction

[0048] Cellular wireless service providers have begun planning and developing next-generation networks to support denser deployments of user devices with higher bandwidth. Furthermore, the increasing reliance on wireless connectivity has raised user expectations for quality of service and seamless availability of wireless connectivity everywhere.

[0049] Cloud Radio Access Network (C-RAN) is an example of a network architecture that provides wireless connectivity to wireless terminals based on a centralized cloud-based access network. However, C-RAN deployment relies on the expensive deployment of fiber optic infrastructure to connect base stations to each other and to a central network controller. Furthermore, this architecture requires planning, and deployment can be relatively slow due to the labor and resources required to lay fiber optic cables. Therefore, C-RAN and similar solutions are expensive and cannot be quickly deployed (or dismantled) to meet short-term increases in demand for wireless services. Moreover, when such deployments reach their maximum capacity, incremental deployment is often not possible without significantly altering the existing infrastructure.

[0050] The techniques described in this document can be used to overcome such problems in wireless network implementations. In one example, network nodes can be deployed using short-range, high-speed millimeter-wave links. Such devices have minimal footprint and power requirements and can be quickly deployed and dismantled to meet the time- and geo-specific needs of wireless services.

[0051] In another beneficial aspect, this technology can be used to deploy networks that provide short links between base stations or network nodes, thereby providing reduced latency, jitter, and fronthaul traffic loading in wireless networks.

[0052] In another advantageous aspect, the disclosed technology can be used to manage soft handover, whereby the user equipment (UE) and N neighboring base stations (typically N=3) constitute a cooperative multipoint (COMP) service area.

[0053] In another advantageous aspect, the embodiments can benefit from increased network performance without requiring any changes or replacements to existing antennas on the tower; for example, no new millimeter-wave links or computing platforms need to be set up. The inventors' rough calculations have shown that the embodiments have the potential to increase network capacity by at least two times and improve the signal-to-interference-to-noise ratio (SINR) by at least 5 dB.

[0054] Some embodiments of the disclosed distributed COMP technology can be used to address intra-cell and inter-cell interference using a computer platform with all three sectors across all towers in a joint processing cluster, or alternatively, to address inter-sector interference and weak coverage at cell edges. One advantage is that the physical front-end (e.g., antennas on the towers) may not need to be changed, but the technology can be implemented to improve performance.

[0055] As further described in this document, in some embodiments, a distributed COMP may include a group of cell towers, where all cell towers carry Remote Radio Header (RRH) functionality, and one of them carries the computing power for the cluster and is connected to the network for TCP / IP traffic. In other words, no fronthaul to the network is required. Cluster formation can be performed using one of the techniques described in this document. Clustering offers the advantages of shared resource management and load balancing.

[0056] Embodiments of the disclosed technology can be implemented in example systems, such as Figure 1A , Figure 1B , Figure 1C and Figure 1D As shown.

[0057] Figure 1AAn example of a mobile wireless network 100 is shown. In this simplified diagram, a network-side node 104 provides wireless connectivity to a wireless terminal 102. The wireless terminal 102 can be, for example, a smartphone, tablet, Internet of Things (IoT) device, smartwatch, etc. The network node 104 can be a base station of a cell that establishes and operates wireless communication. The communication channel between the wireless terminal 102 and node 104 can include reflectors that easily distort signal transmission to and from the wireless terminal 102, such as buildings, trees, or moving objects (such as vehicles). During operation, the wireless terminal 102 can move away from node 104 and may need to be handed over to another network node (not explicitly shown) or share connectivity with it. In some cases, network node 104 can operate collaboratively with other nodes to provide multi-point transmission / reception to the wireless terminal 102, so that the mobility of the wireless terminal 102 does not hinder connectivity to wireless services.

[0058] Figure 1B An example of a fixed wireless access system 130 is shown. A hub 102, including transmission facilities (such as cell towers), is configured to send transmissions to and receive transmissions from a plurality of locations 104. For example, the locations could be user homes or office buildings. As described throughout this document, the disclosed embodiments can achieve extremely high cell capacity fixed wireless access when compared to conventional fixed access technologies. In implementations, some of the technologies disclosed herein may be embodied at the hub 102 or at transceiver devices located at location 104.

[0059] Figure 1C Another configuration of the fixed access wireless communication system 160 is shown, in which hops are used to approach the user. For example, one cell tower can transmit / receive from another cell tower and then relay the transmission between the originating cell tower and the user, thus extending the range of the fixed wireless access system. The backhaul can connect the transmission tower 102 to an aggregation router. For example, in one configuration, data can be fed between the base station at the hub and the fiber optic hub aggregation router using a 10Gbps fiber optic connection. Advantageously, by using a hub / home access point (AP) configuration as the transmission point, this technology can be deployed without altering any network bandwidth characteristics for hard-to-reach areas. In implementations, some of the techniques disclosed herein can be embodied at the macro tower 102 or at transceiver devices located elsewhere.

[0060] Figure 1DA simplified wireless network is illustrated to highlight certain aspects of the disclosed technology. A transmitter transmits wireless signals to a receiver in the wireless network. Some transmissions in the network are differently referred to as downlink or downstream transmissions, where network-side nodes (such as base stations) act as transmitters of wireless signals, and one or more user equipments act as receivers of these wireless signals. For some other transmissions, such as... Figure 1D As described, the transmission direction can be reversed. Such transmissions are often referred to as uplink or upstream transmissions. For such transmissions, one or more user equipments act as transmitters of wireless signals, and network-side nodes (such as base stations) act as receivers of these signals (e.g.,...). Figure 1D (As depicted in the document). Other types of transmissions in the network may include device-to-device transmissions, sometimes referred to as direct or sideband transmissions. While for convenience, this document primarily uses the terms "downlink" and "uplink," similar techniques can be used for other scenarios where transmissions are performed in both directions—for example, incoming or incoming transmissions received by a wireless device and outgoing or outgoing transmissions initiated by a wireless device. For example, a downlink transmission could be an incoming transmission to a user equipment and an outgoing transmission to a network device. Similarly, an uplink transmission could be an incoming transmission to a network device and an outgoing transmission from a wireless device. Therefore, for some embodiments, terms such as "incoming" and "outgoing" transmissions may also be used to describe the disclosed techniques without introducing any 3GPP-specific or other radio protocol-specific meanings into the terms "uplink" and "downlink."

[0061] In some embodiments, the base station has L physical antennas. These antennas can be arranged as a linear antenna array or any other configuration. A spatial precoder (or simply precoder) is a complex vector of L elements that assigns different weights to the transmitted / received signals from different antennas, thereby spatially shaping the wavefront of the resulting signal. Spatial shaping (or precoding) is orthogonal to the time and frequency dimensions. This means that different precoders can be applied for different frequency and time resources. This is further explained in detail in Section 6.

[0062] In Frequency Division Multiplexing (FDM) networks, transmissions to and from a base station can occupy different frequency bands (each band can occupy contiguous or discontinuous spectrum). In Time Division Multiplexing (TDM) networks, transmissions to and from a base station occupy the same frequency band, but are separated in the time domain using TDM mechanisms (such as time-slot-based transmission). Other types of multiplexing are also possible (e.g., Code Division Multiplexing, Orthogonal Time-Frequency Space (OTFS) Multiplexing, Spatial Multiplexing, etc.). Generally, various multiplexing schemes can be combined with each other. For example, in a spatial multiplexing system, the directional or azimuth difference between two endpoints (e.g., user equipment and network stations (such as base stations)) can be used to isolate transmissions to and from two different user equipments.

[0063] Embodiments of the disclosed technology provide various improvements to the operation of wireless networks and equipment, including:

[0064] 1) Based on instantaneous measurements over finite frequency bands and short time periods, accurate channel prediction is performed on the same frequency band or different adjacent frequency bands, as described in Chapter 2.

[0065] 2) Using predicted channel state information. For example, Section 2 describes some techniques for predicting channels at different time instances, frequencies, and spatial locations, and Sections 3 through 5 describe some techniques for reciprocal calibration and estimation.

[0066] 3) Use the same time and frequency resources to support the transmission of multiple information streams to multiple devices, as described in Chapter 6.

[0067] 2. Channel estimation for OTFS systems

[0068] This chapter provides an overview of channel estimation in OTFS systems, with a particular focus on channel estimation and scheduling for large numbers of users. Figure 2 The diagram illustrates a wireless system with a multi-antenna base station and multiple user antennas. Each transmission from a user antenna to one of the base station antennas (or vice versa) experiences a different channel response (assuming the antennas are physically sufficiently separated). For efficient communication, the base station uses precoding to improve the user's received signal-to-interference-to-noise ratio (SINR). However, for precoding to work, the base station needs to accurately estimate the downlink channel to the user during the transmission time.

[0069] In some embodiments, and when the channel is not static and the number of users is extremely large, some challenges of such precoding systems include:

[0070] - Accurately and efficiently estimate all required channels

[0071] - Predict channel changes during downlink transmission time.

[0072] A typical solution in a system with a small number of users and a static channel is for each user to transmit known pilot symbols (reference signals) from each of its antennas. These pilots are received by all base station antennas and used to estimate the channel. Importantly, these pilot symbols do not experience significant interference, resulting in high-quality channel estimation. For this reason, they are typically transmitted simultaneously in a manner orthogonal to other transmissions. Multiple pilots can be packaged in an orthogonal (or nearly orthogonal) manner using different methods, but these methods are generally limited by the number of pilots that can be packaged together (depending on channel conditions) without causing significant interference to each other. Therefore, when the number of user antennas is high and the channel is not static, it is difficult to have an efficient system. The amount of transmission resources required for uplink pilots can consume a considerable amount of system capacity or even make it impractical. For channel prediction, it is generally assumed that the channel is completely static and will not change from the time of estimation until the end of downlink transmission. This assumption often leads to significant degradation of non-static channels.

[0073] It is assumed that the downlink and uplink channels are reciprocal, and that after calibration, it is possible to compensate for differences in the uplink-downlink and downlink-uplink channel responses. Some example implementations of calibration procedures using reciprocity are further discussed in Section 2.

[0074] Embodiments of the disclosed technology include a system and method for packing and separating multiple non-orthogonal pilots, and a method for channel prediction. In this system, it is possible to pack a considerably larger number of pilots together compared to other commonly used methods, thus allowing for accurate channel prediction for precoding.

[0075] 2.1 Second-order training statistics

[0076] The system includes an initial training step in which all users send uplink orthogonal pilots to the base station. Although these pilots are orthogonal, they can be sent at a very low rate (e.g., one per second) and therefore will not overload the system too much. The base station receives multiple N of these pilots. SOS Such transmissions are used to calculate the second-order statistics (covariance) for each channel.

[0077] Figure 3 An example of such a system is shown, where a 1-millisecond subframe consists of a downlink portion (DL), a guard period (GP), and an uplink portion (UL). Some of the uplink portion is dedicated to orthogonal pilots (OP) and non-orthogonal pilots (NOP). Each specific user is scheduled to transmit its pilot every 1000 subframes (equivalent to 1 second) on these resources. Upon receiving an NOP with pilots... SOS N subframes (equivalent to N)SOS After (seconds), the base station will calculate the second-order statistics of the channel.

[0078] The calculation of the second-order statistics for the user antenna u is defined as follows:

[0079] - For each received subframe i = 1, 2, ..., N with orthogonal pilots SOS And for each of the L base station receiving antennas, from the pilot along the entire frequency band (N f The channel is estimated using (N grid elements) and stored as a grid with dimension (N). f ·L)×N SOS matrix H (u) The i-th column.

[0080] - Calculate the covariance matrix in(·) H It is a Hermitian operator.

[0081] -For channel H (u) In the case of a non-zero mean, both the mean and the covariance matrix should be determined.

[0082] To accommodate potential future changes in the channel response, the second-order statistics can be updated shortly after the training step is complete. This can be done by retransmitting N... SOS The orthogonal pilots can be recalculated from scratch, or updated incrementally. One possible approach is to remove H... (u) The first column is calculated and a new column is added at the end, and then the covariance matrix is ​​recalculated again.

[0083] The interval at which these orthogonal pilots need to be repeated depends on the channel's stationarity time, such as the time it takes for the second-order statistics to remain approximately constant. This time can be chosen as a system-determined constant or can be adapted to the environment. Specifically, the user can determine this by observing the downlink broadcast pilot symbols in the second-order statistics and requesting resources to transmit uplink pilots when a significant change is observed. In another embodiment, the base station can use the frequency of retransmission requests from the user to detect channel changes and restart the process of calculating the channel's second-order statistics.

[0084] To reduce computational load, it may be necessary to... We use principal component analysis (PCA) to calculate {λ}. (u) Arranged in a diagonal matrix In K (u) The most dominant eigenvalues ​​and their corresponding eigenvector matrices V (u) Typically, K (u)This will be approximately the number of reflectors along the wireless path. The covariance matrix can then be approximated as...

[0085] 2.2 Non-orthogonal pilot

[0086] For the user antenna u, the non-orthogonal pilot (NOP) P (u) It can be defined as a set of known symbols on a frequency grid of elements and of size N. NOP The pseudo-random sequence. The base station can schedule many users to transmit their non-orthogonal pilots within the same subframe using overlapping time and frequency resources. The base station will then be able to separate these pilots and obtain high-quality channel estimates for all users using the methods described below.

[0087] The size is (L·N) NOP A vector Y of 1×1 is defined as the signal received by the base station through all its antennas at the frequency grid elements of the shared non-orthogonal pilot. Let V is the eigenvector matrix V that extracts the positions of non-orthogonal pilots along the first dimension (frequency-space). (u) .

[0088] The base station can apply a minimum mean square error (MMSE) estimator to separate the pilot signals for each user antenna:

[0089] -For each user antenna u, calculate

[0090]

[0091]

[0092] In this paper, ⊙ is defined as element-wise multiplication. For matrix A and vector B, the A⊙B operation involves copying vector B to match the size of matrix A before applying element-wise multiplication.

[0093] If principal component analysis (PCA) is not used, the covariance matrix can be directly calculated as follows:

[0094]

[0095]

[0096] -For a user antenna set u∈U shared on the same resources, calculate

[0097]

[0098] And find its reciprocal. Note that this might be achieved by finding R. YY ( The advantageous eigenvalues ​​and their corresponding eigenvector matrices ( And use PCA is applied using approximate reciprocals.

[0099] - For each user antenna u, calculate the pilot separation filter.

[0100]

[0101] - For each user antenna u, its non-orthogonal pilot is separated by calculating the following formula.

[0102]

[0103] It should be noted that It is the channel response over the frequency grid elements of the non-orthogonal pilots of L base station receiving antennas. It can also be interpolated along the frequency to obtain the channel response over the entire bandwidth.

[0104] 2.3 Prediction Training

[0105] The method for separating non-orthogonal pilots described in the previous chapter is applied to train different users for prediction. In this step, the user transmits uplink non-orthogonal pilots on consecutive subframes, which are divided into three distinct parts, as shown in... Figure 4 As shown in the example.

[0106] 1. Past – First N past These subframes will be used later to predict future subframes.

[0107] 2. Delay – the next N latency Each subframe is used to calculate the latency required for prediction and precoding.

[0108] 3. The Future – The Last N future A subframe (usually one) is used, where the channel at the downlink portion will be predicted later.

[0109] Each user is scheduled N PR Next, in the consecutive N past +N latency +N future Uplink non-orthogonal pilots are transmitted in each subframe. It should be noted that within a single uplink symbol in a subframe, both orthogonal and non-orthogonal pilots can be packaged together (but the number of orthogonal pilots will be significantly less than the number of non-orthogonal pilots). The base station applies a pilot separation filter to the non-orthogonal pilots for each user and calculates... To reduce storage and computation, the channel response can be compressed using the eigenvector matrix calculated in the second-order statistical step.

[0110]

[0111] For subframes that are part of the "past" section, Stored as a matrix The columns in the array, where i = 1, 2, ..., N PR Using all or part of non-orthogonal pilots to interpolate the channel over all or part of the downlink portion of the "future" subframe, using Compress it and store it as Calculate the following covariance matrix:

[0112]

[0113]

[0114]

[0115] After all N have been scheduled PR After predicting the training subframes, the average covariance matrix for each user is calculated.

[0116]

[0117]

[0118]

[0119] Finally, for each user, the MMSE prediction filter is calculated.

[0120]

[0121] and its error variance for the pre-encoder

[0122]

[0123] 2.4 Scheduling precoded downlink transmission

[0124] For each subframe with precoded downlink transmission, the base station should schedule all users of this transmission in N. past Uplink non-orthogonal pilots are transmitted within consecutive subframes, thus beginning the N preceding frames. past +N latency Subframes, such as Figure 5 As shown. The base station separates the non-orthogonal pilot signals for each user, compresses them, and stores the channel response as... Then, a prediction filter is applied to obtain the future portion of the compressed channel response.

[0125]

[0126] Finally, the uncompressed channel response is calculated as

[0127]

[0128] Base stations can correct for differences in reciprocal channels by applying phase and amplitude correction α(f) to each frequency grid element.

[0129]

[0130] Then, using the participating users and To calculate the precoder used for downlink transmission.

[0131] 2.5 Uplink Pilot Scheduling

[0132] If multiple orthogonal resources (e.g., different time slots or different frequency grid elements) are available for pilot transmission during a frame, then a set of uplink pilots to be transmitted can be divided into multiple groups, such that each group is transmitted on a different resource. A criterion for dividing into multiple groups could be, for example, achievable pilot SINR. Transmission of non-orthogonal pilots leads to a reduction in achievable pilot SINR, which is more pronounced the stronger the alignment of the vector space containing the correlation matrices from different users. Therefore, arranging users into multiple groups so that two pilots with very similar correlation matrices are not transmitted simultaneously improves performance. However, other criteria are also possible. For example, achieving a high pilot SINR might be wasteful for users with only low SINR during data transmission; therefore, achieving an optimal "match" between pilot SINR and data SINR could be another possible criterion.

[0133] Embodiments of the disclosed technology described in this section may be characterized by, but are not limited to, the following features:

[0134] - A wireless system in which network nodes perform precoded downlink transmissions supporting a large number of users based on second-order statistics of the channel. The precoded downlink transmissions consist of channel prediction, reciprocity adjustment, and precoding.

[0135] - A system that includes a mixture of uplink orthogonal and non-orthogonal pilots.

[0136] - Calculate the second-order statistics of the channel based on orthogonal pilots.

[0137] - The computation using second-order statistics and channel estimation separates non-orthogonal pilots from multiple users.

[0138] - Train the system to predict channel estimates.

[0139] - Schedule non-orthogonal uplink pilots based on second-order statistics.

[0140] - Use PCA to compress the channel response

[0141] 3. Reciprocity calibration of communication channels

[0142] This chapter covers reciprocal calibration of communication channels used for reverse channel estimation. In recent years, many new technologies have been introduced into wireless communications to meet the growing need for available bandwidth. For example, in popular communication standards such as LTE, the amount of bandwidth, measured as the total number of bits per second or bits per hertz per second, has steadily increased over the years. This trend is expected to grow further due to the proliferation of smartphones and multimedia streaming services.

[0143] In wireless networks, a portion of the available bandwidth is typically used for system overhead signaling, which can be used to maintain system operational efficiency. Examples of overhead signaling include the transmission of pilot signals and system information. Due to the time-varying nature of communication channels between mobile endpoints, system messages may need to be exchanged more frequently, and the overhead can eventually become significant. The embodiments described in this document can be used to mitigate this bandwidth overhead and address other problems faced in wireless communication systems.

[0144] Figure 6 An example block diagram of a reciprocal communication channel is shown. A composite wireless channel from A to B can be represented as:

[0145] For a reciprocal channel, assume that for the complex scalar λ...

[0146] In the presence of analog and RF components, non-reciprocal analog and RF components C TX,A C RX,A C RX,B C TX,B In the case of a non-reciprocal channel, ideally, for simplicity, it is beneficial if each matrix is ​​a diagonal matrix. This embodiment can also utilize a design that minimizes the coupling between the Tx and Rx paths.

[0147] Similarly, the multiple channel from B to A is given by the following equation:

[0148] If all C matrices can be estimated a priori, the BS-UE channel can be estimated from the UE-BS channel. In this case, it may not be necessary to feed back channel state information for transmit beamforming, thus making upstream bandwidth available for data instead of requiring the transmission of channel state information. Estimation of the C matrix can also improve system efficiency. In some embodiments disclosed herein, reciprocity calibration can be performed by calibrating the Tx and Rx on the BS and UE sides during startup or a pre-specified time period. The diagnostic matrix C can be estimated. TX,A C RX,AC RX,B C TX,B These matrices can be re-estimated and periodically updated. The rate of change of the C matrix will typically be slow and can be correlated with factors such as the operating temperature of the electronics used for Tx and Rx.

[0149] 3.1 Brief Discussion

[0150] In point-to-multipoint (P2MP) and fixed wireless access (FWA) systems, multi-user MIMO (MU-MIMO) is used to increase system throughput. One component of MU-MIMO is beamforming based on a transmit precoder at the base station (BS) transmitter. The BS transmits signals simultaneously to all user equipment (UEs) (e.g., n of them).

[0151] In operation, n-1 signals intended for n-1 individual UEs will act as interference to the target UE. A precoder is transmitted to cancel the interference generated at the target UE by the n-1 unintentional signals intended for other UEs. Downlink channel state information (CSI) is used to construct the precoder.

[0152] In non-inherent beamforming techniques, CSI is fed back from the UE to the BS via a feedback uplink channel. However, a significant amount of data bandwidth is used for this, thus impacting overall system throughput efficiency.

[0153] For Time Division Duplex (TDD) systems, the physical channels in the air (sometimes called radio channels) are reciprocal during channel coherence time; for example, the uplink (UE to BS) and downlink (BS to UE) are identical (in SISO (transpose in MIMO)). However, channel reciprocity no longer holds when the transceiver front-end (FE) hardware is also considered. This is due to the asymmetric characteristics of the RF hardware. These include PA nonlinearity, RF chain crosstalk, phase noise, LNA nonlinearity and noise factor, carrier and clock drift, etc.

[0154] In some embodiments, the calibration mechanism can be designed to calibrate non-reciprocal components of the wireless link, allowing embodiments to estimate the downlink by observing the uplink with the aid of these calibration coefficients. If this is feasible, CSI feedback is not required (as in the case of non-inherent beamforming), thus improving overall system throughput efficiency. The associated beamforming is sometimes also referred to as inherent beamforming. The techniques disclosed in this patent document can be used to address the problems discussed above and other issues.

[0155] 3.2 Symbols

[0156] In the description of this article, h a1a2This represents the channel from transmitter (TX) a1 to receiver (RX) a2. This symbol differs from the conventional MIMO channel symbol. In the conventional approach, this would be represented as h. a2a1 Additionally, the conjugate of complex quantities is denoted by *, for example, conj(h) = h*.

[0157] 3.3 Reciprocity calibration for precoding

[0158] Precoded transmission is based on the understanding of the exact channel response between the transmitting antenna of a first terminal (typically a base station (BS)) represented by A and the receiving antenna of a second terminal (typically a consumer premises equipment (CPE) or user equipment (UE)) represented by B. This channel response can be considered to consist of three distinct parts, such as... Figure 3 As shown. First, the channel response of the transmitter in terminal A. Second, the channel responses of different reflectors. Third, the channel response of the receiver in terminal B. The transmitter channel response can be attributed to the transmitter chain circuitry, such as power amplifiers, digital-to-analog converters (DACs), and frequency up-converters. The receiver channel response can be attributed to the receiver-side circuitry, such as low-noise blocks (LNBs), frequency down-converters, and analog-to-digital converters (ADCs).

[0159] There are two main differences between the channel response at terminals A and B and the channel response of the wireless channel reflector:

[0160] 1. In a time-division duplex (TDD) system, the channel response of a wireless channel reflector is reciprocal, while the channel response of a terminal is not.

[0161] 2. The channel response of a wireless channel reflector can change rapidly (e.g., within 1 to 10 milliseconds, depending on the reflector and the Doppler of the terminal), but the channel response of the terminal changes slowly, mainly with temperature.

[0162] Several methods are described in the literature to obtain the complete channel response from terminal A to B. For example, an explicit method involves sending a known reference signal from terminal A to B and having terminal B transmit the value of the received reference signal back to terminal A. This is often referred to as explicit feedback. However, each value must be represented by multiple bits, and in systems with multiple antennas at terminal A, numerous user terminals, and significant Doppler effects causing rapid changes in the propagation channel, the amount of information that needs to be transmitted can severely degrade the overall system efficiency. In extreme cases with high-order Doppler, it may be impossible to feed back all the required channel state information (CSI) quickly enough, resulting in outdated CSI and suboptimal precoding.

[0163] Conversely, TDD systems can use a method known as "reciprocity calibration" to obtain the relationship between the non-reciprocal components of the channel responses in the following two transmission directions: AB (from A to B) and BA (from B to A). Terminal B first transmits a known reference signal that allows terminal A to calculate the AB channel response. Using the knowledge of the non-reciprocity relationship, terminal A can adjust the BA channel response to be suitable for precoding the transmission back to terminal B.

[0164] More formally, for a multi-carrier TDD system using multi-carrier modulation, where the channel can be described as a complex value in the frequency domain for a given subcarrier (tone), the three components of the AB channel response can be expressed as: H CH and Similarly, the three components of the BA channel response are H CH and The overall downlink (AB) channel response is as follows:

[0165]

[0166] And the overall uplink (BA) channel response is

[0167]

[0168] According to H AB and H BA The reciprocity calibration factor can be written as

[0169]

[0170] Therefore, if H is known at terminal A BA Then H can be calculated. AB =αH BA The remaining question is how to obtain α. It should be noted that for multi-carrier systems, the above equations (55) to (57) will provide reciprocal calibration values ​​and channel responses on a subcarrier-by-subcarrier basis for the subcarriers on which the reference signal is transmitted.

[0171] The literature contains various methods for calculating the reciprocity calibration factor. The most direct method utilizes explicit feedback, as described above, but H is only fed back when α is recalculated. AB Because the transmitter and receiver channel responses change relatively slowly, the feedback rate is typically around several minutes, and therefore represents negligible overhead for a modest number of terminals and antennas. However, when the number of antennas in terminal A and the number of CPEs (terminal B) are large, as may be the case in a massively multi-input multiple-output (MIMO) system with many subscribers, the feedback overhead can consume a significant portion of the system capacity.

[0172] Another method is to have terminal A transmit a reference signal between its own antennas and only for... and To calculate the calibration factor. That is, to obtain:

[0173]

[0174] This led to

[0175]

[0176] Terminal A can then use terminal B to... and The contribution was removed from all subsequent precoded transmissions. A reference symbol is pre-encoded. This technique can be called relative calibration. Although this method does not require feedback H at all. BA However, requiring Terminal A to transmit to itself during the calibration process and then to a CPE that may be hundreds or even thousands of meters away can present dynamic range challenges. It is generally expected that the same hardware gain stages used in the transmit chain during calibration will be used as those used for transmission, because the gain stages must be switched between calibration and transmission, which may alter the dynamic range. and The properties of.

[0177] This document describes a novel method for calculating reciprocity calibration factors that avoids the dynamic range problem of relative calibration while maintaining a high level of efficiency when scaling to a larger number of antennas and terminals. As described herein, a reference signal transmitted for calibration at the same power level as typical signal transmission is therefore better suited for capturing and calibrating distortions caused by the transmit / receive circuitry.

[0178] 3.4 Reciprocal calibration via receiver-side inversion

[0179] Suppose terminal A transmits a known reference signal via a subset of multicarrier tones, and P is a specific reference signal at one of those tones. For example, terminal A can use every M-th subcarrier for reference signal transmission, where M is an integer. For example, in a practical system, M could be 8 or 16. Terminal B receives...

[0180] Y B =H AB ·P+W (60)

[0181] Where W is additive white Gaussian noise with zero mean and variance N0. It should be noted that the above equation is a scalar equation because it represents the received signal at a single subcarrier. For each subcarrier on which a signal is transmitted, there will be such an equation. Terminal B from Y B To estimate H AB And then find its inverse. To avoid singularities and handle large dynamic ranges, regularization forcing zeros can be used to calculate the inverse.

[0182]

[0183] Terminal B then uses the same tone to... The transmission returns to terminal A. This transmission should quickly follow the first transmission, especially in the presence of Doppler, to ensure H... CH Maintain relative constancy. Terminal A then receives...

[0184]

[0185] Ignoring noise terms that can be averaged over multiple transmissions, it can be seen that Y B It is the reciprocal of the reciprocity calibration factor:

[0186]

[0187] Since these are scalar values, the inversion process is performed on H. AB and Y B The two are direct. Here, the reciprocal reciprocity calibration factor represents the ratio of the circuit channel from terminal B to terminal A to the circuit channel from terminal A to terminal B.

[0188] In a multicarrier system, the above process can be repeated over multiple tones and the results interpolated to generate a full set of calibration factors over the bandwidth of interest. This full set can be obtained, for example, by averaging or interpolating the calibration factors, which are the subcarriers of the transmitted reference signal. Since the Tx and Rx contributions of both terminals A and B will be relatively flat in frequency, it should be possible to use a sparse subgrid of tones with appropriate interpolation to obtain a precise level of calibration.

[0189] The channel estimation results described above can be compared with H CH The channel estimation is combined to obtain the overall channel H. AB and H BA The estimate.

[0190] 4. Second-order statistics for FDD reciprocity

[0191] This chapter covers using second-order statistics of wireless channels to achieve reciprocity in frequency division duplex (FDD) systems. Implementing such a pre-coded system in FDD systems may present the following challenges:

[0192] - Due to different carrier frequencies, the downlink channel response differs from the uplink channel response. Furthermore, the responses of the transmitting and receiving RF components in the base station and user equipment differ.

[0193] - For non-static channels, the base station needs to predict the channel during the transmission time.

[0194] In some embodiments, the base station may send reference signals (pilots) to the user equipment before each precoded downlink transmission. The user will receive these and send them back to the base station as uplink data. The base station will then estimate the downlink channel and use it for precoding. However, this solution is very inefficient because it consumes a large portion of the uplink capacity to transmit the received reference signals back. The system may even become unfeasible as the number of user and / or base station antennas increases. Furthermore, in non-static channels, round-trip time can degrade the quality of channel prediction.

[0195] 4.1 Second-order statistical training

[0196] For simplicity, we consider the case of a single user antenna and L base station antennas, but this can be easily extended to any number of users. Figure 7 The system setup is shown in the diagram. The base station predicts N in different frequency bands and subsequent frequencies based on the uplink channel response. latency Downlink response in each subframe.

[0197] To achieve this, the system performs an initial training phase consisting of multiple sessions, where in each session i = 1, 2, ..., N training In this process, the following steps are taken:

[0198] - At subframe n, the user equipment transmits a reference signal (RS) in the uplink. The base station receives these signals using L base station antennas and estimates the uplink channel. .

[0199] - in subframe n+N latency At this point, the base station transmits a reference signal from all its antennas in the downlink. The user equipment receives the reference signal and transmits it back as uplink data in subsequent subframes. The base station calculates a downlink channel estimate for this signal. In different implementations, the UE may calculate the channel estimate and send it as uplink data to the base station.

[0200] - Base station calculation second-order statistics

[0201]

[0202]

[0203]

[0204] In this article, (·) H It is a Hermitian operator. For channels with a non-zero mean, both the mean and covariance matrix must be determined. Upon completion of the training session, the base station averages the second-order statistics:

[0205]

[0206]

[0207]

[0208] Then, it calculates the covariance of the prediction filter and the estimation error:

[0209] C prediction =R DL，UL ·(R UL ) -1

[0210] R E =R DL -C prediction ·(R DL，UL ) H

[0211] Principal component analysis can be used to approximate R. UL Find the inverse of λ. We compute {λ}, arranged in a diagonal matrix D = diag(λ1, λ2, ..., λ). K R in ) UL We have the K most dominant eigenvalues ​​and their corresponding eigenvector matrix V. Typically, K will be approximately the number of reflectors along the wireless path. The covariance matrix can then be approximated by R. UL ≈V·D·(V) H And the reciprocal is .

[0212] It should be noted that the number of training sessions is limited and they can be completed at a very low rate (such as one per second) and therefore will not overload the system too much.

[0213] To accommodate potential future changes in the channel response, the second-order statistics can be updated shortly after the training phase is complete. This can be done by initiating a new N... training This can be done by recalculating from scratch, either by updating the existing statistics incrementally for each session.

[0214] The interval between repeated training steps depends on the channel's stationarity time, such as the time it takes for the second-order statistics to remain approximately constant. This time can be chosen as a system-defined constant or adapted to the environment. The base station or user can detect changes in the channel's second-order statistics and initiate a new training phase. In another embodiment, the base station can use the frequency of retransmission requests from users to detect channel changes and restart the process of calculating the channel's second-order statistics.

[0215] 4.2 Scheduling precoded downlink transmission

[0216] For each subframe with precoded downlink transmission, the base station should schedule all users of this transmission to proceed in the preceding N... latency Each subframe transmits an uplink reference signal. The base station will estimate the uplink channel response and use it to predict the expected downlink channel response.

[0217] H DL =C prediction ·H UL

[0218] Then, the downlink channel response H DL and prediction error covariance R E Calculations for the precoder.

[0219] 5. Examples of reciprocal geometric precoding

[0220] Embodiments of the disclosed technology include a method for applying MU-MIMO (Multi-User Multiple-Input Multiple-Output) in a wireless system. In MU-MIMO, a transmitter (typically a cellular base station) with multiple antennas transmits to multiple independent devices (also referred to as UEs, User Equipments) on the same time and frequency resources, each device having one or more receive antennas. To enable the receiving devices to correctly decode their own target data, a precoder is applied to the transmitted signals, which typically attempts to maximize the desired received signal level at the receiving devices and minimize interference from transmissions to other devices. In other words, the SINR (Signal-Interference-Noise Ratio) is maximized at each receiving device. The transmitted signals are arranged in layers, with each layer carrying data to a specific user equipment.

[0221] A spatial precoder is a precoder that operates in the spatial domain by applying different weights and phases to the transmission to each antenna in each layer. This shapes the wavefront of the transmitted signal and drives more of its energy toward the target device, while minimizing the amount of energy sent toward other devices. Figure 8 An example of a spatial precoder is shown.

[0222] For the sake of simplicity in the following description, without loss of generality, the downlink transmitting device is referred to as a base station (BS) and the downlink receiving device is referred to as a UE (see example). Figure 1A ).

[0223] 5.1 Codebook-based precoding

[0224] In this technique, there exists a set of predefined, known precoders available for both the BS and the UE. Upon receiving a precoded transmission, the UE can blindly assume that each of the precoders is used and attempt to decode the received signal accordingly. This approach is not very efficient, especially when the codebook is large. Another approach is feedback-based. The UE analyzes the reception of a known reference signal by computationally applying different precoders based on the codebook. The UE selects the precoder that maximizes its received SINR and sends feedback to the BS, where the precoder is the preferred precoder.

[0225] In some implementations, this technology has the following limitations:

[0226] (1) The codebook has a finite number of entries and therefore may not have a sufficiently good spatial resolution to optimally address all cases of the target UE. In addition, the computational complexity at the UE increases as the codebook grows larger.

[0227] (2) Each UE selects its own optimal precoder; however, this precoder may not be optimal for other UEs. To address this issue, the BS needs to carefully select a set of UEs for each precoded transmission, in such a way that their precoders are as orthogonal as possible. This imposes significant constraints on the scheduler at the BS, especially in scenarios with a large number of layers.

[0228] 5.2 Precoding based on explicit feedback

[0229] According to the dirty paper coding theorem, we can deduce that if all channels from the BS antenna to the receiving UE antenna are known, we can optimally precode the transmissions to all UEs. Implementing this precoding scheme in a real-world system is challenging and may require the UE to send feedback to the BS via the received downlink channel. When either the UE or the radio channel reflector is mobile, the feedback channel response may no longer represent the channel state at the time the precoder was applied, and prediction may also be necessary. It should be noted that, in a sense, this precoder attempts to inverse the channel.

[0230] 5.3 Reciprocal Geometric Precoding

[0231] A wireless channel is a superposition of reflections. A geometric precoder is based on the geometry of these reflectors. This geometry tends to change relatively slowly compared to typical communication timescales. For example, considering the spatial domain, the angle of arrival (AoA) of a ray from a wireless reflector (or directly from the UE) to the BS antenna will be relatively constant and frequency-independent over a timescale of tens of milliseconds. This differs from the time- and frequency-dependent channel state. The reciprocity of the wireless channel allows information about the channel to be obtained from uplink transmissions (UE to BS) or downlink precoded transmissions (BS to UE).

[0232] The geometric precoder projects the transmission of each layer into a subspace that spans the reflector of a particular user and is orthogonal to reflectors of other layers as much as possible. This subspace is time- and frequency-independent and depends only on the geometry of the channel. The channel geometry is captured using the covariance matrix. The proposed technique uses an uplink reference signal to calculate the channel response at each of the BS receive antennas and the covariance matrix of these measurements.

[0233] For example, in an LTE / 5G NR system, the BS can use the uplink sounding reference signal (SRS) or uplink demodulation reference signal (DMRS) transmitted by the UE to calculate the channel response at different time and frequency resource elements and thereby calculate the spatial covariance matrix.

[0234] More formally, let i = 1, ..., K be user (or layer) indices and L represent the number of BS antennas. Let H i (f, t) is a complex column vector that represents the sequence of numbers at times t = 1, ..., N. t and frequencies f = 1, ..., N f Channel response at the next L BS antennas. It should be noted that N t It can be 1 and N f It can also represent a small portion of the bandwidth used. The L×L covariance matrix can be directly calculated using the following formula.

[0235]

[0236] In this article, (·) H It is either an Hermitian operator, or indirectly using techniques such as maximum likelihood (e.g., the Toeplitz maximum likelihood technique).

[0237] 5.4 Searching the Vector Space

[0238] Let K represent the number of users transmitting pre-coded data and R... i Let represent its uplink spatial covariance matrix. It is also assumed that each user has some normalized uplink power allocation, which is determined by q.i ≥0 means and satisfies

[0239] The optimal uplink vector space V_i^*, spanning the desired channel from the user to the BS and orthogonal to channels from other users, is the vector space that maximizes the SINR at the BS:

[0240]

[0241] In this paper, the numerator is the signal and the denominator is the variance of the interference and additive noise.

[0242] In this article, It can be directly calculated as the largest eigenvector of the next uplink SINR matrix:

[0243]

[0244] 5.5 Downlink Duality

[0245] Due to the reciprocal nature of wireless channels, the same vector space calculated for the uplink can also be used for downlink precoding. Therefore, the optimal vector space for the downlink can be obtained using only the uplink reference signal. This contrasts with explicit feedback methods, which require the actual channel state information of the downlink to be transmitted as data in the uplink; or codebook-based precoding methods, which require feedback from the selected precoder.

[0246] However, the selected uplink power allocation is not dual and therefore not optimal for the downlink. In the uplink, the BS receives different channels at each layer and projects them all into a single vector space, while in the downlink, the UE receives transmissions in different vector spaces on the same channel.

[0247] It can be mathematically proven that there exists a dual power allocation p for the downlink. i ≥0, thus satisfying This allows for the same SINR as the uplink:

[0248]

[0249] 5.6 Downlink Power Allocation

[0250] To calculate the dual downlink power allocation, we define a user cross-interference matrix with the following entries. :

[0251]

[0252] In this paper, i, j = 1, ..., K. It should be noted that the uplink double-crossing interference matrix can also be calculated.

[0253] It can be mathematically proven that from A (DL) The normalized absolute values ​​of the elements of the largest eigenvector are used to derive the optimal power allocation for the downlink, expressed as: :

[0254]

[0255] It should be noted that this power allocation is statistically based on an equal SINR at each receiving UE. However, when scheduling users, the BS can adjust this power allocation according to downlink traffic requirements to allow for different SINRs for different UEs.

[0256] 5.7 Pre-encoder

[0257] The precoder for user i is calculated as

[0258]

[0259] Here, conj represents the conjugate operation.

[0260] 5.8 Example of a reference signal

[0261] This type of precoder, which projects the transmitted signal into different vector spaces, does not "invert" the channel, and the UE must equalize the channel. Therefore, the UE must receive a precoded reference signal as well as precoded data. The reference data can be one of the conventional reference signals, such as a demodulated reference signal or a probe reference signal. Alternatively or additionally, new reference signals can be used to facilitate the calculations described herein.

[0262] 5.9 Scheduling

[0263] When the number of available users for precoded downlink transmission is greater than K, the BS may want to specifically select K users that are as spatially separated as possible. The BS can use the spatial covariance matrix R i To identify this group of users.

[0264] 5.10 Example Procedure

[0265] An example procedure for computing a reciprocal geometric precoder is as follows:

[0266] (1) Select uplink power allocation (which can be simply uniform allocation, q i =1 / K).

[0267] (2) For each user i, receive the uplink reference signal and calculate the channel response H. i(f, t)

[0268] (3) For each user i, calculate the covariance matrix R from the received channel response. i

[0269] (4) For each user i, calculate the uplink SINR matrix. And find its largest eigenvector.

[0270] (5) Calculate the downlink user cross-interference matrix A (DL) And find its largest eigenvector.

[0271] (6) For each user i, calculate the downlink power allocation p. i Based on

[0272] (7) For each user i, compute the geometric precoder P i Based on p i and

[0273] 6. Spectrum-sharing wireless system

[0274] Spectrum-sharing wireless systems transmit multiple streams of information on the same time and frequency resources. Similar systems are also known as multi-user multiple-input multiple-output (MU-MIMO) systems. Typically, these systems have two different types of communication signals:

[0275] In the downlink, these transmitted signals are directed to all user equipment. They can consist of reference signals, control channels, broadcast channels, etc. In the uplink, these transmitted signals originate from multiple user equipment and can consist of reference signals, control channels, random access channels, etc.

[0276] User-specific – In the downlink, these transmitted signals are targeted at one or more user equipments (UEs) sharing the same spectrum. Each UE has its own specific data stream (also called a layer). In the uplink, these transmitted signals originate from multiple UEs and contain specific data streams from each UE that are shared on the same spectrum.

[0277] For example, in 3GPP Long Term Evolution (LTE) or 5G New Radio (5G NR) systems, the common downlink signal can be the Cell Reference Signal (CRS), the Physical Downlink Control Channel (PDCCH), and the Physical Broadcast Synchronization Channel (PBSCH); the common uplink signal can be the Sound Reference Signal (SRS), the Physical Uplink Shared Control Channel (PUSCH), and the Physical Random Access Channel (PRACH); the user-specific downlink signal can be the Physical Downlink Shared Channel (PDSCH); and the user-specific uplink signal can be the Physical Uplink Control Channel (PUCCH).

[0278] In some implementations, the overlay of multiple user-specific data streams on the same frequency and time resources is achieved through the use of multiple antennas at the base station and the spatial domain. Different spatial precoders are applied to each data stream targeting a specific user equipment. In existing systems, the selection of the precoder relies on downlink channel feedback, codebook selection, or beam-matching indexing of the channel response. Some of these methods perform poorly, and some overload the system with the amount of feedback transmissions it must handle within a given time budget. These closed-loop methods typically exhibit poor mobility performance.

[0279] Even in FDD systems, implementations of spectrum-shared wireless systems can schedule and communicate with multiple user equipment on the same frequency and time resources on both the downlink and uplink using only a small set of uplink channel measurements, and are highly efficient and robust for mobility.

[0280] In existing wireless systems, not all user equipment (UEs) support advanced MU-MIMO transmission modes. These legacy UEs can operate under the assumption that spectrum sharing is not present at all. These UEs may lack any means of providing any kind of downlink channel feedback, or may only have partial means, and may not support pre-coded reference signals, which may be required for equalization of pre-coded data transmission. In these embodiments, it is even possible to perform spectrum-sharing transmissions to and from these legacy UEs without any modification to their existing hardware or software.

[0281] 6.1 Example Implementation of a Common Precoder

[0282] Let P cThis refers to a common precoder. In the downlink, the purpose of the common precoder is to transmit signals that will reach all user equipment (UEs) in the base station sector or area served by the base station. In the uplink, the common precoder is used to receive signals from multiple UEs that are not from a small group of known UEs. It should be noted that in uplink processing, it is actually applied to the "post-encoder" of the received signal. However, for simplicity, the term "precoder" will also be used for the uplink.

[0283] An example of a common precoder is an isotropic precoder that generates signals with equal angular energy. Mathematically, such a precoder is a discrete delta function in the spatial domain (e.g., spatial positioning across antenna array elements) and a constant value in the transformed angular domain.

[0284] P c = [0, ..., 0, 1, 0, ..., 0]

[0285]

[0286] in It is the Discrete Fourier Transform.

[0287] Figure 9 This precoder is illustrated. It should be noted that a common precoder does not need to be constant in time and frequency. Different time and frequency resources can use different common precoders. The semicircle 902 represents constant energy at all angles. The black asterisk represents user equipment (or user gear). The small blue and red circles 904 represent antennas, and the numbers below them are the precoder weights.

[0288] 6.2 Example Implementation of a User Equipment-Specific Precoder

[0289] make For a user-specific precoder for user i, where Let l = 1, ..., L be complex weights. In the downlink, the purpose of a user-specific precoder is to maximize the received signal energy at a specific user equipment while minimizing interference to other receiving user equipments. In other words, it maximizes the signal-to-interference-plus-noise ratio (SINR) at that specific user equipment. In the reciprocal uplink, the purpose of the precoder (postcoder) is to maximize the received signal energy from a specific user equipment at the base station while minimizing received interference signals from other transmitting user equipments. Figure 10An example of this precoder is shown. The blue shapes represent the radiation pattern. Most of the energy is concentrated towards UE#1 (as shown in lobe 1002), which is the target user equipment, while the minimum energy is directed towards UE#2 (another receiving user equipment). The weights applied to each antenna are shown below the antennas in array 1004.

[0290] 6.3 Example Implementation of Downlink Sharing of Physical Channels

[0291] In the downlink, base stations can use their frequency and time resources to multiplex different physical channels. Some of these channels can be transmitted using a common precoder, while others can be transmitted using a user-specific precoder. Table 5 illustrates examples of this multiplexing of physical channels. It should be noted that each frequency and time resource element can be transmitted using one or more precoders, depending on the number of data streams sharing that element. User-specific precoded data will typically share resource elements with multiple user equipments. However, a common precoder can also be used to accomplish the transmission of data for a single user equipment on a resource element.

[0292] Table 5 shows an example of downlink physical channel sharing using 3GPP terminology. The grid represents frequency and time resources (22 x 14). The same information is also encoded in grayscale. Figure 11A As shown in the image. Italicized entries (in...) Figure 11A The common precoding is indicated by entries with the same gray level, and non-italicized entries (with common gray level encoding) indicate user-specific precoding. Lines 1-7 represent user-specific precoded data transmission (PDSCH) for multiple user equipments, as well as some common precoded reference signals (CRS) and common precoded control channels (PDDCH). Lines 8-11 represent common precoded broadcast channel transmissions (PBCH). Lines 12-15 represent common precoded single-user equipment data transmission (PDSCH) without spectrum sharing. Lines 16-22 represent user-specific precoded data transmission (PDSCH) with reference signals (DMRS) for multiple user equipments and common precoded reference signals (CRS).

[0293] Table 5: Examples of Shared Downlink Physical Channels

[0294]

[0295]

[0296] 6.4 Example Implementation of Uplink Sharing of Physical Channels

[0297] Different uplink physical channels can be multiplexed within frequency and time resources. The base station receives and processes uplink transmissions from all sources at all its antennas.

[0298] The common channel (which can represent transmissions not originating from a small group of known user equipment) is processed using a common precoder P_c(l,f,t). The data received and processed at the base station is:

[0299] In this paper, f and t are frequency and time indices, respectively, and X... i (f, t) are uplink data symbols from user equipment i, H i (l, f, t) is the frequency channel response from user equipment i to antenna l, and n(l, f, t) is the additive noise term.

[0300] Similarly, user-specific channels are processed using their user-specific precoder:

[0301]

[0302] The operation of applying a user-specific precoder to the received uplink signal acts as a channel decoupler, converting the MU-MIMO link into a decoupled SISO link. Parallel systems. This enables the parallel implementation of independent receivers (such as...) at the base station. Figure 14 (As shown).

[0303] Table 6 (and Figure 11B The diagram illustrates an example of this multiplexing of physical channels. Here, the selection of the precoder type is also done on a resource element basis. User-specific precoded data will typically share resource elements with multiple user equipments. However, a common precoder can also be used to process data from a single user on a resource element.

[0304] Table 6 shows an example of uplink physical channel sharing using 3GPP terminology. The grid represents frequency and time resources (20 x 14). Italicized and normally grayscale entries represent common precoding, while non-italicized and normally grayscale entries represent user-specific precoding. Rows 1-4 represent user-specific uplink data transmission (PUSCH) with demodulation reference signals (DMRS) from multiple user equipments, which will be processed using a user-specific precoder. Rows 5-8 represent common uplink control channel transmissions (PUCCH) to be processed using a common precoder. Rows 9-12 represent common uplink random access channel transmissions (PRACH) to be processed using a common precoder. Rows 13-16 represent user-specific uplink data transmissions (PUSCH) with demodulation reference signals (DMRS) from multiple user equipments, which will be processed using a user-specific precoder, except for the last column, which has common sounding reference signals (SRS) that can be processed using a common precoder. Lines 17 to 20 contain a single user-specific data transmission including a demodulation reference signal, which can be processed using a common precoder or a user-specific precoder.

[0305] Table 6: Examples of Shared Uplink Physical Channels

[0306]

[0307] 6.5 Example of the initial process

[0308] This paper describes the process required for user equipment to transmit / receive data on a shared spectrum. Prior to this, the base station could schedule users to transmit / receive as a single user equipment without any spectrum sharing.

[0309] An example process can be as follows:

[0310] 1. User equipment transmits uplink reference signals. These reference signals can be dedicated to channel sensing or can be part of uplink data transmission. For example, SRS or uplink DMRS in LTE / 5G NR.

[0311] 2. The base station can calculate the uplink channel response H based on the received reference signal. i (l, f, t).

[0312] 3. Base stations can calculate the spatial covariance matrix R of dimension L×L. i There are different methods for calculating this covariance matrix. For example, for N... f Each sound and N t The rank-1 covariance matrix of each time sample is averaged, and the result is calculated directly from the channel response:

[0313]

[0314] In this article, (·) H It is the Hermitian conjugate operator. Other more advanced techniques can also be applied to compute R. i Such as maximum likelihood or parameterized covariance construction.

[0315] 4. The base station can detect the dominant angle of arrival (AOA) of the radiated wave. The concept of dominant AOA assumes that the radio channel reflection typically arrives with an angular span around the main beam. This step is useful for scheduling users with some angular separation. Different techniques can be used to calculate the dominant AOA. For example, the spatial channel response can be transformed to the angular domain and the angle with the highest energy can be detected. Alternatively, more sophisticated techniques for detecting reflector angles, such as L⁻¹ minimization and maximum likelihood, can be applied. If a user does not have a distinguishable dominant AOA, such as in some cases of completely non-line-of-sight (NLOS) or extremely large angular spans, the base station can decide to keep this user equipment as a single user and not share its spectrum with other devices.

[0316] 5. Once the base station has calculated the spatial covariance matrix and primary AOA of the user equipment, it is ready to schedule spectrum-sharing uplink or downlink transmissions. It should be noted that both measurements are robust to mobility and not very sensitive, as they depend only on the geometry of the channel, which typically changes slowly. The base station can refresh and update these metrics based on channel conditions and / or the rate of change of channel conditions.

[0317] 6.6 Scheduling Examples

[0318] For spectrum-shared wireless systems, scheduling algorithms need to consider user angular separation in addition to standard metrics such as traffic requirements (throughput, latency, etc.) and channel conditions (frequency response, SINR, etc.). Minimum angular separation varies with the number of base station antennas, beamforming, and required SINR. For a group of users requiring downlink or uplink transmission scheduling within a specific time frame, the scheduling algorithm needs to allocate user equipment in a two-dimensional plane of frequency and angle. Using the detected primary AOA, the scheduling algorithm selects user equipment with sufficient angular separation to minimize cross-interference among all user equipment sharing the same frequency and time resource elements. Figure 12 An example of this scheduling for four user equipments is shown. Beam patterns 1202, 1204, 1206, and 1208 represent four UEs drawn along the angular axis in the horizontal direction. On the right, one possible method for separating these transmissions includes using the time / frequency positions of 1204 and 1208 separated in the angular domain, and similarly combining transmissions 1202 and 1206 to occur at the same time / frequency.

[0319] 6.7 Example of pre-encoder calculation

[0320] Once a set of user equipment has been selected for spectrum-shared transmission, the base station can calculate the precoder to be applied to downlink transmission or uplink reception based on their covariance matrix. The precoder can be calculated as a vector that maximizes certain criteria (often related to SINR).

[0321] In its general form, a precoder can satisfy the following conditions:

[0322] A. Maximize the signal energy in a corner sector. This concentrates the energy towards the primary AOA of the target user equipment.

[0323] B. Minimize signal energy in some corner sectors. This reduces interference to other user equipment sharing the spectrum.

[0324] C. Minimize the signal energy in a certain corner sector compared to the reference beam. This makes the beamforming match the reference beam (which is usually the beam of a common precoder).

[0325] In the downlink, the precoder's energy can also be scaled through some power allocation to further control the received SINR of each user equipment, as described in previous chapters.

[0326] As an example, the precoder calculation for two user equipments may include: calculating the precoder of the first user equipment as a vector that maximizes the signal energy at the main AOA of the first user equipment while minimizing the signal energy in the direction of the main AOA of the second user equipment, and calculating the precoder of the second user equipment as a vector that maximizes the signal energy at the main AOA of the second user equipment while minimizing the signal energy in the direction of the main AOA of the first user equipment.

[0327] 6.8 Examples of precoding in FDD

[0328] The precoder calculation is based solely on uplink channel measurements. Generally, the calculated precoder is correct for the uplink frequency and should only be applied to uplink reception. In FDD, for the downlink, the calculated precoder should be scaled up or down according to the ratio of the downlink to the uplink frequency.

[0329] The following equation explains the scaling process of a linear antenna array with an antenna spacing of Δx. Let P UL Let f be the calculated precoder vector, and let α = f DL / f UL Let be the frequency ratio. The continuous space function of the uplink precoder can be expressed as:

[0330]

[0331] The downlink precoder vector is obtained by applying continuous downlink precoder functions in the spatial domain. Obtained through sampling, and is defined as The scaled version based on factor α, i.e.

[0332]

[0333] In this paper, the discrete precoder vector for the downlink is:

[0334]

[0335] In this paper, l = 1, ..., L. It should be noted that this scaling operation can also be implemented as uplink precoder vectors scaled by a factor α. -I Resampling operation.

[0336] Alternatively, for the covariance matrix R i Some methods for parameterized construction allow the detected main AOA to be scaled by a factor α, thereby generating a scaled covariance matrix suitable for the downlink frequency, without requiring further scaling of the precoder vector.

[0337] Figure 15A An example of scaling with a scaling factor of 0.5 is shown. Figure 15A In the diagram, the original estimated channel response is denoted by X. This represents, for example, the result of a measurement performed on the uplink signal. Circular samples represent the scaled response derived from the three equations above.

[0338] Figure 15B Another example where the scaling factor is 2 is shown. Although Figure 15A and Figure 15B The examples in the document are relatively simple scaling factors, but they are included to further explain the concept of scaling operations disclosed in this document.

[0339] 6.9 Example of pre-compensation

[0340] To support legacy user equipment that does not support precoded reference signals, pre-compensation should be performed on its precoded QAM symbols. For example... Figure 13As shown, the pre-compensation factor scales all precoded QAM symbols in the user-specific data stream transmitted to this user equipment in the downlink. The purpose of the pre-compensation factor is to compensate for the difference in channel response between the user-specific precoder and the common precoder. Thus, the receiving device receives the user-specific precoded transmission, which has a channel response similar to the common precoded channel response. The user equipment can then use the reference signal transmitted when using the common precoder to equalize its user-specific data transmission.

[0341] exist Figure 13 In this process, the covariance matrix and the common precoder are used to compute the user-specific precoder vector P_us, power allocation λ, and precompensation β. Then, each QAM (or QPSK) symbol X used for this user-specific stream is scaled by λ and β, and then multiplied by the precoder. The output is a scaled and precoded vector Y.

[0342] For example, in LTE, legacy equipment may only support Transport Mode 1 (TM1) and is not designed to receive multi-user transmissions or use precoded reference signals for equalization (DMRS). The only available reference signal for PDSCH data equalization is the Cell Reference Signal (CRS). In spectrum-sharing systems, as described in this document, the CRS can be precoded using a common precoder, and multiple PDSCH transmissions can be precoded using user-specific precoders, thus sharing the same spectrum. Due to the precompensation of QAM symbols, the user equipment will receive CRS and PDSCH with the same channel response and will be able to equalize and decode them.

[0343] 6.10 Example of base station architecture

[0344] Spectrum sharing systems can be implemented at base stations with independent parallel receivers / transmitters, such as... Figure 14 As shown. No joint processing is required in the receiver or transmitter to eliminate cross-interference between users. Only the precoder's calculations take into account the different users sharing the spectrum.

[0345] like Figure 14 As shown, signals destined for / from the antenna array used for transmitting or receiving signals can be processed as follows. The uplink receiver circuitry can receive signals from the antenna array. A reference signal portion can be passed to a reference signal processing system that performs covariance and angle-of-arrival calculations. The results of these calculations are provided to the scheduler and / or pre-encoder / power divider for future use. User-specific signals can be passed through post-encoders Pc, Pus,1…Pus,N for N user equipments, and the corresponding post-processed signals can be used by a data receiver that performs demodulation / error correction coding, etc.

[0346] On the transmitting side, the stream for each user equipment can be passed through the pre-encoder and downlink transmission circuitry and applied to the antenna array for transmission in the downlink direction.

[0347] 6.11 Examples of extending to multi-layer communication

[0348] The scheme described in the previous subsections can be easily extended from single-polarized antennas to dual-polarized antennas. Each of the L base station antennas can be a dual-polarized antenna, and the user equipment can also have a dual-polarized antenna. Using this configuration, it is possible to transmit two independent data streams (or layers) from the base station to the user equipment and from the user equipment to the base station. For example... Figure 16 As seen, each dual-polarized antenna at the base station forms a 2x2 link with the dual-polarized antenna at the user equipment. Both dual-polarized antennas can use the same accurate precoder. The covariance matrix used for precoder calculation can be derived from the uplink channel response of either dual-polarized antenna or both.

[0349] Figure 16 An example of a dual-polarized link between a base station and a user equipment (UE) is shown. In this example, the base station's antenna is located on the linear antenna array on the left, labeled 'X', and the UE is located on the right. The dual-polarized antenna of each base station forms a 2x2 link to the dual-polarized antenna of the UE.

[0350] like Figure 17 As seen in the examples, this concept of multiple layers per user equipment can be further extended to more than two layers by using additional antenna arrays spaced apart from each other at the base station and multiple dual-polarized antennas at the user equipment.

[0351] Figure 17 An example of multiple layers per user equipment is shown. The base station has two antenna arrays, each with L dual-polarized antennas. The user equipment has two dual-polarized antennas. This is equivalent to L 4x4 links to the user equipment.

[0352] 6.12 Example of expansion to multiple base stations

[0353] As described above, the multi-layer scheme can be implemented on separate base stations spaced apart from each other. Each base station can have one or more antenna arrays, and user equipment can have multiple antennas. The transmission / reception of each base station can be independent of other base stations or coordinated using sidelinks.

[0354] 7. Examples of the operational advantages of the described technology

[0355] The various techniques described throughout this document offer several operational advantages through features that distinguish them from conventional precoding techniques and digital communication systems.

[0356] For example, in one advantageous aspect, the AOA can be measured based on any and all electromagnetic emissions from the user equipment. For example, in various embodiments, reference signal transmissions or control signal transmissions (e.g., on the uplink physical control channel PUCCH) or data transmissions (e.g., on the uplink physical data transmission channel PUSCH) received at the network station can be processed to determine the AOA. (Already referenced...) Figure 9 , Figure 10 and Figure 11A Some example techniques are described.

[0357] In some embodiments, a network station may perform decomposition and separation to resolve multiple transmitters and their reflections. For example, a user equipment may include multiple antennas, each transmitting its own electromagnetic signal. (Reference) Figures 9 to 14 The described technique allows for the estimation of AOA for each reflection of a signal transmitted by each user equipment.

[0358] In some embodiments, the reliability of the measured AOA values ​​can be improved by applying mathematical functions such as averaging, denoising, or iterative filtering to process multiple measurements collected over multiple uplink transmissions.

[0359] As described in this document, AOA estimation can be advantageously used to determine precoding and scheduling transmissions to and from user equipment. Furthermore, angular accuracy can be improved by adapting and adjusting the periodicity of uplink reference signal transmissions from user equipment based on dynamic channel conditions. The network station can also adjust the periodicity of the uplink reference signal based on available network bandwidth. Channel dynamics can be based on measured user equipment mobility or reflector / scatterer mobility, or both. For example, in some embodiments, the network station can schedule user equipment to transmit uplink reference signals such that the greater the channel mobility, the higher the frequency at which the uplink reference signal is transmitted to the network station. In some embodiments, for a particular wireless device within the angular proximity range of several other wireless devices, for example, when the number of other wireless devices in a given angular period is greater than a threshold, a more refined AOA measurement can be achieved by making the wireless device transmit uplink reference signal transmissions more frequently than if there were fewer wireless devices within its angular proximity range.

[0360] 8. Examples of methods and implementations of the disclosed technology

[0361] In some embodiments, and at least in the context of Section 6, the following technical solutions use one or more of the techniques described herein.

[0362] 1. A wireless communication system comprising: a network station (e.g., 110 or 102); and a plurality of user equipments (e.g., 120), wherein spatial user equipment separation is dynamically calculated by the network station, and data transmission on the same time and frequency resources is shared among the plurality of user equipments in the downlink and / or uplink, wherein the network station derives the spatial user equipment separation based on uplink channel measurements. For example, Figures 1A to 1D An example of a wireless communication system is shown.

[0363] 2. The system as described in Solution 1, wherein the uplink channel measurement is derived from an uplink reference signal. For example, Sections 2 and 3 describe example techniques for performing uplink channel measurements.

[0364] 3. A system as described in any one of Solutions 1 to 2, wherein the network station derives the spatial user equipment separation in the absence of feedback information regarding downlink channel measurements from multiple user equipments. As described throughout the document, the network station may use only uplink measurements and may not use or request any feedback messages from user equipment regarding downlink channel quality.

[0365] 4. The system as described in any one of solutions 1 to 3, wherein the downlink and uplink are frequency division duplex. For example, in an LTE system, two different frequency bands are used for uplink and downlink transmission.

[0366] 5. The system as described in any one of solutions 1 to 4, wherein data transmission between the network station and multiple user equipments uses a dual-polarized antenna. Section 6.11 describes additional examples.

[0367] 6. The system of any one of solutions 1 to 5, wherein the network station includes L dual-polarized antennas, and the user equipment includes at least one dual-polarized antenna, and wherein data transmission is performed on L 2x2 links between each of the L dual-polarized antennas and the at least one dual-polarized antenna, where L is an integer. Section 6.11 describes additional examples of various dual-polarized antenna configurations.

[0368] 7. The system as described in solutions 1 to 6, wherein the system is a Long Term Evolution (LTE) or 5G New Radio (5G NR) system, and the reference signal is a detection reference signal or a demodulation reference signal. As described in this document, the disclosed techniques can be used in conventional LTE or upcoming 5G wireless systems.

[0369] 8. The system of any one of solutions 2 to 7, wherein the network station receives the uplink reference signal according to the schedule of uplink reference signal transmission generated by the network station and communicated to multiple user equipments.

[0370] 9. The system as described in Solution 8, wherein the scheduling is configured to cause different mobile devices to perform uplink reference signal transmission at different occurrence frequencies based on the measured channel dynamics for the different mobile devices.

[0371] 10. The system of any one of solutions 1 to 9, wherein the dynamically calculated spatial user equipment separation is calculated using an angle of arrival (AOA) estimate for each user equipment, wherein the AOA estimate for a given user equipment is calculated by averaging multiple signal receptions from a given user equipment at different frequencies or at different times.

[0372] Referring to the solutions listed above, in some embodiments, only uplink channel measurements are used to determine the spatial separation of different user equipment, and precoding is therefore applied to downlink signal transmission. Such a scheme can be implemented in FDD or TDD systems. Additional implementation examples are provided in Section 6.

[0373] 11. A wireless communication method implemented by a network station in a wireless system comprising a network station and multiple user devices (e.g., Figure 18 The method shown (1800) includes transmitting (1810) a transmission symbol from a network station to at least one user equipment by processing via a first precoder and a pre-compensation stage, wherein the pre-compensation stage is selected such that a transmission symbol receivable at the at least one user equipment appears as if the transmission symbol was processed by a second precoder different from the first precoder. Some examples are disclosed in Section 6.

[0374] 12. The method as described in Solution 11, wherein the first precoder is a user equipment-specific precoder and the second precoder is a common precoder. Section 6 provides examples of common precoders and user equipment-specific precoders.

[0375] 13. The method as described in Solution 12, wherein the second preencoder is approximately an isotropic preencoder. For example, the preencoder may be nominally designed to be isotropic, or have equal magnitudes in all directions. However, due to practical considerations, the directivity may vary by a few dB (e.g., within + / - 0.5 dB flatness).

[0376] 14. The method of any one of solutions 11 to 14, wherein the transmitted symbols are transmitted using a dual-polarized antenna. Section 6.11 describes additional examples of dual polarization.

[0377] 15. The method of any one of solutions 11 to 14, comprising determining a first precoder based on reference signal transmissions received from the at least one user equipment.

[0378] 16. The method of solution 15, wherein determining the first precoder is performed by estimating the angle of arrival (AOA) estimate from the at least one user equipment, wherein the AOA estimation is processed on one or more received transmissions from the at least one user equipment, wherein the plurality of received transmissions includes reference signal transmissions and / or other control transmissions and / or data transmissions.

[0379] 17. A wireless communication method (e.g., Figure 19 The method shown (1900) includes: determining (1910) a first precoder specific to a second wireless device for precoding transmissions by a first wireless device, wherein the first precoder is determined to match a second precoder in a specific angular sector, and wherein the first precoder is determined based on channel measurements of transmissions from the second wireless device to the first wireless device. Here, the first and second wireless devices may be network stations and / or user equipment, depending on channel directivity.

[0380] 18. The method of solution 17, further comprising performing the transmission from the first wireless device to the second wireless device using a first precoder for precoding the transmission. For example, the first precoder may be a downlink channel precoder at a different frequency than the uplink and may be derived entirely from uplink signal measurements, as described throughout the document.

[0381] 19. The method of any one of solutions 17 to 18, further comprising using a first precoder for post-coding the transmission to perform reception from the second wireless device implemented by the first wireless device. (For example, regarding...) Figure 14 As described, the post encoder can be used to process the received signal.

[0382] 20. The method of any one of solutions 17 to 19, wherein the transmission is for a specific corner sector. For example, Section 6 and Figure 10 An example of using corner beams is described, where a specific corner sector is covered by wireless transmission (or reception).

[0383] 21. The method of any one of solutions 17 to 20, wherein the second pre-encoder is approximately an isotropic pre-encoder. As previously discussed, the ideally identical angular response flatness can vary within tolerances such as + / - 0.5 dB due to practical considerations such as device geometry and nonlinearity.

[0384] 22. The method of any one of solutions 17 to 21, wherein the first wireless device is a base station and the second wireless device is a user equipment.

[0385] 23. The method of any one of solutions 17 to 22, wherein the first wireless device is a user equipment and the second wireless device is a base station.

[0386] 24. The method of any one of solutions 18 to 24, wherein the first precoder is determined entirely based on channel measurements of transmissions from the second wireless device to the first wireless device. For example, section 6 discloses techniques for determining the precoder by relying solely on measurements of the uplink signal.

[0387] 25. The method as described in solutions 17, wherein the first precoder is determined by performing a scaling operation on channel measurements of transmissions from the second wireless device to the first wireless device. For example, Section 6 describes some examples of scaling operations.

[0388] 26. The method of any one of solutions 17 to 25, comprising determining a first precoder based on reference signal transmissions received from the at least one user equipment.

[0389] 27. The method of solution 26, wherein determining the first precoder is performed by estimating the angle of arrival (AOA) estimate from the at least one user equipment, wherein the AOA estimation is processed on one or more received transmissions from the at least one user equipment, wherein the plurality of received transmissions includes reference signal transmissions and / or other control transmissions and / or data transmissions.

[0390] 28. A wireless communication method (e.g., Figure 20 The method shown (2000) includes: determining (2010) a user equipment-specific precoder for application to signal transmission from a network station to the user equipment; and transmitting (2020) a stream of data symbols to the user equipment by precoding using the user equipment-specific precoder, wherein the user equipment-specific precoder is unknown to the user equipment, and wherein the symbol stream has no reference signal for receiver-side channel equalization. Some example ways in which this method can be implemented are described in Sections 2 and 6. For example, the user equipment-specific precoder is unknown to the user equipment because the network station can fully determine this decoder based on uplink channel measurements and the user equipment does not need to perform downlink calculations or provide feedback signals to the network station.

[0391] 29. The method described in solution 28, wherein the user equipment-specific precoder is not signaled from a codebook that can be searched by the user equipment.

[0392] 30. The method of any one of solutions 28 to 29, wherein determining the user equipment-specific precoder comprises determining the user equipment-specific precoder entirely based on measurements performed on transmissions from the user equipment, wherein the transmissions do not include feedback information about transmissions destined for the user equipment.

[0393] 31. The method of any one of solutions 28 to 30, wherein the network station is a Long Term Evolution (LTE) or 5G New Radio (5G NR) base station, and wherein the symbol stream is a Physical Downlink Shared Channel (PDSCH) without any demodulation reference signal (DMRS).

[0394] 32. A wireless communication method (e.g., Figure 21 The method shown (2100) includes: determining (2110) a first precoder by a network station based on measurements of one or more uplink signals received on an uplink channel; determining (2120) a second precoder by scaling the first precoder using a scaling factor; and performing (2130) downlink transmission on a downlink channel using the second precoder, wherein the downlink channel and the uplink channel are frequency-division duplex. Sections 5 and 6 describe some example techniques that can be used to implement this method.

[0395] 33. The method as described in solution 32, wherein the scaling factor is proportional to the frequency ratio of the downlink channel to the uplink channel.

[0396] 34. The method as described in any one of solutions 32 to 33, wherein the first precoder is determined based on the spatial covariance matrix. Section 4 provides examples of the spatial covariance matrix R_i and various ways of calculating this matrix.

[0397] 35. The method of any one of solutions 32 to 34, wherein determining the second pre-encoder comprises determining the second pre-encoder in a frequency band different from that of the first pre-encoder. Additional details are described with reference to section 6.

[0398] 36. The method of any one of solutions 32 to 35, further comprising: performing another downlink transmission by precoding using a common precoder common to all user equipment.

[0399] 37. A wireless communication method (e.g., Figure 22The method shown (2200) includes: determining (2210) a spatial covariance matrix by a network station operating in a frequency division duplex wireless system based on measurements of uplink signals received from a user equipment on an uplink channel; and performing (2220) downlink transmission on a downlink channel by precoding using a precoder corresponding to a scaled version of the spatial covariance matrix. Additional details and examples are described in sections 5 and 6.

[0400] 38. The method described in solution 37, wherein the spatial covariance matrix is ​​scaled using the ratio between the downlink channel frequency and the uplink channel frequency.

[0401] 39. The method of solution 37, wherein the spatial covariance matrix is ​​determined by estimating the channel response matrix and determining the spatial covariance matrix based on the channel response matrix.

[0402] 40. The method of any one of solutions 37 to 39, further comprising estimating the primary angle of arrival (AOA) of the uplink signal and using the AOA when scheduling subsequent transmissions to the user equipment.

[0403] 41. The method of any one of solutions 37 to 40, wherein the spatial covariance matrix is ​​determined based on the master AOA.

[0404] 42. The method of any one of solutions 37 to 41, wherein the main AOA is estimated to have the angle with the highest received energy.

[0405] 43. The method of solution 40, wherein the scheduling allocates time and frequency resources to subsequent transmissions by grouping the user equipment and other user equipment having a different primary AOA compared to the primary AOA.

[0406] 44. The method of any one of solutions 40 to 43, wherein estimating the primary AOA includes improving accuracy by processing multiple AOA measurements over multiple transmissions of the uplink signal.

[0407] 45. The method as described in solution 44, wherein the number of AOA measurements used for estimation is proportional to the measured mobility of the user equipment.

[0408] 46. ​​The method as described in solution 45, wherein the network station controls the user equipment to perform uplink transmission periodically in proportion to the measured mobility.

[0409] 47. A wireless communication method implemented by a network station in a wireless system (e.g., Figure 23The method shown (2300) includes: determining (2310) the angle of arrival (AOA) corresponding to the plurality of user equipments based on transmissions received from the plurality of user equipments; grouping (2320) the plurality of user equipments into a device group based on the AOA of the plurality of user equipments; and scheduling (2330) subsequent transmissions in the wireless system such that the same time and frequency resources are used for transmissions to or from user equipments in the same group, wherein subsequent transmissions to or from the plurality of user equipments use a pre-encoder or post-encoder determined entirely based on transmissions received from the plurality of user equipments. (Sections 4 to 5 and...) Figure 14 Some examples of this technology are provided.

[0410] 48. A wireless communication method implemented by a network station in a wireless system (e.g., Figure 24 The method shown (2400) includes: receiving (2410) signals comprising uplink transmissions from a plurality of user equipments, wherein the uplink transmissions share the same time and frequency resource elements; and segmenting (2420) the received signals into parallel independent data streams by dynamically applying a user equipment-specific post-encoder to the received signals, wherein the user equipment-specific post-encoder is an angle filter determined entirely from uplink measurements and designed to angle-filter desired user transmissions in each parallel independent data stream and reject other interfering transmissions. (Sections 4-5 and References) Figure 14 The description describes some examples of this method.

[0411] 49. A wireless communication method implemented by a network station in a wireless system (e.g., Figure 25 The method shown (2500) includes: applying (2510) a user-equipment-specific precoder to parallel independent data streams corresponding to multiple user equipments; combining (2520) the results of the application to generate a signal for transmission achieved by sharing the same time and frequency resources; and transmitting (2530) the signal to the multiple user equipments on a downlink channel, wherein the user-equipment-specific precoder is an angle filter determined entirely from uplink measurements and designed to minimize interference to other users. (Sections 4-5 and References) Figure 14 The description describes some examples of this method.

[0412] 50. The method of any one of solutions 47 to 49, wherein the network station controls a plurality of user equipments to perform uplink transmission of reference signals based on measured channel dynamics of the uplink channel between each user equipment and the network station.

[0413] 51. The method of any one of solutions 47 to 50, wherein the accuracy of the measurement of the pre-encoder or angle of arrival specific to the user equipment is improved by averaging over multiple observations.

[0414] 52. A wireless communication method (e.g., Figure 26 The method shown (2600) includes: determining (2610) precoding by a network station for transmission to a plurality of user equipments in a wireless coverage area of ​​the network station, wherein the transmission to the plurality of user equipments includes the use of a multi-carrier modulation scheme, and wherein for each user equipment, the corresponding precoding is identical on all carriers of the multi-carrier modulation scheme; and generating (2620) one or more transmission waveforms for transmission to one or more of the plurality of user equipments by processing according to the precoding. (Sections 4 to 5 and References) Figure 14 The description describes some examples of this approach. In some embodiments, the term "identical" may mean "identical within a certain range." For example, practical considerations associated with the implementation may impose limitations on the degree of identicalness or flatness of the precoder. For example, a tolerance of + / -0.5 dB may be observed, but the precoder can still be considered flat or identical across all subcarriers. Some implementations use a "zero-forcing" technique, where certain unwanted subcarriers are "zeroed out" by the precoder, which behaves as null values ​​(e.g., attenuated by 10 dB or 20 dB or more at certain frequencies). However, unlike this zero-forcing technique, some embodiments of precoders that are "identical" across different carriers can avoid this zero-forcing attenuation at certain frequencies. In such cases, "identical" may simply mean that the precoder's attenuation at any frequency is unlikely to exceed a threshold amount compared to any other frequency in the transmission band. The threshold may be, for example, 0.5 dB, 3 dB, or 6 dB, depending on the characteristics of the wireless channel and reflectors experienced by the transmission between the user equipment and the network equipment.

[0415] In the solution described above, multicarrier modulation can correspond to orthogonal time-frequency space (OTFS) modulation or orthogonal frequency division multiplexing (OFDM) modulation, in which orthogonal phase shift keying (QPSK) or orthogonal amplitude modulation (QAM) symbols are used to modulate multiple subcarriers or tones respectively.

[0416] 53. The method of solution 52, wherein the precoding is based on spatial precoding determined for estimated angles of arrival for multiple user devices.

[0417] 54. The method of any one of solutions 52 to 53, wherein one or more transmission waveforms destined for one or more of the plurality of user equipment occupy overlapping time and frequency resources.

[0418] 55. The method of any one of solutions 52 to 54, wherein one or more transmission waveforms destined for one or more of a plurality of user equipments occupy the same time and frequency resources.

[0419] 56. The method of solution 52, wherein the corresponding precode for each user equipment is calculated by estimating a single precoder on all carriers. Some examples are described in sections 2 through 6 of this document. For example, the equations in sections 6.4 through 6.8 disclose some example implementations of the precoder.

[0420] 57. A wireless communication device comprising a processor and a wireless transceiver, wherein the processor is configured to perform a method as described in any one of solutions 11 to 56 using the transceiver for transmitting or receiving signals.

[0421] It should be understood that techniques that can be implemented by devices in wireless systems are disclosed to precode transmissions destined for other devices in one direction based on transmissions received in the reverse direction and the determination of the channel state based on the received transmissions. On one hand, this approach avoids the overhead and operational inefficiency associated with using codebooks or channel state feedback reports.

[0422] Figure 27 An example of a wireless transceiver device 2700 is shown. Device 2700 can be used to implement a node or UE or a network-side resource to perform channel estimation / prediction tasks. Device 2700 includes a processor 2702, optional memory (2704), and transceiver circuitry 2706. Processor 2702 can be configured to implement the techniques described in this document. For example, processor 2702 can use memory 2704 to store code, data, or intermediate results. Alternatively, the memory can be located internally within the processor. Transceiver circuitry 2706 can perform tasks of transmitting or receiving signals. This can include, for example, data transmission / reception via a wireless link (such as Wi-Fi, millimeter wave, or another link) or a wired link (such as a fiber optic link).

[0423] The disclosed and other embodiments, modules, and functional operations described in this document can be implemented in digital electronic circuits or computer software, firmware, or hardware, including the structures disclosed in this document and their structural equivalents or combinations thereof. The disclosed and other embodiments can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer-readable medium for execution by or control of the operation of a data processing apparatus. The computer-readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of a substance that influences machine-readable propagation signals, or combinations thereof. The term "data processing apparatus" encompasses all means, devices, and machines for processing data, including, for example, a programmable processor, a computer, or multiple processors or computers. In addition to hardware, the apparatus may include code that creates an execution environment for a computer program of question, such as code constituting processor firmware, a protocol stack, a database management system, an operating system, or combinations thereof. Propagation signals are artificially generated signals, such as machine-generated electrical, optical, or electromagnetic signals, which are generated to encode information for transmission to a suitable receiver device.

[0424] Computer programs (also referred to as programs, software, software applications, scripts, or code) can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, including as standalone programs or modules, components, subroutines, or other units suited to a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored as a part of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinating files (e.g., a file storing one or more modules, subroutines, or code sections). A computer program can be deployed to execute on a single computer, or on multiple computers located at a single site or distributed among multiple sites and interconnected via a communication network.

[0425] The processes and logic flows described in this document can be executed by one or more programmable processors, which execute one or more computer programs to perform functions by manipulating input data and generating outputs. The processes and logic flows can also be executed by dedicated logic circuits, and the devices can be implemented as dedicated logic circuits, such as FPGAs (Field-Programmable Gate Arrays) or ASICs (Application-Specific Integrated Circuits).

[0426] Processors suitable for executing computer programs include, for example, general-purpose and special-purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor receives instructions and data from read-only memory or random access memory, or both. The basic components of a computer are a processor for executing instructions and one or more memory devices for storing instructions and data. Typically, a computer will also include one or more mass storage devices for storing data, such as magnetic disks, magneto-optical disks, or optical disks, or operatively coupled thereto to receive data from or transfer data to or to both. However, a computer does not need to have such devices. Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and memory devices, including, for example, semiconductor memory devices, such as EPROMs, EEPROMs, and flash memory devices; magnetic disks, such as internal hard disks or removable disks; magneto-optical disks; and CD-ROMs and DVD-ROMs. The processor and memory may be supplemented by or incorporated into special-purpose logic circuitry.

[0427] Although this patent document contains many specific aspects, these should not be construed as limiting the scope of the claimed invention or the content that may be claimed, but rather describe features specific to particular embodiments. Certain features described herein in the context of individual embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented separately in multiple embodiments or in any suitable sub-combination. Furthermore, although features may be described above as functioning in certain combinations and even as originally claimed, in some cases, one or more features in the claimed combination may be removed from the combination, and the claimed combination may refer to sub-combinations or variations of sub-combinations. Similarly, although operations are depicted in a specific order in the drawings, this should not be construed as requiring such operations to be performed in the specific order shown or sequentially, or to perform all shown operations to achieve the desired result.

[0428] Only some examples and implementations are disclosed. Based on the disclosed content, variations, modifications, and enhancements can be made to the described examples and implementations, as well as other implementations.

Claims

1. A wireless communication system, comprising: Website; as well as Multiple user devices, Specifically, spatial user equipment separation, dynamically calculated by the network station, is used to share data transmission on the same time and frequency resources among the multiple user equipment in the downlink and / or uplink; and The network station derives the spatial user equipment separation based on uplink channel measurements. Specifically, the network station derives the spatial user equipment separation in the absence of feedback information related to downlink channel measurements from the multiple user equipments. The process of deriving the spatial user equipment separation includes: determining an uplink precoder based on the uplink channel measurements, and determining a downlink precoder corresponding to a scaled version of the uplink precoder; and Specifically, the downlink precoder is used to precode the downlink transmission.

2. The system as claimed in claim 1, wherein, The uplink channel measurement is derived from the uplink reference signal.

3. The system as described in claim 1, wherein, The downlink and the uplink are frequency division duplex.

4. The system as claimed in claim 1, wherein, The data transmission between the network station and the plurality of user equipment uses a dual-polarized antenna.

5. The system as claimed in claim 1, wherein, The network station includes L dual-polarized antennas, and the user equipment includes at least one dual-polarized antenna, wherein data transmission is performed on L 2x2 links between each of the L dual-polarized antennas and the at least one dual-polarized antenna, where L is an integer.

6. The system of claim 1, wherein, The system is a Long Term Evolution (LTE) or 5G New Radio (5G NR) system, and the reference signal is a detection reference signal or a demodulation reference signal.

7. The system as claimed in claim 2, wherein, The uplink reference signal is received by the network station according to the scheduling of uplink reference signal transmission generated by the network station and conveyed to the multiple user equipments.

8. The system of claim 7, wherein, The scheduling is configured to cause different mobile devices to perform uplink reference signal transmission at different occurrence frequencies based on the measured channel dynamics of the different mobile devices.

9. The system of claim 1, wherein, The dynamically calculated spatial user equipment separation is calculated using an angle of arrival (AOA) estimate for each user equipment, wherein the AOA estimate is calculated for the given user equipment by averaging multiple signal receptions from the given user equipment at different frequencies or at different times.

10. A wireless communication method, comprising: A first wireless device determines a first precoder, specific to the second wireless device, for precoding the transmission, wherein the first precoder is determined to match the second precoder in a specific angular sector, and wherein the first precoder is determined based on channel measurements of the transmission from the second wireless device to the first wireless device. The first precoder is determined in the absence of feedback information from the second wireless device related to the transmission channel measurement from the first wireless device to the second wireless device, and the first precoder is determined by performing a scaling operation on the channel measurement results of the transmission from the second wireless device to the first wireless device. The transmission from the first wireless device to the second wireless device is performed using the first precoder for precoding the transmission.

11. The method of claim 10, further comprising: The reception from the second wireless device, implemented by the first wireless device, is performed using the first precoder for post-encoding the transmission.

12. The method of claim 10, wherein, The transmission is for the specific corner sector.

13. The method of claim 10, wherein, The second precoder is approximately an isotropic precoder.

14. The method of claim 10, wherein, The first wireless device is a base station, and the second wireless device is a user equipment.

15. The method of claim 10, wherein, The first wireless device is a user equipment, and the second wireless device is a base station.

16. The method of claim 10, wherein, The first precoder is determined entirely based on channel measurements of transmissions from the second wireless device to the first wireless device.

17. The method of claim 10, comprising: The first precoder is determined based on the reference signal transmission received from the second wireless device.

18. The method of claim 17, wherein, The determination of the first precoder is performed by estimating the angle of arrival (AOA) from at least one user equipment, wherein the AOA estimation is processed on one or more received transmissions from the at least one user equipment, wherein the received transmissions include reference signal transmissions and / or other control transmissions and / or data transmissions.

19. A wireless communication method, comprising: The first precoder is determined by the network station based on measurements of one or more uplink signals received on the uplink channel; A second precoder is determined by scaling the first precoder using a scaling factor, wherein the second precoder is determined in the absence of feedback information from the user equipment related to downlink channel measurements; and Downlink transmission is performed on a downlink channel using the second precoder, wherein the downlink channel and the uplink channel are frequency division duplex.

20. The method of claim 19, wherein, The scaling factor and the downlink channel frequency f DL With the uplink channel frequency f UL The frequency is proportional to the ratio, Among them, the continuous space function of the uplink precoder Given from the following: ， Among them, P UL It is the uplink precoder vector. L is the antenna spacing, and L is the number of antennas at the network station. , and / or Among them, the continuous space function of the downlink precoder Given from the following: ， Where α=f DL / f UL It is the ratio between the downlink channel frequency and the uplink channel frequency.

21. The method of claim 19, wherein, The first precoder is determined based on the spatial covariance matrix.

22. The method of claim 19, wherein, Determining the second precoder includes determining the second precoder in a frequency band different from the frequency band of the first precoder.

23. The method of claim 19, further comprising: Another downlink transmission is performed by precoding using a common precoder shared by all user equipment.

24. A wireless communication method, comprising: The uplink precoder is determined by a network station operating in a frequency division duplex wireless system based on measurements of the uplink signal received from the user equipment on the uplink channel. as well as Downlink transmission is performed on the downlink channel by precoding with a downlink precoder corresponding to a scaled version of the uplink precoder, wherein the downlink precoder is determined in the absence of feedback information from the user equipment relating to downlink channel measurements.

25. The method of claim 24, wherein, The downlink precoder uses the downlink channel frequency f. DL uplink channel frequency f UL Scaling is based on the ratio between them. Wherein, the continuous space function of the uplink precoder Given from the following: ， Among them, P UL It is the uplink precoder vector. L is the antenna spacing, and L is the number of antennas at the network station. , and / or Wherein, the continuous space function of the downlink precoder Given from the following: ， Where α=f DL / f UL It is the ratio between the downlink channel frequency and the uplink channel frequency.

26. The method of claim 24, wherein, The uplink precoder is determined to be based on a spatial covariance matrix, wherein the spatial covariance matrix is ​​based on a channel response matrix.

27. The method of claim 24, further comprising: Estimate the main angle of arrival (AOA) of the uplink signal; as well as The AOA is used when scheduling subsequent transmissions to the user equipment.

28. The method of claim 27, wherein, The downlink precoder is further determined based on the main AOA.

29. The method of claim 27, wherein, The main AOA is estimated to be the angle with the highest received energy.

30. The method of claim 27, wherein, The scheduling allocates time and frequency resources to the subsequent transmissions by grouping the user equipment and other user equipment that have a different primary AOA compared to the primary AOA.

31. The method of claim 27, wherein, Estimating the primary AOA includes improving accuracy by processing multiple AOA measurements over multiple transmissions of the uplink signal.

32. The method of claim 31, wherein, The number of AOA measurements used for the estimation is proportional to the measured mobility of the user equipment.

33. The method of claim 32, wherein, The network station controls the user equipment to perform uplink transmission periodically in proportion to the measured mobility.

34. A wireless communication device, comprising a processor and a wireless transceiver, wherein, The processor is configured to perform the method as described in any one of claims 10 to 33 using the transceiver for transmitting or receiving signals.

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