Port information signaling

Abstract

To provide a method and an apparatus for multi-channel communication.SOLUTION: A method includes: precoding a reference signal port in a spatial domain and a frequency domain by determining pairs of spatial domain component and a frequency domain component based on a sounding reference signal received from a communication device, where the frequency domain component is arranged in a cluster comprising one or more frequency domain components, the frequency domain component is enabled to pair with at least one of the spatial domain components with at least two clusters; transmitting information of the precoding to another communication device; and combining the precoding with a report of the precoding received in a response from the other communication device.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to methods, apparatus, and computer program products for signaling port information between communication devices. [Background technology]

[0002] A communication session can be established between two or more communication devices, such as user or terminal devices, base stations / access points, and / or other nodes. A communication session may be realized, for example, by a communication network and one or more compatible communication devices. A communication device on the network side provides an access point to the system and is equipped with appropriate signal transmission and reception equipment to enable communication, e.g., to allow other devices to access the communication system. A communication session may include, for example, communication of data to carry communications such as voice, video, electronic mail (email), text messages, multimedia, and / or content data. Non-limiting examples of services provided include two-way or multi-way calls, data communication, multimedia services, and access to a data network system such as the Internet.

[0003] In a mobile or wireless communication system, at least a portion of a communication session between at least two devices occurs over a wireless or radio link. Examples of wireless systems include public local area mobile networks (PLMNs), satellite-based communication systems, and various wireless local networks, e.g., wireless local area networks (WLANs). A user can access a wide area communication system by means of an appropriate communication device or terminal. A user's communication device may be referred to as user equipment (UE) or user device.

[0004] A communication device is provided with appropriate signal transmission and reception equipment to enable communication, e.g., to enable access to a communication network or direct communication with other users. A user's communication device can access carriers provided by stations, e.g., base stations, in the radio access network and transmit and / or receive communications on the carriers. A characteristic of modem systems is the capability for multipath operation. A communication device can communicate via multiple paths. Multipath communication may be achieved by a configuration known as multiple-input / multiple-output (MIMO).

[0005] Communication systems and associated devices typically operate according to given standards and specifications that govern what various entities associated with the system are permitted to do and how that should be accomplished. The standards also typically define the communication protocols and / or parameters to be used for connectivity. One example of a communication system is UTRAN (3G Radio). Other examples of communication systems are the Long Term Evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio access technology and the so-called fifth-generation (5G) or new radio (NR) networks. 5G is being standardized by the Third Generation Partnership Project (3GPP). Successive versions of the standard are known as releases (Rel). 3GPP's 5G NR standardization work is currently underway to further enhance MIMO channel state information (CSI) feedback by leveraging partial uplink / downlink (UL / DL) reciprocity of certain channel statistics. Summary of the Invention

[0006] According to one aspect, a method for multi-channel communication is provided, the method including: precoding a reference signal port in the spatial and frequency domains by determining pairs of spatial and frequency domain components based on a sounding reference signal received from a communication device, wherein the frequency domain components are arranged in clusters comprising one or more frequency domain components, enabling pairing of at least one of the spatial domain components with at least two clusters of frequency domain components; transmitting information of the precoding to other communication devices; and combining the precoding with reports of precoding received in responses from the other communication devices.

[0007] According to one aspect, a method for multi-channel communication is provided, the method including: transmitting a sounding reference signal to a communication device; receiving, in a response from the communication device, precoding information including information of reference signal ports in the spatial domain and the frequency domain defined by pairs of spatial domain components and frequency domain components, wherein the frequency domain components are arranged in clusters comprising one or more frequency domain components, enabling pairing of at least one of the spatial domain components with at least two clusters of the frequency domain components; performing a port selection operation based on the clustered information of the frequency domain components; and preparing and transmitting a report based on the selection operation.

[0008] According to one aspect, an apparatus is provided that includes at least one processor and at least one memory containing computer program code, the at least one memory and the computer program code being configured to cause the apparatus, using the at least one processor, to perform at least the following: precoding a reference signal port in the spatial and frequency domains by determining pairs of spatial and frequency domain components based on a sounding reference signal received from a communication device, wherein the frequency domain components are arranged in clusters comprising one or more frequency domain components, allowing pairing of at least one of the spatial domain components with at least two clusters of frequency domain components; transmitting information of the precoding to other communication devices; and combining the precoding with reports of precoding received in responses from the other communication devices.

[0009] According to one aspect, an apparatus is provided that includes at least one processor and at least one memory containing computer program code, wherein the at least one memory and the computer program code are configured to cause the apparatus, using the at least one processor, to at least: transmit a sounding reference signal to a communication device; receive from the communication device precoding information including information of reference signal ports in the spatial domain and the frequency domain defined by pairs of spatial domain components and frequency domain components, wherein the frequency domain components are arranged in clusters comprising one or more frequency domain components, enabling pairing of at least one of the spatial domain components with at least two clusters of the frequency domain components; perform a port selection operation based on the clustered information of the frequency domain components; and prepare and transmit a report based on the selection operation.

[0010] According to a more detailed aspect, the report received from the selecting communication device includes a precoder matrix indication. The combining includes generating a recovered precoding for use in the communication.

[0011] A portion of the frequency domain compression operation can be performed before transmitting the precoding information, and the communication device receiving the precoding is configured to perform another portion of the frequency domain compression operation. A majority of the frequency domain compression operation may be performed in a device performing the precoding rather than in a device receiving the precoding. A smaller portion of the combined frequency domain compression operation may be performed in a device receiving the precoding information.

[0012] Transmitting the precoding information may include transmitting a channel state information reference signal based on the precoding for use in selecting a precoding pair associated with the channel state information reference signal port or ports. Selection of the precoding pair associated with the channel state information reference signal port or ports can then be performed. A precoding matrix indicator report may be transmitted in the response, the report based on the channel state information reference signal port or precoding pair selected by the communication device receiving the channel state information reference signal.

[0013] The communications device may be configured to participate in the calculation of frequency-domain components from a restricted subset of a discrete Fourier transform codebook for pairs of spatial and frequency-domain components, and to report, in response to a channel state information report request, information of a selection of non-zero coefficients from a sequence formed by the frequency-domain components calculated for all space-frequency components measured at the reference signal port, as well as an indicator indicating the space-frequency pair and the frequency-domain component corresponding to the reported non-zero coefficient.

[0014] A restricted subset of the discrete Fourier transform components may be provided. The subset may include a window of continuous components or a set of non-contiguous components of the discrete Fourier transform codebook that includes at least one zero component. The restricted subsets of DFT components may be of the same or different sizes, or may be components for different groups of space-frequency pairs.

[0015] Partial reciprocity of cluster delays in the channel between the communicating devices may be assumed as a basis for operation.

[0016] The size of the cluster may be determined based at least in part on the uncertainty of the predicted cluster delay.

[0017] Precoder weights may be calculated, and the calculated precoder weights may be combined with precoder matrix indicator information received from the communication device to select to restore the precoding.

[0018] Means for performing the operations and functions disclosed herein may also be provided.

[0019] A computer software product may be provided that employs at least some of the functionality disclosed herein. According to one aspect, the computer program includes instructions for performing at least one of the methods described herein.

[0020] Certain embodiments will now be described in further detail, by way of example only, with reference to the following examples and accompanying drawings. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 illustrates an example of a system in which the present invention can be practiced. [Figure 2] FIG. 2 illustrates an example of a control device. [Figure 3] 1 is a signaling flowchart between two communication devices. [Figure 4] 1 is a flowchart according to a particular example. [Figure 5] 1 is a flowchart according to a particular example. [Figure 6] FIG. 10 is a diagram showing an example of SD and FD components determined for two SD beams based on a received SRS. [Figure 7] FIG. 10 is a diagram illustrating an example of pairing of SD and FD components and port selection based on the pairing. [Figure 8] FIG. 10 is a diagram illustrating yet another example. [Figure 9] FIG. 10 is a diagram illustrating yet another example. [Figure 10] FIG. 10 is a diagram illustrating yet another example. DETAILED DESCRIPTION OF THE INVENTION

[0022] The following description provides an illustrative description of some possibilities for practicing the present invention. Although this specification may refer to "an," "one," or "several" examples or embodiments in several places in the text, this does not necessarily mean that each reference is to the same example of an embodiment or that a particular feature applies only to a single example or embodiment. Single features of different examples and embodiments may be combined to provide other embodiments.

[0023] A wireless communication system provides wireless communications to devices connected thereto. Typically, access points such as base stations are provided to enable communications. Below, various scenarios are described using a 3GPP 5G radio access architecture with MIMO capabilities as an example of an access architecture. However, embodiments are not necessarily limited to the architecture. Some examples of suitable system options are Universal Mobile Telecommunications System (UMTS) Radio Access Network (UTRAN or E-UTRAN), Long Term Evolution (LTE), LTE-A (LTE Advanced), Wireless Local Area Network (WLAN or Wi-Fi), Worldwide Interoperability for Microwave Access (WiMAX), Bluetooth®, Personal Communications Services (PCS), ZigBee®, Wideband Code Division Multiple Access (WCDMA), systems using Ultra-Wideband (UWB) technology, sensor networks, Mobile Ad Hoc Networks (MANET), Cellular Internet of Things (IoT) RAN, and Internet Protocol Multimedia Subsystem (IMS), or any combination and further development thereof.

[0024] 1 shows a wireless system 1 comprising a radio access system 2. The radio access system may comprise one or more access points, or base stations 12. A base station may provide one or more cells. An access point may include any node capable of transmitting / receiving radio signals (e.g., a 3GPP 5G base station such as a TRP, gNB, eNB, etc., a user device such as a UE, etc.).

[0025] A communication device 10 is located within the coverage area of ​​the wireless access system 2, and therefore the device 10 is able to listen to an access point 12. Communication 11 from the device 10 to the access point 12 is typically referred to as the uplink (UL). Communication 13 from the access point 12 to the device 10 is typically referred to as the downlink (DL). In the example, the downlink is shown schematically as comprising up to four beams per polarization in the spatial domain (SD).

[0026] It should be noted that the wide area communication system is illustrated only as cloud 1 and may comprise several elements not shown for clarity. For example, a 5G base system may be comprised of a terminal or user equipment (UE), a 5G radio access network (5GRAN) or next-generation radio access network (NG-RAN), a 5G core network (5GC), one or more application functions (AFs), and one or more data networks (DNs). The 5G-RAN may comprise one or more gNodeBs (GNBs) or one or more gNodeB (GNB) distributed unit functions connected to one or more gNodeB (GNB) centralized unit functions. The 5GC may comprise entities such as a network slice selection function (NSSF), a network publishing function, a network repository function (NRF), a policy control function (PCF), a unified data management (UDM), an application function (AF), an authentication server function (AUSF), an access and mobility management function (AMF), and a session management function (SMF).

[0027] The device 10 may be any suitable communication device adapted for wireless communication. The wireless communication device may be provided by any device capable of transmitting and receiving radio signals. Non-limiting examples include a mobile station (MS) (e.g., a mobile device such as a mobile phone or what is known as a "smartphone"), a computer equipped with a wireless interface card or other wireless interface equipment (e.g., a USB dongle), a personal digital assistant (PDA) or tablet equipped with wireless communication capabilities, a machine-type communication (MTC) device, an Internet of Things (IoT) type communication device, or a combination thereof. The device may be provided as part of another device. The device may receive signals over an air or radio interface via appropriate equipment for reception and may transmit signals via appropriate equipment for transmitting radio signals. Communication may occur via multiple paths. Multiple antenna elements are provided to enable MIMO type communication devices 10 and 12. These are represented schematically by antenna arrays 14 and 15.

[0028] A communications device, such as the access point 12 or the user device 10, is provided with a data processing device comprising at least one processor and at least one memory. Figure 2 shows an example of a data processing device 50 comprising processors 52, 53 and one or more memories 51. Figure 2 further shows the connections between elements of the device and interfaces for connecting the data processing device to other components of the device.

[0029] The at least one memory may include at least one ROM and / or at least one RAM. The communication device may comprise other possible components for use in executing the software and hardware-assisted tasks it is designed to perform, including controlling access to and communicating with the access system and other communication devices, and implementing the features of device positioning described herein. At least one processor may be coupled to the at least one memory. The at least one processor may be configured to execute appropriate software code to implement one or more of the following aspects. The software code may be stored in at least one memory, for example, at least one ROM.

[0030] The following uses 5G terminology to describe specific aspects of measurements, configurations, and signaling for multipath or multi-beam wireless transmission-related operations. In frequency division duplex (FDD)-based systems, full uplink-downlink (UL-DL) channel reciprocity cannot be assumed due to the duplex distance between the uplink (UL) channel and the downlink (DL) channel. However, partial channel reciprocity can be assumed based on certain characteristics, such as angle of departure (AoD), angle of arrival (AoA), and propagation multipath delay. The UL-DL partial reciprocity property can be taken into account in signaling between communicating devices. For example, a gNB can predict a UL sounding reference signal (SRS) to obtain delay-related information, such as a frequency-domain (FD) component, which may be the same as the UE selection made via a DL channel state information reference signal (CSI-RS). The gNB can then use the selected FD component to further precode the beamformed CSI-RS resource, which already includes a spatial-domain (SD) beam. To convey multiple sets of FD components via CSI-RS, more CSI-RS ports need to be configured. This can result in a significant increase in DL CSI-RS resource consumption in proportion to the number of FD components. For example, if each SD beam contains the same number of FD components forming multiple CSI-RS ports, the consumed CSI-RS resources are multiplied by the increase in the number of precoded FD components. To control the total CSI-RS port and CSI-RS resource overhead, each SD beam may contain a different number of FD components according to UL sounding reference signal (SRS) measurements. The gNB can also indicate to the UE the mapping relationship between the CSI-RS ports and the SD-FD beam pairs.

[0031] It is recognized that MIMO CSI feedback operations can be enhanced by leveraging partial uplink / downlink reciprocity of certain channel statistics, such as angle and delay. It has already been suggested that enhancements to CSI measurement and reporting can be based on evaluation, and if necessary, specifying port selection codebook extensions where the information relates to angle and delay (e.g., based on existing 3GPP Rel. 15 / 16 Type II port selection) is expected to be based on SRS in gNBs by utilizing UL / DL reciprocity of angle and delay, with the remaining DL CSI reported by the UE. This primarily targets frequency division duplexing (FDD) in frequency range 1 (FR1) to achieve a better tradeoff between UE complexity, performance, and reporting overhead. For example, the Type II port selection (PS) codebook was enhanced in 3GPP Rel. 16 by introducing a frequency domain (FD) compression operation to the 3GPP Rel. 15 Type II port selection codebook. Such an extended Type II PS codebook is described, for example, in Section 5.2.2.2.6 of 3GPP TS38.214 v16.3.0 of September 2020.

[0032] FIG. 3 shows an example signaling flowchart between two communication devices, more specifically, between a UE 10 and a gNB 12. The UE transmits an SRS 30 to the gNB. The gNB can then determine a set of DL precoding vector pairs from the SRS (precoder pair set) by leveraging partial UL-DL reciprocity. The gNB precodes each CSI-RS port across transmit (tx) antennas and frequency units using one or more pairs of the precoder pair set. The precoded CSI-RS is then transmitted to the UE 10 via message 32. The UE then calculates one or more frequency-domain components of the configured set for each precoder pair and prepares a PMI report. The PMI includes the precoder pair selection and their corresponding combining coefficients. The PMI is signaled to the gNB via message 34. The gNB combines the PMI with the previously prepared precoder pair set to obtain a recovered precoder for use in data and DMRS communications 36.

[0033] 4 illustrates an example flowchart of an operation of a device in an access network, such as the access point 12 of FIG. 1, to achieve more efficient use of resources for signaling information related to reference signal port information for multi-channel communication. In the method, the device receives a sounding reference signal received from another communication device at 100. The device can then perform precoding of the reference signal port in the spatial and frequency domains at 102 by determining pairs of spatial and frequency domain components based on clustering of the frequency components. The clustering includes arranging the frequency domain components into clusters containing one or more frequency domain components, thereby enabling pairing of at least one of the spatial domain components with at least two clusters of frequency domain components. At 104, the precoding information can be signaled to the other communication device and later used to prepare a combination of the precoding with a port selection report received from the other device at 106.

[0034] The other devices can use the precoding information signaled to them in selecting a port as part of their CSI reporting in a reciprocity-based port selection operation. The combination achieves recovered precoding that can be used for data transmission to the other devices. More detailed examples of possible ways to use clustered precoding are provided below.

[0035] FIG. 5 shows a flowchart of an example of operation in a device, such as device 10 of FIG. 1, that receives precoding information. At 200, the device can transmit a sounding reference signal to a communication device and then receive precoding information from the communication device. In response to transmitting the sounding reference signal, the device can then receive precoding information from the communication device at 202, including information on reference signal ports in the spatial and frequency domains defined by pairs of spatial and clustered frequency domain components. The frequency domain components are arranged into clusters including one or more frequency domain components, such that at least one of the spatial domain components can be paired with at least two clusters of frequency domain components. Then, at 204, a port selection operation is performed based on the clustered information of the frequency domain components. After the selection, at 206, a report can be signaled based on the selection operation. Examples of calculations and measurements for preparing a report and using the report in other devices are provided below.

[0036] In the following, an extended codebook structure for signaling port selection channel state information (PS CSI) is described in more detail as an example. In a particular example, the extension can be realized in conjunction with a frequency-domain (FD) compression operation. The compression operation can be moved, at least partially or mostly, from the UE to the gNB. The extension is based on the assumption of partial reciprocity of cluster delays in the UL and DL channels, as well as flexibility in the use of frequency-domain components.

[0037] According to one example, a split FD compression operation is provided, in which, instead of all calculations being performed in the UE or the gNB, calculations for some FD components are retained in the UE 10 and some calculations are performed in the gNB 12. For example, the current port selection codebook specified in 3GPP Rel-16 specifies that all of these calculations be performed in the UE. Alternatively, the gNB may perform the majority of the calculations. The flexible solution described herein offers particular advantages because it allows for a reduction in the number of spatial domain (SD-FD) pairs used by the gNB to precode the CSI-RS ports, thereby reducing reference signal overhead. The accuracy of the precoder matrix recovered from the PMI reported by the UE and the gNB itself through reciprocity-based calculations may also be improved. This is because the UE can be configured to calculate one or more discrete Fourier transform (DFT) components within an uncertainty window for each SD component-FD component pair used to precode the CSI-RS ports. The UE can then report to the gNB the FD component that the gNB already knows based on the UL SRS, which the gNB can use to provide a more accurate prediction.

[0038] Instead of reporting only one FD component per precoded SD-FD pair, the gNB can configure the UE to calculate several FD components within a window corresponding to an identified cluster of FD components. The UE can then select which coefficients to report within the cluster.

[0039] The CSI reporting mechanism can be configured to operate the gNB to precode the CSI-RS port in both the spatial and frequency domains by spatial-domain component-frequency-domain component pairs, where each spatial-domain component is paired with one or more clusters of frequency-domain components, and a cluster can include one or more frequency-domain components.

[0040] One frequency-domain component of a cluster comprising two or more frequency-domain components can be selected by the gNB to precode the CSI-RS port together with the spatial-domain component. This can be the first frequency-domain component of the cluster. The UE can be configured, for example, to calculate the first three frequency-domain components for that CSI-RS port. For example, assuming there are N_3 = 13 frequency units and the cluster for beam 0 consists of DFT components 6, 7, and 8 (a total of 13 components), the gNB can configure the UE to precode the CSI-RS port using pair (beam 0, FD component 6) and calculate FD components 0, 1, and 2. This is equivalent to the gNB using three CSI-RS ports precoded by pair (beam 0, FD component 6), pair (beam 0, FD component 7), and pair (beam 0, FD component 8), and the UE being configured to calculate only FD component 0. Due to the properties of the DFT, the gNB can also use different FD components (e.g., x) for that cluster and also outside the cluster. In such a case, the UE is configured to calculate the FD components x1, x2, x3 such that (x+[x1, x2, x3]) mod N_3=[6, 7, 8].

[0041] The size of the clusters can be configured based on the uncertainty window. Clusters can be used flexibly. Different clusters may have the same or different numbers of FD components. Each SD beam may be paired with one or more clusters. Different SD beams may have the same or different numbers of clusters. The concept of "clustering" of frequency domain (FD) components can be understood to refer to clusters that may appear, for example, as restrictions on an FD codebook configured via a window of a given length.

[0042] A cluster may contain one or more adjacent FD components selected by the gNB, but only the first FD component in the cluster is precoded via the CSI-RS port for the SD beam.

[0043] The UE may be configured to calculate frequency-domain components from a restricted subset of a Discrete Fourier Transform (DFT) codebook for each space-frequency pair. A restriction on the FD components (Wf) that the UE needs to calculate may be provided. The UE then selects which combining coefficients (i.e., FD calculations) to report. The UE may report the values ​​of these coefficients and their locations, for example, in a bitmap of size P × M(DL), where P is the number of SD-FD pairs and M(DL) is the size of the FD subset. The UE may not need to report Wf if the size of this bitmap is small enough when M(DL) is small.

[0044] The configuration can be achieved, for example, by semi-static configuration such as Radio Resource Control (RRC) configuration, Medium Access Control - Control Element (MAC-CE), or dynamic signaling such as using the Downlink Control Information (DCI) field.

[0045] A restricted subset of DFT components can be provided that includes a window of continuous components or a set of non-contiguous components of the DFT codebook that includes at least one component 0. This is the first component in the DFT codebook, which is preferred because it provides an "average" measurement. The restricted subsets of DFT components can be the same or different sizes, or components for different groups of space-frequency pairs.

[0046] In response to receiving the CSI-RS port information from the gNB, the UE may report back a selection of non-zero coefficients from a sequence formed by the frequency-domain components calculated by the UE for all spatial-frequency components measured in the CSI-RS port, and an indicator indicating the space-frequency pair and UE-calculated frequency-domain component corresponding to the reported coefficient.

[0047] To further illustrate the principles disclosed herein, a more detailed example will be described with reference to Figures 6 and 7 and the 3GPP Rel-16 eType II codebook. According to the 3GPP 5G standard, layer l and all N t N transmit antennas and N precoding matrix indicator (PMI) subbands t ×N3 precoder matrix is

[0048]

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[0049] The third action in the UE is to r Extract layer representations from the receive antennas. This behavior is not specified, but is typically

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[0050] Extending FDD CSI reporting can be based on the assumption of cluster delay and angle reciprocity in FDD operation, allowing the gNB to predict the set of dominant SD-FD component pairs and use them to precode the CSI-RS ports. This allows some or even most of the SD and FD compression operations to be moved from the UE to the gNB.

[0051] The gNB can predict the UL channel by measuring the sounding reference signal (SRS) and determine P SD-FD pairs of vectors. These are

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[0052]

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[0053] Figure 6 shows an example of the decomposition of the UL channel in K = 2 spatial beams (Beam 0, Beam 1) and M(UL) = 6 FD components. The SD and FD components can be determined at the gNB based on SRS measurements. The FD components can be derived from a DFT codebook. The beam representation in the transform domain exposes the dominant cluster delay measured on that beam.

[0054] The double arrow denotes the uncertainty associated with the cluster delay prediction at the gNB, which may be caused, for example, by UL-DL delay reciprocity mismatch, UL channel prediction impairments, and aging effects due to the time elapsed between the UL channel prediction from the SRS and the DL channel prediction from the CSI-RS.

[0055] Furthermore, applying a DFT vector as a precoding weight across frequency units of a CSI-RS port beamformed by a particular spatial beam corresponds to a circular shift of the beam representation in the transform domain. This is shown on the left side of Figure 7, where an example is given for pairing of SD and FD components for the example case of Figure 6. More specifically, possible clustered pairings of SD-FD components at the gNB are presented. The clusters are defined by windows 20. The pair selection at the UE is then presented in the table on the right. In this case, the UE selects M for each SD-FD pair. (DL)= 2 FD components (0 and 1). Shaded cells correspond to selected SD-FD pairs for which non-zero coefficients can be reported.

[0056] In the example of Figure 7, the gNB forms clusters of FD components based on window 20. Note that the lowest row y4 refers to the FD component numbers in Figure 6, which show the FD component predictions by the gNB based on UL channel measurements. The corresponding prediction at the UE may be different, e.g., have a strong component in y5 for beam 1.

[0057] The size of the window can be specified to take into account the uncertainty. The gNB can pair each spatial beam with the first representative of a cluster. An example has three clusters for beam 0 and three clusters for beam 1. Overall, the gNB can perform KM (UL) = 12 possible combinations. For precoding of CSI-RS ports, each cluster can be moved to FD position 0 by precoding the port with the first FD component of the cluster. It should be appreciated that different numbers of clusters, FD components per cluster, and beams can be selected.

[0058] For simplicity, P CSI-RS P distinct SD-FD component pairs and P such that = P CSI-RS It can be assumed that there is a one-to-one mapping between this port and the

[0059] N PRB The P CSI-RS sequences used across the PRBs may be introduced into a bandwidth portion (BWP) configured for CSI reporting.

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[0060]

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[0061] The CSI-RS measurements on PRBk are

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[0062] As mentioned above, the number of SD-FD component pairs P is multiplied by the number of CSI-RS ports P such that there is a one-to-one mapping between SD-FD component pairs and ports. CSI-RS However, many-to-one mapping may also be employed to reduce the overhead of DL reference signals, in which case the above expression is modified to include the mapping and unmapping operations. Examples for many-to-one mapping operations are shown in Figures 8, 9, and 10 and will be described in more detail later.

[0063] The extended port selection codebook structure can be considered based on Equation (1),

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[0064] In this case, the UE only calculates the FD component 0, and the DFT operation does not need to be performed by the UE in the frequency domain. In this case, the precoder variant in the frequency domain can be determined at the gNB, so the PMI reported by the UE is the same for all subbands.

[0065] M greater than 1 (DL) The value of M is considered in the example of Figure 7. In this case, some of the precoder variations in frequency can be determined not only in the gNB but also in the UE. (DL)When M = 3, it can correspond to the PS codebook of 3GPP Rel-16 eType II, where there is no restriction on the FD codebook in the UE and FD precoding of the CSI-RS port in the gNB is not required. (DL) The SD-FD component pairing at the gNB and pair selection at the UE are shown for the case of M = 2. (DL) Setting M to a value greater than 1 may be beneficial to reduce the number of SD-FD pairs and therefore the number of CSI-RS ports required. For each FD component identified by the gNB, (DL) The accuracy of the reported PMI may also be improved by allowing the UE to select the best delay (i.e., FD component) within the uncertainty window of the PMI.

[0066] Parameter M (DL) When ξ > 1, the PMI reported by the UE may be different for different subbands. The UE can contribute by determining frequency domain variants of the precoder. The gNB receives these in the PMI report and can then combine the variants with the precoder variant in frequency calculated by the gNB based on the partial reciprocity assumption.

[0067] SD-FD pair is PM (DL) The pair can be selected by the UE from the possible pairs

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[0068] To determine the linear combination coefficients for each SD-FD pair and receive antenna, the UE uses r=0,…,N r P×N3 matrix for -1

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[0069] At this stage, the UE can determine the strongest spatial layer from a linear combination of the receive antennas. This operation is performed by performing a single singular value decomposition (SVD) on the P × N r matrix of

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[0070] In the 3GPP Rel-16 eType II codebook (CB), this layer extraction is typically performed per subband before applying the FD components. However, when FD precoding is applied to the CSI-RS port, the phase relationship between subbands cannot be easily preserved if the eigenvectors are extracted before the summation in (10). The eigenvectors are determined within each subband with phase uncertainty, which can be adjusted, for example, to reduce the phase jump between subbands before FD compression. However, when FD precoding is applied at the gNB, these phase adjustments at the UE would change the phase relationship between subbands, effectively changing the effect of the precoder weights applied at the frequency at the gNB.

[0071] After layer processing, the UE receives the

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[0072] Regarding the existence of restrictions on SD-FD pair selection in 3GPP Rel-15 / 16, port selection is constrained to a group of L contiguous ports, where the port groups are separated by d ≤ L ports, and the same port is used for both polarizations. Conversely, 3GPP Rel-17 allows unconstrained or free selection, where selection is extended to a set of P SD-FD pairs, which is the number of ports P. CSI-RS There is a greater possibility.

[0073] Considering the PMI recovery and reciprocity precoder representation, M (DL)Note that if k = 1, the UE reports only FD component 0 from the selected SD-FD pair. 0,l ,k 1,l ,…,k L-1,l Let be the index of the L selected SD-FD pairs for layer l, and k j,l ∈{0,…,P-1}.

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[0075] M (DL) In the general case shown in Figure 7 where ≥ 1,

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[0076] It should be noted that although the above examples are described with reference to user equipment (UE) and gNB, similar principles can be applied to any device capable of multi-beam communication.

[0077] According to a possibility, multiple precoding pairs are mapped within the same CSI-RS port. This is another possibility to reduce the number of ports that need to be reported. Here, by exploiting the fact that each frequency unit consists of multiple PRBs precoded with the same frequency component weight, it is possible to use a code division multiplexing (CDM) code for this multiplexing of pairs into a single port. P SD-FD precoding pairs and P CSI-RS An example of a many-to-one mapping operation between ≦P CSI-RS ports is shown in Figure 8, which shows a functional block diagram of operations performed at the gNB. The reverse one-to-many unmapping operation is performed at the UE, as shown in the functional block diagram of UE operations in Figure 9. Figure 10 shows an example of this many-to-one mapping.

[0078] In the example, the bandwidth portion (BWP) configured for CSI reporting is divided into N3 frequency units, each of which is

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[0079] A device for multi-channel communication may comprise means for precoding a reference signal port in the spatial and frequency domains by determining pairs of spatial and frequency domain components based on a sounding reference signal received from the communication device, wherein the frequency domain components are arranged in clusters comprising one or more frequency domain components, enabling pairing of at least one of the spatial domain components with at least two clusters of frequency domain components; means for transmitting information of the precoding to other communication devices; and means for combining the precoding with reports of precoding received in responses from the other communication devices.

[0080] Another device for multi-channel communication may comprise means for transmitting a sounding reference signal to a communication device; means for receiving, in a response from the communication device, precoding information including information of reference signal ports in the spatial domain and the frequency domain defined by pairs of spatial domain components and frequency domain components, wherein the frequency domain components are arranged in clusters comprising one or more frequency domain components, enabling pairing of at least one of the spatial domain components with at least two clusters of frequency domain components; means for performing a port selection operation based on the clustered information of the frequency domain components; and means for preparing and transmitting a report based on the selection operation.

[0081] Although the above describes exemplary embodiments, it should also be noted that there are several variations and modifications that can be made to the disclosed solutions without departing from the scope of the present invention. Different features from different embodiments may be combined.

[0082] Accordingly, embodiments may vary within the scope of the appended claims. In general, some embodiments may be implemented in hardware or special purpose circuits, software, logic, or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software that may be executed by a controller, microprocessor, or other computing device, but the embodiments are not limited thereto. While various embodiments may be illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is well understood that these blocks, apparatus, systems, techniques, or methods described herein may be implemented in, by way of non-limiting example, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing device, or some combination thereof.

[0083] The embodiments may be implemented by computer software stored in a memory and executable by at least one data processor of the participating entities, or by hardware, or by a combination of software and hardware. Furthermore, in this regard, it should be noted that any of the above procedures may represent program steps, or interconnected logic circuits, blocks, and functions, or a combination of program steps and logic circuits, blocks, and functions. Software may be stored on physical media such as memory chips, or memory blocks implemented within a processor, magnetic media such as hard disks or floppy disks, and optical media such as DVDs and their data variants, CDs.

[0084] The memory may be any type of memory suitable for the local technology environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed and removable memory, etc. The data processor may be any type of processor suitable for the local technology environment and may include, by way of non-limiting examples, one or more of a general purpose computer, a special purpose computer, a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a gate-level circuit, and a processor based on a multi-core processor architecture.

[0085] Alternatively or additionally, some embodiments may be implemented using circuitry configured to perform one or more of the functions and / or method steps described above, which may be provided within a network entity and / or a communication device and / or a server and / or a device.

[0086] The term "circuit" as used in this application means (a) hardware-only circuit implementations (e.g., analog and / or digital-only implementations); (b) (i) combinations of analog and / or digital hardware circuitry with software / firmware; and (ii) any portion of hardware processors, software, and memory with software (including digital signal processors) that operate together to cause a communications device and / or device and / or server and / or network entity to perform the various functions described above; A combination of hardware circuits and software, such as (c) hardware circuitry and / or a processor, such as a microprocessor or portion of a microprocessor, that requires software (e.g., firmware) for operation, but the software may be absent when not required for operation; It can refer to one or more or all of the following:

[0087] This definition of circuit applies to all uses of the term within this application, including any claims. As a further example, the term circuit as used herein also covers merely a hardware circuit or processor(s) or portion of a hardware circuit or processor and its(their) accompanying software and / or firmware implementations. The term circuit also covers, for example, integrated devices.

[0088] It should be noted that while the embodiments are described with respect to particular architectures, similar principles can be applied to other systems. Thus, while particular embodiments are described by way of example with reference to particular example architectures for wireless networks, technologies, standards, and protocols, the features described herein may be applied to any other suitable forms of systems, architectures, and devices other than those specifically illustrated and described in the above examples. It should also be noted that different combinations of different embodiments are possible. While the above describes example embodiments, it should also be noted herein that there are several variations and modifications that can be made to the disclosed solutions without departing from the spirit and scope of the present invention.

Claims

1. 1. A method for multi-channel communication, comprising: precoding a reference signal port in the spatial and frequency domains by determining pairs of spatial and frequency domain components based on a sounding reference signal received from a communication device, the frequency domain components are arranged in clusters comprising one or more frequency domain components; enabling pairing of at least one of the spatial domain components with at least two clusters of frequency domain components; Steps and transmitting information of the precoding to other communication devices; combining said precoding with reports of precoding received in responses from said other communication devices; A method comprising:

2. 10. The method of claim 1, wherein the report received from the other communication device includes a precoder matrix indication, and wherein the combining step includes generating a recovered precoding for use in communicating with the other communication device.

3. 3. The method of claim 1, further comprising: performing a portion of a frequency domain compression operation before transmitting the precoding information to the communication device, the communication device being configured to perform another portion of the frequency domain compression operation.

4. The method of claim 3 , comprising performing a majority of the frequency domain compression operation at the device performing the precoding other than the communication device.

5. transmitting the precoding information to the communication device based on the precoding for use in selecting a channel state information reference signal port or a precoding pair associated with the port; receiving a precoding matrix indicator report based on a channel state information reference signal port or precoding pair selected by the communication device; The method according to any one of claims 1 to 4, comprising:

6. 6. The method of claim 1, comprising: configuring the communication device to participate in the calculation of frequency domain components from a restricted subset of a discrete Fourier transform codebook for pairs of spatial domain components and frequency domain components; and receiving, in response to a channel state information report request, from the communication device, information of a selection of non-zero coefficients from a sequence formed by the frequency domain components calculated by the communication device for all space-frequency components measured at the reference signal port, and an indicator indicating the space-frequency pairs and the frequency domain components calculated by the communication device and corresponding to the reported non-zero coefficients.

7. 7. The method of claim 1, comprising the step of providing a restricted subset of Discrete Fourier Transform components, said subset comprising a window of continuous components or a set of non-contiguous components of a Discrete Fourier Transform codebook comprising at least component 0, and / or said restricted subset of DFT components may be of the same or different size, or components for different groups of space-frequency pairs.

8. 8. The method of claim 1, comprising assuming partial reciprocity of cluster delays in a channel between the communication devices and / or determining the size of the cluster based at least in part on uncertainty in the predicted cluster delays.

9. 9. The method of claim 1, comprising the steps of: calculating precoder weights; and combining the calculated precoder weights with precoder matrix indicator information received from the communication device to recover the precoding.

10. 1. A method for multi-channel communication, comprising: transmitting a sounding reference signal to a communication device; receiving, in a response from the communication device, precoding information including information of reference signal ports in the spatial and frequency domains defined by pairs of spatial and frequency domain components, wherein the frequency domain components are arranged in clusters comprising one or more frequency domain components, allowing pairing of at least one of the spatial domain components with at least two clusters of the frequency domain components; performing a port selection operation based on the clustered information of frequency domain components; preparing and transmitting a report based on said selection; A method comprising:

11. The method of claim 10 , wherein the report includes a precoder matrix indication for use in generating a recovered precoding by the other communication device.

12. 12. The method of claim 10 or 11, comprising the step of performing a frequency domain compression operation after receiving the information of the precoding from the communication device, wherein another frequency domain compression operation has been applied to the received information of the precoding by the communication device.

13. 13. The method of claim 12, comprising performing a lesser portion of the combined frequency domain compression operation at the device that receives the precoding information other than the communication device that performs the precoding.

14. selecting a channel state information reference signal port or a precoding pair associated with said port; preparing and transmitting a precoding matrix indicator report or a precoding pair based on the selected channel state information reference signal port; 14. The method of any one of claims 10 to 13, comprising:

15. participating in the computation of frequency domain components from a restricted subset of a discrete Fourier transform codebook for pairs of spatial and frequency domain components; signaling information of a selection of a non-zero coefficient from a sequence formed by frequency domain components calculated for all space-frequency components measured at the reference signal port, and an indicator indicating the space-frequency pair and the frequency domain component corresponding to the reported non-zero coefficient; 15. The method of any one of claims 10 to 14, comprising:

16. 16. The method of claim 10, comprising receiving a restricted subset of discrete Fourier transform components, the subset comprising a window of continuous components or a set of non-contiguous components of a discrete Fourier transform codebook that includes at least component 0.

17. 1. An apparatus comprising at least one processor and at least one memory containing computer program code, the at least one memory and the computer program code being operable by the at least one processor to perform at least: precoding a reference signal port in the spatial and frequency domains by determining pairs of spatial and frequency domain components based on a sounding reference signal received from a communication device, wherein the frequency domain components are arranged in clusters comprising one or more frequency domain components, allowing pairing of at least one of the spatial domain components with at least two clusters of frequency domain components; transmitting the precoding information to other communication devices; combining the precoding with reports of precoding received in responses from the other communication devices; An apparatus configured to cause the apparatus to perform the following:

18. 20. The apparatus of claim 17, wherein the report received from the other communication device includes a precoder matrix indication, and the apparatus is configured to generate a recovered precoding based on the precoding and the precoder matrix indication for use in communicating with the other communication device.

19. 19. The apparatus of claim 17 or 18, wherein the apparatus participates in the calculation of frequency domain components from a restricted subset of a discrete Fourier transform codebook for pairs of spatial domain components and frequency domain components, and is configured to receive, in response to a channel state information report request, from the communications device, information of a selection of non-zero coefficients from a sequence formed by frequency domain components calculated by the communications device for all space-frequency components measured at the reference signal port, and an indicator indicating the frequency domain components calculated by the communications device that correspond to the space-frequency pairs and the reported non-zero coefficients.

20. 20. The apparatus of claim 17, configured to provide a restricted subset of Discrete Fourier Transform components, said subset comprising a window of continuous components or a set of non-contiguous components of a Discrete Fourier Transform codebook including at least component 0, and / or said restricted subset of DFT components may be of the same or different size or components for different groups of space-frequency pairs.

21. performing a portion of a frequency domain compression operation before transmitting the precoding information to the communication device, the communication device being configured to perform another portion of the frequency domain compression operation; operating under an assumption of partial reciprocity of cluster delays in a channel between said communication devices; determining the size of the cluster based at least in part on the uncertainty of a predicted cluster delay; or calculating precoder weights and combining the calculated precoder weights with precoder matrix indicator information received from the communication device to recover the precoding; 21. The apparatus of any one of claims 17 to 20, configured to perform at least one of the following:

22. 1. An apparatus comprising at least one processor and at least one memory containing computer program code, the at least one memory and the computer program code being operable by the at least one processor to perform at least: transmitting a sounding reference signal to a communication device; receiving, from the communication device, precoding information including information of reference signal ports in the spatial and frequency domains defined by pairs of spatial and frequency domain components, the frequency domain components being arranged in clusters comprising one or more frequency domain components, allowing pairing of at least one of the spatial domain components with at least two clusters of the frequency domain components; performing a port selection operation based on the clustered information of the frequency domain components; preparing and transmitting a report based on said selection; An apparatus configured to cause the apparatus to perform the following:

23. 23. The apparatus of claim 22, wherein the report includes a precoder matrix indication for use in generating a recovered precoding by the other communication device.

24. 24. The apparatus of claim 22 or 23, configured to perform a frequency domain compression operation after receiving the information of the precoding from the communication device, wherein another frequency domain compression operation has been applied to the received information of the precoding by the communication device.

25. 25. The apparatus of claim 24, configured to perform a smaller portion of a combined frequency domain compression operation than the portion performed in the communications device that performs the precoding.

26. Selecting a channel state information reference signal port or a precoding pair associated with the port based on the clustered information of precoding; and preparing and transmitting a precoding matrix indicator report or a precoding pair based on the selected channel state information reference signal port. The device according to any one of claims 22 to 25, configured so as to

27. participate in the computation of frequency domain components from a restricted subset of a discrete Fourier transform codebook for pairs of spatial and frequency domain components; signaling information of a selection of a non-zero coefficient from a sequence formed by frequency domain components calculated for all space-frequency components measured at the reference signal port, and an indicator indicating the space-frequency pair and the frequency domain component corresponding to the reported non-zero coefficient; The device according to any one of claims 22 to 26, configured so as to

28. 28. An apparatus according to any one of claims 22 to 27, configured to receive a restricted subset of discrete Fourier transform components, said subset comprising a window of continuous components or a set of non-contiguous components of a discrete Fourier transform codebook including at least component 0.

29. 1. A non-transitory computer-readable medium containing program code for causing a processor to execute instructions for a method in a communications device, the method comprising: precoding a reference signal port in the spatial and frequency domains by determining pairs of spatial and frequency domain components based on a sounding reference signal received from a communication device, wherein the frequency domain components are arranged in clusters comprising one or more frequency domain components, allowing pairing of at least one of the spatial domain components with at least two clusters of the frequency domain components; transmitting information of the precoding to other communication devices; combining said precoding with reports of precoding received in responses from said other communication devices; 1. A non-transitory computer-readable medium comprising:

30. 1. A non-transitory computer-readable medium containing program code for causing a processor to execute instructions for a method in a communications device, the method comprising: transmitting a sounding reference signal to a communication device; receiving, in a response from the communication device, precoding information including information of reference signal ports in the spatial and frequency domains defined by pairs of spatial and frequency domain components, wherein the frequency domain components are arranged in clusters comprising one or more frequency domain components, allowing pairing of at least one of the spatial domain components with at least two clusters of the frequency domain components; performing a port selection operation based on the clustered information of the frequency domain components; preparing and transmitting a report based on said selection; 1. A non-transitory computer-readable medium comprising:

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