Port Information Signaling

Abstract

A method and apparatus for multi-channel communication are disclosed, which includes: 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 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 frequency domain components; transmitting information of the precoding to other communication devices; and combining the precoding with reports of the precoding received in responses from the other communication devices.

Description

Technical Field

[0001] The present disclosure relates to a method, an apparatus, and a computer program product for signaling port information between communication devices.

Background Art

[0002] A communication session can be established between two or more communication devices such as a user device or terminal device, a base station / access point, 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 provided with appropriate signal transmitting and receiving devices in order to enable communication, for example, to enable other devices to access the communication system. A communication session may include, for example, the communication of data for carrying communications such as voice, video, email, text messages, multimedia, and / or content data. Non-limiting examples of the services provided include two-way or multi-way calls, data communication, multimedia services, and access to data network systems such as the Internet.

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

[0004] A communication device is provided with appropriate signal transmitting and receiving devices to enable communication, for example, to enable access to a communication network or direct communication with other users. A user's communication device can access a carrier wave provided by a station, such as a base station, in a wireless access network and transmit and / or receive communication on the carrier wave. The feature of a modem system is the function of multipath operation. A communication device can communicate via multiple paths. Multipath communication may be realized by a configuration known as multiple-input / multiple-output (MIMO).

[0005] Communication systems and related devices typically operate according to given standards and specifications that permit what various entities associated with the system are allowed to do and how it should be realized. Usually, the communication protocols and / or parameters to be used for connections are also defined. An example of a communication system is UTRAN (3G wireless). Other examples of communication systems are the Long-Term Evolution (LTE) of Universal Mobile Telecommunications System (UMTS) radio access technology and the so-called fifth generation (5G) or New Radio (NR) networks. 5G is standardized by the Third Generation Partnership Project (3GPP). Successive versions of the standards are known as Releases (Rel). In the 3GPP's 5G NR standardization work, further expansion of MIMO channel state information (CSI) feedback is underway by leveraging the partial uplink / downlink (UL / DL) reciprocity of specific channel statistical data. SUMMARY OF THE INVENTION

[0006] According to one aspect, a method for multi-channel communication is provided. The method includes precoding reference signal ports in the spatial domain and the frequency domain by determining a pair of a 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 within a cluster including one or more frequency domain components, and the precoding includes at least one pairing of at least one of the spatial domain components with at least one cluster of the frequency domain components; transmitting precoding information to the communication device; and combining a precoding report received in a response from the communication device with the precoding.

[0007] According to one aspect, a method for multi-channel communication is provided. The method includes 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 a pair of a spatial domain component and a frequency domain component, where the frequency domain component is arranged within a cluster including one or more frequency domain components, and the precoding includes at least one pairing of at least one of the spatial domain components with at least one cluster 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 including computer program code, the at least one memory and the computer program code being configured to cause the at least one processor to at least precode reference signal ports in a spatial domain and a frequency domain by determining a pair of a spatial domain component and a frequency domain component based on a sounding reference signal received from a communication device, wherein the frequency domain component is arranged within a cluster including one or more frequency domain components, and the precoding includes at least one pairing of at least one of the spatial domain components with at least one of the clusters of the frequency domain components; transmit precoding information to the communication device; and combine a report of the precoding received in a response from the communication device with the precoding.

[0009] According to one aspect, an apparatus is provided that includes at least one processor and at least one memory including computer program code, the at least one memory and the computer program code being configured to cause the at least one processor to at least transmit a sounding reference signal to a communication device; receive precoding information from the communication device, the precoding information including information on reference signal ports in a spatial domain and a frequency domain defined by a pair of a spatial domain component and a frequency domain component, wherein the frequency domain component is arranged within a cluster including one or more frequency domain components, and the precoding includes at least one pairing of at least one of the spatial domain components with at least one of the 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 selected communication device includes a precoder matrix indicator. Combining includes generating a restored precoding for use in communication.

[0011] A portion of the frequency domain compression operation can be performed before transmitting the precoding information, and the communication device that receives the precoding is configured to perform another portion of the frequency domain compression operation. Most of the frequency domain compression operation may be performed at the device that performs the precoding rather than at the device that receives the precoding. A smaller portion of the combined frequency domain compression operation may be performed at the device that receives the precoding information.

[0012] Transmitting the precoding information may include transmitting a channel state information reference signal based on the precoding for use in the selection of a channel state information reference signal port or a precoding pair associated with the port. Then, the selection of the channel state information reference signal port or the precoding pair associated with the port can be performed. The precoder matrix indicator report may be transmitted within the response, and the report is based on the channel state information reference signal port or precoding pair selected by the communication device that receives the channel state information reference signal.

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

[0014] There may be provided a restricted subset of discrete Fourier transform components. The subset can include a window of consecutive components or a set of non-consecutive components of a discrete Fourier transform codebook that includes at least one component 0. The restricted subset of DFT components can be of the same or different sizes, or can be components for different groups of spatio-frequency pairs.

[0015] Partial reciprocity of cluster delays in the channel between communication 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] Pre-coder weights may be calculated. The calculated pre-coder weights may be combined with pre-coder matrix indicator information received from a communication device selected to perform pre-coding.

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

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

[0020] Next, some aspects are described in further detail by way of example with reference to the following examples and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021]

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Embodiments for Carrying Out the Invention

[0022] The following description gives an illustration of some possibilities for practicing the present invention. Although this specification may refer to "a", "one", or "some" examples or embodiments in several places in the text, this does not necessarily mean that each reference is made 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 also be combined to provide other embodiments.

[0023] A wireless communication system provides wireless communication to devices connected therein. Usually, an access point such as a base station is provided to enable communication. Hereinafter, various scenarios are described using a 3GPP 5G wireless access architecture with MIMO function as an example of an access architecture. However, the embodiments are not necessarily limited to architectures and the like. Some examples of options for a suitable system are Universal Mobile Telecommunication System (UMTS) wireless 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 (registered trademark), Personal Communication Service (PCS), ZigBee (registered trademark), Wideband Code Division Multiple Access (WCDMA), Ultra Wideband (UWB) technology-based systems, sensor networks, Mobile Ad Hoc Networks (MANET), Cellular Internet of Things (IoT) RAN and Internet Protocol Multimedia Subsystem (IMS), or any combination thereof and further developments.

[0024] FIG. 1 shows a wireless system 1 including a wireless access system 2. The wireless access system can include one or more access points, or base stations 12. The base station can provide one or more cells. The access point can include any node capable of transmitting / receiving a wireless signal (for example, a 3GPP 5G base station such as a TRP, gNB, eNB, a user device such as a UE, etc.).

[0025] The communication device 10 is located within the service area of the wireless access system 2, and thus, the device 10 can listen to the access point 12. The communication 11 from the device 10 to the access point 12 is usually called the uplink (UL). The communication 13 from the access point 12 to the device 10 is usually called the downlink (DL). In the example, the downlink is schematically shown to comprise up to four beams per polarization within the spatial domain (SD).

[0026] Note that the wide area communication system is shown only as the cloud 1 and can comprise several elements not shown for clarity. For example, a 5G-based system may be provided by 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 (AF), and one or more data networks (DN). The 5G-RAN may comprise one or more g-node Bs (gNB), or one or more g-node B (gNB) distributed unit functions connected to one or more g-node B (gNB) central unit functions. The 5GC may also comprise entities such as a network slice selection function (NSSF), a network exposure function, a network repository function (NRF), a policy control function (PCF), an integrated 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] Device 10 can be any suitable communication device adapted for wireless communication. The wireless communication device may be provided by any device capable of transmitting and receiving wireless signals. Non-limiting examples include a mobile station (MS) (such as a mobile device known as a mobile phone or a "smartphone"), a computer equipped with a wireless interface card or other wireless interface equipment (such as a USB dongle), a personal digital assistant (PDA) or tablet equipped with a wireless communication function, 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 can receive signals on an air interface or a wireless interface via a suitable receiving device and can transmit signals via a suitable device for transmitting wireless signals. Communication can occur via multiple paths. To enable MIMO type communication devices 10 and 12, multi-antenna elements are provided. These are schematically represented by antenna arrays 14 and 15.

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

[0029] 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 the execution of tasks assisted by software and hardware designed to perform, including control of access to and communication with access systems and other communication devices, and implementation of the features described herein for device positioning. At least one processor may be coupled to at least one memory. 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] In the following, specific aspects of measurements, configurations, and signaling for multipath, or operations related to multi-beam wireless transmission, are described using 5G terminology. In a frequency division duplexing (FDD)-based system, the reciprocity of the full uplink-downlink (UL-DL) channel 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 specific characteristics such as the angle of departure (AoD), angle of arrival (AoA), and delay of the propagation multipath. The partial reciprocity characteristics of UL-DL can be taken into account in the signaling between communication devices. For example, the gNB can predict the UL sounding reference signal (SRS) to obtain delay-related information such as frequency domain (FD) components, which can be the same as the UE selection performed via the DL channel state information reference signal (CSI-RS). The gNB can then further precode the beamformed CSI-RS resource that already includes the spatial domain (SD) beam using the selected FD components. To transmit multiple sets of FD components via the CSI-RS, more CSI-RS ports need to be configured. This can lead to a significant increase in DL CSI-RS resource consumption proportional to the number of FD components. For example, if each SD beam contains the same number of FD components that form multiple CSI-RS ports, the consumed CSI-RS resources are multiplied by the increase in the precoded FD components. To control the total number of CSI-RS ports and the overhead of CSI-RS resources, each SD beam may contain a different number of FD components according to the measurement of the UL sounding reference signal (SRS). The gNB can also indicate to the UE the mapping relationship of the CSI-RS ports with the pair of SD-FD beams.

[0031] It is recognized that it is possible to extend the MIMO CSI feedback operation by leveraging the partial uplink / downlink reciprocity of specific channel statistical data such as angle and delay. It has already been suggested that the extension to CSI measurement and reporting can be based on an evaluation, and if necessary, specifying a port selection codebook extension when the information relates to angle and delay (e.g., based on the existing 3GPP Rel.15 / 16 Type II port selection) is expected to be based on SRS at the gNB by utilizing the UL / DL reciprocity of angle and delay, and the remaining DL CSI is reported by the UE. This is mainly targeted at frequency division duplexing (FDD) in frequency range 1 (FR1) in order to achieve a better trade-off among UE complexity, performance, and reporting overhead. For example, the Type II port selection (PS) codebook was extended in 3GPP Rel-16 by introducing a frequency domain (FD) compression operation to the 3GPP Rel.15 Type II port selection codebook. The Type II PS codebook extended in such a way is described, for example, in section 5.2.2.2.6 of 3GPP TS38.214 v16.3.0 in September 2020.

[0032] Figure 3 shows a signaling flowchart by way of example between two communication devices, more specifically between UE10 and gNB12. The UE transmits SRS30 to the gNB. Then, the gNB can 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 the transmit (tx) antennas and frequency units using one or more pairs of the precoder pair set. Then, the precoded CSI-RS is transmitted to UE10 by message 32. Thereafter, the UE calculates one or more frequency domain components of a set configured for each precoder pair and prepares a PMI report. The PMI includes the selection of precoder pairs and their corresponding coupling coefficients. The PMI is signaled to the gNB by message 34. The gNB combines the previously prepared precoder pair set and the PMI to obtain a restored precoder for use in data and DMRS communication 36.

[0033] FIG. 4 shows an example flowchart of the operation at a device provided in an access network, such as access point 12 in FIG. 1, for realizing more efficient use of resources for signaling information regarding reference signal port information for multi-channel communication. In the method, at 100, the device receives a sounding reference signal received from another communication device. Next, at 102, the device can perform precoding of the reference signal ports in the spatial domain and the frequency domain by determining a pair of a spatial domain component and a frequency domain component based on clustering of frequency components. The clustering includes arranging frequency domain components within a cluster including one or more frequency domain components, such that at least one pairing of a spatial domain component with at least two clusters of frequency domain components becomes possible. At 104, the precoding information can be signaled to another communication device and can later be used at 106 to prepare for the combination of the precoding with a port selection report received from another device.

[0034] Another device can use the precoding information signaled to it in the selection of ports as part of the CSI report in the reciprocity-based port selection operation. The combination realizes the restored precoding that can be used for data transmission to another device. A more detailed example of a possible method for using the clustered precoding is given below.

[0035] FIG. 5 shows an example flowchart of operations in a device that receives precoding information, e.g., device 10 of FIG. 1. 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 the transmission of the sounding reference signal, the device can then receive, at 202, from the communication device, precoding information including information on reference signal ports in a spatial domain and a frequency domain defined by a pair of a spatial domain component and a clustered frequency domain component. The frequency domain component is arranged within a cluster 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 the 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 for the preparation of the report and calculations and measurements for the use of the report in other devices are given below.

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

[0037] According to one example, a split FD compression operation is provided, where instead of all calculations being performed at the UE or gNB, some of the calculations for the FD components are held at the UE 10 and some are performed at the gNB 12. For example, the current port selection codebook specified in 3GPP Rel-16 stipulates that all of these calculations are performed at the UE. Potentially, the gNB performs most of the calculations. The flexible solution described herein enables reducing the number of spatial domain (SD-FD) pairs used by the gNB to precode CSI-RS ports, thereby reducing the overhead of the reference signals, presenting a particular advantage. The accuracy of the precoder matrix recovered from the PMI reported by the UE and gNB's own 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 the uncertainty window for each SD component - FD component pair used to precode CSI-RS ports. The UE can then report to the gNB the FD components that the gNB already knows based on the UL SRS, and the gNB can use this to provide a more accurate prediction.

[0038] Instead of reporting just one FD component per precoded SD-FD pair, the gNB can configure the UE to calculate some of the FD components within a window corresponding to the identified clusters 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 such that the gNB precodes CSI-RS ports in both the spatial domain and the frequency domain with spatial domain component - frequency domain component pairs, where each spatial domain component is paired with one or more clusters of frequency domain components. 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 to calculate, for example, the first three frequency domain components for its CSI-RS port. For example, assuming that there are N_3 = 13 frequency units and the cluster for beam 0 is composed of DFT components 6, 7, 8 (a total of 13 components exist), the gNB can precode the CSI-RS port using the pair (beam 0, FD component 6) and configure the UE to calculate FD components 0, 1, 2. This is equivalent to the gNB using three CSI-RS ports precoded by the pairs (beam 0, FD component 6), (beam 0, FD component 7), (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) within and outside the cluster. In such a case, the UE is configured to calculate FD components x1, x2, x3 such that (x + [x1, x2, x3]) mod N_3 = [6, 7, 8].

[0041] The size of the cluster can be configured based on the uncertainty window. The cluster 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 a limitation of an FD codebook configured through a window of a given length.

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

[0043] The UE can be configured to calculate frequency domain components from a restricted subset of a discrete Fourier transform (DFT) codebook for each spatial-frequency pair. There may be a limit on the FD components (Wf) that the UE needs to calculate. The UE then selects which combination coefficients (i.e., FD calculations) should be reported. The UE can report the values and their positions of these coefficients, for example, within 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 realized by, for example, radio resource control (RRC) configuration, semi-static configuration such as media access control-control element (MAC-CE), or dynamic signaling such as the use of a downlink control information (DCI) field.

[0045] A restricted subset of DFT components can be provided that includes a window of consecutive components of a DFT codebook containing at least one component 0 or a set of non-consecutive components. This is the first component of the DFT codebook and is preferred as it provides an "average" measurement value. The restricted subset of DFT components can be of the same or different sizes or components for different groups of spatial-frequency pairs.

[0046] In response to receiving CSI-RS port information from the gNB, the UE can return a report of the selection of non-zero coefficients from the sequence formed by the frequency domain components calculated by the UE for all spatial components-frequency components measured within the CSI-RS port, and an indicator showing the spatial-frequency pairs corresponding to the reported coefficients and the frequency domain components calculated by the UE.

[0047] To further illustrate the principles disclosed herein, more detailed examples are described with reference to FIGS. 6 and 7 and the 3GPP Rel-16 eType II codebook. According to the 5G standard of 3GPP, layer l and all N t transmitting antennas and N 3 precoding matrix indicator (PMI) subbands for N t ×N 3 precoder matrices can be represented as

[0048]

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[0049] The third operation at the UE is to extract the layer representation from N r receiving antennas. Although this operation is not specified, usually, for t = 0,..., N 3 - 1,

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[0050] Extending the FDD CSI report can be based on the assumptions of the delay and angle reciprocity of the clusters in the FDD operation. As a result, the gNB can predict the set of dominant SD-FD component pairs and use them to precode the CSI-RS ports. This makes it possible to move some or even most of the compression operations of SD and FD 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 components and FD components can be determined at the gNB based on SRS measurements. The FD components can be derived from the DFT codebook. The beam representation in the transform domain discloses the dominant cluster delay measured on that beam.

[0054] Both arrows denote the uncertainty associated with the cluster delay prediction at the gNB. This uncertainty may be caused, for example, by a mismatch in UL-DL delay reciprocity, an obstacle to UL channel prediction, and an aging effect resulting from the time elapsed between the UL channel prediction from SRS and the DL channel prediction from CSI-RS.

[0055] Furthermore, applying the DFT vector as the precoding weight over the frequency units of the CSI-RS ports beamformed by a specific spatial beam corresponds to a cyclic 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 the pairing of the SD and FD components in the case of the example of Figure 6. More specifically, a possible clustered pairing of the SD-FD components at the gNB is presented. The cluster is defined by window 20. Then, the pair selection at the UE is presented in the table on the right side. In this case, the UE has M for each SD-FD pair(DL) It is configured to calculate two FD components (0 and 1). The shaded cells correspond to the selected SD-FD pairs and can report non-zero coefficients for them.

[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 showing the FD component prediction by the gNB based on UL channel measurements. The corresponding prediction at the UE may be different, for example, it may have a strong component at y5 for beam 1.

[0057] The size of the window can be defined taking into account the uncertainty. The gNB can pair each spatial beam with the first representative component of the cluster. An example has three clusters for beam 0 and three clusters for beam 1. Overall, the gNB selects 6 out of KM (UL) = 12 possible combinations. For precoding of the CSI-RS ports, each cluster can be moved to FD position 0 by precoding the port having the first FD component of the cluster. Understand that different numbers of clusters, FD components per cluster, and beams can be selected.

[0058] For simplicity, assume that there is a one-to-one mapping between P CSI-RS separate SD-FD component pairs such that P = P and P CSI-RS ports.

[0059] N PRB The P CSI-RS sequences used over N PRBs can be introduced into a bandwidth part (BWP) configured for CSI reporting.

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[0060]

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[0061] The CSI-RS measurements on PRBk are given by the matrix

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[0062] As described above, assuming that the number P of SD-FD component pairs is equal to the number P of CSI-RS ports so that there is a one-to-one mapping between the SD-FD component pairs and the ports. CSI-RS However, in some cases, a many-to-one mapping may also be adopted to reduce the overhead of the DL reference signal. In that case, the above expression is modified to include the operations of mapping and demapping. Examples of the many-to-one mapping operation are shown in FIGS. 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 FD component 0, and the DFT operation does not need to be performed by the UE in the frequency domain. In this case, since the deformed form of the precoder in the frequency domain can be determined at the gNB, the PMI reported by the UE is the same for all subbands.

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

[0066] The parameter M (DL) When > 1, the PMI reported by the UE may be different for different sub-bands. The UE can contribute to the operation by determining the deformation form of the precoder in the frequency domain. The gNB receives these in the PMI report and can then combine the deformation forms with the deformation forms of the precoder at the frequencies calculated by the gNB based on the assumption of partial reciprocity.

[0067] The SD-FD pairs can be selected by the UE from PM (DL) possible pairs, and the effective FD components calculated by the UE for pair

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[0068] To determine the linear combination coefficients for each SD-FD pair and receive antenna, the UE forms a matrix of P×N for r = 0, …, N r in the case of -1 3 and

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

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[0070] In the 3GPP Rel-16 eType II codebook (CB), this layer extraction is usually performed for each sub-band before applying the FD component. However, when FD precoding is applied to the CSI-RS port, the phase relationship between sub-bands cannot be easily preserved if the eigenvectors are extracted before the sum in (10). The eigenvectors are determined within each sub-band with phase uncertainty, which can be adjusted, for example, to reduce the phase jumps between sub-bands before FD compression. However, when FD precoding is applied at the gNB, these phase adjustments at the UE will change the phase relationship between sub-bands and should effectively change the effect of the precoder weights applied at the frequencies at the gNB.

[0071] After layer processing, the UE can select a subset of the strongest non-zero coefficients from P coefficients such as

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[0072] Regarding the existence of restrictions in the SD-FD pair selection within 3GPP Rel-15 / 16, the port selection is restricted to a group of L consecutive ports, the port groups are separated by d≤L ports, and the same port is used for both polarizations. Conversely, 3GPP Rel-17 allows unrestricted or free selection, and the selection is extended to a set of P SD-FD pairs, which may be larger than the number of ports P CSI-RS .

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

[0074]

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

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[0076] Note that the above example is described with reference to a user equipment (UE) and a gNB, but the same principle can be applied to any device capable of multi-beam communication.

[0077] If possible, 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. In this specification, by leveraging the fact that each frequency unit is composed of multiple PRBs precoded by the weights of the same frequency component, it is possible to use a code division multiplexing (CDM) code for this multiplexing of pairs to a single port. An example of the many-to-one mapping operation between P SD-FD precoding pairs and P CSI-RS ≤ P CSI-RS ports is shown in FIG. 8, which shows a functional block diagram of the operations performed at the gNB. The reverse one-to-many demapping operation is performed at the UE, as shown in the functional block diagram of the UE operations in FIG. 9. FIG. 10 shows an example of this many-to-one mapping.

[0078] In the example, the bandwidth part (BWP) configured for CSI reporting is divided into N 3 frequency units, and each frequency unit

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[0079] A device for multi-channel communication can determine a pair of spatial domain components and frequency domain components based on a sounding reference signal received from a communication device, thereby precoding reference signal ports in the spatial domain and frequency domain, where the frequency domain component is arranged within a cluster comprising one or more frequency domain components, and at least one pairing of the spatial domain component with at least two clusters of the frequency domain components is made possible; means for transmitting precoding information to another communication device; and means for combining the precoding report received in the response from the other communication device with the precoding.

[0080] Another device for multi-channel communication can include means for transmitting a sounding reference signal to a communication device, and means for receiving, within a response from the communication device, precoding information including information on reference signal ports in a spatial domain and a frequency domain defined by a pair of a spatial domain component and a frequency domain component, wherein the frequency domain component is arranged within a cluster including one or more frequency domain components, and at least one pairing of the spatial domain component with at least two clusters of the frequency domain components is possible, 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] The above describes exemplary embodiments, but it should also be noted that there are some 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 dedicated circuitry, software, logic, or any combination thereof. For example, some aspects may be implemented in hardware, and other aspects may be implemented in firmware or software executable by a controller, microprocessor, or other computing device, but the embodiments are not limited thereto. Various embodiments may be illustrated and described as block diagrams, flowcharts, or using some other pictorial representation, but these blocks, devices, systems, techniques, or methods described herein are, by way of non-limiting example, hardware, software, firmware, dedicated circuitry or logic, general-purpose hardware or a controller or other computing device, or any combination thereof.

[0083] Embodiments may be implemented by computer software stored in a memory and executable by at least one data processor of an entity involved, or by hardware, or by a combination of software and hardware. Further in this regard, note that any of the above procedures can 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 in a physical medium such as a memory chip, or a memory block implemented within a processor, a magnetic medium such as a hard disk or a floppy disk, and an optical medium such as, for example, a DVD and its data variant form, a CD.

[0084] The memory may be any type of memory suitable for the local technical 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 memory and removable memory. The data processor may be any type of processor suitable for the local technical environment, and may include, by way of non-limiting example, one or more of a general-purpose computer, a dedicated 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. The circuitry may be configured to perform one or more of the functions and / or method procedures described above. The circuitry may be provided within a network entity and / or a communication device and / or a server and / or a device.

[0086] The term "circuitry" as used in this application refers to the following (a) a circuit implementation form of only hardware (such as an implementation form of only analog circuitry and / or digital circuitry), and (b) (i) A combination of analog and / or digital hardware circuits with software / firmware, and (ii) A hardware processor, software, and any part of memory having software (including a digital signal processor) that operates together to cause a communication device and / or device and / or server and / or network entity to perform the various functions described above such as a combination of a hardware circuit and software, and (c) A hardware circuit that requires software for operation (e.g., firmware), and / or a processor such as a microprocessor or a part of a microprocessor, where the software may not be present when not required for operation, and can refer to one or more or all of them.

[0087] This definition of a circuit applies to all uses of this term within this application, including any claims. As a further example, the term circuit as used in this application also covers a mere hardware circuit or a processor (or processors) or a part of a hardware circuit or processor and its (or their) accompanying software and / or firmware implementation. The term circuit also covers, for example, an integrated device.

[0088] Although the embodiments are described with respect to a particular architecture, it should be noted that the same principles can be applied to other systems. Accordingly, while particular exemplary architectures for wireless networks, technologies, standards, and protocols are referenced and particular embodiments are described by way of example, the features described herein may be applied to any other suitable form of system, architecture, and device 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 exemplary embodiments, it should also be noted herein that there are some 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 performed by a base station, 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 user equipment, the frequency domain components are arranged in clusters comprising one or more frequency domain components; and precoding the reference signal port includes pairing one of the spatial domain components with one of the frequency domain components of the cluster. Steps and transmitting a precoded reference signal port to the user equipment; providing a configuration indicating a number M of frequency domain components to be calculated for a reference signal port by the user equipment; combining the precoding with a report of precoding received in a response from the user equipment; A method comprising:

2. 2. The method of claim 1, wherein the report received from the user equipment includes a precoder matrix indication, and the combining step includes generating a recovered precoding for use in communications with the user equipment.

3. 3. The method of claim 1, comprising performing a part of a frequency domain compression operation before transmitting the precoding information to the user equipment, the user equipment being configured to perform another part of the frequency domain compression operation.

4. 4. The method of claim 3, comprising performing a majority of the frequency domain compression operation in a device other than the user equipment that performs the precoding.

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

6. configuring the user equipment to compute M frequency domain components from a restricted subset of a Discrete Fourier Transform codebook for each selected reference signal port; receiving from the user equipment information of a selection of non-zero coefficients from a sequence formed by the M frequency domain components calculated by the user equipment for each selected reference signal port and an indicator of the reference signal port corresponding to the reported non-zero coefficient; The method of any one of claims 1 to 5, further comprising:

7. The method of claim 6 , wherein the information is received in response to a channel state information report request.

8. The method of claim 6 or 7, wherein the information further indicates frequency domain components corresponding to the reported non-zero coefficients.

9. 9. The method of claim 1, comprising providing a restricted subset of Discrete Fourier Transform components, said subset comprising at least one of a window of continuous components or a set of non-contiguous components of a Discrete Fourier Transform codebook including at least component 0, or said restricted subset of DFT components being of the same or different size, or components for different groups of space-frequency pairs.

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

11. 11. The method of any one of claims 1 to 10, comprising the steps of calculating precoder weights and combining the calculated precoder weights with precoder matrix indicator information received from the user equipment to recover the precoding.

12. 1. A method for multi-channel communication performed by a user equipment, comprising: transmitting a sounding reference signal to a base station; receiving a reference signal port precoded in the spatial and frequency domains with pairs of spatial and frequency domain components in response to the sounding reference signal from the base station, the frequency domain components being arranged in clusters comprising one or more frequency domain components, and precoding the reference signal port includes pairing one of the spatial domain components with one of the frequency domain components of the cluster; receiving a configuration indicating a number M of frequency domain components to be calculated for a reference signal port by the user equipment; performing a port selection operation based on the received reference signal port; preparing and transmitting a report to the base station based on the selection action; A method comprising:

13. The method of claim 12 , wherein the report includes a precoder matrix indication for use in generating a recovered precoding by the base station.

14. 14. The method of claim 12 or 13, comprising the step of performing a frequency domain compression operation after receiving the precoded reference signal port from the base station, wherein another frequency domain compression operation has been applied to the received precoded reference signal port by the base station.

15. 15. The method of claim 14, comprising performing a lesser portion of a combined frequency domain compression operation at the user equipment than at the base station that performs the precoding.

16. selecting a channel state information reference signal port or a precoding pair associated with said channel state information reference signal port; preparing and transmitting a precoding matrix indicator or a precoding pair based on the selected channel state information reference signal port; 16. The method of any one of claims 12 to 15, comprising:

17. computing M frequency domain components from a restricted subset of the discrete Fourier transform codebook for each selected reference signal port; signaling information of a selection of a non-zero coefficient from the sequence formed by the M frequency domain components calculated for each selected reference signal port and an indicator indicating the reference signal port corresponding to the reported non-zero coefficient; 17. The method of any one of claims 12 to 16, comprising:

18. 20. The method of claim 17, wherein the information is signaled in response to a channel state information report request.

19. The method of claim 17 or 18, wherein the information further indicates frequency domain components corresponding to the reported non-zero coefficients.

20. 20. A method according to claim 12, 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 including at least component 0.

21. 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 adapted to execute, using the at least one processor, 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 user equipment, the frequency domain components being arranged in clusters comprising one or more frequency domain components, and precoding the reference signal port including pairing one of the spatial domain components with one of the frequency domain components of the cluster; transmitting a precoded reference signal port to the user equipment; providing an arrangement indicating a number M of frequency domain components calculated by the user equipment for a reference signal port; combining the precoding with a report of precoding received in a response from the user equipment; An apparatus configured to cause the apparatus to perform the steps of:

22. 22. The apparatus of claim 21, wherein the report received from the user equipment 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 communications with the user equipment.

23. 23. The apparatus of claim 21 or 22, configured to configure the user equipment to calculate M frequency domain components from a restricted subset of a Discrete Fourier Transform codebook for each selected reference signal port, and configured to receive from the user equipment information of a selection of a non-zero coefficient from a sequence formed by the M frequency domain components calculated by the user equipment for each selected reference signal port, and an indicator indicating the reference signal port corresponding to the reported non-zero coefficient.

24. 24. The apparatus of claim 23, wherein the information is received in response to a channel state information report request.

25. 25. The apparatus of claim 23 or 24, wherein the information further indicates frequency domain components corresponding to the reported non-zero coefficients.

26. 26. The apparatus of claim 21, configured to provide a restricted subset of Discrete Fourier Transform components, the subset comprising at least one of a window of continuous components or a set of non-contiguous components of a Discrete Fourier Transform codebook including at least component 0, or the restricted subset of DFT components being components of the same or different size, or for different groups of space-frequency pairs.

27. performing a portion of a frequency domain compression operation before transmitting the precoding information to the user equipment, the user equipment 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 user equipment; determining the size of the clusters based at least in part on the uncertainty of the predicted cluster delay; or calculating precoder weights and combining the calculated precoder weights with precoder matrix indicator information received from the user equipment to recover the precoding. The apparatus according to any one of claims 21 to 26, configured to perform at least one of the following:

28. 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 adapted to execute, using the at least one processor, at least transmitting a sounding reference signal to a base station; receiving, from the base station, in response to the sounding reference signal, a reference signal port precoded in the spatial and frequency domains with pairs of spatial and frequency domain components, the frequency domain components being arranged in clusters comprising one or more frequency domain components, and precoding the reference signal port including pairing one of the spatial domain components with one of the frequency domain components of the cluster; receiving a configuration indicating a number M of frequency domain components to be calculated for a reference signal port by the apparatus; performing a port selection operation based on the received reference signal port; preparing and transmitting a report to the base station based on said selecting operation; An apparatus configured to cause the apparatus to perform the steps of:

29. 30. The apparatus of claim 28, wherein the report includes a precoder matrix indication for use in generating a recovered precoding by the base station.

30. 30. The apparatus of claim 28 or 29, configured to perform a frequency domain compression operation after receiving the precoded reference signal port from the base station, wherein another frequency domain compression operation has been applied to the received precoded reference signal port by the base station.

31. 31. The apparatus of claim 30, configured to perform a smaller portion of a combined frequency domain compression operation than the portion performed in the base station that performs the precoding.

32. Select a channel state information reference signal port or a precoding pair associated with the channel state information reference signal 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 apparatus according to any one of claims 28 to 31, configured so as to

33. Compute M frequency domain components from a restricted subset of the discrete Fourier transform codebook for each selected reference signal port; signaling information of a selection of a non-zero coefficient from a sequence formed by the M frequency domain components calculated for each selected reference signal port and an indicator indicating the reference signal port corresponding to the reported non-zero coefficient. The apparatus according to any one of claims 28 to 32, configured so as to

34. 34. The apparatus of claim 33, wherein the information is signaled in response to a channel state information report request.

35. 35. The apparatus of claim 33 or 34, wherein the information further indicates frequency domain components corresponding to the reported non-zero coefficients.

36. 36. An apparatus according to any one of claims 28 to 35, configured to receive 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 including at least component 0.

37. A non-transitory computer readable medium comprising program code for causing a processor to execute instructions for the method according to any one of claims 1 to 12 or any one of claims 13 to 20.

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