Apparatus and method for channel estimation in IRS assisted wireless networks

Abstract

A user equipment for communicating with a base station (110) over a communication channel over a smart reflective surface. The user equipment (130) is configured to control the IRS (120) to operate in a plurality of reflective configurations to reflect a plurality of pilot signals sent from the base station (110) to the UE (130) to probe channels between the base station (110), the IRS (120) and the UE (130). The plurality of reflection configurations of the IRS (120) comprise: a first set of reflection configurations for estimating, by the UE (130) through the IRS (120), a channel covariance matrix (CCM) of the communication channel between the base station (110) and the UE (130), and a second set of reflection configurations for estimating, by the UE (130) through the IRS (120), a channel covariance matrix (CCM) of the communication channel between the base station (110) and the UE (130) through the IRS (120). And a second set of reflection configurations for estimating, by the UE (130), the communication channel between the base station (110) and the UE (130) through the IRS (120).

Description

Technical Field

[0001] The present invention relates to wireless communication networks. More specifically, the present invention relates to an apparatus and method for channel estimation, which is at least partially controlled by a user equipment in a wireless network assisted by an intelligent reflecting surface (IRS). Background Art

[0002] An intelligent reflecting surface (IRS) has the potential to shape the channel environment in a wireless network according to desired conditions. An IRS is a planar array composed of a large number (almost) of passive, low-cost, and low-power-consuming reflecting elements with reconfigurable parameters. Each of these elements is used to reflect the incident radio waves with individually configurable phase shifts (and optionally individually configurable amplitudes), thereby forming a reflected beam, the direction of which can be actively controlled by correspondingly selecting the phase shifts of the reflecting elements. One or more IRSs can be easily integrated into the walls or ceilings of halls and buildings.

[0003] IRSs can be used in wireless communications for different purposes, such as for indoor and industrial IoT communications, where an IRS can support concentrating the transmit power in the direction of a low-power user equipment (UE), and in favorable cases, establishing a LOS-like communication link with the low-power UE. Generally, an IRS has hundreds of antenna elements, capable of forming highly directive and focused beams and generating high antenna gains. The reflected beam is formed by a (predefined) set of phase shifts (and optionally a set of amplitudes) applied to the antenna elements, and these sets of phase shifts and amplitudes applied to the antenna elements can be configured and controlled by a base station (such as a gNB). For this purpose, an IRS can accommodate a controller directly connected to the base station. Summary of the Invention

[0004] An object of the present invention is to provide an improved apparatus and method for channel estimation in a wireless network, especially in a cellular network using an IRS.

[0005] The above and other objects are achieved by the subject matter of the independent claims. Other implementations are apparent from the dependent claims, the description, and the drawings.

[0006] According to a first aspect, a UE is provided for communicating with a base station over a communication channel via an IRS. The UE is configured to control the IRS to operate in multiple reflection configurations to reflect multiple pilot signals transmitted from the base station to the UE, so as to probe the channel between the base station, the IRS, and the UE. The multiple reflection configurations of the IRS include: a first set of reflection configurations for the UE to estimate the channel covariance matrix (CCM) of the communication channel between the base station and the UE via the IRS; a second set of reflection configurations for the UE to estimate the communication channel between the base station and the UE via the IRS. Although the first set of reflection configurations of the IRS can provide a first rough estimate of the channel conditions, the second set of reflection configurations of the IRS can estimate the communication channel more accurately.

[0007] In another possible implementation of the first aspect, the UE is configured to determine the CCM based on the multiple pilot signals received from the base station that are reflected by the IRS in the first set of reflection configurations.

[0008] In another possible implementation of the first aspect, the UE is configured to determine the second set of reflection configurations based on the CCM.

[0009] In another possible implementation of the first aspect, the UE is configured to determine the second set of reflection configurations based on multiple eigenvectors of the CCM.

[0010] In another possible implementation of the first aspect, the UE is configured to determine the second set of reflection configurations based on multiple eigenvectors of the CCM having the largest eigenvalues.

[0011] In another possible implementation of the first aspect, the UE is configured to update the CCM based on the multiple pilot signals received from the base station that are reflected by the IRS in the first set of reflection configurations. If the value of the difference metric between the updated CCM and the previous CCM is greater than a threshold, the UE can be configured to update the second set of reflection configurations based on the updated CCM.

[0012] In another possible implementation of the first aspect, the UE is configured to estimate the communication channel between the base station and the UE via the IRS based on the multiple pilot signals received from the base station that are reflected by the IRS in the second set of reflection configurations.

[0013] In another possible implementation of the first aspect, the UE is used to control the IRS to operate with the multiple reflection configurations, so as to reflect the multiple pilot signals from the base station to the UE based on codebook reflection. The codebook can define the mapping between multiple codes and the multiple reflection configurations.

[0014] In another possible implementation of the first aspect, the UE is used to receive IRS configuration information from the IRS in response to a configuration information request. The UE can also be used to generate the codebook based on the IRS configuration information.

[0015] In another possible implementation of the first aspect, the UE is used to control the IRS to operate with the multiple reflection configurations, so as to reflect the multiple pilot signals of the base station in multiple time slots. Each time slot may include: one or more pilot time slots for accommodating one or more of the multiple pilot signals from the base station; one or more data time slots for accommodating one or more of the multiple data signals from the base station.

[0016] In another possible implementation of the first aspect, each time slot includes: one or more pilot time slots for controlling the IRS to operate with one or more of the first set of reflection configurations; one or more pilot time slots for controlling the IRS to operate with one or more of the second set of reflection configurations.

[0017] In another possible implementation of the first aspect, the one or more pilot time slots of the first time slot among the multiple time slots include one or more pilot time slots for controlling the IRS to operate with the first subset of the first set of reflection configurations and / or the second set of reflection configurations; the one or more pilot time slots of the second time slot among the multiple time slots include one or more pilot time slots for controlling the IRS to operate with the second subset of the first set of reflection configurations and / or the second set of reflection configurations. The first subset of the first set of reflection configurations and / or the second set of reflection configurations may be different from the second subset of the first set of reflection configurations and / or the second set of reflection configurations.

[0018] In another possible implementation of the first aspect, if the number of the one or more pilot time slots of each time slot is less than or equal to the number of reflection configurations of the second set of reflection configurations, the UE is further used to send a request to the base station to adjust the number of pilot time slots in each time slot.

[0019] In another possible implementation of the first aspect, the UE is used to control the IRS to operate in the multiple reflection configurations by adjusting the respective signal amplitudes and / or respective signal phase shifts of each of the multiple reflection elements of the IRS.

[0020] In another possible implementation of the first aspect, the UE is further used to communicate with the base station based on the communication channel between the base station and the UE estimated through the IRS.

[0021] According to a second aspect, there is provided a method for operating a UE to communicate with a base station over a communication channel through an IRS. The method includes: controlling the IRS to operate in multiple reflection configurations so as to reflect multiple pilot signals sent from the base station to the UE to detect the channel between the base station, the IRS, and the UE; the multiple reflection configurations of the IRS include: a first set of reflection configurations for the UE to estimate the CCM of the communication channel between the base station and the UE through the IRS; a second set of reflection configurations for the UE to estimate the communication channel between the base station and the UE through the IRS.

[0022] The method according to the second aspect of the present invention can be executed by the UE according to the first aspect of the present invention. Therefore, other features of the method according to the second aspect of the present invention directly come from the functions of the UE according to the first aspect of the present invention and the different implementations of the UE described above and below.

[0023] According to a third aspect, there is provided an IRS for assisting communication between a base station and a UE over a communication channel. The IRS includes multiple reflection elements with adjustable phase and / or amplitude, and is used to support multiple reflection configurations. The IRS operates in multiple reflection configurations so as to reflect multiple pilot signals sent from the base station to the UE to detect the channel between the base station, the IRS, and the UE. The multiple reflection configurations of the IRS include: a first set of reflection configurations for the UE to estimate the CCM of the communication channel between the base station and the UE through the IRS; a second set of reflection configurations for the UE to estimate the communication channel between the base station and the UE through the IRS.

[0024] In another possible implementation of the third aspect, the IRS operates in the multiple reflection configurations so as to reflect the multiple pilot signals sent from the base station to the UE based on a codebook. The codebook can define the mapping between multiple codes and the multiple reflection configurations.

[0025] In another possible implementation of the third aspect, the IRS is used to respond to a configuration information request from the UE and send IRS configuration information to the UE to generate the codebook based on the IRS configuration information.

[0026] In another possible implementation of the third aspect, the IRS is used to operate with the multiple reflection configurations to reflect the multiple pilot signals transmitted from the base station in multiple time slots. Each time slot may include: one or more pilot time slots for accommodating one or more of the multiple pilot signals from the base station; and one or more data time slots for accommodating one or more of the multiple data signals from the base station.

[0027] In another possible implementation of the third aspect, each time slot may include: one or more pilot time slots for the IRS to operate with one or more of the reflection configurations in the first set of reflection configurations; and one or more pilot time slots for the IRS to operate with one or more of the reflection configurations in the second set of reflection configurations.

[0028] In another possible implementation of the third aspect, the one or more pilot time slots of the first time slot among the multiple time slots include one or more pilot time slots for the IRS to operate with the first set of reflection configurations and / or a first subset of the second set of reflection configurations; the one or more pilot time slots of the second time slot among the multiple time slots include one or more pilot time slots for the IRS to operate with the first set of reflection configurations and / or a second subset of the second set of reflection configurations. The first subset and the second subset of the first set of reflection configurations and / or the second set of reflection configurations may be different.

[0029] According to a fourth aspect, a method for operating an IRS is provided for assisting communication between a base station and a UE over a communication channel. The IRS includes a plurality of reflection elements with adjustable phase and / or amplitude for supporting multiple reflection configurations. The method includes: the IRS operating with multiple reflection configurations to reflect multiple pilot signals transmitted from the base station to the UE to detect the channel between the base station, the IRS, and the UE; the multiple reflection configurations of the IRS including: a first set of reflection configurations for the UE to estimate the CCM of the communication channel between the base station and the UE through the IRS; and a second set of reflection configurations for the UE to estimate the communication channel between the base station and the UE through the IRS.

[0030] The method according to the fourth aspect of the present invention can be executed by the IRS according to the third aspect of the present invention. Therefore, other features of the method according to the fourth aspect of the present invention directly come from the functions of the IRS according to the third aspect of the present invention and different implementation manners of the IRS described above and below.

[0031] According to a fifth aspect, there is provided a base station for communicating with a UE over a communication channel via an IRS. The base station is configured to transmit a plurality of pilot signals, such that the IRS operating in a plurality of reflection configurations reflects the plurality of pilot signals in a plurality of time slots. Each time slot includes: one or more pilot time slots for transmitting one or more of the plurality of pilot signals; and one or more data time slots for transmitting one or more of a plurality of data signals. In response to a request received from the UE, the base station is configured to adjust the number of the one or more pilot time slots for each time slot.

[0032] In another possible implementation manner of the fifth aspect, the plurality of reflection configurations of the IRS include: a first set of reflection configurations for estimating, by the UE via the IRS, a CCM of the communication channel between the base station and the UE; and a second set of reflection configurations for estimating, by the UE via the IRS, the communication channel between the base station and the UE. The base station may be configured to receive information on the first set of reflection configurations of the IRS and / or information on the second set of reflection configurations of the IRS from the UE and / or the IRS.

[0033] According to a sixth aspect, there is provided a method for operating a base station to communicate with a UE over a communication channel via an IRS. The method includes: transmitting a plurality of pilot signals, such that the IRS operating in a plurality of reflection configurations reflects the plurality of pilot signals in a plurality of time slots, wherein each time slot includes: one or more pilot time slots for transmitting one or more of the plurality of pilot signals; and one or more data time slots for transmitting one or more of a plurality of data signals. The method further includes: in response to a request received from the UE, adjusting the number of the one or more pilot time slots for each time slot.

[0034] The method according to the sixth aspect of the present invention can be executed by the base station according to the fifth aspect of the present invention. Therefore, other features of the method according to the sixth aspect of the present invention directly come from the functions of the base station according to the fifth aspect of the present invention and different implementation manners of the base station described above and below.

[0035] According to a seventh aspect, there is provided a computer program product comprising a computer-readable storage medium for storing program code which, when executed by a computer or a processor, causes the computer or the processor to execute the method according to the second aspect, the method according to the fourth aspect and / or the method according to the sixth aspect.

[0036] One or more embodiments will be described in detail in the accompanying drawings and the following description. Other features, objects, and advantages will be apparent from the specification, the drawings, and the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the drawings:

[0038] Figure 1 is a schematic diagram of a wireless network, the wireless network including a UE according to one embodiment, an IRS according to one embodiment, and a base station according to one embodiment;

[0039] Figure 2 is a schematic diagram of a first set of reflection configurations located at IRS 120 according to one embodiment;

[0040] Figure 3 is a schematic diagram of a time slot implemented by an embodiment disclosed herein;

[0041] Figures 4a to 4c is a schematic diagram of the detection based on multiple reflection configurations implemented by an embodiment disclosed herein;

[0042] Figure 5 is a signaling diagram of a communication session between a base station according to one embodiment, an IRS according to one embodiment, and a UE according to one embodiment;

[0043] Figure 6 is a flowchart of a method for operating a UE according to one embodiment to communicate with a base station according to one embodiment over a communication channel via an IRS according to one embodiment;

[0044] Figure 7 is a flowchart of a method for operating an IRS according to one embodiment to assist communication between a base station according to one embodiment and a UE according to one embodiment over a communication channel;

[0045] Figure 8 is a flowchart of a method for operating a base station according to one embodiment to communicate with a UE according to one embodiment over a communication channel via an IRS according to one embodiment.

[0046] In the following, the same reference numerals refer to the same or at least functionally equivalent features. Detailed implementation manners

[0047] In the following description, reference is made to the accompanying drawings which form a part hereof, and which illustrate, by way of example, specific aspects of embodiments of the present invention or specific aspects in which embodiments of the present invention may be used. It should be understood that the embodiments of the present invention may be used in other aspects and may include structural or logical changes not described in the drawings. Therefore, the following detailed description should not be construed in a limiting sense, and the scope of the present invention is defined by the appended claims.

[0048] For example, it should be understood that the disclosure related to the described method is also applicable to the corresponding device or system for performing the method, and vice versa. For example, if one or more specific method steps are described, the corresponding device may include one or more units (e.g., functional units) to perform the one or more described method steps (e.g., one unit performs one or more steps, or multiple units respectively perform one or more of the multiple steps), even if such one or more units are not explicitly described or illustrated in the drawings. In addition, if a specific device is described based on one or more units (e.g., functional units), the corresponding method may include a step to perform the functions of the one or more units (e.g., one step performs the functions of one or more units, or multiple steps respectively perform the functions of one or more of the multiple units), even if such one or more steps are not explicitly described or shown in the drawings. In addition, it should be understood that, unless otherwise specifically indicated, the features of the various exemplary embodiments and / or aspects described herein may be combined with each other.

[0049] Figure 1 is a schematic diagram of a wireless network 100, which includes a user equipment (UE) 130 according to one embodiment, an intelligent reflecting surface (IRS) 120 according to one embodiment, and a base station 110 according to one embodiment. Figure 1 illustrates an exemplary scenario solved by the embodiments disclosed herein, that is, a wireless network 100 including an IRS 120 installed, for example, on the wall of a factory hall. The wireless network 100 further includes a base station 110, which may be implemented as a gNB 110. In Figure 1In the exemplary embodiment shown, the base station 110 is located at a certain position (especially a fixed position) and serves one UE 130 among a plurality of UEs 130 (especially mobile UEs 130). The IRS 120 can be a planar array composed of a large number (especially more than 100 or more than 1000) of (almost) passive reflecting elements with reconfigurable parameters. Each of these elements can be used to reflect the incident radio waves with individually configurable phase shifts and / or amplitudes, thereby forming a reflected beam (or simply a beam), and the direction of the reflected beam can be actively controlled by correspondingly selecting the phase shifts of the reflecting elements of the IRS 120. In one embodiment, the IRS 120 is controlled by the UE 130. As Figure 1 shown, if there are enough elements available in the IRS 120, the environment can be configured, i.e., Figure 1 the factory hall in the example shown, so that similar LOS-like channel conditions can be established for any UE 130 in the factory hall (even in the presence of obstacles such as machines 140), and this channel condition is created by the direct link from the base station 110 through the associated IRS 120, forming a reflected beam pointing to the UE 130.

[0050] As Figure 1 shown, the UE 130 can include a processing circuit 131 and a transceiver 133. The processing circuit 131 can be implemented in hardware and / or software. The hardware can include digital circuits, or analog and digital circuits. The digital circuits can include components such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), digital signal processors (DSPs), or one or more general-purpose processors. In addition, the UE 130 can include a memory 135 for storing executable program code, which, when executed by the processing circuit 131, causes the UE 130 to perform the functions and operations described herein.

[0051] Similarly, the base station 110 may include a processing circuit 111 and a transceiver 113. The processing circuit 111 may be implemented in hardware and / or software. The hardware may include a digital circuit, or an analog circuit and a digital circuit. The digital circuit may include components such as an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a digital signal processor (DSP), or one or more general-purpose processors. In addition, the base station 110 may include a memory 115 for storing executable program code, which, when executed by the processing circuit 111, enables the base station 110 to perform the functions and operations described herein.

[0052] UE 130 may move while receiving reflected beams, for example, on a path from initial position 137 to final position 139. The path, initial position 137, and / or final position 139 may be determined by processing circuitry 131 of UE 130 and / or may be stored in memory 135 of UE 130 before UE 130 moves.

[0053] Similar to a standard multiple-input-multiple-output (MIMO) system, to fully exploit the benefits of the IRS 120, accurate channel information for the IRS 120 link needs to be obtained. A scheme for channel estimation may include sending a pilot signal known to both the gNB and the UE 130 from the gNB to the UE 130. If the signal is received and the information of the signal pilot is obtained, the UE 130 can estimate the required channel. In the case where the UE 130 (which may be a mobile robot 130, for example) is mobile, channel estimation is more challenging due to the mobility of the robot. High mobility reduces the size of the channel coherence block, i.e., the number of time slots and frequency slots where the channel is (approximately) constant. As is known, in this case, a larger portion of the available resources needs to be used for training (i.e., the number of pilot signals required for channel estimation), thereby reducing the effective data throughput. Regardless of the mobile conditions, the large number of elements included in the IRS 120 is an additional challenge: if a direct estimation method such as the least square (LS) method is used, the required training overhead will increase with the number of elements (i.e., antennas of the IRS 120), thus becoming too large to meet the requirements. This further reduces the effective data throughput.

[0054] According to the following reference Figure 2 , Figure 3 and Figures 4a to 4cIn an embodiment of the present invention described further, a user equipment (UE) 130 is used to communicate with a base station 110 via an IRS 120 on a communication channel, particularly on a communication channel of a wireless network 100.

[0055] The UE 130 is used to control the IRS 120 to operate in a variety of reflection configurations 151, 153 (as Figures 4a to 4c shown), so as to reflect a plurality of pilot signals from the base station 110 to the UE 130 to detect the channel between the base station 110, the IRS 120, and the UE 130.

[0056] The various reflection configurations 151, 153 of the IRS 120 include: a first set of reflection configurations 151 (according to Figure 2 ), which is used by the UE 130 to estimate the channel covariance matrix (CCM) of the communication channel between the base station 110 and the UE 130 via the IRS 120; a second set of reflection configurations 153 (according to Figures 4a to 4c ), which is used by the UE 130 to estimate the communication channel between the base station 110 and the UE 130 via the IRS 120. Figures 4a to 4c Exemplary various reflection configurations used by the IRS 120 in three different time slots are shown, including a varying first reflection configuration 151 (referred to as beam 1 in Figures 4a to 4c ) and a constant second set of reflection configurations 153 (referred to as beams 2, 3, and 4 in Figures 4a to 4c ).

[0057] The UE 130 can be used to determine the CCM based on a plurality of pilot signals received from the base station 110 reflected by the IRS 120 in the first set of reflection configurations 151. The UE 130 can be used to determine the second set of reflection configurations 153 based on the CCM. More specifically, the UE 130 can be used to determine the second set of reflection configurations 153 based on a plurality of eigenvectors of the CCM, particularly based on a plurality of eigenvectors of the CCM having the largest eigenvalues.

[0058] The UE 130 can be used to update the CCM based on a plurality of pilot signals received from the base station 110 reflected by the IRS 120 in the first set of reflection configurations 151. If the value of the difference metric between the updated CCM and the previous CCM is greater than a threshold, the UE 130 can be used to update the second set of reflection configurations 153 based on the updated CCM.

[0059] As a supplement to UE 130, IRS 120 is used to assist in the communication between base station 110 and UE 130 over a communication channel. IRS 120 includes a plurality of reflection elements with adjustable phase and / or amplitude, and is used to support multiple reflection configurations 151, 153. IRS 120 is used to operate in multiple reflection configurations 151, 153, so as to reflect a plurality of pilot signals sent from base station 110 to UE 130 to detect the channel between base station, IRS 120 and UE 130.

[0060] UE 130 can also be used to control IRS 120 to operate in multiple reflection configurations 151, 153 by adjusting the respective signal amplitude and / or respective signal phase shift of each of the plurality of reflection elements of IRS 120.

[0061] UE 130 can be used to control IRS 120 to operate in multiple reflection configurations 151, 153, so as to reflect a plurality of pilot signals sent from base station 110 to UE 130 based on a codebook. The codebook can define the mapping between a plurality of codes and multiple reflection configurations 151, 153. As a supplement, IRS 120 can be used to operate in multiple reflection configurations 151, 153, so as to reflect a plurality of pilot signals sent from base station 110 to UE 130 based on a codebook.

[0062] Base station 110 is used to communicate with UE 130 over a communication channel through IRS 120. As Figure 3 further shown, base station 110 is used to send a plurality of pilot signals, so that IRS 120 operating in multiple reflection configurations 151, 153 reflects a plurality of pilot signals in multiple time slots 161, 163. Each time slot 161, 163 includes: one or more pilot time slots 165, 167 for sending one or more of the plurality of pilot signals; one or more data time slots ( Figure 3 also schematically shown as the blank space between the ends of pilot time slots 165, 167 and time slots 162, 163 respectively) for sending one or more of the plurality of data signals. Base station 110 is also used to adjust the number of one or more pilot time slots 165, 167 for each time slot 161, 163 in response to a request received from UE 130. Base station 110 can be used to receive information about the first and / or second set of reflection configurations 153 used by IRS 120 from UE 130 and / or IRS 120, so that base station 110 knows the specific configuration used by IRS 120 during each time slot.

[0063] UE 130 can be used to estimate the communication channel between base station 110 and UE 130 through IRS 120 based on a plurality of pilot signals received from base station 110 reflected by IRS 120 in the second set of reflection configurations 153.

[0064] UE 130 can also be used to communicate with the base station 110 based on the communication channel between the base station 110 and the UE 130 estimated by the IRS 120.

[0065] UE 130 can be used to control the IRS 120 to operate in multiple reflection configurations 151, 153, so as to reflect multiple pilot signals transmitted from the base station 110 in multiple time slots 161, 163. Accordingly, the IRS 120 can be used to operate in multiple reflection configurations 151, 153, so as to reflect multiple pilot signals transmitted from the base station 110 in multiple time slots 161, 163.

[0066] As Figure 3 shown, each of the time slots 161, 163 may include: one or more pilot time slots 165, 167 for accommodating one or more of the multiple pilot signals from the base station 110; and one or more data time slots for accommodating one or more of the multiple data signals from the base station 110.

[0067] Each of the time slots 161, 163 includes: one or more pilot time slots 165, 167 for controlling the IRS 120 to operate in one or more of the reflection configurations in the first set of reflection configurations 151; and one or more pilot time slots 165, 167 for controlling the IRS 120 to operate in one or more of the reflection configurations in the second set of reflection configurations 153.

[0068] One or more of the pilot time slots 165 of the first time slot 161 among the multiple time slots 161, 163 may include one or more pilot time slots 165 for controlling the IRS 120 to operate in the first subset of the first set of reflection configurations 151 and / or the second set of reflection configurations 153; one or more of the pilot time slots 167 of the second time slot 163 among the multiple time slots 161, 163 may include one or more pilot time slots 167 for controlling the IRS 120 to operate in the second subset of the first set of reflection configurations 151 and / or the second set of reflection configurations 153. The first subset of the first set of reflection configurations 151 and / or the second set of reflection configurations 153 may be different from the second subset of the first set of reflection configurations 151 and / or the second set of reflection configurations 153. As described above, Figures 4a to 4c illustrates exemplary multiple reflection configurations used by the IRS 120 in three different time slots, including a varying first reflection configuration 151 (referred to as beam 1 in Figures 4a to 4c ) and a constant second set of reflection configurations 153 (referred to as beams 2, 3, and 4 in Figures 4a to 4c ).

[0069] As will be described in the following Figure 5As described in more detail below, if the number of one or more pilot time slots 165, 167 in each time slot 161, 163 is less than or equal to the number of reflection configurations of the second set of reflection configurations 153, the UE 130 can also be used to send a request to the base station 110 to adjust the number of pilot time slots 165, 167 in each time slot 161, 163.

[0070] As will be described in more detail below Figure 5 As will be described in further detail below, the IRS 120 can be used to send IRS configuration information to the UE 130 in response to a configuration information request from the UE 130 to generate a codebook based on the IRS configuration information. As a supplement, the UE 130 can be used to receive IRS configuration information from the IRS 120 in response to a configuration information request. The UE 130 can also be used to generate a codebook based on the IRS configuration information.

[0071] Therefore, the UE 130 can configure each antenna oscillator of the IRS 120 with different phases and / or amplitudes, thus achieving a more flexible design than a fixed reflection beam set. By adjusting the second set of reflection configurations 153, i.e., the beam of the IRS 120, during channel estimation, the minimized channel estimation MSE can be achieved based on using the CCM information as auxiliary information and the information about the MMSE estimation process used by the UE 130. Specifically, the MMSE estimation process can be linear.

[0072] As described above, the CCM can be estimated at the UE 130 based on the pilots sent by the base station 110 through the IRS 120, especially in the downlink. The second set of reflection configurations 153, i.e., the beam for adjustment, can be directly calculated at the UE 130 and then directly sent from the UE 130 to the IRS 120. Therefore, the UE 130 can control the IRS 120, where the UE 130 can fully control the IRS 120 with the authorization of the base station 110 of the wireless network 100.

[0073] Figure 2 is a schematic diagram of the first set of reflection configurations 151 located at the IRS 120 according to one embodiment, Figure 3 is a schematic diagram of the time slots 161, 163. As Figure 2 shown, the IRS 120 can include a controller 121. The controller 121 of the IRS 120 can be used to communicate with the UE 130 and / or the base station 110, especially through the communication interface of the IRS 120.

[0074] The first set of reflection configurations 151 can be used together with the pilot time slots 165, 167, i.e., the training pilot set m << N, where N is the number of IRS elements. As Figure 3As shown, m = 4 pilot time slots 165, 167 can be sent in each of the time slots 161, 163. During this channel sounding phase, IRS 120 can switch between the beams of the first set of reflection configurations 151 for each pilot time slot, that is, m fixed beams will be probed in the m = 4 pilot time slots 165, 167. Therefore, it is possible to estimate the instantaneous channels between the base station, IRS, and UE, and calculate the CCM based on these estimated channels over multiple coherence blocks.

[0075] As described above, during channel sounding using m pilots, two different beam sets for the dynamic configuration of IRS 120 can be used. The first set of reflection configurations 151 (i.e., the first set) includes the fixed beams required to estimate the CCM, such as the fixed beams of the original configuration. The second set of reflection configurations 153 (i.e., the second set) includes T individual beams derived from the CCM for accurately estimating the instantaneous channels between the base station, IRS, and UE.

[0076] Since the CCM can change slowly over time (i.e., in the time slots 161, 163), it is not necessary to estimate the first set of reflection configurations 151 (i.e., the fixed beams) in each of the time slots 161, 163. Therefore, those beams can be distributed over consecutive time slots 161, 163 or can be sent only at fixed time intervals, for example, every nth time slot 161, 163.

[0077] Figures 4a to 4c is a schematic diagram of the sounding based on multiple reflection configurations 151, 153. As Figures 4a to 4c shown, one beam of the first set of reflection configurations 151 can be probed in each of the time slots 161, 163. On the other hand, to accurately estimate the instantaneous channels between the base station, IRS, and UE, it may be necessary to estimate the second set of reflection configurations 153 (i.e., the individual beams) more frequently. Therefore, for example, if T < m, as Figures 4a to 4c shown, the same individual beam can be probed in each time slot, where the same 3 individual beams of the second set of reflection configurations 153 are probed in each of the time slots 161, 163. For a larger set of individual beams of the second set of reflection configurations 153, such as for T > m and a slowly varying channel, the individual beams of the second set of reflection configurations 153 can be distributed over multiple consecutive time slots 161, 163, similar to the description of the estimation of the fixed beams of the first set of reflection configurations 151.

[0078] As described above, UE 130 can be used to control IRS 120 to operate with multiple reflection configurations 151, 153, so as to receive multiple pilot signals from the base station 110 to UE 130 based on codebook reflections. The codebook can include IRS beamforming vectors, and the IRS beamforming vectors can be used to quantize individual IRS beams. Both UE 130 and IRS 120 know the codebook.

[0079] The first process of the codebook-based process may include one or more of the following steps:

[0080] In the first step of the first process, an initial setup may be performed. IRS 120 may be configured with m fixed beams of the first set of reflection configurations 151 for channel estimation based on m pilots. For example, this configuration may be done by the base station 110 in a conventional manner.

[0081] In the second step of the first process, the UE 130 may estimate the CCM based on channel measurements in multiple consecutive time slots 161, 163.

[0082] In the third step of the first process, the UE 130 may determine T individual beams of the second set of reflection configurations 153 according to the CCM to accurately estimate the instantaneous channel between the base station, IRS, and UE.

[0083] In the fourth step of the first process, the UE 130 may use a codebook to quantize the T individual beams of the second set of reflection configurations 153 and send these codewords to the controller 121 of the IRS 120.

[0084] In the fifth step of the first process, the controller 121 of the IRS 120 may construct two beam sets for channel sounding, which respectively represent subsets of the first set of reflection configurations 151 and the second set of reflection configurations 153. In the case of T < m, the first beam set (i.e., the subset of the first set of reflection configurations 151) may include (m - T) beams, which can be configured by using (m - T) beams among the m fixed beams in each time slot 161, 163. This makes it necessary to use time slots 161, 163 to probe all m fixed beams of the first set of reflection configurations 151 with a size of m. The second beam set (i.e., the subset of the second set of reflection configurations 153) may include the T individual beams sent by the UE 130.

[0085] In the sixth step of the first process, the controller 121 of the IRS 120 may configure the IRS 120 with the beam sets of the first set of reflection configurations 151 and the second set of reflection configurations 153 for each time slot 161, 163 for channel sounding.

[0086] In the seventh step of the first process, the UE may use the first set of reflection configurations 151 to estimate and update the CCM, and use the second set of reflection configurations 153 to accurately estimate the instantaneous channel between the base station, IRS, and UE.

[0087] In the eighth step of the first process, if the updated CCM is significantly different from the CCM for the T individual beams used to derive the second set of reflection configurations 153 (e.g., possibly due to the movement of UE 130), the T individual beams of the second set of reflection configurations 153 can be updated and sent to the controller 121 of IRS 120. After the eighth step, the process can jump back to the third step of the first process.

[0088] In summary, the base station 110, IRS 120, and UE 130 are used to configure the IRS beams by UE 130 (e.g., robot 130) for channel sounding based on at least two beam sets (i.e., multiple reflection configurations 151, 153). The first set of reflection configurations 151 can use fixed beams for CCM estimation, while the second set of reflection configurations 153 can use individual beams (i.e., for the IRS-UE link) to accurately estimate the instantaneous channel between the base station, IRS, and UE. The beams of the second set of reflection configurations 153 can be derived from the CCM and can be dynamically changed according to mobility conditions, etc. To achieve efficient IRS configuration, UE 130 and IRS 120 can use a predefined codebook to quantize the individual beams. For example, UE 130 can select a suitable beam from the codebook and send the index of the beam to IRS 120. This process can be repeated whenever the CCM changes.

[0089] The processes and embodiments described above and below are particularly advantageous for robotic features. Different from a standard UE 130, a robot can directly be aware of its movement / mobility (as shown by the initial position 137 and the final position 139 in Figure 1 ), and can use this information to directly optimize signaling and predict when individual beams need to be updated based on the CCM. In addition, the robot can request the base station 110 to change the number of pilots used for CCM estimation based on its mobility conditions. It should be understood that the processes and embodiments described above and below still apply to a standard UE 130, and the standard UE 130 can apply this method when the CCM changes.

[0090] The above process involves the case where the number T of individual beams is less than the available pilot slots m in each time slot (T < m). According to the embodiments described below, the process can be used for the case where T ≥ m. For those cases, assume that k is the smallest integer that satisfies T < km, i.e., k specifies the number of time slots 161, 163 required to probe the complete set of T individual beams of the second set of reflection configurations 153.

[0091] In the case where km > T > m, the second process can include one or more steps among the first to fourth steps of the first process. The second process can also include one or more of the following steps:

[0092] In the fifth step of the second process, after receiving the codeword, the controller 121 of the IRS 120 can construct two beam sets for channel sounding. The first set of reflection configurations 151 may include (km - T) beams, which can be configured by obtaining (km - T) beams from m fixed beams every k-th time slot 161, 163. This makes it take time slots to probe all the beams of the first set of reflection configurations 151 (i.e., the original fixed beam set with size m). The second set of reflection configurations 153 may include m beams, which are configured by obtaining m beams from the T individual beams in each time slot l ≠ k, and (T mod m) beams from the T individual beams in every k-th time slot 161, 163.

[0093] In the sixth step of the second process, the controller 121 of the IRS 120 can configure the IRS 120 with the beam sets of the first set of reflection configurations 151 and the second set of reflection configurations 153 for each time slot 161, 163 for channel sounding.

[0094] The seventh step of the second process may correspond to the seventh step of the first process.

[0095] The eighth step of the second process may correspond to the eighth step of the first process.

[0096] In the case of km = T, the third process may include one or more steps among the first to fourth steps of the first process. The third process may also include one or more steps among the following steps:

[0097] In the fifth step of the third process, after receiving the codeword, the controller 121 of the IRS 120 can construct two beam sets of the first set of reflection configurations 151 and the second set of reflection configurations 153 for channel sounding. The first set of reflection configurations 151 may include m fixed beams, which can be used for transmission in every n-th time slot (n ≥ k + 1); the second set of reflection configurations 153 may include m beams, which are configured by obtaining m beams from the T individual beams in each time slot l ≠ n.

[0098] In the sixth step of the third process, the controller 121 of the IRS 120 can configure the IRS 120 with the beam sets of the first set of reflection configurations 151 and the second set of reflection configurations 153 for each time slot 161, 163 for channel sounding.

[0099] The seventh step of the third process may correspond to the seventh step of the first process or the seventh step of the second process.

[0100] The eighth step of the third process may correspond to the eighth step of the first process or the eighth step of the second process.

[0101] Figure 5 is a signaling diagram of a communication session between a base station 110 according to an embodiment, an IRS 120 according to an embodiment, and a UE 130 according to an embodiment. Through the Figure 5 signaling shown, the first process, the second process, and / or the third process, as well as other embodiments described above and below, can be implemented. Before the communication session, the base station 110, the IRS 120, and the UE 130 may have been synchronized to achieve beam switching synchronized with the symbol clock based on one or more communication protocols of the wireless network 100.

[0102] In Figure 5 step 501, to control and configure the IRS 120, the UE 130 may first send a configuration request to the controller 121 of the IRS 120.

[0103] In Figure 5 step 503, the IRS 120 may respond with its IRS configuration, which may include information about the array type, the number of antennas, the antenna spacing, etc. Based on the received IRS configuration, the UE 130 may directly determine a codebook, which may be used to quantize individual beams.

[0104] In Figure 5 step 505, the base station 110 may configure the IRS 120 with m fixed beam configurations of the first set of reflection configurations 151 for channel sounding. The base station 110 may also configure pilot time slots 165, 167 for each time slot 161, 163 accordingly.

[0105] In Figure 5 step 507, during channel sounding, the base station 110 transmits its pilots in the m pilot time slots 165, 167 of each time slot 161, 163, and the IRS 120 may switch between the m fixed beams. The UE 130 may perform channel estimation.

[0106] In Figure 5 step 509, after estimating the channel, on multiple channel coherence blocks, the UE 130 may determine the CCM and may derive T individual beams of the second set of reflection configurations 153 quantized based on the codebook.

[0107] In Figure 5 step 511, the UE 130 may send the individual beams of the second set of reflection configurations 153 to the IRS 120 to achieve reconfiguration of the m beams used for channel sounding based on the first set of reflection configurations 151 including fixed beams and the second set of reflection configurations 153 including individual beams.

[0108] In Figure 5In step 513, the next channel sounding phase can be performed with the reconfigured beams, i.e., IRS 120 can now switch between m reconfigured beams while the base station 110 transmits its pilot time slots 165, 167.

[0109] In Figure 5 step 515, the UE 130 can update the CCM based on the measurements obtained with the fixed beams configured for the first set of reflections 151 over multiple channel coherence blocks. If the CCM changes substantially, new individual beams can be generated and then computed and quantized by the UE 130 based on the codebook.

[0110] In Figure 5 step 517, the UE 130 can send the updated individual beams to the IRS 120 to enable the update of the second set of reflection configurations 153.

[0111] In Figure 5 step 519, the next channel sounding phase can be performed using the updated individual beams in the second set of reflection configurations 153.

[0112] As Figure 5 further shown, if the UE 130 may have only partial control of the IRS 120, i.e., if the base station 110 may maintain some degree of control over the IRS 120, the following optional steps can be performed.

[0113] In Figure 5 optional step 521, the UE 130 can request the base station 110 to send more pilots for each of the time slots 161, 163, e.g., in the case where high mobility (e.g., fast movement along the path in Figure 1 above) results in a short channel coherence interval. Then, the UE 130 can request the base station 110 to change the number of pilot time slots m sent for each of the time slots 161, 163. This may also mean increasing the number m of fixed beams in the original set (i.e., the first set of reflection configurations 151).

[0114] In Figure 5 optional step 523, the base station 110 can confirm or reject the request.

[0115] In Figure 5 optional step 525, in the case of confirmation, the base station 110 can configure the pilot time slots 165, 167 according to the new number m and can accordingly notify and / or configure the controller 121 of the IRS 120. Then, the new configuration can be applied in the next channel sounding phase.

[0116] Advantageously, compared with conventional methods with little additional signaling from the robot / UE 130 to the IRS 120, the embodiments disclosed above and below can achieve significant performance improvements. Due to the increased degrees of freedom, different phase shifts and / or amplitudes can be used to configure each IRS antenna oscillator, thus forming arbitrary beams, so that the performance can be improved and a more flexible design than conventional methods can be achieved. Since the optimal IRS phase shift configuration (in the form of individual beams of the second set of reflection configurations 153) is used during channel estimation, the performance can be further improved. This channel estimation can explicitly minimize the MSE based on the CCM information for individual IRS-UE links, which is different from conventional methods that use fixed configurations (especially configurations independent of the CCM).

[0117] The embodiments disclosed above and below enable the use of an arbitrary IRS beamforming codebook, such as a Hadamard codebook, without having to use a DFT codebook for beam quantization.

[0118] Figure 6 is a flowchart of a method 600 for operating the UE 130 according to one embodiment to communicate with a base station 110 according to one embodiment over a communication channel via an IRS 120 according to one embodiment.

[0119] Method 600 includes controlling 601 the IRS 120 to operate in multiple reflection configurations 151, 153 to reflect multiple pilot signals sent from the base station 110 to the UE 130 to probe the channel between the base station, the IRS 120, and the UE 130. The multiple reflection configurations 151, 153 of the IRS 120 include: a first set of reflection configurations 151 for the UE 130 to estimate the channel covariance matrix (CCM) of the communication channel between the base station 110 and the UE 130 via the IRS 120; and a second set of reflection configurations 153 for the UE 130 to estimate the communication channel between the base station 110 and the UE 130 via the IRS 120.

[0120] According to one embodiment, method 600 can be executed by the UE 130. Therefore, other features of method 600 directly come from the functions of the UE 130 and its different embodiments described above and below.

[0121] Figure 7 is a flowchart of a method 700 for operating an IRS 120 according to one embodiment to assist communication between a base station 110 according to one embodiment and a UE 130 according to one embodiment over a communication channel. As described above, the IRS 120 includes a plurality of reflection elements with adjustable phases and / or amplitudes to support multiple reflection configurations 151, 153.

[0122] Method 700 includes operating 701 IRS 120 in multiple reflection configurations 151, 153 to reflect multiple pilot signals sent from base station 110 to UE 130, so as to detect the channels between the base station, IRS 120, and UE 130. Among them, the multiple reflection configurations 151, 153 of IRS 120 include: a first set of reflection configurations 151 for UE 130 to estimate the channel covariance matrix (CCM) of the communication channel between base station 110 and UE 130 through IRS 120; a second set of reflection configurations 153 for UE 130 to estimate the communication channel between base station 110 and UE 130 through IRS 120.

[0123] According to one embodiment, method 700 may be executed by IRS 120. Therefore, other features of method 700 directly come from the functions of IRS 120 and its different embodiments described above and below.

[0124] Figure 8 is a flowchart of method 800 for operating base station 110 according to one embodiment to communicate with UE 130 according to one embodiment over a communication channel through IRS 120 according to one embodiment.

[0125] Method 800 includes transmitting 801 multiple pilot signals, so that IRS 120 operating in multiple reflection configurations 151, 153 reflects multiple pilot signals in multiple time slots 161, 163. Among them, each time slot 161, 163 includes: one or more pilot time slots 165, 167 for transmitting one or more of the multiple pilot signals; one or more data time slots for transmitting one or more of the multiple data signals.

[0126] Method 800 further includes: in response to a request received from UE 130, adjusting 803 the number of one or more pilot time slots 165, 167 for each time slot 161, 163.

[0127] According to one embodiment, method 800 may be executed by base station 110. Therefore, other features of method 800 directly come from the functions of base station 110 and its different embodiments described above and below.

[0128] Those skilled in the art should understand that the "blocks" ("units") in various drawings (methods and devices) represent or describe the functions of the embodiments of the present invention (not necessarily independent "units" in hardware or software), thus equally describing the functions or features of the device embodiments and method embodiments (unit equivalent to step).

[0129] In the multiple embodiments provided in this application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the described device embodiments are merely exemplary. For example, the unit division is only a logical function division, and there can be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Additionally, the mutually coupled or directly coupled or communication connection shown or described can be realized through some interfaces. The indirect coupling or communication connection between devices or units can be achieved in electronic, mechanical, or other forms.

[0130] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units. They can be located in one position or distributed on multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the embodiment solution.

[0131] Furthermore, the functional units in the embodiments of the present invention can be integrated into one processing unit, or each unit can physically exist separately, or two or more than two units can be integrated into one unit.

Claims

1. A user equipment UE (130) for communicating with a base station (110) over a communication channel via an intelligent reflecting surface IRS (120), characterized in that, The UE (130) is configured to: control the IRS (120) to operate in multiple reflection configurations (151, 153) to reflect multiple pilot signals sent from the base station (110) to the UE (130) for probing the channel between the base station, the IRS (120), and the UE (130); the multiple reflection configurations (151, 153) of the IRS (120) include: a first set of reflection configurations (151) for the UE (130) to estimate the channel covariance matrix CCM of the communication channel between the base station (110) and the UE (130) via the IRS (120); a second set of reflection configurations (153) for the UE (130) to estimate the communication channel between the base station (110) and the UE (130) via the IRS (120).

2. The UE (130) according to claim 1, wherein The UE (130) is configured to determine the CCM based on the multiple pilot signals received from the base station (110) reflected by the IRS (120) in the first set of reflection configurations (151).

3. The UE (130) according to claim 1 or 2, characterized in that, The UE (130) is configured to determine the second set of reflection configurations (153) based on the CCM.

4. The UE (130) according to claim 3, characterized in that, The UE (130) is configured to determine the second set of reflection configurations (153) based on multiple eigenvectors of the CCM.

5. The UE (130) according to claim 4, characterized in that, The UE (130) is configured to determine the second set of reflection configurations (153) based on multiple eigenvectors of the CCM having the largest eigenvalues.

6. The UE (130) according to any one of claims 2 to 5, characterized in that, The UE (130) is configured to update the CCM based on the multiple pilot signals received from the base station (110) reflected by the IRS (120) in the first set of reflection configurations (151), wherein if the value of the difference metric between the updated CCM and the previous CCM is greater than a threshold, the UE (130) is configured to update the second set of reflection configurations (153) based on the updated CCM.

7. The UE (130) according to any one of the above claims, characterized in that, The UE (130) is configured to estimate the communication channel between the base station (110) and the UE (130) via the IRS (120) based on the multiple pilot signals received from the base station (110) reflected by the IRS (120) in the second set of reflection configurations (153).

8. The UE (130) according to any one of the above claims, characterized in that, The UE (130) is configured to control the IRS (120) to operate in the multiple reflection configurations (151, 153) to reflect the multiple pilot signals sent from the base station (110) to the UE (130) based on a codebook, where the codebook defines the mapping between multiple codes and the multiple reflection configurations (151, 153).

9. The UE (130) according to claim 8, characterized in that, The UE (130) is configured to receive IRS configuration information from the IRS (120) in response to a configuration information request, and the UE (130) is further configured to generate the codebook based on the IRS configuration information.

10. The UE (130) according to any one of the above claims, characterized in that, The UE (130) is used to control the IRS (120) to operate in the multiple reflection configurations (151, 153) so as to reflect the multiple pilot signals transmitted from the base station (110) in multiple time slots (161, 163), where each time slot (161, 163) includes: one or more pilot time slots (165, 167) for accommodating one or more of the multiple pilot signals from the base station (110); and one or more data time slots for accommodating one or more of the multiple data signals from the base station (110).

11. The UE (130) according to claim 10, characterized in that, Each of the time slots (161, 163) includes: one or more pilot time slots (165, 167) for controlling the IRS (120) to operate in one or more of the reflection configurations in the first set of reflection configurations (151); and one or more pilot time slots (165, 167) for controlling the IRS (120) to operate in one or more of the reflection configurations in the second set of reflection configurations (153).

12. The UE (130) according to claim 10 or 11, characterized in that, The one or more pilot time slots (165) of the first time slot (161) among the multiple time slots (161, 163) include one or more pilot time slots (165) for controlling the IRS (120) to operate in a first subset of the first set of reflection configurations (151) and / or the second set of reflection configurations (153); the one or more pilot time slots (167) of the second time slot (163) among the multiple time slots (161, 163) include one or more pilot time slots (167) for controlling the IRS (120) to operate in a second subset of the first set of reflection configurations (151) and / or the second set of reflection configurations (153), where the first subset of the first set of reflection configurations (151) and / or the second set of reflection configurations (153) is different from the second subset of the first set of reflection configurations (151) and / or the second set of reflection configurations (153).

13. The UE (130) according to any one of claims 10 to 12, characterized in that, If the number of the one or more pilot time slots (165, 167) in each of the time slots (161, 163) is less than or equal to the number of reflection configurations of the second set of reflection configurations (153), the UE (130) is further used to send a request to the base station (110) to adjust the number of the pilot time slots (165, 167) in each of the time slots (161, 163).

14. The UE (130) according to any one of the above claims, characterized in that, The UE (130) is used to control the IRS (120) to operate in the multiple reflection configurations (151, 153) by adjusting the corresponding signal amplitude and / or the corresponding signal phase shift of each of the multiple reflection elements of the IRS (120).

15. The UE (130) according to any one of the above claims, characterized in that, The UE (130) is further used to communicate with the base station (110) based on the communication channel between the base station (110) and the UE (130) estimated through the IRS (120).

16. A method (600) for operating a user equipment UE (130) to communicate with a base station (110) over a communication channel via an intelligent reflecting surface IRS (120), characterized in that, The method (600) includes: Control (601) the IRS (120) to operate in multiple reflection configurations (151, 153) to reflect multiple pilot signals transmitted from the base station (110) to the UE (130) to probe the channel between the base station, the IRS (120), and the UE (130), wherein the multiple reflection configurations (151, 153) of the IRS (120) include: a first set of reflection configurations (151) for the UE (130) to estimate the channel covariance matrix CCM of the communication channel between the base station (110) and the UE (130) through the IRS (120); a second set of reflection configurations (153) for the UE (130) to estimate the communication channel between the base station (110) and the UE (130) through the IRS (120).

17. An intelligent reflecting surface IRS (120), characterized in that, For assisting communication between the base station (110) and the user equipment UE (130) on a communication channel, the IRS (120) includes a plurality of reflection elements with adjustable phase and / or amplitude to support multiple reflection configurations (151, 153), and the IRS (120) is configured to: Operate in multiple reflection configurations (151, 153) to reflect multiple pilot signals transmitted from the base station (110) to the UE (130) to probe the channel between the base station, the IRS (120), and the UE (130); The multiple reflection configurations (151, 153) of the IRS (120) include: a first set of reflection configurations (151) for the UE (130) to estimate the channel covariance matrix CCM of the communication channel between the base station (110) and the UE (130) through the IRS (120); a second set of reflection configurations (153) for the UE (130) to estimate the communication channel between the base station (110) and the UE (130) through the IRS (120).

18. The IRS (120) according to claim 17, characterized in that, The IRS (120) operates in the multiple reflection configurations (151, 153) to reflect the multiple pilot signals transmitted from the base station (110) to the UE (130) based on a codebook, wherein the codebook defines the mapping between multiple codes and the multiple reflection configurations (151, 153).

19. The IRS (120) according to claim 18, characterized in that, The IRS (120) is configured to send IRS configuration information to the UE (130) in response to a configuration information request from the UE (130) to generate the codebook based on the IRS configuration information.

20. The IRS (120) according to any one of claims 17 to 19, characterized in that, The IRS (120) is configured to operate in the multiple reflection configurations (151, 153) to reflect the multiple pilot signals transmitted from the base station (110) in multiple time slots (161, 163), where each time slot (161, 163) includes: one or more pilot time slots (165, 167) for accommodating one or more of the multiple pilot signals from the base station (110); and one or more data time slots for accommodating one or more of the multiple data signals from the base station (110).

21. The IRS (120) according to claim 20, characterized in that, Each of the time slots (161, 163) includes: one or more pilot time slots (165, 167) for the IRS (120) to operate in one or more of the first set of reflection configurations (151); and one or more pilot time slots (165, 167) for the IRS (120) to operate in one or more of the second set of reflection configurations (153).

22. The IRS (120) according to claim 20 or 21, characterized in that, The one or more pilot time slots (165) of the first time slot (161) among the multiple time slots (161, 163) include one or more pilot time slots (165) for the IRS (120) to operate in a first subset of the first set of reflection configurations (151) and / or the second set of reflection configurations (153); the one or more pilot time slots (167) of the second time slot (163) among the multiple time slots (161, 163) include one or more pilot time slots (167) for the IRS (120) to operate in a second subset of the first set of reflection configurations (151) and / or the second set of reflection configurations (153), where the first subset and the second subset of the first set of reflection configurations (151) and / or the second set of reflection configurations (153) are different from each other.

23. A method (700) for operating an intelligent reflecting surface IRS (120), characterized in that, For assisting communication between the base station (110) and the user equipment UE (130) over a communication channel, the IRS (120) includes a plurality of reflection elements with adjustable phase and / or amplitude to support multiple reflection configurations (151, 153), and the method (700) includes: Operating (701) the IRS (120) in multiple reflection configurations (151, 153) to reflect the multiple pilot signals transmitted from the base station (110) to the UE (130) to probe the channel between the base station, the IRS (120), and the UE (130); the multiple reflection configurations (151, 153) of the IRS (120) include: a first set of reflection configurations (151) for the UE (130) to estimate the channel covariance matrix CCM of the communication channel between the base station (110) and the UE (130) through the IRS (120); and a second set of reflection configurations (153) for the UE (130) to estimate the communication channel between the base station (110) and the UE (130) through the IRS (120).

24. A base station (110) for communicating with a user equipment UE (130) over a communication channel via an intelligent reflecting surface IRS (120), characterized in that, The base station (110) is configured to: Transmit a plurality of pilot signals, so that the IRS (120) operating in a plurality of reflection configurations (151, 153) reflects the plurality of pilot signals in a plurality of time slots (161, 163), wherein each time slot (161, 163) includes: one or more pilot time slots (165, 167) for transmitting one or more of the plurality of pilot signals; one or more data time slots for transmitting one or more of the plurality of data signals; In response to a request received from the UE (130), adjust the number of the one or more pilot time slots (165, 167) for each time slot (161, 163).

25. The base station (110) according to claim 24, characterized in that, The plurality of reflection configurations (151, 153) of the IRS (120) include: a first set of reflection configurations (151) for the UE (130) to estimate the channel covariance matrix CCM of the communication channel between the base station (110) and the UE (130) through the IRS (120); a second set of reflection configurations (153) for the UE (130) to estimate the communication channel between the base station (110) and the UE (130) through the IRS (120), wherein at the IRS (120), the base station (110) is configured to receive information about the first and / or the second set of reflection configurations (153) from the UE (130) and / or the IRS (120).

26. A method (800) for operating a base station (110) to communicate with a user equipment UE (130) over a communication channel via an intelligent reflecting surface IRS (120), characterized in that, The method (800) includes: Transmit (801) a plurality of pilot signals, so that the IRS (120) operating in a plurality of reflection configurations (151, 153) reflects the plurality of pilot signals in a plurality of time slots (161, 163), wherein each time slot (161, 163) includes: one or more pilot time slots (165, 167) for transmitting one or more of the plurality of pilot signals; one or more data time slots for transmitting one or more of the plurality of data signals; In response to a request received from the UE (130), adjust (803) the number of the one or more pilot time slots (165, 167) for each time slot (161, 163).

27. A computer program product, characterized in that, The computer program product includes a computer-readable storage medium for storing program code, which when executed by a computer or a processor, causes the computer or the processor to execute the method (600) according to claim 16, the method (700) according to claim 23, or the method (800) according to claim 26.

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