Wireless communication device, method of operating wireless communication device and method of operating base station communicating with wireless communication device

Abstract

A method for operating a wireless communication apparatus including a plurality of antennas according to an exemplary embodiment of the present disclosure includes: determining an antenna subset including at least one of the plurality of antennas; transmitting a sounding reference signal (SRS) exchange signal to a base station via at least one antenna in the antenna subset; receiving a channel state information-reference signal (CSI-RS) transmitted from the base station using a first beam; selecting a precoding matrix indicator (PMI) based on the CSI-RS; transmitting the selected PMI to the base station; and receiving a signal transmitted from the base station using a second beam, the second beam being determined based on the SRS exchange signal and the PMI.

Description

Technical Field

[0001] This disclosure relates generally to wireless communications, and more specifically to wireless communications using beamforming techniques based on defined channel characteristics. [Cross-reference to related applications]

[0002] This application is based on and claims priority over Korean Patent Application No. 10-2021-0003565, which was filed on January 11, 2021, with the Korean Intellectual Property Office. The full disclosure of the Korean Patent Application is incorporated herein by reference. Prior Technology

[0003] Beamforming refers to the method of using multiple antennas to transmit or receive directional signals. As an example, a base station (BS) can use beamforming to transmit downlink signals to a terminal. To determine the desired beam, the base station can assume that the radio channels between the uplink (terminal to base station) and downlink (base station to terminal) are reciprocal, i.e., that a channel reciprocity condition exists. In this case, the base station can use beamforming to transmit the downlink signal based on the downlink channel condition estimated from the uplink signal received from the terminal. However, due to various factors, the uplink channel and downlink channel may differ, which can lead to inaccurate downlink channel information, resulting in suboptimal beamforming. Summary of the Invention

[0004] This disclosure provides a wireless communication method and a wireless communication device for optimizing downlink beam determination of a base station by transmitting a "sounding reference signal (SRS) exchange signal" using techniques such as antenna selection or beam selection.

[0005] In one embodiment, a method of operating a wireless communication apparatus including a plurality of antennas according to an exemplary embodiment of the present disclosure includes: determining an antenna subset including at least one of the plurality of antennas; transmitting an SRS-switched signal to a base station via at least one antenna in the antenna subset; receiving a channel state information-reference signal (CSI-RS) transmitted from the base station via a first beam; selecting a precoding matrix indicator (PMI) based on the CSI-RS; transmitting the selected PMI to the base station; and receiving a signal transmitted from the base station via a second beam, the second beam being determined based on the SRS-switched signal and the PMI.

[0006] In another embodiment, a wireless communication device according to an exemplary embodiment of the present disclosure includes: a plurality of antennas; a radio-frequency integrated circuit (RFIC) including a switching network connected to the plurality of antennas; the switching network being configured to transmit an SRS switching signal to a base station via at least one antenna included in the antenna subset; and a processor being configured to: determine an antenna subset including at least one of the plurality of antennas; select a PMI to be provided to the base station based on CSI-RS transmitted from the base station using a first beam; and process the signal transmitted from the base station using a second beam, the second beam being determined based on the SRS switching signal and the PMI.

[0007] In another embodiment, a method for communicating between an operating base station and a wireless communication device including a plurality of antennas according to an exemplary embodiment of the present disclosure includes: receiving an SRS exchange signal transmitted using an antenna subset including at least one of the plurality of antennas; estimating uplink channel information based on the SRS exchange signal; estimating downlink channel information based on the estimated uplink channel information; determining and forming a first beam based on the estimated downlink channel information; transmitting CSI-RS via the first beam and receiving PMI from the wireless communication device; determining and forming a second beam based on the received SRS exchange signal and the received PMI, and transmitting a signal including data via the second beam.

[0008] In another embodiment, a method of operating a wireless communication device comprising multiple antennas involves determining a subset of antennas comprising at least two, but fewer than, of the multiple antennas. An SRS-switched signal comprising an SRS sequence is transmitted to a base station, wherein each of the SRSs is transmitted by a different one of the at least two antennas in the antenna subset. A reference signal transmitted from the base station via a first beam is received, and a PMI is selected based on the reference signal. The selected PMI is transmitted to the base station. Thereafter, a signal transmitted from the base station via a second beam, the second beam being determined based on the SRS-switched signal and the PMI, is received. Simple Explanation of the Diagram

[0009] Embodiments of the invention will be more clearly understood by reading the following detailed description in conjunction with the accompanying drawings, in which:

[0010] Figure 1A is a block diagram schematically illustrating a wireless communication system according to an exemplary embodiment of the present disclosure, and Figure 1B is a diagram illustrating the radio channel between the wireless communication device shown in Figure 1A and the base station.

[0011] Figure 2 is a flowchart illustrating a method for operating a wireless communication device and base station in a wireless communication system according to an exemplary embodiment of the present disclosure.

[0012] Figures 3A and 3B are flowcharts illustrating corresponding examples of a method for exchanging a transmit detection reference signal (SRS) according to exemplary embodiments of the present disclosure.

[0013] Figure 4 is a flowchart illustrating an example of a method for transmitting SRS-switched signals according to a sequential antenna selection method in accordance with an exemplary embodiment of the present disclosure.

[0014] Figures 5A and 5B are flowcharts illustrating examples of a method for transmitting SRS-switched signals according to an opportunity antenna selection method in accordance with exemplary embodiments of the present disclosure.

[0015] Figure 6 is a flowchart illustrating an example of a method for transmitting SRS-switched signals according to an antenna spatial correlation-based selection method, based on an exemplary embodiment of the present disclosure.

[0016] Figures 7A, 7B, and 7C are flowcharts illustrating examples of methods for transmitting SRS-switched signals according to an antenna selection method based on reinforcement learning, in accordance with exemplary embodiments of the present disclosure.

[0017] Figure 8 is a flowchart illustrating an example of a method for tracking a final subset of antennas according to an exemplary embodiment of this disclosure.

[0018] Figures 9A and 9B are flowcharts illustrating examples of a method for selecting a precoding matrix indicator (PMI) according to an exemplary embodiment of the present disclosure.

[0019] Figures 10A, 10B, and 10C are block diagrams illustrating the structure of a wireless communication device according to an exemplary embodiment of the present disclosure. Implementation

[0020] In the following, embodiments of the concept of the invention will be described in detail with reference to the accompanying drawings.

[0021] FIG1A is a block diagram schematically illustrating a wireless communication system 10 according to an exemplary embodiment of the present disclosure, and FIG1B is a diagram illustrating the radio channel between the wireless communication device 100 shown in FIG1A and the base station 110.

[0022] The wireless communication system 10 can refer to any system including the wireless communication device 100 and the base station 110. For example, the wireless communication system 10 can be any of a New Radio (NR) system, a 5th generation (5G) wireless system, a Long Term Evolution (LTE) system, an LTE-Advanced system, a Code Division Multiple Access (CDMA) system, a Global System for Mobile Communication (GSM) system, or a Wireless Local Area Network (WLAN) system. In the case of a CDMA system, this can be implemented in various CDMA versions such as wideband CDMA (WCDMA), time division synchronization CDMA (TD-SCDMA), CDMA2000, and similar versions. In the following description, the wireless communication system 10 will be primarily illustrated with reference to 5G and / or LTE systems, but it should be understood that the exemplary embodiments disclosed herein are not limited thereto.

[0023] The wireless communication network of the wireless communication system 10 can support multiple users to communicate by sharing available network resources. For example, in the wireless communication network, various multiple access methods such as Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), Orthogonal Frequency Division Multiplexing (OFDM)-FDMA, OFDM-TDMA, OFDM-CDMA, and similar methods can be used to provide information.

[0024] Base station (BS) 110 may be part of wireless communication system 10. BS 110 may typically be a fixed station communicating with multiple user equipment (UEs), but in other instances, UEs may be configured to act as base stations. BS 110 may communicate with another BS 112 and may exchange data and control information by communicating with UEs and / or other "cells" (e.g., other BSs that typically serve a specific geographic area). For example, a BS may be referred to as a cell, Node B, evolved-Node B (eNB), next-generation Node B (gNB), sector, site, base transceiver system (BTS), access point (AP), relay node, remote radio head (RRH), radio unit (RU), small cell, and similar names. In this specification, the term "BS" can comprehensively refer to some area or function covered by the Base Station Controller (BSC) in CDMA, Node B in WCDMA, eNB in ​​LTE, gNB or sector (site) in NR and the like, and can cover the owners of various coverage areas such as megacell, macrocell, microcell, picocell, femtocell, relay nodes, RRH, RU and small cell communication range.

[0025] The wireless communication device 100 (hereinafter, for the sake of brevity, may be referred to interchangeably simply as "device 100") may be a UE in the wireless communication system 10. "UE" may be a fixed UE or a mobile UE, and may refer to various devices capable of transmitting and receiving data and / or control information by communicating with the BS. For example, a UE may be referred to as a terminal device, mobile station (MS), mobile terminal (MT), user terminal (UT), subscriber station (SS), wireless device, handheld device, and similar names.

[0026] As shown in Figure 1A, the wireless communication system 10 may include multiple base stations (BSs) (e.g., 110 and 112) and a system controller 120. In other instances, the wireless communication system 10 may include one or more additional cells and multiple network entities. BSs 110 and 112 may communicate with device 100 or another cell to transmit and receive data signals or control information. Wireless communication device 100 may communicate with the wireless communication system 10 and may also receive signals from broadcast station 114. Furthermore, wireless communication device 100 may receive signals from GNSS satellites 130. Device 100 may support radio technologies used for various wireless communications.

[0027] The technical specifications disclosed herein can be applied between communication entities forming uplink and downlink channels in a wireless communication system 10. In the following description, device 100 and BS 110 will be referred to as the communication entities to which the technical specifications disclosed herein are applied.

[0028] Downlink channel 102 and uplink channel 104 can form a data connection path between device 100 and BS 110. It can be assumed that the state of downlink channel 102 is the same as or similar to the state of uplink channel 104 (reciprocity condition). When the downlink channel and the uplink channel are similar, this can be referred to as a "calibratable reciprocity condition," where calibration can be performed to effectively achieve reciprocity between the uplink and downlink channels. In the following description, reciprocity (non-reciprocity condition) is assumed to exist regardless of whether calibration is performed. Reciprocity between downlink channel 102 and uplink channel 104 can exist in a time-division duplex (TDD) based wireless communication system, where the uplink and downlink share the same spectrum, but uplink and downlink transmissions are separated in the time domain. In frequency division duplex (FDD) based wireless communication systems where the uplink and downlink use different spectrums, reciprocity can also be predicted or achieved through calibration.

[0029] BS 110 can receive a sounding reference signal (SRS) transmitted by at least one of a plurality of antennas included in device 100. In embodiments disclosed herein, BS 110 typically receives an SRS sequence from at least two (a subset of) the antennas of device 100, wherein each antenna transmits one SRS in the sequence. This SRS sequence may be referred to as an "SRS exchange signal". For example, when device 100 includes a plurality of antennas, at least two of the antennas may be selected sequentially in a predetermined order, and each of the at least two antennas may transmit an SRS, which may be received by BS 110 and, in some cases, by the cell. BS 110 may estimate an uplink channel 104 for each antenna of device 100 and, assuming channel reciprocity, use the estimated uplink channel to estimate downlink channel information.

[0030] However, even if the transmitter or receiver is calibrated to meet channel reciprocity, the channels through which it transmits and receives uplink and downlink signals may differ due to implementation issues with device 100. For example, if the number of transmit / receive antennas of the terminal differs from the number of transmit / receive radio frequency (RF) chains, or if there are constraints on the SRS resources allocated from BS 110, then in a conventional system, BS 110 cannot obtain complete downlink channel information from the signals received from device 100.

[0031] Furthermore, when BS 110 restricts SRS resources for each device to support multi-user multiple-input multiple-output (MU-MIMO), device 100 is assigned limited SRS resources, for example, using fewer frequencies and / or time slots for channel measurements compared to an unconstrained SRS resource scenario. When transmitting SRS in a conventional manner with limited resources, beamforming using downlink channel information obtained from BS 110 may be suboptimal.

[0032] The wireless communication system 10 according to the exemplary embodiments of this disclosure uses the antenna or beam selection method of the device 100 to efficiently transmit SRS and efficiently acquire downlink channels, thereby achieving beamforming-based communication with improved performance.

[0033] Referring further to Figure 1B, device 100 may include m antennas 1 to m, and BS 110 may include n antennas 1 to n. Device 100 and BS 110 can use the corresponding antennas to implement mutual beamforming-based communication, multi-input and multi-output (MIMO)-based communication, and similar communication. Since the configuration shown in Figure 1B increases the theoretical channel transmission capacity, the transmission rate can be improved, and frequency efficiency can be significantly improved.

[0034] The uplink channel hj(1) corresponding to the j-th antenna of the wireless communication device 100 j (m,j are integers) may include channels h1,j,h2,j,...,hn,j corresponding to the respective n antennas of BS 110. BS 110 may receive SRS transmitted from the j-th antenna of device 100 and use the received SRS to estimate the uplink channel hj. Assuming channel reciprocity, BS 110 may estimate the downlink channel based on the uplink channel hj, generate a downlink signal using the estimated downlink channel, and transmit the downlink signal to device 100 via at least one of the n antennas.

[0035] The description of the uplink channel hj corresponding to the j-th antenna of device 100 can be applied to the uplink channels corresponding to other antennas of device 100, and based on the above, the technical concepts disclosed herein will be explained below.

[0036] It should be noted that the terms "antenna selection" and "beam selection" are used interchangeably throughout this specification. The term "antenna selection" will be used primarily below to illustrate some of the technical concepts disclosed herein.

[0037] Figure 2 is a flowchart illustrating a method of operating a device 100 and a BS 110 in a wireless communication system according to an exemplary embodiment of the present disclosure. In this method, the wireless communication system 10 may include device 100 and BS 110, and in operation S210, device 100 may transmit an "SRS exchange signal" to BS 110 using SRS exchange resources set by BS 110. (During previous signal exchanges with BS 110, device 100 may have already learned of the SRS exchange resources.) As previously described, the SRS exchange signal includes a plurality of SRS transmitted sequentially, wherein each SRS is transmitted from a corresponding antenna of device 100. "SRS exchange resources" can be defined as a set of uplink resource elements (REs) (e.g., a set of frequencies and / or time slots used for SRS transmission) used by device 100 when transmitting an SRS signal for the purpose of obtaining channel information for downlink beamforming from BS 110. BS 110 may allocate SRS exchange resources to device 100.

[0038] According to one embodiment, the available resources of BS 110 for transmitting SRS switching signals are limited. In this scenario, there are fewer SRS switching resources allocated by BS 110 for SRS switching signals than the number of receiving antennas of device 100. In this case, only some antennas are used for transmission ("First Scenario"). For example, suppose there are 5 wireless communication devices in a cell covered by BS 110, and each wireless communication device 100 includes 4 antennas. If there are 16 resources available for allocation by BS 110, some of the 5 wireless communication devices cannot be allocated 4 SRS switching resources (assuming the switching resources are intended to be used simultaneously).

[0039] In another scenario, due to hardware limitations of the wireless communication device 100 when transmitting SRS exchange signals, there may be a situation where only some antennas are used for transmission ("Second Scenario"). This corresponds to a situation where the number of Tx radio frequency (RF) chains of device 100 is less than the number of receiving antennas of 100. For example, due to hardware limitations of device 100, the number of receiving antennas may be four, but the number of transmitting antennas may be limited to two.

[0040] In the following discussion, for ease of understanding of the concepts taught herein, an example is presented in which device 100 has four receiving antennas. In other examples, the concepts are applied to device 100 with more or fewer antennas.

[0041] The operation of antenna selection and antenna switching will be further explained below with reference to Figures 3A and 3B.

[0042] In operation S220, BS 110 can estimate uplink channel information based on the received SRS exchange signal. In operation S230, BS 110 can estimate downlink channel information by performing operations such as calibration based on the estimated uplink channel information. Here, calibration refers to a series of processes in which the uplink and downlink channels are corrected by RF filters to satisfy reciprocity throughout the signal path (e.g., from the baseband at transmission to the baseband at reception). BS 110 can use the estimated downlink channel information to determine beamforming in operation S240, and use beamforming to transmit Channel State Information-Reference Signal (CSI-RS) in operation S250. Depending on which antenna is selected, the CSI-RS transmitted by BS 110 to device 100 may include different information.

[0043] In operation S260, device 100 can select a precoding matrix indicator (PMI) based on the received CSI-RS, and in operation S270, transmit the selected PMI to BS 110. When selecting a PMI, device 100 can consider information about the selected antenna and, accordingly, select the optimal PMI.

[0044] In operation S280, BS 110 can use the information obtained from the SRS exchange signal received in operation S210 and the information obtained from the PMI received in operation S270 to determine the final downlink beamforming, and in operation S290, it transmits downlink signals including data or the like by means of the antenna beam determined by beamforming.

[0045] The beam determined in operation S280 may be referred to as the "final beam" below, and may be defined in matrix form as follows.

[0046] [Equation 1] [ x , =, F ] [ SRS ] [ F ] [ PMI ] [ s ]

[0047] [F ] [ SRS The number of antennas in BS 110 × the number of CSI-RS antenna ports can be defined as a matrix of beams based on the SRS exchanged signals received from device 100, and [ F ] [ PMI (Number of CSI-RS antenna ports × Number of data layers or data streams) can be defined as a matrix of beams based on the PMI received from device 100. [ s (Number of data layers or data streams × 1) can be defined as a matrix including the downlink signals of the data that BS 110 wants to transmit to device 100.

[0048] BS 110 can use the owner of the information obtained from the SRS exchange signal and PMI to form the final synthesized beam, and beamforming can be performed using device 100. [ F ] [ SRS ]and [ F ] [ PMI It can be expressed as [ F ] [ SRS ]_ [ PMI (It is the matrix of the final synthesized beam), that is, it takes the form of a beam. [ x (Number of BS antennas × 1) corresponds to the final signal transmitted from BS 110 to device 100.

[0049] Based on the above operating method, the device 100 adaptively transmits SRS switching signals and adaptively transmits PMI to optimize the acquisition of downlink channel information and the beamforming decision of BS 110.

[0050] Meanwhile, the CSI-RS corresponding to the downlink reference signal and the SRS corresponding to the uplink reference signal illustrated with reference to FIG2 are merely examples of reference signals that can be applied in the method. Alternative reference signals may include a pilot signal for channel estimation transmitted by the BS in the downlink and a pilot signal for channel estimation transmitted by the wireless communication device in the uplink.

[0051] Figures 3A and 3B are flowcharts illustrating examples of a method for transmitting SRS exchange signals according to exemplary embodiments of the present disclosure.

[0052] Figure 3A illustrates the process of determining an antenna subset to select the antennas used to transmit SRS exchange signals in operation S210 shown in Figure 2.

[0053] In operation S310a, BS 110a may transmit a downlink reference signal to wireless communication device 100a (hereinafter referred to as "device 100a"). Device 100a may estimate downlink channel information based on the received CSI-RS in operation S320a, and determine an antenna subset based on the estimated downlink channel information in operation S330a. The antenna subset may be determined based on at least one of the signal-to-interference-plus-noise ratio (SINR) of the wireless communication device, the transmit / receive characteristics of the antenna, and the linearity of the transmit power amplifier. In operation S340a, device 100a may transmit an SRS-switched signal using at least one of the antennas included in the determined antenna subset.

[0054] In exemplary embodiments, methods for determining antenna subsets may include a method for sequentially determining antenna subsets and then exchanging antenna subsets according to the transmission cycle of the SRS exchange signal; a method for non-periodicly exchanging antenna subsets after determining antenna subsets based on a gain / signal quality metric of a specific beam; a method for exchanging antenna subsets after determining antenna subsets based on the spatial correlation between the receiving antennas of a wireless communication device; and a method for exchanging antenna subsets according to an update cycle after determining antenna subsets based on reinforcement learning. A detailed description of this is provided below with reference to FIG4.

[0055] Referring to Figure 3B, the process of selecting a beam to transmit an SRS switching signal in operation S210 as shown in Figure 2 is illustrated.

[0056] In operation S310b, BS 110b can transmit a downlink reference signal to wireless communication device 100b ("device 100b"). Device 100b can estimate downlink channel information based on the received CSI-RS in operation S320b, and determine the beam for transmitting SRS-switched signals from each antenna based on the estimated downlink channel information in operation S330b. For example, 100b can use the estimated downlink channel information to select a beam with good reception performance and spatial characteristics from a previously designed beamcodebook, or it can design a new beamcodebook if no pre-designed beamcodebook exists. In operation S340b, the determined beam can be used to transmit the SRS-switched signal.

[0057] Table 1 below shows the beam codebook according to an embodiment of this disclosure.

[0058]

[0059] Referring to Table 1, in this example, it is assumed that there are four antennas in device 100b, and four beams can be formed from each antenna. For example, the beam codebook includes indices of a pre-coded matrix shared in device 100b and BS 110b. The elements of each antenna used for beam configuration can be expressed as arbitrary complex values. For example, the real component of the second beam of antenna #4 is A42, and the imaginary component is B42.

[0060] Table 2 below shows the beam codebook according to an embodiment of this disclosure.

[0061]

[0062] Referring to Table 2, among the elements used to configure the third antenna, the element for the third beam can be composed of 1.

[0063] Figure 4 is a flowchart illustrating an example of a method for transmitting SRS-switched signals according to a sequential antenna selection method in accordance with an exemplary embodiment of the present disclosure.

[0064] The example shown in Figure 4 illustrates a method for transmitting SRS-switched signals by sequentially determining antenna subsets and then switching the antenna subsets according to the SRS transmission cycle. This can be referred to as the "sequential antenna selection method".

[0065] In Figure 4, it is assumed that the number of receiving antennas of device 100 is 4, and that SRS switching signals are transmitted to BS 110 using two transmitting antennas, which is fewer than the number of receiving antennas. That is, it is assumed that the size of the antenna subset determined by device 100 is 2. For example, this corresponds to a situation where BS 110 allocates two SRS switching resources to device 100 (first scenario), or where only two antennas are used due to hardware limitations of device 100.

[0066] In an embodiment, when the indices of the first antenna, the second antenna, the third antenna, and the fourth antenna are {0, 1, 2, 3} respectively, a subset consisting of the combination of two antennas used to transmit SRS exchange signals from the first antenna to the fourth antenna can be configured as follows.

[0067] Antenna subset: {0,1}{0,2}{0,3}{1,2}{1,3}{2,3}

[0068] In an exemplary embodiment, the device 100 may determine each of the six possible antenna subsets in a predefined order.

[0069] Here, for example, the fact that the antenna subsets are determined sequentially means that the six possible antenna subsets are selected sequentially from {0,1}, {0,2}, {0,3}, {1,2}, {1,3}, and {2,3} for each transmission cycle of the SRS exchange signal.

[0070] For example, in operation S402, 100 may determine the subset of antennas to transmit the SRS switching signal as {0,1} during the first SRS switching transmission cycle. That is, device 100 may determine to transmit the SRS switching signal using the first antenna and the second antenna among the four antennas. In some embodiments, device 100 may determine each of the antenna subsets in a different order than described above.

[0071] In operation S404, after using the first antenna to transmit SRS_0 as the SRS switching signal and the second antenna to transmit SRS_1 as the SRS switching signal, the BS 110 can design the downlink beam F_SRS using SRS_0 and SRS_1 in operation S406. The BS110 can transmit CSI-RS via the F_SRS beam in operation S408.

[0072] Device 100 can select PMI based on the received CSI-RS in operation S410, and feed back the PMI to BS 110 in operation S412. BS 110 can use the received PMI to design the downlink beam F_PMI in operation S414, and transmit a downlink signal including data to device 100 in operation S416 by using the final beam determined by F_SRS and F_PMI.

[0073] As an exemplary embodiment, operations S402 to S416 can be performed by device 100 within the time corresponding to the first SRS switching signal transmission cycle, and can be referred to as Cycle 1. In the second SRS switching signal transmission cycle corresponding to Cycle 2, the antenna subset {0,2} is determined to transmit SRS switching signals, and for example, in Cycle 4 corresponding to the fourth SRS switching signal transmission cycle, the antenna subset {1,2} is determined to transmit SRS_1 and SRS_2 to BS 110.

[0074] In operation S418, after repeating a number of SRS switching transmission cycles, the device 100 may determine, in the fourth SRS switching transmission cycle, the subset of antennas to transmit the SRS switching signal as {1,2}. That is, the device 100 may determine to transmit the SRS switching signal using the second and third antennas of the four antennas. In some embodiments, the device 100 may determine each of the antenna subsets in a different order than described above.

[0075] In operation S420, after using the first antenna to transmit SRS_0 as the SRS switching signal and the second antenna to transmit SRS_1 as the SRS switching signal, BS 110 can design the downlink beam F_SRS using SRS_0 and SRS_1 in operation S422. BS 110 can transmit CSI-RS via the F_SRS beam in operation S424.

[0076] Device 100 can select PMI based on the received CSI-RS in operation S426, and feed back the PMI to BS 110 in operation S428. BS 110 can use the received PMI to design the downlink beam F_PMI in operation S430, and transmit a downlink signal including data to wireless communication device 100 using the final beam determined by F_SRS and F_PMI in operation S432.

[0077] According to the method shown in Figure 4, device 100 can monitor the "gain" of the final beam at each SRS-switched signal transmission cycle and sequentially consider all possible antenna subsets to find the optimal antenna combination. Here, "beam gain" or simply "gain" or "gain value" can be defined as a relative term for the signal quality of a signal transmitted by an antenna beam from a base station and received by a wireless communication device (e.g., 100) (since the distance between BS 110 and device 100 is typically unknown). In the following text, the terms "gain" and "signal quality" are used interchangeably. Gain can be determined by the power of the signal received by device 100, the signal-to-noise ratio (SNR) of the signal received by device 100, the signal-to-interference-plus-noise ratio (SINR) of the signal received by device 100, and / or frequency efficiency.

[0078] According to embodiments disclosed herein, the subset of antennas ultimately selected as the optimal antenna combination may be referred to as the "final antenna subset".

[0079] It should be noted that in the examples above, the antenna subset size of 2 is used to help understand the concepts taught in this article. In other examples, more or fewer antennas can form an antenna subset.

[0080] Figures 5A and 5B are flowcharts illustrating examples of a method for transmitting SRS-switched signals according to an opportunity antenna selection method in accordance with exemplary embodiments of the present disclosure.

[0081] Figure 5A illustrates a method for transmitting SRS-switched signals after determining an antenna subset based on the gain value of a specific beam, by non-periodicly switching the antenna subset. This can be referred to as one of the "opportunistic antenna selection methods".

[0082] In opportunistic antenna selection methods, a specific value corresponding to the beam gain is preset as a threshold value. [ B ] [ th Furthermore, when the gain value of the final beam determined as an arbitrary antenna subset is less than a threshold value, different antenna subsets can be immediately determined regardless of the order. When the gain value of the final beam determined as an arbitrary antenna subset is greater than a threshold value, the process of determining another antenna subset and transmitting SRS exchange signals can be stopped, and the corresponding antenna subset can be declared as the optimal antenna combination. That is, the corresponding antenna subset can be determined as the "final antenna subset".

[0083] Simultaneously, after the final antenna subset is determined, device 100 can use any tracking period to track the optimal antenna combination. There may be methods to change one antenna included in the previously determined final antenna subset, and there may be methods to change one or more antennas. When the gain of the final beam decreases rapidly, the antennas included in the previously determined final antenna subset may not be selected, or the final antenna subset itself may be replaced by another antenna subset. Tracking and the tracking period can be determined based on indicators related to changes in the radio channel.

[0084] Specifically, referring to FIG5A, the device 100 can determine any subset of antennas for transmitting SRS switching signals in operation S510a, and after operation S510a, operations S210 to S290 as described with reference to FIG2 can be performed, and their detailed information will be omitted.

[0085] In operation S520a, as an exemplary embodiment, the device 100 can monitor the gain value of the final beam received in operation S290. In operation S530a, the device 100 can determine whether the monitored gain value of the final beam exceeds a threshold value. [ B ] [ th ].

[0086] In operation S540a, when the gain value of the final beam monitored by device 100 exceeds the threshold value... [ B ] [ th When [the antenna subset is determined], the antenna subset determined in operation S510a can be determined as the final antenna subset.

[0087] On the other hand, when the gain value of the final beam monitored by device 100 is less than or equal to the threshold value [ B ] [ th When the process returns to operation S510a to determine the antenna subset, for example, device 100 may return to operation S510a, select antenna subset {2,3}, and use the third and fourth antennas to transmit SRS switching signals.

[0088] Figure 5B illustrates a method for transmitting SRS-switched signals after determining an antenna subset based on the channel gain values ​​corresponding to all antennas of the channel receiving CSI-RS, by aperiodically swapping the antenna subset. This can be referred to as one of the "opportunistic antenna selection methods".

[0089] In an embodiment, when the channel gains corresponding to all antennas of the channel receiving CSI-RS have similar values, the apparatus 100 may determine the antenna subset identified in an operation similar to S510b as the final antenna subset. According to embodiments, the criteria for whether the channel gains have similar values ​​can be set in different ways.

[0090] On the other hand, when there is a relatively large difference in channel gain corresponding to all antennas of the channel receiving CSI-RS, the device 100 may return to an operation similar to S510b of determining the antenna subset and continue to try to transmit SRS exchange signals using a new antenna subset.

[0091] The device 100 can determine any subset of antennas for transmitting SRS exchange signals in operation S510b, and after operation S510b, it can perform operations S210 to S290 as illustrated in FIG2 (details omitted here).

[0092] In operation S520b, as an exemplary embodiment, the device 100 may monitor the gain value of the channel receiving CSI-RS in operation S290. In operation S530b, the device 100 may determine whether the absolute value of the difference between the monitored channel gain values ​​exceeds a threshold value. [ C ] [ th ].

[0093] When the absolute value of the difference between the gain values ​​of the channels monitored in operation S520b exceeds the threshold value [ C ] [ th During operation S540b, device 100 can determine the final antenna subset as the antenna subset determined in operation S510b.

[0094] On the other hand, when the gain value of the final beam monitored by device 100 is less than or equal to the threshold value [ C ] [ th When the process returns to operation S510b, which determines the antenna subset, the device 100 may return to operation S510b, select the antenna subset {2,3}, and then periodically or continuously transmit SRS switching signals using the third and fourth antennas.

[0095] Simultaneously, after determining the final antenna subset, device 100 can track the optimal antenna combination using any tracking period. This can be achieved by changing one antenna included in the previously determined final antenna subset, or by changing one or more antennas. During tracking, if the gain of the final beam rapidly decreases, the antennas included in the previously determined final antenna subset may not be selected, or the final antenna subset itself may be replaced by another antenna subset. Tracking and the tracking period can be determined based on indicators related to changes in the radio channel.

[0096] Figure 6 is a flowchart illustrating an example of a method for transmitting SRS-switched signals according to an antenna spatial correlation-based selection method in accordance with an exemplary embodiment of the present disclosure.

[0097] Specifically, Figure 6 illustrates a method for transmitting SRS-switched signals according to the method of switching antenna subsets ("Method 3") after determining the antenna subset based on the spatial correlation between the receiving antennas of the wireless communication device. Method 3 may be referred to as the "selection method based on antenna spatial correlation".

[0098] Spatial correlation between antennas can be defined as an index indicating the degree of interference between antennas, determined by factors such as the distance between them. For example, when the spatial correlation between antennas is low, different signals can be transmitted independently by the antennas. Accordingly, according to the embodiments disclosed herein, low spatial correlation between antennas is desirable for the antenna subset of SRS-switched signals. A method for considering spatial correlation between antennas may have the purpose of transmitting signals by antennas, which ensures relatively independent channels by selecting antenna combinations based on channel information.

[0099] Spatial correlation between antennas can be determined by frequency band, cell type covered by BS, separation distance between antennas, polarization, and similar factors.

[0100] According to an embodiment, the antenna subsets can be arranged in order of lowest to highest spatial correlation among the receiving antennas of device 100, and then sequentially determined as the antenna subsets to transmit SRS exchange signals.

[0101] Alternatively, the antenna subsets can be arranged in order of highest to lowest spatial correlation among the receiving antennas of the device 100, and then sequentially determined as the antenna subsets to transmit SRS exchange signals.

[0102] In another embodiment, the arrangement of multiple antennas of device 100 can be considered to exchange antenna subsets without measuring spatial correlation. For example, the antenna subsets can be arranged in the following order from the antenna combination with the largest antenna separation distance value.

[0103] Antenna subset: {0,3}{0,2}{1,3}{0,1}{1,2}{2,3}

[0104] Referring to Figure 6, in operation S610, device 100 can arrange antenna subsets in a low-correlation order among the antennas. In operation S620, one of the antenna subsets listed in operation S610 is sequentially selected and determined as the i-th antenna subset. After operation S620, operations S210 to S290 as described with reference to Figure 2 can be performed (redundant descriptions omitted).

[0105] In operation S630, device 100 monitors the gain value of the final beam. For example, assuming that the number of antennas included in device 100 is 4 and the antenna subset is a combination of two antennas, there are a total of six possible antenna subsets, and operations S620 to S630 are repeated a total of six times.

[0106] In operation S640, when the monitoring of the final beam gain value of all antenna subsets is completed, in operation S650, the antenna subset with the maximum gain value can be determined as the final antenna subset.

[0107] Simultaneously, after determining the final antenna subset, device 100 can track the optimal antenna combination using any tracking period. This can be achieved by changing one antenna included in the previously determined final antenna subset, or by changing one or more antennas. During tracking, if the gain of the final beam rapidly decreases, the antennas included in the previously determined final antenna subset may not be selected, or the final antenna subset itself may be replaced by another antenna subset. Tracking and the tracking period can be determined based on indicators related to changes in the radio channel.

[0108] Furthermore, according to one embodiment, if an SRS switching resource is allocated by BS 110 for the SRS switching signal according to the "first scenario" (mentioned above), then after determining the antenna subset based on the antenna's receiving performance, the device 100 can switch the antenna subset to transmit the SRS switching signal. For example, the antenna subset can be determined sequentially after antennas with high antenna receiving power are arranged in ascending order or antennas with low antenna receiving power are arranged in ascending order.

[0109] Figures 7A to 7C are flowcharts illustrating examples of a method for transmitting SRS-switched signals according to an antenna selection method based on reinforcement learning, in accordance with exemplary embodiments of the present disclosure.

[0110] Referring to Figures 7A to 7C, after determining the antenna subset based on reinforcement learning according to the method of changing the antenna subset according to the update cycle, the SRS switching signal can be transmitted. This can be called the "reinforcement learning-based antenna selection method".

[0111] Reinforcement learning is a type of machine learning and can be defined as a method in which an agent defined in a specific environment identifies the current state and selects an action or sequence of actions that maximizes the reward from a selection of actions. Reinforcement learning can be implemented by a reinforcement learning device 1010c of device 100, and the operation of the reinforcement learning device 1010c will be described later with reference to FIG10C.

[0112] According to embodiments disclosed herein, the antenna selection method based on reinforcement learning includes a Q-learning-based antenna selection method and a Bandit learning-based antenna selection method.

[0113] Figure 7A is a flowchart illustrating a method for transmitting SRS-switched signals according to a Q-learning-based antenna selection method during reinforcement learning.

[0114] The Q function, expressed as "(state, action)," is a pair of states and actions, and can be defined as a function that predicts the expected value of the utility that will be provided by performing a given action in a given state. According to an embodiment, device 100 may select an antenna combination with a large Q value, i.e., Q(S,A).

[0115] In an embodiment, an action can be defined as the action of selecting an antenna combination for determining an antenna subset, and a state (i.e., the state when a particular antenna is selected) can be defined as parameters associated with the downlink channel. Parameters associated with the downlink channel can be determined by correlation in the time, spatial, and frequency domains, as well as the strength of the downlink signal. A reward can be defined as a reception performance index of the downlink signal including data received from device 100 via CSI-RS or using the final beam. The reception performance of the downlink signal can be determined by the block error rate (BLER), frequency efficiency, and the strength of the downlink signal.

[0116] Table 3 shows the Q table according to an embodiment of this disclosure.

[0117]

[0118] Referring to Table 3, for example, A_1 may refer to the case where the subset of antennas determined by device 100 is {0,1}. S_1 may refer to the state corresponding to one of the downlink-related parameter values, which can have up to M possible states due to various factors such as correlation in the time, space, and frequency domains, as well as the strength of the downlink signal.

[0119] Q(S_M,A_N) takes the action of selecting a subset of antennas including the Nth antenna combination, and may refer to the Q value in the case of a state corresponding to the parameters numbered by M based on the antenna combination.

[0120] In an exemplary embodiment, the update operation of Q can be expressed as follows.

[0121] [Equation 2]

[0122] [ α ] can be defined as a learning rate factor, and can have a value greater than 0 and less than or equal to 1. [ R Corresponding to the reward value, and [ γ [] is a discount factor, and can be defined as a value that indicates how important the current reward is relative to the reward to be obtained in the future. [ Q ]( [ S ]', [A] can be defined as the expected optimal Q value in the future state S'.

[0123] Specifically, device 100 can initialize Q(S,A) to arbitrary values ​​in operation S710a, which is the first operation of the Q-learning-based algorithm. After initializing Q, the following process is repeated for each scenario:

[0124] In operation S720a, device 100 selects whether to take an action randomly with probability e or to take an action satisfying probability (1-e). The action. In operation S730a, device 100 observes the reward based on the selected action and the new state value S', and updates the Q value using [Equation 2] in operation S740a, i.e., calculates... [ Q ] [ new ]( [ S ], [A]). In operation S750a, device 100 determines whether the scene has ended, and if device 100 determines that the scene has not ended, it updates S' to S in operation S760a.

[0125] According to an embodiment, the device 100 can select an antenna combination constituting an antenna subset based on Q, and after determining the antenna subset, calculate the state and reward, and update Q based on the updated Q to determine another antenna subset.

[0126] Figure 7B is a flowchart illustrating a method for transmitting SRS-switched signals during reinforcement learning based on an antenna selection method using an Upper Confidence Bound (UCB) algorithm.

[0127] The UCB algorithm can be defined as an algorithm that finds an upper bound (i.e., the UCB value) with a high expected reward probability at a specific time t based on observations during that time period. For example, the UCB is updated for each action of selecting antenna combinations included in a subset of antennas, and device 100 can select a subset of antennas that includes antenna combinations with large UCBs. This can be referred to as one of the "antenna selection methods based on Bandit learning".

[0128] In an exemplary embodiment, the UCB value can be expressed as follows.

[0129]

[0130] In an exemplary embodiment, the reward and the empirical mean of the reward can be expressed as follows.

[0131]

[0132] [ T ] [ k ]( [ t The number of times the corresponding antenna subset is selected up to time t can be defined as the number of times the antenna subset is selected. [ δ ] can be defined as a learning parameter. Additionally, [ X ] [ k ]( [ t ]) can be defined as the reward for the k-th action observed at time t. Additionally, It can be defined as the cumulative average of the experience rewards up to time t.

[0133] For example, device 100 can calculate the UCB at time t in operation S710b, and can select the antenna combination that maximizes the calculated UCB in operation S720b. Additionally, device 100 can measure the CSI-RS channel by selecting one of the antenna combinations selected in operation S730b. Device 100 can use [Equation 4] in operation S740b to calculate the reward and the empirical average of the reward.

[0134] The UCB algorithm can be performed in operations S710b to S740b, and operations S710b to S740b can be repeated any number of times.

[0135] Figure 7C is a flowchart illustrating a method for transmitting SRS-switched signals during reinforcement learning based on a probability distribution-based antenna selection method.

[0136] As an example, device 100 may determine an antenna subset by using a value representing a preference for selecting an antenna combination as a probability. This may be referred to as an "antenna selection method based on Bandit learning".

[0137] The initial probability of the preference can be arbitrarily set to... , where K can be defined as the number of antenna combinations, i.e., the number of all possible antenna subsets. In operation S710c, device 100 can determine an antenna subset including antenna combinations selected according to the learned probability distribution.

[0138] As an exemplary embodiment, the probability of preference can be expressed as follows.

[0139]

[0140] In operation S720c, device 100 can set a positive reward or a negative reward based on an index indicating the performance of the CSI-RS channel assigned to the selected antenna combination. For example, an index indicating the performance of a CSI-RS channel may include the signal-to-interference plus-noise ratio (SINR).

[0141] In an exemplary embodiment, the reward may be calculated as follows.

[0142] [Equation 6]

[0143] In operation of S720c, device 100 can use [Equation 6] to calculate rewards based on the performance of the CSI-RS channel.

[0144] Alternatively, the device 100 can be operated in S730c by introducing weights. [ w This can be used to update the rewards for antenna combinations with high correlation. For example, this can be done by multiplying the (k-1)th reward and the (k+1)th reward by their respective weights. [ w ] [1] and [ w ] [2] To update the rewards. Next, the device 100 updates the probability distribution value in operation S740c by accumulating rewards for a predetermined time.

[0145] As an exemplary embodiment, the probability distribution of the accumulated rewards can be expressed as follows.

[0146]

[0147] The probability distribution-based antenna selection method can be operated in S710c to S740c, and S710c to S740c can be repeated any number of times.

[0148] In the aforementioned reinforcement learning-based antenna selection schemes, actions can be applied by extending the selection of antenna combinations used to determine antenna subsets and select transmit power. For example, an action can be defined as follows.

[0149] Action_i: Select the first antenna and the third antenna & set the transmit power of the first antenna to P_level4 and the transmit power of the third antenna to P_level2.

[0150] Action_j: Select antenna 0 and antenna 3 & set the transmit power of antenna 0 to P_level1 and the transmit power of antenna 3 to P_level2.

[0151] For example, P_level2 may refer to the power corresponding to level 2 set by device 100.

[0152] Figure 8 is a flowchart illustrating an example of a method for tracking a final subset of antennas according to an exemplary embodiment of this disclosure.

[0153] Referring to Figure 8, a method for tracking the final antenna subset determined by the method illustrated with reference to Figures 4 to 7C is shown.

[0154] Using the embodiments shown in Figures 4 to 7C, in operation S810, device 100 can determine a final subset of antennas configured with the optimal antenna combination. After determining the final antenna subset, in operation S820, device 100 can track the optimal antenna combination using any tracking period, and in operation S830, it can change one antenna or change one or more antennas included in the previously determined final antenna subset based on the tracking results.

[0155] As an example, when the gain of the final beam decreases rapidly, the antennas included in the previously determined final antenna subset may not be selected, or the final antenna subset itself may be replaced by another antenna subset. For example, if the antenna subset size is 3, the antennas may be changed to one, two, or different antenna subsets with different antenna subset sizes of 3. Tracking and period are determined based on indicators related to changes in the radio channel, and the tracking period may be a value corresponding to a multiple of the transmission period of the SRS exchange signal. For example, the tracking period may be determined based on the Doppler characteristic, which serves as an index that changes with the time of the radio channel, and when the Doppler transition value of the wireless communication device is large, the tracking period may be set to be short, and when the Doppler transition value is small, the tracking period may be set to be long.

[0156] Figures 9A and 9B are flowcharts illustrating examples of a method for selecting a precoding matrix indicator (PMI) according to an exemplary embodiment of the present disclosure.

[0157] Due to the limitations of scenarios 1 and 2 above, when 100a and 100b use limited SRS resources and antennas to transmit SRS, beamforming using downlink channel information obtained from the BS will result in a loss. Therefore, methods for selecting the PMI to minimize signal loss using downlink beamforming received by devices 100a and 100b may include PMI selection methods based on channel application weights, reinforcement learning-based PMI selection methods, and similar methods.

[0158] Figure 9A is a flowchart illustrating a method for selecting a weighted PMI according to an exemplary embodiment of this disclosure.

[0159] Referring to FIG9A, an example of a PMI selection method for minimizing redundancy of information received by device 100a and minimizing signal loss using beamforming is shown. Specifically, the PMI can be selected by applying different weights to the channels corresponding to antennas used for transmitting SRS exchange signals and antennas not used for transmitting SRS exchange signals.

[0160] For example, in operation S902a, device 100a can determine the subset of antennas to transmit the SRS switching signal as {0,1} during the first SRS switching transmission cycle. In operation S904a, after using the first antenna to transmit SRS_0 as the SRS switching signal and using the second antenna to transmit SRS_1 as the SRS switching signal, BS 110 can design the downlink beam F_SRS using SRS_0 and SRS_1 in operation S906a. BS 110a can transmit CSI-RS using the F_SRS beam in operation S908a. Assuming the channels used for CSI-RS reception are h0, h1, h2, and h3, in operation S910a, device 100a can set the weights applied to each channel as w0, w1, w2, and w3. w0 to w3 can be determined according to the selection and purpose when transmitting the SRS switching signal. For example, the weights w0 and w1 of the first and second antennas used for transmitting SRS switching signals, and the weights w2 and w3 of the third and fourth antennas not used for transmitting SRS switching signals, can be set in different ways. In operation S912a, device 100a can use the information obtained by applying weights to each channel [w0×h0, w1×h1, w2×h2, w3×h3] to select the PMI, and in operation S914a, the selected PMI is fed back to BS 110a.

[0161] According to one embodiment, the weights can be set to have larger values ​​as the gain of the channel corresponding to the antenna decreases. Alternatively, the weights can be set such that the gain of all channels corresponding to the weighted antennas is the same.

[0162] Figure 9B is a flowchart illustrating a reinforcement learning-based method for selecting a PMI according to an exemplary embodiment of this disclosure.

[0163] Referring to Figure 9B, a method for selecting PMI based on reinforcement learning is shown in the antenna combination selection method.

[0164] According to an embodiment, in operation S902b, device 100b can determine the subset of antennas to transmit the SRS switching signal as {0,1} during the first SRS switching transmission cycle. In operation S904b, after using the first antenna to transmit SRS_0 as the SRS switching signal and using the second antenna to transmit SRS_1 as the SRS switching signal, BS 110b can design the downlink beam F_SRS using SRS_0 and SRS_1 in operation S906b. BS 110b can transmit CSI-RS using the F_SRS beam in operation S908b. In operation S912b, device 100 can use reinforcement learning to select the PMI. Specifically, Q-learning and Bandit learning based on UCB, as well as gradient bandit learning-based methods for selecting the PMI in Bandit learning, can be applied. As an example, an action can be defined as selecting a PMI, a state can be defined as the performance index of the channel receiving CSI-RS signals, and a reward can be defined as the performance index of the channel receiving downlink signals using the final beam. That is, device 100b can select the PMI that maximizes the "performance of the final beam receiving channel" corresponding to the reward by identifying the state representing the performance of the channel used to receive CSI-RS signals among the selectable PMIs. The wireless communication device 100b can feed back the selected PMI to BS 110b in operation S914b.

[0165] Figures 10A to 10C are block diagrams illustrating the structure of a wireless communication device according to an exemplary embodiment of the present disclosure.

[0166] Figure 10A is a block diagram illustrating the structure of a wireless communication device based on an antenna selection method according to an exemplary embodiment of the present disclosure.

[0167] Referring to FIG10A, device 100a may include first antennas 1 to m-th antennas m, radio-frequency integrated circuit (RFIC) 1002a, and processor 1006a. RFIC 1002a may include switching network 1004a and first RF chains to n-th RF chains. RFIC 1002a may include multiple RF chains, and device 100a may include multiple RFICs. Switching network 1004a may be connected to first antennas 1 to m-th antennas m. In some cases, only one RF chain may be in RFIC 1002a, or it may be connected to each individual antenna.

[0168] According to the exemplary embodiments of this disclosure, the processor 1006a can freely identify the downlink reference signal based on the SRS switching resources set by BS 110a. The processor 1006a can use the downlink reference signal to generate downlink channel information, select an antenna combination including at least one of the first antenna 1 to the mth antenna m, determine an antenna subset including the corresponding antenna combination, and control the switching network 1004a based on the determined antenna subset.

[0169] According to an exemplary embodiment of this disclosure, the switching network 1004a can be connected to the processor 1006a. Furthermore, the switching network 1004a can select at least one of the antennas included in an antenna subset determined by the processor 1006a. SRS switching signals can be transmitted to the BS 110a via the selected antenna.

[0170] According to an embodiment of this disclosure, processor 1006a can select a PMI based on CSI-RS received from BS 110a using a first beam, and can transmit the selected PMI to the BS. BS 110a can use the final beam to transmit downlink signals including data or the like, and processor 1006a can process the received downlink signals. The final beam can be determined using information obtained from SRS exchange signals and information obtained from the PMI.

[0171] Figure 10B is a block diagram illustrating the structure of a wireless communication device based on a beam selection method according to an exemplary embodiment of the present disclosure.

[0172] Referring to FIG10B, device 100b may include first antennas 1 to m-th antennas m, RFIC 1002b, and processor 1006b. RFIC 1002b may include beamformer 1004b and first RF chains to n-th RF chains. RFIC 1002b may include multiple RF chains, and device 100b may include multiple RFICs. Beamformer 1004b may be connected to first antennas 1 to m-th antennas m. In some cases, only one RF chain may be in RFIC 1002b, or it may be connected to each individual antenna.

[0173] According to the exemplary embodiments disclosed herein, the processor 1006b can freely identify the downlink reference signal using the SRS switching resources set by the BS 110b. The processor 1006b can use the downlink reference signal to generate downlink channel information and can use previously shared beamcodebook information to select a beam. When no pre-shared beamcodebook exists, the processor 1006b can design the optimal beam. The processor 1006b can design a new beam considering reception performance and spatial characteristics, and can control the beamformer 1004b based on the determined beam.

[0174] The beamformer 1004b according to an exemplary embodiment of this disclosure can be connected to the processor 1006b. Furthermore, the beamformer 1004b can form a beam based on beam information selected (or designed) by the processor 1006b. An SRS switching signal can be transmitted to the BS 110b via the formed beam.

[0175] According to an embodiment of this disclosure, processor 1006b can select a PMI based on CSI-RS received from BS 110b using a first beam, and can transmit the selected PMI to the BS. BS 110b can use the final beam to transmit downlink signals including data or the like, and processor 1006b can process the received downlink signals. The final beam can be determined using information obtained from SRS exchange signals and information obtained from the PMI.

[0176] Figure 10C is a block diagram illustrating the structure of a wireless communication device based on a reinforcement learning method according to an exemplary embodiment of the present disclosure.

[0177] Referring to FIG10C, the wireless communication device 100c may include a first antenna 1 to an m-th antenna m, an RFIC 1002c, and a processor 1006c. The processor 1006c may include a machine learning device 1010c, which is used to implement a reinforcement learning-based antenna selection method, a reinforcement learning-based beam selection method, or a reinforcement learning-based PMI selection method.

[0178] For example, the machine learning device 1010c can observe the state, select an action, and calculate the reward and Q to implement the Q-based antenna selection method shown in Figure 7A. That is, the machine learning device 1010c can implement the operations for reinforcement learning disclosed in Figures 7A to 7C and Figure 8B, and their detailed descriptions will be omitted.

[0179] As an example, in the Q-learning-based antenna selection method shown in Figure 7A, the machine learning device 1010c can use the Q table in [Table 3] to calculate Q(S,A) with the maximum value in a given state, and select the antenna combination corresponding to the corresponding Q value based on the learned information.

[0180] Although the concept of the invention has been specifically shown and illustrated with reference to embodiments thereof, it should be understood that various changes in form and detail may be made thereto without departing from the spirit and scope of the following claims and their equivalents.

[0181] 1, 2, m, n: Antenna

[0182] 10: Wireless Communication System

[0183] 100, 100a, 100b: Wireless communication devices / equipment

[0184] 100c: Wireless communication device

[0185] 102: Downlink Channel

[0186] 104: Uplink Channel

[0187] 110, 110a, 110b, 112: Base Stations (BS)

[0188] 114: Broadcasting Station

[0189] 120: System Controller

[0190] 130: Satellite

[0191] 1002a, 1002b, 1002c: Radio Frequency Integrated Circuits (RFICs)

[0192] 1004a: Switching Network

[0193] 1004b: Beamformer

[0194] 1006a, 1006b, 1006c: Processors

[0195] 1010c: Machine Learning Device

[0196] Bth, Cth: Threshold values

[0197] F_SRS, F_PMI: Downlink beam

[0198] S': State value / Future state

[0199] S210, S220, S230, S240, S250, S260, S270, S280, S290, S310a, S310b, S320a, S320b, S330a, S330b, S340a, S340b, S402, S404, S40 6. S408, S410, S412, S414, S416, S418, S420, S422, S424, S426, S428, S430, S432, S510a, S510b, S520a, S520b, S530a, S530b, S54 0a, S540b, S610, S620, S630, S640, S650, S710a, S710b, S710c, S720a, S720b, S720c, S730a, S730b, S730c, S740a, S740b, S740c, S750a, S760a, S810, S820, S830, S902a, S902b, S904a, S904b, S906a, S906b, S908a, S908b, S910a, S912a, S912b, S914a, S914b: Operation

Claims

1. A method of operating a wireless communication device including a plurality of antennas, the method comprising: Determine multiple antenna subsets, each of the multiple antenna subsets comprising at least two antennas from the multiple antennas; The system sequentially transmits a detection reference signal exchange signal, including multiple detection reference signals (SRS), to the base station via the multiple antenna subsets in order from the first of the multiple antenna subsets having the maximum separation distance between the at least two antennas to the last of the multiple antenna subsets having the shortest separation distance between the at least two antennas; receives channel state information-reference signal (CSI-RS) transmitted from the base station via a first beam; selects a precoding matrix indicator (PMI) based on the channel state information-reference signal; and transmits the selected precoding matrix indicator to the base station. And receive signals transmitted from the base station via a second beam, the second beam being determined based on the detection reference signal exchange signal and the precoding matrix indicator.

2. The method of claim 1, wherein determining the plurality of antenna subsets is performed when the number of probe reference signal switching resources allocated by the base station for the probe reference signal switching signal is less than the number of receiving antennas of the wireless communication device.

3. The method of claim 1, wherein determining the plurality of antenna subsets is performed when the number of radio frequency (RF) chains of the wireless communication device is less than the number of receiving antennas of the wireless communication device.

4. The method as described in claim 1, further comprising: Monitor the gain value of the second beam; And the final antenna subset is determined based on the gain value of the monitored second beam.

5. The method of claim 4 further includes calculating the gain value of the second beam by at least one of the power of the received signal, the signal-to-noise ratio (SNR) of the received signal, the frequency efficiency, and the decoding performance of the received signal.

6. The method of claim 4, wherein the sequential transmission of the probe reference signal exchange signal is performed in a sequential transmission cycle of the probe reference signal exchange signal, wherein the probe reference signal exchange signal is transmitted by a corresponding one of the plurality of antenna subsets in each of the transmission cycles.

7. The method of claim 4 further includes determining the antenna subset as the final antenna subset when the gain value of the monitored second beam exceeds a predetermined threshold.

8. The method of claim 1, wherein determining the plurality of antenna subsets is performed without measuring the spatial correlation between the plurality of antennas.

9. The method as described in claim 1 further includes determining a subset of antennas based on reinforcement learning.

10. The method as described in claim 4, further comprising: The final subset of antennas is tracked for each tracking cycle; And to change at least one antenna included in the antenna subset based on the tracking results.

11. The method of claim 1, comprising determining a final antenna subset based on at least one of the signal-to-interference-plus-noise ratio (SINR) of the wireless communication device, the transmit / receive characteristics of the antenna, and the linearity of the transmit power amplifier.

12. The method of claim 1, wherein selecting the precoding matrix indicator includes selecting the precoding matrix indicator based on information about the weights applied to the channel state information-reference signal reception channel.

13. The method of claim 1, wherein selecting the precoding matrix indicator includes selecting the precoding matrix indicator based on reinforcement learning.

14. A wireless communication device, comprising: Multiple antennas; A radio frequency integrated circuit (RFIC) includes a switching network connected to the plurality of antennas, wherein the switching network is configured to transmit a probe reference signal switching signal including a plurality of probe reference signals (SRS) to a base station via at least one antenna in an antenna subset of the plurality of antennas; and a processor configured to: determine the antenna subset based at least in part on the linearity of a transmit power amplifier; select a precoding matrix indicator (PMI) to be provided to the base station based on a channel state information-reference signal (CSI-RS) transmitted from the base station via a first beam; and process a signal transmitted from the base station via a second beam, the second beam being determined based on the probe reference signal switching signal and the precoding matrix indicator, wherein the processor is configured to monitor the gain value of the second beam and determine the final antenna subset based on the monitored gain value of the second beam.

15. The wireless communication apparatus as claimed in claim 14, wherein, When the number of probe reference signal exchange resources allocated by the base station for the probe reference signal exchange signal is less than the number of receiving antennas of the wireless communication device, the processor is configured to determine the subset of antennas.

16. The wireless communication apparatus as claimed in claim 14, wherein, When the number of radio frequency (RF) chains of the wireless communication device is less than the number of receiving antennas of the wireless communication device, the processor is configured to determine the subset of antennas.

17. The wireless communication apparatus of claim 14, wherein the processor is configured to sequentially determine each of a plurality of antenna subsets for each transmission cycle of the probe reference signal exchange signal.

18. A method for operating a base station to communicate with a wireless communication device including multiple antennas, the method comprising: Receive a probe reference signal exchange signal comprising multiple probe reference signals (SRS), the probe reference signal exchange signal being transmitted sequentially by the multiple antenna subsets in order from the first of the multiple antenna subsets having the maximum separation distance between at least two antennas to the last of the multiple antenna subsets having the shortest separation distance between said at least two antennas; Uplink channel information is estimated based on the probe reference signal exchange signal; downlink channel information is estimated based on the estimated uplink channel information; a first beam is determined and formed based on the estimated downlink channel information, wherein a channel status information-reference signal (CSI-RS) is transmitted by the first beam; a precoding matrix indicator (PMI) is received from the wireless communication device; and a second beam is determined and formed based on the received probe reference signal exchange signal and the received precoding matrix indicator, wherein a signal including data is transmitted by the second beam.

19. The method of claim 18, wherein the gain value of the second beam is monitored by the wireless communication device, and wherein the final antenna subset is determined by the wireless communication device based on the monitored gain value of the second beam.